JP5434826B2 - Vehicle travel control device - Google Patents

Description

  The present invention relates to a vehicle travel control device, and more particularly, to a vehicle travel control device that corrects and controls the steering angles of front wheels and rear wheels so that the vehicle travels along a target locus (target travel line).

  Various vehicle travel control devices that control the trajectory of a vehicle so that the vehicle travels along a target trajectory have been proposed. For example, in Patent Document 1 below, a lane tracking is performed in which a target trajectory of a vehicle is set based on road lane information in front of the vehicle, and an automatic steering actuator is controlled so that a deviation between the target trajectory and the forward gaze point of the vehicle is reduced. An apparatus is described.

JP 2001-48035 A JP 2007-269180 A

[Problems to be Solved by the Invention]
According to the lane tracking device described in Patent Document 1, it is possible to prompt the driver to perform a steering operation or to correct the steering angle of the steered wheels by controlling the steering torque so that the vehicle travels along the target locus. it can.

  However, in the lane tracking device described in Patent Document 1, the lane information of the road ahead of the vehicle for setting the target locus of the vehicle and the information of the front gazing point of the vehicle corresponding to the actual locus of the vehicle are acquired. A vehicle information acquisition means such as a camera is essential. Further, since the target trajectory is basically determined based on the lane information, the target trajectory of the vehicle cannot always be set to a trajectory according to the driver's desire. Furthermore, in a situation where there is no lane information on the road ahead of the vehicle or in a situation where lane information cannot be obtained, the target locus cannot be set, and therefore the vehicle cannot travel along the target locus.

  In Patent Document 2, a steering control device that sets a target trajectory of a vehicle based on a steering angle and a vehicle speed and controls the steering transmission ratio variable device so as to reduce a deviation between the target trajectory and the actual trajectory of the vehicle is disclosed. Have been described. According to the steering control device described in Patent Document 2, the steering angle of the steered wheels can be controlled so that the vehicle travels along the target locus.

  However, the steering control device described in Patent Document 2 requires vehicle information acquisition means such as GPS for obtaining the actual locus of the vehicle. In addition, since the steering angle of the steered wheels is feedback controlled based on the deviation between the target locus and the actual locus, the steering angle cannot be controlled unless the actual locus is obtained. Thus, the vehicle cannot preferably travel along the target locus.

  In order to solve the above problem, for example, the target of the steered wheels for causing the vehicle to travel along the target locus necessary for the vehicle to reach the target arrival position in the target traveling direction based on the driver's steering operation amount and the vehicle speed. It is conceivable to calculate the rudder angle and control the rudder angle of the steered wheels based on the target rudder angle. According to the control of the steering angle of the steered wheels, the steered wheels are controlled so that the trajectory of the vehicle becomes a trajectory according to the driver's wishes without requiring acquisition of outside information for obtaining the target trajectory and actual trajectory of the vehicle. The rudder angle can be controlled without delay.

  The steered wheels are generally front wheels, and if the vehicle speed is constant, the amount of turning state of the vehicle such as the yaw rate of the vehicle and the roll angle of the vehicle is uniquely determined by the steering angle of the front wheels. Therefore, if the rudder angle of the front wheels is controlled to the target rudder angle for achieving the target trajectory of the vehicle, the amount of turning state of the vehicle may become excessive.

  The yaw moment for driving the vehicle along the target trajectory is not limited to the yaw moment due to the cornering force of the front wheel, and the yaw moment due to the cornering force can be generated also by the rear wheel by controlling the steering angle of the rear wheel. it can. In addition, by controlling the steering angle of both the front and rear wheels, only the steering angle of the front wheel controls the amount of turning state of the vehicle while ensuring the cornering force of the entire vehicle necessary to achieve the target trajectory of the vehicle. It can be controlled to a value different from the case where it is done.

  Therefore, it is determined whether or not the amount of turning state of the vehicle is likely to be excessive, and when there is a concern, the amount of turning state of the vehicle becomes excessive by controlling the steering angle of the rear wheels in addition to the front wheels. It is preferable to drive the vehicle along the target trajectory while preventing the vehicle from traveling.

The present invention has been made in view of the above-described problems in a conventional travel control device that controls the trajectory of a vehicle so that the vehicle travels along a target trajectory. The main object of the present invention is to control the steering angles of the front wheels and the rear wheels so that the vehicle trajectory becomes a target trajectory in accordance with the driver's desire while preventing the amount of turning state of the vehicle from becoming excessive. That is.
[Means for Solving the Problems and Effects of the Invention]

According to the present invention, the main problem described above is that the front wheel steering angle control means for changing the relationship of the steering angle of the front wheels with respect to the steering operation amount of the driver, and the rear wheel steering angle independently of the front wheels in the running control device for a vehicle with a wheel steering angle control means, when the predetermined start condition or update condition for control of the trajectory of vehicles is judged to be satisfied, in the driver that point The target traveling direction is determined based on the steering operation amount of the vehicle and the angle determined based on the steering operation amount of the driver at the time point is used as a reference angle, and the vehicle front and rear are determined from the vehicle position at the time point. The target arrival position is determined at a position that exists on a straight line drawn in the direction inclined by the reference angle with respect to the direction and that depends on the vehicle speed from the position of the vehicle at the time, and the driver's position at the time Vehicle based on steering operation amount and vehicle speed Calculates the provisional target rudder angle of the front wheels for driving the vehicle along the target trajectory necessary to reach the target arrival position in the target traveling direction, and the vehicle proceeds to the target based on the provisional target rudder angle. The amount of turning state of the vehicle until reaching the target arrival position in the direction is estimated, and when the magnitude of the turning state amount is equal to or less than a reference value, the front wheel rudder angle control means based on the provisional target rudder angle The steering angle of the front wheel is controlled, and when the magnitude of the turning state quantity exceeds the reference value, the target based on the turning state quantity of the vehicle corrected so that the magnitude of the turning state quantity does not exceed the reference value A target rudder angle of front wheels and rear wheels for driving the vehicle along a locus is calculated, and the rudder angle of the front wheels is controlled by the front wheel rudder angle control means based on the target rudder angle of the front wheels. After the above based on the target rudder angle It is achieved by the travel control apparatus for a vehicle and controlling the steering angle of the rear wheels (the construction of claim 1) by the steering angle control means.

  As will be described in detail later, the amount of steering operation by the driver is related to the direction from the current position of the vehicle to the target arrival position with reference to the current traveling direction of the vehicle, and the vehicle speed is from the current position of the vehicle to the target arrival position. Is related to the distance. The driver's steering operation amount is also related to the target traveling direction when the vehicle reaches the target arrival position.

A time point at which it is determined that a preset start condition or update condition for the control of the vehicle trajectory is satisfied is referred to as a reference time point. According to the configuration of the first aspect, the vehicle travels along the target locus for the vehicle to reach the target arrival position in the target traveling direction based on the steering operation amount and the vehicle speed of the driver at the reference time. The target rudder angle of the steered wheel is calculated, and the rudder angle of the steered wheel is controlled based on the target rudder angle. In particular, the target traveling direction is determined based on the driver's steering operation amount at the reference time, and the target arrival position is determined based on the angle determined based on the driver's steering operation amount at the reference time. As a result, it is determined to be a position that lies on a straight line drawn in a direction inclined by a reference angle with respect to the front-rear direction of the vehicle from the position of the vehicle at the reference time point and is a distance depending on the vehicle speed from the vehicle position at the reference time point The

  When the amount of turning state is equal to or less than the reference value, the front wheel rudder angle control means controls the front wheel rudder angle based on the provisional target rudder angle. On the other hand, when the magnitude of the turning state quantity exceeds the reference value, the vehicle is caused to travel along the target locus based on the turning state quantity of the vehicle corrected so that the magnitude of the turning state quantity does not exceed the reference value. The target rudder angles of the front wheels and the rear wheels are calculated. Further, the steering angle of the front wheels is controlled based on the target steering angle of the front wheels, and the steering angle of the rear wheels is controlled based on the target steering angle of the rear wheels.

Accordingly, it is not necessary to obtain information on the outside of the vehicle for obtaining the target locus or actual locus of the vehicle, and it is also possible to obtain the actual locus based on the information on the outside of the vehicle based on the deviation between the target locus and the actual locus. It is not necessary to perform feedback control. Therefore, the steering angle of the steered wheels can be controlled without delay so that the vehicle trajectory becomes a trajectory in accordance with the driver's desire, and the vehicle can travel along the target trajectory desired by the driver.
In particular, the target arrival position can be determined based on the driver's steering operation amount and vehicle speed at the reference time, and the target traveling direction can be determined based on the driver's steering operation amount at the reference time. In addition, the angle determined based on the amount of steering operation of the driver at the reference time is set as the reference angle, and a straight line drawn in a direction inclined by the reference angle with respect to the vehicle longitudinal direction from the vehicle position at the reference time. The target arrival position can be determined as a position at a distance that depends on the vehicle speed from the position of the vehicle at the reference time point. Therefore, the target locus of the vehicle for the vehicle to reach the target arrival position in the target traveling direction can be obtained based on the driver's steering operation amount and the vehicle speed at the reference time.

  Further, according to the configuration of claim 1, in the steering angle control of only the front wheels, when the magnitude of the turning state quantity exceeds the reference value, the magnitude of the turning state quantity is corrected so as not to exceed the reference value. Based on the turning state quantity, the target rudder angles of the front wheels and the rear wheels are calculated. Therefore, it is possible to cause the vehicle to travel along the target locus while reliably preventing the turning state quantity from becoming excessively large.

  According to the first aspect of the present invention, when the magnitude of the turning state amount does not exceed the reference value even in the steering angle control of only the front wheels, the steering angle of the front wheels is controlled based on the provisional target steering angle. The rudder angle is not controlled. Therefore, the control of the vehicle trajectory can be simplified as compared with the case where the steering angles of the front wheels and the rear wheels are controlled regardless of whether the magnitude of the turning state quantity exceeds the reference value.

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 1, the corrected turning state quantity of the vehicle is such that the magnitude of the turning state quantity is For the region exceeding the reference value, the magnitude of the turning state amount is corrected to be reduced to the reference value, and for the region where the turning state amount does not exceed the reference value, the turning state amount is It is configured to be obtained by increasing and correcting the magnitude of the turning state amount so as not to exceed a reference value (configuration of claim 2).

  According to the configuration of the second aspect, in the region where the magnitude of the turning state quantity exceeds the reference value, the magnitude of the turning state quantity is reduced and corrected to the reference value, and the front wheel is based on the corrected turning state quantity of the vehicle. And the target rudder angle of the rear wheel is calculated. Accordingly, the steering angles of the front wheels and the rear wheels can be controlled so that the vehicle travels along the target locus while preventing the magnitude of the turning state amount from exceeding the reference value.

  According to the second aspect of the present invention, in the region where the magnitude of the turning state quantity does not exceed the reference value, the magnitude of the turning state quantity is corrected to increase so that the magnitude of the turning state quantity does not exceed the reference value. The target steering angles of the front wheels and the rear wheels are calculated based on the corrected amount of turning state of the vehicle. Therefore, the total amount of the turning state amount of the vehicle until the vehicle reaches the target arrival position is larger than the case where the turning state amount is not corrected to increase in the region where the turning state amount does not exceed the reference value. The fear of shortage can be reduced.

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 1, the corrected turning state quantity of the vehicle is such that the magnitude of the turning state quantity is For a region that exceeds a correction determination value that is smaller than a reference value, the magnitude of the turning state amount is corrected to be reduced below the reference value, and for a region in which the magnitude of the turning state amount does not exceed the correction determination value, The turning state quantity is calculated by increasing the magnitude of the turning state quantity so that the magnitude of the turning state quantity does not exceed the correction determination value.

  According to the configuration of the third aspect, in the region where the magnitude of the turning state quantity exceeds the correction determination value smaller than the reference value, the magnitude of the turning state quantity is corrected to be reduced below the reference value, and the corrected vehicle Based on the turning state quantity, the target rudder angles of the front wheels and the rear wheels are calculated. Accordingly, the steering angles of the front wheels and the rear wheels can be controlled so that the vehicle travels along the target locus while preventing the magnitude of the turning state amount from exceeding the reference value.

  According to the third aspect of the present invention, in the region where the magnitude of the turning state quantity does not exceed the correction judgment value, the magnitude of the turning state quantity increases so that the magnitude of the turning state quantity does not exceed the correction judgment value. The target steering angles of the front wheels and the rear wheels are calculated based on the corrected amount of turning state of the vehicle. Therefore, the total amount of the turning state amount of the vehicle until the vehicle reaches the target arrival position, compared to the case where the turning state amount is not corrected to increase in the region where the turning state amount does not exceed the correction determination value. The risk of shortage can be reduced.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 2 or 3, the integrated value of the reduction correction amount for the magnitude of the turning state amount and the turning state The integral values of the amount of increase correction of the amount are configured to be substantially equal to each other (configuration of claim 4).

  According to the above configuration, the integral value of the reduction correction amount for the magnitude of the turning state amount and the integral value of the increase correction amount for the magnitude of the turning state amount are substantially equal to each other. Therefore, it is possible to prevent an excess or deficiency in the total amount of the turning state amount of the vehicle until the vehicle reaches the target arrival position due to the correction of the magnitude of the turning state amount.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration according to any one of claims 1 to 3, the amount of turning state of the vehicle includes the yaw rate and roll angle of the vehicle. It is configured to be either one (configuration of claim 5).

  According to the fifth aspect of the present invention, it is possible to prevent the yaw rate from becoming excessive when the vehicle turning state amount is the yaw rate, and when the vehicle turning state amount is the roll angle, the roll angle. Can be prevented from becoming excessively large.

  Further, according to the present invention, in order to effectively achieve the main problem described above, in the configuration according to any one of claims 1 to 3, the target trajectory is a straight line indicating the target traveling direction. Of the exponential function with the elapsed time from the time point as an index variable in virtual orthogonal coordinates with the perpendicular line drawn from the vehicle position at the time point to the time coordinate axis as the distance coordinate axis. It is comprised so that it may be a curve (structure of Claim 6).

  According to the configuration of the sixth aspect, in a virtual orthogonal coordinate system, a straight line indicating the target traveling direction is a time coordinate axis, and a perpendicular line drawn from the vehicle position at the reference time point to the time coordinate axis is a distance coordinate axis. Thus, the target trajectory can be obtained as an exponential function curve using the elapsed time from the reference time as an exponent variable.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration according to any one of claims 1 to 3, the rudder angle of the front wheels and the target rudder angle at the time point are as follows. The steering angle of the front wheels is modified so that the magnitude of the deviation from the wheel becomes smaller (the structure of claim 7).

  According to the configuration of the seventh aspect, the steering angle of the front wheels is corrected so that the magnitude of the deviation between the steering angle of the front wheels and the target steering angle at the reference time becomes small. Therefore, the steering angle of the front wheels can be efficiently controlled in a feed-forward manner so that the steering angle of the front wheels becomes the target steering angle, and the steering angle of the front wheels is set to the target steering angle without requiring the driver's steering operation. be able to.

  According to the present invention, in order to effectively achieve the main problem described above, the deviation between the actual rudder angle of the front wheels and the target rudder angle in the configuration according to any one of claims 1 to 3 described above. The rudder angle of the front wheels is modified so that the size of the front wheel becomes smaller (structure of claim 8).

  According to the above configuration, the rudder angle of the front wheels is corrected so that the deviation between the actual rudder angle of the front wheels and the target rudder angle becomes small. Therefore, the steering angle of the front wheels can be accurately controlled in a feedback manner so that the steering angle of the front wheels becomes the target steering angle, and the steering angle of the front wheels can be set to the target steering angle even if the steering operation is performed by the driver. Can do.

  Since the feedback control is performed on the steering angle of the front wheels, the delay in the control of the steering angle of the front wheels is much smaller than in the case of a conventional vehicle travel control device in which the feedback control is performed on the trajectory of the vehicle. .

According to the present invention, in order to effectively achieve the main problems described above, in the configuration according to any one of claims 1 to 8, the position of the vehicle at the time point and the target arrival position DOO as the direction of the reference line a straight line connecting the target traveling direction is configured like configured (claim 9 which is determined in a direction the reference angle inclined with respect to the reference line of the direction at the target position ).

According to the configuration of claim 9 , the direction inclined at the reference angle with respect to the direction reference line at the target arrival position, with the straight line connecting the position of the vehicle at the reference time point and the target arrival position as the direction reference line Can be determined in the target traveling direction.

According to the present invention, in order to effectively achieve the main problems described above, in the configuration according to any one of claims 1 to 3, the operation of the locus is not performed. determining the magnitude is opened start condition of the steering operation amount of the rate of change of the driver after becoming larger than the first reference value for determining the magnitude is opened start condition of the steering operation amount of the rate of change of person configured to determine the conditions for starting the control of the track when it is smaller than the second reference value for is satisfied (the configuration of claim 1 0).

  Generally, when the driver changes the course of the vehicle, the steering operation amount is first changed relatively quickly, and then the change in the steering operation amount is moderated. Therefore, it is possible to determine the necessity of starting or updating the control of the vehicle trajectory based on the transition of the change rate of the steering operation amount of the driver.

According to this configuration 1 0, in the situation where the control of the trajectory has not been performed, a first reference value for determining the magnitude is opened start condition of the steering operation amount of the rate of change of the driver when it becomes smaller than the second reference value for determining the start condition after becoming larger than can be determined that the condition for starting the control of the trajectory is established by the determination.

According to the present invention, in order to effectively achieve the main problems described above, in the situation where the trajectory is controlled in the configuration according to any one of claims 1 to 3, the operation is performed. the magnitude of the steering operation amount of the change rate of the driver to determine a further new conditions after becoming larger than the first reference value for the magnitude of the steering operation amount of the rate of change of user to determine a further new conditions configured to determine an update condition of the control of the second of said trajectory when it becomes smaller than the reference value is established for (structure of claim 1 1).

According to this configuration 1 1, in the situation where the control trajectory is being performed, a first reference value for the magnitude of the steering operation amount of the change rate of the driver to determine the update condition when it becomes smaller than the second reference value for determining the update conditions after becoming larger than can be determined that the update condition of the control trajectory is established by the determination.

According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 6, the distance from the vehicle to the coordinate axis of the time at the time point is used as the reference distance. A target distance is obtained as a product of a reference distance and a natural exponential function having an elapsed time from the time point as an index variable, and the target locus is obtained as a line connecting the position of the target distance from the coordinate axis of the time. It is the (structure of claim 1 2).

According to this configuration 1 2 calculates the target distance elapsed time from the reference distance and the reference point as the product of the natural exponential function of the exponent of the variable, as a line connecting the position of the target distance from axis of time The target trajectory can be obtained.

According to the invention, to the aspect of the effective, in the configuration of the first aspect 2, since the change in the outside of the visual information related to the needs of the steering operation is generated A general time required for a person to perceive a change in the visual information is ΔT, a Weber ratio is −k, an elapsed time from the time point is t, and an index of the natural exponential function is − (k / ΔT ) configured to be the t (the construction of claim 1 3).

According to this configuration 1 3, the exponent of the natural exponential function - because it is (k / ΔT) t, it obtains a target distance of the vehicle to suit the perception characteristics of the human, thereby matching the perceptual characteristics of the human The target trajectory of the vehicle can be obtained.

According to the invention, to the aspect of the effective, at either one of the configurations of the claims 1 to 1 3, wherein the steering angle control means is operated by the driver Semi-by-wire steering angle control means having steering transmission ratio variable means for changing the steering transmission ratio by driving the steering wheel relative to the steering input means, and control means for controlling the steering transmission ratio variable means. arranged at (structure of claim 1 4).

According to this configuration 1 4, steering wheel by at the vehicle having a steering angle control means Semibaiwaiya type having a steering transmission ratio varying means to vary the steering transmission ratio by the steering transmission ratio varying means Can be controlled.

According to the invention, to the aspect of the effective, at either one of the configurations of the claims 1 to 1 3, wherein the steering angle control means, the steering angle of the steering wheel Steering means for changing, means for detecting the steering operation amount of the driver with respect to the steering input means, and normally controlling the steering means based on the steering operation amount of the driver, and if necessary, It is comprised so that it may be a by-wire type rudder angle control means which has a control means which controls the said steering means without depending on steering operation (structure of Claim 15 ).

According to the configuration of claim 15 , in the vehicle provided with the by-wire type steering angle control means, the steering angle of the steered wheels can be controlled without depending on the steering operation of the driver by controlling the steering means. Can be controlled.

  According to one preferable aspect of the present invention, in the configuration according to any one of the first to third aspects, when the magnitude of the turning state amount is equal to or less than a reference value, the traveling control device controls the steering angle of the rear wheel. Is maintained at 0 (preferred embodiment 1).

According to another preferred aspect of the present invention, in the configuration according to any one of the first to third aspects, the travel control device includes a driver's steering operation amount, a vehicle speed, a provisional target steering angle of the front wheels, and And a provisional target based on the driver's steering operation amount and vehicle speed at the time when it is determined that a preset start condition or update condition is established for the control of the vehicle trajectory. It is comprised so that a steering angle may be calculated (Preferred aspect 2).

  According to another preferred aspect of the present invention, in the configuration according to any one of claims 1 to 3, the travel control device travels the vehicle along the corrected turning state amount of the vehicle and the target locus. It is comprised so that the target rudder angle of a front wheel and a rear wheel may be calculated based on the lateral acceleration and vehicle speed of the vehicle for making it (preferable aspect 3).

  According to another preferred aspect of the present invention, in the configuration according to any one of the first to third aspects, the travel control device controls the wheel until a predetermined end condition for controlling the trajectory is satisfied. It is configured to control the corner (preferred aspect 4).

According to another preferred aspect of the present invention, in the configuration according to any one of the first to third aspects, the travel control device satisfies a preset start condition or update condition for the control of the vehicle trajectory. When it is determined that it is not, the steering angle of the front wheels is controlled so that a preset steering transmission ratio is achieved (preferred aspect 5).

  According to another preferred aspect of the present invention, in the configuration of claim 2, the travel control device has a turning state quantity for a part of a region where the magnitude of the turning state quantity does not exceed the reference value. The amount of turning state is corrected to be increased so that the size of the vehicle does not exceed the reference value (preferred aspect 6).

  According to another preferred aspect of the present invention, in the configuration of claim 2, the travel control device is configured such that the turning state amount is large for the entire range in which the turning state amount does not exceed the reference value. The amount of turning state is corrected so as not to exceed the reference value (preferred aspect 7).

  According to another preferred aspect of the present invention, in the configuration of claim 3, the travel control device is in a turning state for a part of a region where the magnitude of the turning state amount does not exceed the correction determination value. The magnitude of the turning state quantity is increased and corrected so that the magnitude of the quantity does not exceed the correction determination value (preferred aspect 8).

  According to another preferred aspect of the present invention, in the configuration of claim 3, the travel control device determines the turning state amount for the entire range in which the magnitude of the turning state amount does not exceed the correction determination value. The magnitude of the turning state quantity is increased and corrected so that the magnitude does not exceed the correction determination value (preferred aspect 9).

  According to another preferred aspect of the present invention, in the configuration of claim 3, the travel control device determines the magnitude of the turning state and the correction judgment for a region where the magnitude of the turning state quantity exceeds the correction judgment value. The magnitude of the turning state amount is reduced and corrected to a reference value or less so that the reduction correction amount increases as the difference from the value increases (preferred aspect 10).

  According to another preferred aspect of the present invention, in the configuration of claim 4, the integral value of the increase correction amount for the magnitude of the turning state amount is the integral value of the reduction correction amount for the magnitude of the turning state amount. It is comprised so that it may be 90% or more and 100% or less (preferable aspect 11).

According to another preferred aspect of the present invention, in the configuration of claim 6, from the time when the traveling control device determines that a preset start condition or update condition is established for the control of the trajectory of the vehicle. elapsed time stores the relation between the steering operation amount and the target steering angle of the vehicle speed and front wheel provisional driver, the elapsed time and the start condition from the time of start condition or update condition is determined to have satisfied the Alternatively, the provisional target rudder angle of the front wheels is calculated from the relationship based on the steering operation amount and the vehicle speed of the driver at the time when it is determined that the update condition is satisfied (preferred aspect 12).

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing a first embodiment of a vehicle travel control device according to the present invention applied to a vehicle equipped with a steering angle varying device, a rear wheel steering device, and an electric power steering device. It is a flowchart which shows the main routine of the traveling control in 1st embodiment. It is a flowchart which shows the establishment determination routine of the start condition of locus | trajectory control in 1st embodiment. It is a flowchart which shows the establishment determination routine of the update conditions of locus | trajectory control in 1st embodiment. It is a flowchart which shows the target rudder angle calculation routine of the wheel in 1st embodiment. It is a graph which shows the relationship between the vehicle speed V and the target steering gear ratio Nt. It is a graph which shows the relationship between steering torque Thd or Thda, and basic assist torque Tpab. It is a graph which shows the relationship between the vehicle speed V and the vehicle speed coefficient Kv. It is a graph which shows the relationship between steering torque Thd or Thda, vehicle speed V, and basic assist torque Tpab. It is a flowchart which shows the target rudder angle calculation routine of the wheel in 3rd embodiment. FIG. 9 is a schematic configuration diagram showing a fifth embodiment of a vehicle travel control device according to the present invention applied to a vehicle equipped with a by-wire type steering device. It is a flowchart which shows the main routine of the traveling control in 5th embodiment. It is a graph which shows the relationship between the steering torque Th0 after correction | amendment, and the basic steering burden reduction torque Tpadb. It is a graph which shows the relationship between the steering torque Th0 after correction | amendment, the vehicle speed V, and the basic steering burden reduction torque Tpadb. It is a flowchart which shows the target rudder angle calculation routine of the wheel in a 1st modification. It is a flowchart which shows the target rudder angle calculation routine of the wheel in a 2nd modification. It is explanatory drawing which shows the case where the vehicle of a two-wheel model changes a course. It is explanatory drawing which shows the case where a vehicle carries out a regular circle | round | yen and draws an arc-shaped locus | trajectory. It is explanatory drawing which shows the circular-arc-shaped locus | trajectory of the vehicle by steady circle turning about the case where the rudder angle of a front wheel is a rudder angle corrected based on the rudder angle and guide rod model corresponding to a driver | operator's steering operation amount. Explanatory diagram showing a minimum amount Δx ″ that allows a person to perceive a change in the horizontal acceleration x ″ and a minimum time ΔT required for a person to perceive a change in the minimum amount minimum amount Δx ″ in a situation where the horizontal acceleration x ″ changes. It is. It is explanatory drawing which shows the case where a vehicle travels by drawing the locus | trajectory of an exponential function from the reference position of a guide rod to the front-end | tip position of a guide rod. FIG. 5 is an explanatory diagram showing a situation in which the vehicle moves to a position between the reference position of the guide rod and the tip position of the guide rod when the vehicle travels while drawing an exponential function locus. It is explanatory drawing which shows decomposition | disassembly of the vehicle speed into the component parallel to the coordinate axis regarding distance, and the coordinate axis regarding time about the condition shown by FIG. It is explanatory drawing which shows the restriction | limiting of the estimation yaw rate YRa by an upper limit about one side partial area correction. It is explanatory drawing which shows the restriction | limiting of the estimation yaw rate YRa by an upper limit about both-sides partial area | region correction | amendment. It is explanatory drawing which shows the restriction | limiting of the estimation yaw rate YRa by an upper limit about one side all area | region correction | amendment. It is explanatory drawing which shows the restriction | limiting of the estimation yaw rate YRa by an upper limit about both-sides all area | region correction | amendment. It is explanatory drawing which shows the restriction | limiting of estimated yaw rate YRa by peak reduction about both-sides all-region correction | amendment. It is explanatory drawing which shows the restriction | limiting of the estimation yaw rate YRa by peak reduction about front side one side all area | region correction | amendment. It is explanatory drawing which shows the restriction | limiting of the estimation yaw rate YRa by peak reduction about the one side all area | region correction | amendment of the rear side. It is a graph which shows the relationship between the vehicle speed V and the reference value YRref. It is explanatory drawing which shows the point of the one side all area | region correction | amendment by the restriction | limiting of the estimation yaw rate YRa by an upper limit. It is explanatory drawing which shows the point of the both-sides all area | region correction | amendment by the restriction | limiting of the estimation yaw rate YRa by an upper limit. The broken line is an explanatory view showing the adaptation of the gain Gp used for the restriction by the peak reduction with respect to the all-sides region correction. A broken line is an explanatory view showing adaptation of the gain Gp used for restriction by peak reduction with respect to one-side full-area correction on the front side. A broken line is an explanatory view showing adaptation of the gain Gp used for restriction by peak reduction with respect to one-side full-area correction on the rear side. It is a graph which shows the relationship between the vehicle speed V and the reference value Rvref.

General Description of Embodiments Prior to the description of specific embodiments, technical matters common to the embodiments will be described generally.
1) Guide rod model

  Since the driver's intention regarding the vehicle trajectory is considered to be reflected in the driver's steering operation amount, the direction of the front wheel that is the steering wheel, that is, the steering angle of the front wheel is considered to be the driver's forward gaze direction. May be. Therefore, a virtual vehicle having a virtual guide rod installed on the front wheel is defined, and it is assumed that the driver is driving the vehicle so that the tip of the guide rod moves along a desired locus. In that case, it is considered that the forward gaze distance, that is, the distance from the vehicle to the position where the driver gazes corresponds to the length of the guide rod and changes according to the vehicle speed.

  In the present specification, a vehicle model provided with the above-described virtual guide rod is referred to as a “guide rod model”. According to the guide rod model, a preferable target trajectory of the vehicle can be set as a trajectory passing through the tip of the guide rod based on the driver's steering operation amount and vehicle speed when the driver tries to change the course of the vehicle. it can.

  Therefore, by controlling the rudder angle of the front wheels so that the vehicle travels along the set target trajectory, the vehicle surrounding information is not required to be acquired by photographing or communicating from outside the vehicle. Can be driven along a preferable target locus.

  In order to facilitate understanding of the vehicle trajectory control based on the guide rod model, it is assumed that the vehicle is a two-wheel model vehicle 104 including a front wheel 100 and a rear wheel 102 as shown in FIG. Consider a case where the vehicle 104 changes its course to a target course 108 that is inclined by an angle φ with respect to a line 106 indicating the front-rear direction. The unit of angle is rad.

  As shown in the figure, it is assumed that a virtual guide rod 110 protrudes from the center O of the front wheel 100 to a point P on the target course 108 along the front-rear direction of the front wheel in the front-rear direction of the vehicle. Let the inclination angle be β. The length of the guide rod 110, that is, the length of the line segment OP is A, and the angle formed by the target course 108 and the guide rod 110 is α. The distance from the center O of the front wheel 100 to the target course 108 is x, and the steering angle of the front wheel 100 is δ (δ = β). Further, the wheel base of the vehicle 104 is WB, and the vehicle speed is V. The unit of length is m, and the unit of time is sec.

  When the minute time dt elapses without the steering angle δ and the vehicle speed V changing, the vehicle 104 moves from the position indicated by the solid line to the position indicated by the broken line, and the accompanying angle φ and distance x The following formulas 1 to 4 are established, where dφ and distance dx are respectively changed. Since the minute time dt is very small, it is considered that the front wheel 100 moves to a point on the guide rod 110 and the rear wheel 102 moves to a point on the line 106 indicating the front-rear direction of the vehicle before movement as shown in the figure. Good.

β = φ-α (1)
x = A * sinα (2)
-WBdφ = Vdt * sinβ (3)
-Dx = Vdt * sinα (4)

Differentiating Equation 2 by α yields Equation 5 below, so dx is expressed by Equation 6 below.
dx / dα = A * cosα (5)
dx = A * cosα * dα (6)

By substituting Equation 6 into Equation 4 above, the following Equation 7 is obtained, so that the length A of the guide rod is expressed by Equation 8 below.
-A * cosα * dα = Vdt * sinα (7)
A =-(Vdt * sinα) / (cosα * dα)
=-(Vdt * tanα) / dα
= −Vdt * {1 / (cosα) ² } (8)

Further, when Equation 3 is solved for Vdt, the following Equation 9 is obtained, and when Equation 9 is substituted into Equation 8, the following Equation 10 is obtained.
Vdt = (− WBdφ) / sinβ (9)
A = − (− WBdφ) / sinβ * {1 / (cosα) ² } (10)

Non-straight running of the vehicle such as turning can be considered as a combination of steady circular running, and when the locus is an arc, the angles α and β are the same. Β is the same as the steering angle δ of the front wheels. Therefore, the length A of the guide rod can be expressed by Equation 11 by rewriting the angles α and β in Equation 10 to the steering angle δ.
A = (WBdφ) / sinδ * {1 / (cosδ) ² } (11)

In equation 11, dφ is the yaw rate YR of the vehicle, and the yaw rate YR is expressed by equation 12 below.
YR = V / WB * δ (12)

Therefore, the length A of the guide rod can be expressed by Expression 13 by substituting Expression 12 into dφ of Expression 11.
A = WB (V / WB * δ) / sinδ * {1 / (cosδ) ² }
= (V * δ) / sinδ * {1 / (cosδ) ² } (13)

  If the sign of the steering angle δ differs depending on whether the turning direction of the vehicle is a left turn or a right turn, if the sign of the steering angle δ is reversed by reversing the turning direction of the vehicle, the sign of sin δ is also the same. Therefore, the length A of the guide rod is always a positive value.

  In the above description, the guide rod model has been described on the assumption that the guide rod 110 has the center O of the front wheel 100 as a reference position and protrudes forward from the reference position along the front-rear direction of the front wheel. However, since it is preferable to consider the vehicle trajectory as the trajectory of the center of gravity of the vehicle, in the following description, the guide rod has the center of gravity of the vehicle as a reference position and the front of the vehicle along the front-rear direction of the front wheel from the reference position. Suppose that

2) Arc-shaped locus As shown in FIG. 19, the steering angle δ and the vehicle speed V of the front wheels are set to constant values, and the vehicle 104 turns in a steady circle, and the arc shape extends from the position P0 to the position P1. Let us consider a case where the vehicle travels while drawing its trajectory Tc. In this case, the line segment corresponding to the guide rod when the center of gravity of the vehicle 104 is at the position P0 extends from the reference point P0 to the tip P1.

Since the motion of the vehicle 104 is a steady circular turning motion, the yaw rate YR of the vehicle is expressed by the above formula 12, and the lateral acceleration LA of the vehicle is expressed by the following formula 14.
LA = YR * V (14)

Therefore, the radius R of the arcuate trajectory Tc is expressed by the following Expression 15.
R ⁼ V 2 / LA
= V ² / (YR * V)
= V / YR
= V / (V / WB * δ)
= WB / δ (15)

  Further, as shown in FIG. 19, a line 106 indicating the front-rear direction of the vehicle 104 and a line 108 indicating the target course are tangent lines that touch the arcuate trajectory Tc at positions P0 and P1, respectively. Let Q1 be the intersection of the lines 106 and 108, and let Q2 be the foot of the perpendicular line that descends from the center Oc of the arc-shaped locus Tc to the guide rod 110. Since the triangle P0OcP1 is an isosceles triangle having the center Oc as a vertex, the angle P0OcQ2 and the angle P1OcQ2 are equal to each other, and these are γ. Also, the angle OcP0Q2 and the angle OcP1Q2 are equal to each other, and these are λ.

As understood from FIG. 19, the following equations 16 and 17 hold. Thus, the angle γ is the same as the angles α and δ.
α + λ = δ + λ = π / 2 (16)
γ + λ = π / 2 (17)

As can be seen from FIG. 19, the length A0 of the line segment corresponding to the guide rod is twice the line segment P0Q2, and the length of the line segment P0Q2 is R * sinγ = R * sinδ. Therefore, the length A0 of the line segment corresponding to the guide rod is expressed by Equation 18.
A0 = 2R * sinδ
= 2 (WB / δ) * sinδ (18)

  The length A0 of the line segment corresponding to the guide rod expressed by Equation 18 does not include the vehicle speed V and does not depend on the vehicle speed V. From the comparison between the length A0 of this line segment and the length A of the guide rod represented by Equation 13, if the rudder angle δ of the front wheel is not corrected, it follows an arcuate path passing through the tip of the guide rod 110. It can be seen that the vehicle cannot be driven. In other words, in order to set the length A0 of the line segment to the same value as the length A of the guide rod represented by Expression 13, the steering angle determined by the driver's steering operation amount and the steering gear ratio (“originally The steering angle of the front wheels must be corrected to a value different from δ).

  As shown in FIG. 20, when the rudder angle of the front wheels is modified from the original rudder angle δ to the modified rudder angle δ ′, the vehicle 104 has an arcuate trajectory Tc passing through the tip P1 ′ of the guide rod 110. Suppose that it can drive along '. Further, it is assumed that the center and radius of the arc-shaped locus Tc ′ are Oc ′ and R ′, respectively.

The radius R ′ is expressed by the following equation 19 corresponding to the above equation 15.
R ′ = WB / δ ′ (19)

Since the triangle P0P1Oc and the triangle P0P1'Oc 'are similar, the following equation 20 holds.
R / R '= A0 / A (20)

Substituting the above equation 13 and the above equations 15, 18, and 19 in which δ is rewritten into δ ′ into this equation 20, the following equation 21 is obtained.
δ ′ / δ = 2WB * sinδ ′ * sinδ * (cosδ ′) ² / (V * δ ′ * δ)
(21)

When the steering angle δ of the front wheel and the corrected steering angle δ ′ are small values, sin δ and sin δ ′ may be regarded as δ and δ ′, respectively, and cos δ ′ is regarded as 1. Good. Therefore, the rudder angle δ ′ after correction is expressed by the following formula 22 obtained by modifying the above formula 21.
δ ′ = (2WB / V) * δ (22)

Assuming that the steering angle as the amount of steering operation of the driver is θ and the steering gear ratio is N, the original steering angle δ of the front wheels is expressed by the following Expression 23. The steering gear ratio N may be constant, or may be a value variably set according to the vehicle speed V, for example.
δ = θ / N (23)

Therefore, the corrected steering angle δ ′ is expressed by the following Expression 24.
δ ′ = (2WB / V) * θ / N (24)

Further, Ta is the time required for the vehicle to travel along the arcuate trajectory Tc 'from the position P0 to the position P1' in a state where the steering angle and the vehicle speed of the front wheels are maintained at constant δ 'and V, respectively. The time Ta is the time required for the circular motion at the yaw rate YR expressed by the equation 25 along the fan-shaped circular arc having the central angle θ of 2γ = 2δ and the radius R ′. Therefore, the time Ta is 1 [sec] as represented by the equation 26, and does not depend on the vehicle speed V.
YR = V / WB * δ ′ (25)
Ta = 2δ / YR
= 2WB * δ / (V * δ ′)
= 2WB * δ / {V * (2WB / V) * δ}
= 1 (26)

  Therefore, in the situation where the original steering angle of the front wheels is δ, the tip of the guide rod 110 is controlled by maintaining the vehicle speed V at a constant value and controlling the steering angle of the front wheels to the corrected steering angle δ ′. The vehicle can be driven along an arcuate trajectory Tc ′ passing through P1 ′. Regardless of the value of the vehicle speed V, the vehicle passes the position P1 'when the time Ta = 1 [sec] has elapsed.

3) Exponential function locus From the above equation 2, the following equation 27 holds. However, from Equation 1, α = φ−β.
x ′ = − V * sin α (27)

From the above equations 2 and 27, the following equation 28 is established, and the equation 28 indicates that the distance x is a variable that changes according to the Weber rule.
x '=-(V / A) x (28)

Solving Equation 28 yields Equation 29. Therefore, by controlling the distance x so as to change according to the equation 29, the distance x can be controlled according to the Weber rule. X ₀ is the value of the distance x when the time t is 0.
x = x ₀ * exp {-(V / A) * t} (29)

Next, let us consider adapting the control of the distance x based on the above equation 29 to human perceptual characteristics. As shown in FIG. 21, when the horizontal acceleration x ″ of the vehicle, which is a differential value of the distance x twice, increases, the minimum amount that a person can perceive the change in the horizontal acceleration x ″ is Δx ″. The minimum time required for a person to perceive the change Δx ″ of the horizontal acceleration x ″ is ΔT. The minimum amount Δx ″ is expressed by the following equation 30 where the rate of change of the horizontal acceleration x ″ is x ″ ′.
Δx ″ = x ″ ′ * ΔT (30)

As can be seen from FIG. 21, the rate of change x ″ ′ of the horizontal acceleration x ″ is expressed by the following equation 31.
x ″ ′ = {(x ″ + Δx ″) − x ″} / {(T + ΔT) −T}
= Δx ″ / ΔT (31)

Since the following equation 32 is obtained by differentiating the equation 28 twice, the following equation 33 is established.
x ″ ′ = − (V / A) * x ″ (32)
x ″ ′ / x ″ = − (V / A) (33)

By substituting the equation 31 into the equation 33 and modifying it, the following equation 34 is obtained.
Δx ″ / x ″ = − (V / A) * ΔT (34)

Since the above equation 34 is an equation forming the Weber ratio, the above equation 34 can be rewritten as the following equation 35 with the Weber ratio being −k. However, k is a positive value represented by Expression 36.
Δx ″ / x ″ = − k (35)
k = (V / A) * ΔT (36)

  The minimum time ΔT is a value with individual differences, but the minimum time ΔT is an average constant value, and the Weber ratio −k is also a constant value.

The above equation 35 is modified as shown in the following equation 37, and the equation 37 is substituted into the above equation 30 and modified to obtain the following equation 38. Then, by solving the following equation 38, the following equation 39 is obtained.
Δx ″ = − k * x ″ (37)
x ″ ′ * ΔT = −k * x ″ (38)
x = x ₀ * exp {− (k / ΔT) * t} (39)

  The above equations 29 and 39 both indicate that the distance x is an exponential function of the time t. According to the equation 39, the Weber ratio that does not depend on the vehicle speed V for the distance x, and hence the trajectory of the preferred exponential function of the vehicle. k and the minimum time ΔT.

Therefore, by controlling the vehicle trajectory using the above equation 39, the following advantages can be obtained as compared with the case where the vehicle locus is controlled using the above equation 29 depending on the vehicle speed V.
(1) Since the above equation 39 does not include the vehicle speed V, the amount of calculation can be reduced and the control can be simplified.
(2) The trajectory of the vehicle can be controlled to a preferable exponential function trajectory adapted to human perceptual characteristics.

  As can be understood from the above description, by controlling the vehicle trajectory by controlling the distance x according to Equation 39, the trajectory of the vehicle can be made an exponential function trajectory that is more favorable for human perception characteristics than an arc-shaped trajectory. it can.

  However, even if the trajectory of the vehicle is set as an exponential trajectory according to the above equation 39, if the time Tb required for the vehicle to reach the position P1 ′ is the same as the time Ta when the trajectory of the vehicle is an arc-shaped trajectory. Is not limited.

Therefore, the above equation 39 is rewritten as the following equation 40, where D is a correction coefficient for setting the time Tb to the same value as the time Ta.
x = x ₀ * exp {− (k / ΔT) D * t} (40)

In order to set the time Tb required for the vehicle to reach the position P1 'as the time Ta, the distance x can be changed to xb when the time t is Ta in Equation 40, with xb being a positive constant close to 0. Therefore, the following equation 41 should be satisfied. Since Ta is 1 [sec], when equation 41 is solved for correction coefficient D, equation 42 is obtained.
_{xb = x 0 * exp {-} (k / ΔT) D * Ta} ...... (41)
D = − (log _e xb−log _e x ₀ ) * ΔT / (k * Ta)
=-(Log _e xb-log _e x ₀ ) * ΔT / k (42)

  As shown in FIG. 22, by controlling the steering angle δ of the front wheels so that the distance x changes in accordance with the above equation 40, an index from the reference position P0 of the guide rod to the tip position P1 ′ of the guide rod is an index. Consider a case where the vehicle travels while drawing a function locus Te.

  Assume that the perpendicular foot drawn from the reference position P0 of the guide rod to the line 108 indicating the target course is the intersection point Q3. The exponential function represented by the above equation 40 is an orthogonal function in which the line 108 indicating the target course is a coordinate axis related to time, the line 106 indicating the longitudinal direction of the vehicle 104 is the coordinate axis related to the distance x, and the intersection Q3 is the origin. It is a function.

Assuming that the distance between the position P1 and the intersection point Q3 and the distance between the position P0 and the position intersection point Q3 are B and C, respectively, the distances B and C are expressed by the following equations 43 and 44, respectively.
B = A * cosδ (43)
C = A * sinδ
= 2R * sinδ * sinδ
= 2 (WB / δ ′) * (sinδ) ² (44)

When the steering angle δ is small, it may be considered that sin δ is equal to δ. Therefore, the distance C is expressed by the following equation 45 by substituting the equation 22 into the equation 44 and setting sin δ = δ. The distance C is a value x ₀ of the distance x when the time t is 0, is a positive value. Thus, it is possible to obtain the distance x ₀ by Equation 46 below corresponding to formula 45.
C = (V / δ) * δ ²
= V * δ (45)
x ₀ = V * | δ | (46)

Thus calculated correction coefficient D and the distance x ₀ by the respective formulas 42 and 46, by controlling the distance x according to equation 40, the time Ta = 1 arrives at the vehicle substantially located P1 'when [sec] has elapsed Thus, the vehicle can travel along the locus Te of the exponential function.

  Next, the control of the steering angle of the front wheels for controlling the vehicle trajectory to a preferable exponential trajectory Te by changing the distance x according to the above equations 40, 42 and 46 will be described.

First, the steering angle δ and the vehicle speed V of the front wheel are set to a constant δ ′ and a constant value, respectively, and the vehicle draws an arc-shaped trajectory Tc ′ from the guide rod reference position P0 to the guide rod tip position P1 ′. Consider the lateral acceleration LAa of the vehicle when traveling. If the slip angle of the vehicle is 0, the lateral acceleration LAa of the vehicle is equal to the product of the yaw rate YR and the vehicle speed V expressed by Equation 25, and is a value obtained by Equation 47 below.
LAa = YR * V
= V / WB * δ '* V
= V ² / WB * δ ′
^{= V 2 / WB * (2WB} / V) * θ / N
= 2V * θ / N (47)

  Further, when the vehicle speed V is set to a constant value and the steering angle δ of the front wheels is variably controlled to δb, the vehicle is expressed by the above equation 40 from the reference position P0 of the guide rod to the tip position P1 ′ of the guide rod. Consider the lateral acceleration LAb of the vehicle when traveling along an exponential function locus Te.

As shown in FIGS. 23 and 24, in the situation where the vehicle has moved to the position P3 between the reference position P0 and the tip position P1 ′, the vehicle speed V is converted into the component Vx parallel to the coordinate axis related to the distance x and the coordinate axis related to time. 48, the following equation 48 is established.
V = (Vx ² + Vy ² ) ^1/2 (48)

Since the component Vx parallel to the coordinate axis with respect to the distance x is equal to the change rate of the distance expressed by the equation 40, the component Vx can be obtained by the following equation 49.
Vx = dx / dt
= | D [x ₀ * exp {-(k / ΔT) D * t}] / dt
= | -V * δ * (k / ΔT * D) * exp {-(k / ΔT) D * t} | (49)

From Expression 48 and Expression 49, it can be seen that a component Vy parallel to the coordinate axis with respect to time can be obtained by Expression 50 below.
Vy = (V ² −Vx ² ) ^1/2 (50)

As shown in FIG. 24, the angle formed by the line 106 indicating the longitudinal direction of the vehicle with respect to the line 112 parallel to the coordinate axis related to the distance x, that is, the angle formed by the component Vx parallel to the coordinate axis related to the distance x with respect to the vehicle speed V. It is assumed that σ. If the slip angle of the vehicle is 0, the following equation 51 is established. Therefore, the angle σ is expressed by the following formula 52.
tanσ = Vy / Vx (51)
σ = tan ⁻¹ (Vy / Vx) (52)

The vehicle lateral component of the component Vx parallel to the coordinate axis with respect to the distance x is defined as Vxx, and the vehicle lateral component of the component Vy parallel to the coordinate axis with respect to time is defined as Vyx. The components Vxx and Vyx in the lateral direction of the vehicle are expressed by equations 53 and 54, respectively.
Vxx = Vx * sinσ (53)
Vyx = Vy * cosσ (54)

Therefore, the lateral speed Vz of the vehicle when the vehicle travels along an exponential function locus Te is expressed by the following equation 55, and the lateral acceleration LAb of the vehicle is expressed by the following equation 56.
Vz = Vyx-Vxx
= Vy * cosσ-Vx * sinσ (55)
LAb = d (Vz) / dt (56)

A deviation ΔLA between the lateral acceleration LAb of the vehicle when the vehicle travels along an exponential locus Te and the lateral acceleration LAa of the vehicle when the vehicle travels along an arcuate locus Tc is expressed by Expression 57. .
ΔLA = LAb−LAa (57)

The yaw rate YR of the vehicle is a value obtained by replacing δ ′ in Equation 25 with δb, and is a value obtained by dividing the lateral acceleration LAb of the vehicle by the vehicle speed V, so Equation 58 is established.
V / WB * δb = LAb / V (58)

Therefore, the steering angle δb of the front wheel for driving the vehicle so as to draw the locus Te of the exponential function is obtained by the following equation 59.
δb = (LAb / V) / (V / WB)
= (WB / V ² ) * LAb (59)

Necessary for driving the vehicle to draw an exponential function locus Te on the basis of the steering angle δa of the front wheels (target steering angle δat = δ ′) for running the vehicle so as to draw an arc-shaped locus Tc ′. Let Δδb be the amount of correction of the steering angle of the front wheels. The correction amount Δδb of the front wheel rudder angle is obtained by the following equation 60 when turning left, and is obtained by equation 61 below when turning left.
Δδb = (WB / V ² ) * ΔLA (60)
Δδb = − (WB / V ² ) * ΔLA (61)

The steering angle δa of the front wheels for driving the vehicle so as to draw an arcuate trajectory Tc ′ is the corrected steering angle δ ′ represented by Expression 24. Therefore, the target rudder angle δ (provisional target rudder angle) bt for driving the vehicle so as to draw an exponential function locus Te is obtained by the following equation 62 when turning left, and when turning right, It is obtained by the following equation 63.
δbt = δ ′ + Δδb
= (2WB / V) * θ / N + (WB / V ² ) * ΔLA (62)
δbt = δ ′ + Δδb
= (2WB / V) * θ / N- (WB / V ² ) * ΔLA (63)

4) Control of rudder angle of front wheels and rear wheels The above description is to drive the vehicle along the target locus by controlling the rudder angle of the front wheels. Trajectory control of the vehicle by controlling the steering angle of the front wheels does not require a rear wheel steering device, and is easier than controlling the trajectory of the vehicle by controlling the steering angles of the front wheels and the rear wheels.

  However, as can be seen from Equation 12, the yaw rate YR of the vehicle is uniquely determined by the steering angle δ of the front wheels if the vehicle speed V is constant. The roll angle of the vehicle is also uniquely determined by the vehicle yaw rate YR. Therefore, depending on the target locus, the yaw rate YR or the roll angle that is the amount of turning state of the vehicle may be excessive.

  According to the control of the steering angles of the front wheels and the rear wheels, the yaw rate YR of the vehicle can be controlled to a value different from the case where only the front wheels are controlled by the steering angle while ensuring the lateral acceleration of the vehicle necessary for the trajectory control. . Therefore, if only the front wheels are controlled, the yaw rate and roll angle of the vehicle may be excessive. In this situation, the yaw rate is controlled by controlling both the front wheel steering angle δf and the rear wheel steering angle δr. It is conceivable to prevent the roll angle from becoming excessive. However, in that case, the rear wheel steering device needs to be mounted on the vehicle.

When the differential value of the slip angle Sa of the vehicle, that is, the slip angular velocity is Sad, the lateral acceleration LA of the vehicle is expressed by the following equation 64.
LA = V (Sad + YR) (64)

  The slip angular velocity Sad and the yaw rate YR in the above equation 64 can be calculated from the following equations 65 and 66. M is the mass of the vehicle, and Lf and Lr are distances in the longitudinal direction of the vehicle between the front and rear axles and the center of gravity of the vehicle, respectively. I is the yaw moment of inertia of the vehicle, and Cf and Cr are the cornering powers of the front and rear wheels, respectively. Further, YRd is a differential value of the yaw rate YR, and s is a Laplace operator.

The coefficients a11, a12, b11, b12, a21, a22, b21, b22 are as follows.

Therefore, if the term of the Laplace operator s is ignored, the slip angular velocity Sad and the yaw rate YR are expressed by the following equations 67 and 68. However, the coefficients Ca to Cd are constant coefficients obtained by solving the above equations 65 and 66 for the slip angular velocity Sad and the yaw rate YR.
Sad = Ca * δf + Cb * δr (67)
YR = Cc * δf + Cd * δr (68)

From the above equations 64 and 67, the following equation 69 is established.
LA / V-YR = Sad
= Ca * δf + Cb * δr (69)

  Therefore, when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels, by limiting the yaw rate YR in each of the above formulas, the lateral acceleration LA of the vehicle is targeted while preventing the yaw rate YR from becoming excessive. It can be a value necessary to achieve the trajectory. That is, by setting the yaw rate YR in the above formulas 68 and 69 to a value smaller than the value in the case of the steering angle control of only the front wheels, the target locus is achieved while preventing the yaw rate from becoming excessive. It is possible to calculate the steering angle δf of the front wheel and the steering angle δr of the rear wheel necessary for the vehicle.

Further, assuming that the height of the center of gravity of the vehicle is H, the roll rigidity of the vehicle is Kr, and the acceleration of gravity is g, the steady roll angle Rv of the vehicle is expressed by the following equation 70.
Rv = M * H * V * YR / (Kr-Mg * H) (70)

Therefore, by substituting YR of the above formulas 68 and 69 into the yaw rate YR of the above formula 70, the roll angle Rv of the vehicle is expressed by the following formulas 71 and 72, with Ce to Ch as constant coefficients.
Rv = Ce * δf + Cf * δr (71)
Rv = Kg * V * LA- (Cg * δf + Ch * δr) V (72)
However, the coefficients Kg, Cg, and Ch are constants represented by the following equations, respectively.
Kg = M * H * / (Kr-Mg * H)
Cg = Kg * Ca
Ch = Kg * Cb

  Therefore, when there is a possibility that the roll angle Rv becomes excessive in the steering angle control of only the front wheels, by restricting the roll angle Rv of the above two formulas, it is possible to prevent the roll angle Rv from being excessive and prevent the vehicle from moving sideways. The acceleration LA can be set to a value necessary for achieving the target locus. That is, in the above formulas 71 and 72, the roll angle Rv is set to a value smaller than the value in the case of the steering angle control of only the front wheels, thereby preventing the roll angle Rv from becoming excessive and preventing the target trajectory. The steering angle δf of the front wheels and the steering angle δr of the rear wheels necessary to achieve the above can be calculated.

5) Limiting method of turning state quantity As will be understood from the above explanation, when there is a possibility that the yaw rate or roll angle, which is the turning state quantity of the vehicle, is excessive, both the front wheel steering angle δf and the rear wheel steering angle δr By appropriately controlling this, it is possible to prevent the yaw rate and roll angle from becoming excessive.

  As described above, the provisional target rudder angle δbt of the front wheels for driving the vehicle so as to draw the trajectory Te of the exponential function can be obtained by the above equation 62 or 63. As can be seen from Equation 12, if the vehicle speed V is constant, there is a unique relationship between the steering angle δ of the front wheels and the yaw rate YR of the vehicle. Therefore, when the target rudder angle δbt of the front wheels is obtained, the yaw rate YR and roll angle Rv until the vehicle reaches the target arrival position that is the end point of the target trajectory are expressed by the above formulas 12 and 70 based on the target rudder angle δbt of the front wheels. It can be estimated in advance.

  Therefore, assuming that the estimated yaw rate and roll angle are YRa and Rva, respectively, the yaw rate and roll angle become excessive by determining whether or not the maximum value of the estimated yaw rate YRa and roll angle Rva exceeds the reference value. It can be determined whether there is a fear. If there is a possibility that the yaw rate or roll angle will become excessive, the yaw rate or roll angle will become excessive by switching from the steering angle control of only the front wheels to the control of the steering angle of the front and rear wheels by one of the following methods. Can be prevented.

  As shown by the broken line in FIG. 24, when the estimated yaw rate YRa exceeds the reference value YRref in the section from the time tc1 to the time tc2, there are two methods for limiting the amount of turning state. explain.

  The reference value YRref may be a constant, but the higher the vehicle speed V, the smaller the allowable yaw rate of the vehicle. Therefore, as shown in FIG. 31, the reference value YRref is preferably variably set according to the vehicle speed V so that the reference value YRref is smaller when the vehicle speed V is high than when the vehicle speed V is low.

5-1) The yaw rate, which is the limited turning state quantity based on the upper limit value of the turning state quantity, is restricted by the upper limit value. It is classified into correction and correction on both sides.

5-1-1) In the section from the one-side partial region correction time point tc1 to tc2, the estimated yaw rate YRa is corrected to the reference value YRref. Based on the corrected estimated yaw rate YRaa, the target rudder angle δft for the front wheels and the target rudder angle δrt for the rear wheels are calculated according to the following equations 73 and 74 corresponding to the equations 68 and 69, respectively. Therefore, in the section from the time point tc1 to tc2, the yaw rate YR is limited with the reference value YRref as the upper limit value as shown by the solid line in FIG. 24, and therefore does not exceed the reference value YRref.
YRaa = Cc * δft + Cd * δrt (73)
LA / V−YRaa = Ca * δft + Cb * δrt (74)

  Thus, when the yaw rate YR is limited, the integrated value YRint of the yaw rate YR from the start or update time t0 of the trajectory control to the time te when the trajectory control ends is the yaw rate YR when the yaw rate YR is not limited. Is smaller than the integral value Rint0. In other words, the direction of the vehicle at the time when the trajectory control ends is different from the direction that should be originally.

  Therefore, it is preferable that the estimated yaw rate YRa is corrected to increase and the integrated value YRint approaches the integrated value Rint0 in at least any region of the section from the time point tc2 to the time point te. The front wheel target rudder angle δft and the rear wheel target rudder angle δrt are preferably calculated according to the above equations 73 and 74 based on the corrected estimated yaw rate YRaa.

  In this case, as shown by the solid line in FIG. 24, the deviation ΔYRa between the estimated yaw rate YRa and the reference value YRref in the section from the time point tc1 to tc2 is added to the estimated yaw rate YRa after the time point tc2 as it is. Good.

  For example, there are i control cycles from time tc1 to time tc2, and i is 1 to n (a positive integer). The deviation ΔYRai of each cycle from the time point tc1 to the time point tc2 is calculated, and the estimated yaw rate YRaa after correction of each cycle is calculated by sequentially adding the deviation ΔYRai to the estimated yaw rate YRai of each cycle from the time point tc2 to the time point tc3. Is done.

  In general, the time from the time point tc3 to the time point te when the control ends is longer than the time period from the time point tc1 to the time point tc2, and it is not necessary to correct the estimated yaw rate in the section from the time point tc3 to the time point te. Therefore, the estimated yaw rate is corrected in the section from time tc1 to time tc3, and trajectory control is performed by controlling the steering angles of both the front wheels and the rear wheels. However, in the sections from time t0 to time tc1 and from time tc3 to time te, the estimated yaw rate is not corrected, and trajectory control is performed by steering angle control of only the front wheels based on the provisional target steering angle δbt.

5-1-2) Both-side partial region correction As shown by the solid line in FIG. 25, the deviation ΔYRa may be divided into a first-half correction amount ΔYRaf and a second-half correction amount ΔYRar. Then, the correction amount ΔYRaf in the first half may be added to the estimated yaw rate YRa of a part of the region before time tc1, and the correction amount ΔYRar of the second half may be added to the estimated yaw rate YRa of a part of the region after time tc2. According to this both-side partial area correction, it is possible to reduce the possibility that the yaw rate will unnaturally change due to the addition correction compared to the case of the one-side partial area correction.

  The correction amounts ΔYRaf and ΔYRar may be a half of the deviation ΔYRa. For example, the deviation ΔYRa is allocated in proportion to the ratio of the time from the time t0 to the time tc1 and the time from the time tc2 to the control time te. It may be a value obtained.

5-1-3) One-side whole area correction As shown by the solid line in FIG. 26, the yaw rate addition correction may be performed in the whole area in the section from the time point tc2 to the time point te. . Based on the corrected estimated yaw rate YRaa, the target steering angles δft and δrt are calculated according to the above equations 73 and 74. According to this one-side all region correction, it is possible to reduce the possibility that the yaw rate changes unnaturally due to the addition correction, as compared with the one-side partial region correction.

  In the one-side all region correction, as shown in FIG. 32, the change time of the deviation ΔYRa is corrected from the time from the time tc1 to the time tc2 to the time from the time tc2 to the time te. A correction amount ΔYRai for each cycle from tc2 to time te is calculated. Then, the corrected estimated yaw rate YRaa of each cycle may be calculated by sequentially adding the correction amount ΔYRai to the estimated yaw rate YRai of each cycle from the time point tc2 to the time point te.

  In the case of one-side full-area correction, addition correction of the estimated yaw rate is performed in all areas in the section from the time point tc2 to the time point te. Therefore, in the section from the time point tc2 to the time point te, the front and rear wheels are corrected. Trajectory control is performed by controlling both steering angles.

5-1-4) Correction of all areas on both sides or as indicated by a solid line in FIG. 27, the correction amount ΔYRaf in the first half is added to the estimated yaw rate YRa of all areas before time tc1, and the correction amount in the second half ΔYRar may be added to the estimated yaw rate YRa of the entire region after time tc2. According to the both-side full area correction, it is possible to reduce the possibility that the yaw rate changes unnaturally due to the addition correction, as compared with the case of the both-side partial area correction.

  In the both-side all region correction, as shown in FIG. 33, the change time is corrected similarly to the one-side all region correction. Further, the correction amounts ΔYRaf and ΔYRar may be a half of the deviation ΔYRa, and for example, the deviation ΔYRa is allocated in proportion to the ratio of the time from the time t0 to the time tc1 and the time from the time tc2 to the control time te. It may be a value obtained.

  24 to 27, the yaw rate YR may be limited to a limit value YRlim that is smaller than the reference value YRref by a predetermined value ΔYRlim. In this case, the restriction is performed in a section from a time point tc1 ′ earlier than the time point tc1 to a time point tc2 ′ later than the time point tc2. The predetermined value ΔYRlim may be a positive constant, but may be variably set according to the vehicle speed V, for example, so as to increase as the vehicle speed V increases.

  In each correction of the estimated yaw rate described above, the integrated value of the increase correction of the estimated yaw rate YRa is the same as the integrated value of the reduction correction due to the limitation of the estimated yaw rate YRa, but the integrated value of the increase correction is the integration of the reduction correction. It may be smaller than the value. However, in order to reduce the degree to which the vehicle orientation at the time when the trajectory control ends is different from the original orientation, the integral value of the increase correction is 90% to 100% of the integral value of the reduction correction. It is preferable that it is 95% or more and 100% or less. The ratio of the increase correction integral value to the reduction correction integral value is preferably higher when the vehicle speed V is high than when the vehicle speed V is low. This also applies to the “restriction due to peak reduction of the turning state amount” described later.

5-2) Limitation due to peak reduction of turning state amount As shown in FIG. 28, when the maximum value YRamax of the estimated yaw rate YRa exceeds the reference value YRref, first, the predetermined value is set to be greater than the reference value YRref. A correction determination value YRdec that is smaller by ΔYRdec is set. Then, time points tp1 and tp2 at which the estimated yaw rate YRa becomes the correction determination value YRdec are determined. The predetermined value ΔYRdec may be a positive constant, but may be variably set according to the vehicle speed V, for example, so as to increase as the vehicle speed V increases.

  The broken lines in FIGS. 34 to 36 indicate the gain Gp used for limiting by peak reduction. The gain Gp increases from 1 and then decreases to 1; a decrease correction interval that decreases from 1 and then increases to 1; and a second increase correction interval that increases from 1 and decreases to 1 And have. The sum of the integral values of “Gp−1” in the first and second increase correction sections is equal to the integral value of “1-Gp” in the decrease correction section.

  Next, a deviation ΔYRamax between the maximum value YRamax and the reference value YRref is calculated, and a positive correction coefficient Kp for the gain Gp is calculated based on the deviation ΔYRamax. In this case, the correction coefficient Kp is calculated to be larger when the deviation ΔYRamax is larger than when the deviation ΔYRamax is small.

  Further, the magnitude is corrected by multiplying the gain Gp by the correction coefficient Kp, and the gain is adapted by correcting the time. In the time correction, the time points tg0 and tge coincide with the time points t0 and te, respectively, and the time point tg1, the decrease correction interval, and the second increase correction interval between the first increase correction interval and the decrease correction interval. The time is adjusted so that the time point tg2 during the period coincides with the time points tp1 and tp2, respectively. FIG. 34 shows an example of adaptation of the gain Gp by correction on both sides of the entire area. FIG. 35 shows an example of adaptation of the gain Gp by front side one-side area correction. Further, FIG. 36 shows an example of adaptation of the gain Gp by correcting the entire area on one side on the rear side.

  Next, the corrected estimated yaw rate YRaa is calculated by multiplying the estimated yaw rate YRa by the adjusted gain Gpa for each cycle. Further, based on the corrected estimated yaw rate YRaa, the front wheel target rudder angle δft and the rear wheel target rudder angle δrt are calculated according to the above equations 73 and 74.

  Examples of the estimated yaw rate YRaa after correction are shown by solid lines in FIGS. 28 to 30 for both-side full-area correction, front-side full-area correction, and rear-side full-area correction, respectively. As can be seen from these figures, according to the restriction due to peak reduction, the corrected estimated yaw rate YRaa does not exceed the reference value YRref, so the vehicle yaw rate YR does not exceed the reference value YRref. Further, the corrected estimated yaw rate YRaa and yaw rate YR can be changed in a manner close to the change of the estimated yaw rate YRa as compared with the case of “restriction by the upper limit value of the turning state amount”.

  In FIG. 28, the time point tg0 coincides with the time point t0 and the time point tge coincides with the time point te, but the time point tg0 is set between the time point t0 and the time point tp1, and the time point tge is the time point tp2 and the time point t It may be set between te (both side partial region correction). In FIG. 29, the time tg0 coincides with the time t0, but the time tg0 may be set between the time t0 and the time tp1 (front side partial area correction). In FIG. 30, the time point tge coincides with the time point te, but the time point tge may be set between the time point tp2 and the time point te (rear side partial area correction).

  It is rare for the estimated yaw rate YRa to exceed the reference value YRref in the region of 2 or more in the process from the start or update of the trajectory control to the end. However, in such a case, restriction by the upper limit value of the turning state amount or restriction by peak reduction may be performed for each region. However, in the case where the two areas of increase / decrease corrections that are adjacent to each other overlap, the boundary point is appropriately set so that these areas do not overlap.

  As described above, the roll angle Rv can be reduced by limiting the yaw rate of the vehicle. Therefore, even when the estimated roll angle Rva exceeds the reference value Rvref, it is possible to prevent the roll angle Rv of the vehicle from becoming excessive due to the restriction by the upper limit value of the yaw rate or the restriction by the peak reduction of the yaw rate. it can.

  In this case, the reference value Rvref may be a positive constant, but the higher the vehicle speed V, the smaller the allowable roll angle of the vehicle. Therefore, as shown in FIG. 37, the reference value Rvref is preferably variably set according to the vehicle speed V so that the reference value Rvref is smaller when the vehicle speed V is high than when the vehicle speed V is low.

6) Steering angle control method As will be understood from the above description, the vehicle is configured to draw an arcuate trajectory Tc 'by controlling the steering angle δ of the front wheels with the steering angle δ' represented by the equation 24 as a target steering angle. Can be run. Further, by controlling the rudder angle δ of the front wheels so that the target rudder angle δbt obtained by the equation 62 or 63 is obtained, the vehicle can be driven along the locus of the exponential function. Further, the yaw rate and roll angle of the vehicle are suppressed by controlling the rudder angles of the front and rear wheels by using the rudder angles δf and δr obtained by the formulas 67 and 69 as the front rudder target rudder angle δft and the rear rudder target rudder angle δrt, respectively. However, the vehicle can be run along the locus of the exponential function.

  In any case of the front wheels and the rear wheels, as a method for controlling the rudder angle to the target rudder angle, both feedforward control and feedback control are possible, each having advantages.

  The feedforward control calculates the target rudder angle when it is determined that the trajectory control should be started (at the start of control), and the wheel rudder angle may be largely changed by the driver's steering operation after the control is started. On the assumption that there is no wheel, the steering angle of the wheel is controlled to the target steering angle.

  In the case of feedforward control, the vehicle trajectory can be made the target trajectory without the driver performing a steering operation, so this control is more proficient in vehicle driving than a driver with a high level of vehicle driving proficiency. This control is suitable for low-level drivers.

  On the other hand, the feedback control calculates the target rudder angle at the start of control, and assumes that the wheel rudder angle may be changed by the steering operation after the control starts. The steering angle of the wheel is controlled to the target steering angle by reducing the deviation.

  In the case of feedback control, the vehicle trajectory can be made the target trajectory even if the driver performs a steering operation, so this control has a vehicle driving proficiency level that is lower than that of a driver who has a low level of vehicle driving proficiency. This control is suitable for high drivers.

  Note that, regardless of the feed forward control or the feedback control that controls the steering angle of the wheel to the target steering angle, the target locus is updated when a preset condition for updating the locus control is satisfied. The trajectory control is updated.

7) Control device for rudder angle of front wheels In order to control the trajectory of the vehicle to the target trajectory, the steering angle of the wheel is corrected by turning the wheel independently of the steering operation of the driver, so that the target rudder angle is obtained. There is a need for a rudder angle control device that can be controlled.

  As a steering angle control device for front wheels, a mechanical steering angle control device in which a steering input means such as a steering wheel and a front wheel as a steering wheel are mechanically connected, and a steering input means and a front wheel are mechanically connected There is a non-mechanical rudder angle control device that is not done.

  The mechanical rudder angle control device drives the front wheels to be steered relative to the steering input means by an actuator. For example, a semi-steer-by-wire type steering device having a steering gear ratio variable device (VGRS) belongs to this. .

  In the non-mechanical steering angle control device, the steering input means and the drive means for driving to steer the front wheels are independent from each other, and both are electrically connected via the control device. For example, steer-by-wire steering The device belongs to this.

  The steering angle control device for the rear wheels is generally a non-mechanical steering angle control device in which the steering input means and the rear wheels are not mechanically connected.

8) Classification of trajectory control and embodiment As will be understood from the above description, whether the turning state amount is limited by the upper limit value and whether the steering angle control is feedforward (FF) control. Trajectory control according to the present invention can be classified according to whether it is feedback (FB) control. The trajectory control according to the present invention can be further classified according to whether or not the rudder angle control device is a mechanical rudder angle control device.

  The first to eighth embodiments described below are classified as shown in Table 1 and Table 2 below according to the classification items. Tables 1 and 2 show a case where the steering angle control device is a mechanical steering angle control device and a case where the steering angle control device is a non-mechanical steering angle control device, respectively.

  In any of the first to eighth embodiments described later, the trajectory control is not started when the traveling control of another vehicle such as the anti-skid control is being executed. Further, when the start condition of the travel control of other vehicles such as the anti-skid control is satisfied in the situation where the trajectory control is being executed, the trajectory control is ended and the travel control of the other vehicle is started.

9) In the case of the mechanical rudder angle control device, the turning radius R when the steering reaction force control vehicle makes a steady circular turn is expressed by the above equation 15. Further, when the curvature of the vehicle trajectory is ρ, the turning radius R is expressed by the following expression 75.
R = 1 / ρ (75)

Therefore, the steering angle δ of the front wheels is expressed by the following formula 76.
δ = WB / R
= Ρ * WB (76)

If the sum of the front wheel caster rail and the pneumatic trail is Lt [m], and the front wheel cornering power is Kf [Nm / rad], the torque Ts around the kingpin axis of the front wheel with a steering angle of δ [rad] is It is represented by the following formula 77.
Ts = -2Lt * Kf * δ (77)

Assuming that the torque at the steering wheel as the steering input means, that is, the steering torque is Th, the torque Ts around the kingpin axis of the front wheel is expressed by the following equation 78 using the steering gear ratio N (see equation 23 above). Is done.
Ts = Th * N (78)

From the above formulas 77 and 78, the following formula 79 is established. Therefore, the steering torque Th is expressed by the following equation 80.
Th * N = -2Lt * Kf * δ (79)
Th = -2Lt * Kf * δ / N (80)

Expression 80 shows the relationship between the steering angle δ of the front wheels and the steering torque Th when the steering torque is not reduced by the power assist. Therefore, Tht expressed by the following equation 81 obtained by substituting equation 23 into equation 80 is the steering torque when the front wheel rudder angle is the original rudder angle δ, that is, the front wheel rudder angle by trajectory control. This is the steering torque when no correction is made.
Tht = -2Lt * Kf * θ / N ² (81)
As described above, when the target trajectory is an exponential function, the steering angle of the front wheels is controlled to the target steering angle δbt of Expression 62 or 63 in a situation where the steering angle should be the original steering angle δ. Therefore, the steering torque Thbt when the steering angle of the front wheels is the target steering angle δbt is expressed by the following equation 82.
Thbt = -2Lt * Kf * δbt / N
= -2Lt * Kf * (δ '+ Δδb) / N (82)

Therefore, the amount of change ΔThbt of the steering torque due to the control of the steering angle of the front wheels accompanying the trajectory control is a deviation between the steering torque Thbt expressed by the formula 82 and the steering torque Th expressed by the formula 81. It is represented by
ΔThbt = Thbt−Th
= −2Lt * Kf * (δ ′ + Δδb) / N + 2Lt * Kf * δ / N
= -2Lt * Kf * {(2WB / V) δ + Δδb} / N + 2Lt * Kf * δ / N
= -2Lt * Kf * {(2WB / V + 1) δ + Δδb} / N (83)

The corrected detected steering torque Thdb obtained by subtracting the steering torque fluctuation amount ΔThbt from the steering torque Thd detected by the torque sensor according to the following equation 84 is the amount of fluctuation in the steering torque due to the control of the steering angle of the front wheels. This is the steering torque eliminated.
Thdb = Thd−ΔThbt
= Thd + 2Lt * Kf * {(2WB / V + 1) δ + Δδb} / N (84)

  Therefore, by calculating the driver's steering burden reduction torque Tpad based on the corrected detected steering torque Thdb, it is possible to eliminate the influence of fluctuations in the steering torque caused by the correction of the steering angle of the front wheels. The sum of the driver's steering burden reduction torque Tpad and the steering torque fluctuation amount ΔThbt is used as the target assist torque Tpat, thereby eliminating the influence of the steering torque fluctuation caused by the correction of the steering angle of the front wheels. The steering burden can be reduced. The steering load reduction torque Tpad may be calculated based on the corrected detected steering torque Thdb and the vehicle speed V so that it increases as the corrected detected steering torque Thdb increases and decreases as the vehicle speed V increases. .

  According to the control of the steering reaction force described above, it is necessary to detect the steering torque Thd, but it is possible to reflect the fluctuation of the steering torque due to factors other than the steering operation. Therefore, in the first and second embodiments described later in which the rudder angle control device is a mechanical rudder angle control device, the target assist torque Tpat is calculated according to the above-described procedure, and the assist torque becomes the target assist torque Tpat. It is controlled as follows.

  When the rudder angle control device is a mechanical rudder angle control device, the driver's steering burden reduction torque Tpad is calculated based on the detected steering torque Thd in a situation where the trajectory control is not performed. The

10) Control of steering reaction force in the case of a non-mechanical steering angle control device When the steering torque Tht represented by the above equation 870 is set as a reference torque, for example, the steering torque detected by the torque sensor is Thd, the following equation 85 The steering torque deviation ΔTh expressed by the formula (1) represents the fluctuation amount of the steering torque caused by the correction of the steering angle of the front wheels.
ΔTh = Thd−Tht (85)

Therefore, the steering torque obtained by removing the steering torque fluctuation ΔTh resulting from the correction of the steering angle of the front wheels from the detected steering torque Thd, that is, the steering torque not including the fluctuation of the steering torque resulting from the correction of the steering angle of the front wheels. Th0 is expressed by Equation 86 below.
Th0 = Thd−ΔTh
= Tht
= -2Lt * Kf * θ / N ² (86)

  The corrected detected steering torque Th0 expressed by the above formula 85 is the steering torque resulting from the correction of the steering angle of the front wheels when the steering angle control device is a mechanical steering angle control device and the steering angle is θ. The steering torque does not include the fluctuation amount of. Therefore, a value obtained by subtracting the steering burden reduction torque Tpad from the corrected detected steering torque Th0 is a preferable steering torque for the driver when the steering angle control device is a mechanical steering angle control device. In this case, the steering load reducing torque Tpad is calculated based on the corrected detected steering torque Th0 and the vehicle speed V so that it increases as the detected steering torque Th0 after correction increases and decreases as the vehicle speed V increases. May be.

Accordingly, when the rudder angle control device is a non-mechanical rudder angle control device, a preferable steering torque Thbt is a value calculated by the following equation 87. If this steering torque Thbt is applied to the steering wheel, it is possible to realize a steering reaction torque that is not affected by the fluctuation of the steering torque due to the correction of the steering angle of the front wheels and that allows the driver to feel an appropriate steering load.
Thbt = Th0−Tpad (87)

  Therefore, in the third and fourth embodiments described later in which the rudder angle control device is a non-mechanical rudder angle control device, the target steering torque Tpbt is calculated according to the above equation 87, and the steering torque becomes the target steering torque Tpbt. It is controlled to become.

  When the rudder angle control device is a non-mechanical rudder angle control device, the steering reaction force control in the situation where the trajectory control is not performed is the control of the steering reaction force in the situation where the trajectory control is performed. Is the same. In other words, the steering torque is controlled to be the target steering torque Tpbt regardless of whether or not the trajectory control is being performed.

  Next, the first to eighth embodiments of the present invention will be sequentially described with reference to the accompanying drawings.

First Embodiment As shown in Table 1 above, this first embodiment has the following features.
Rudder angle control device: Semi-by-wire type Target locus: Exponential function Front wheel rudder angle control: Feed forward Limiting method of turning state amount: Limit by upper limit of yaw rate

  FIG. 1 is a schematic configuration diagram showing a first embodiment of a vehicle travel control device according to the present invention applied to a vehicle equipped with a steering angle varying device, a rear wheel steering device, and an electric power steering device.

  In FIG. 1, the code | symbol 10 has shown the whole traveling control apparatus of 1st embodiment of this invention. The traveling control device 10 is mounted on a vehicle 12 and includes a steering angle varying device 14 and an electronic control device 16 that controls the steering angle varying device 14. In FIG. 1, 18FL and 18FR indicate the left and right front wheels of the vehicle 12, respectively, and 18RL and 18RR indicate the left and right rear wheels, respectively. The left and right front wheels 18FL and 18FR are steered wheels, and a rack and pinion type electric power steering device 22 driven in response to a steering operation of the steering wheel 20 by a driver, and a rack bar 24 and tie rods 26L and 26R. It is steered through.

  The steering wheel 20 functions as a steering input means, and is drivingly connected to the pinion shaft 34 of the power steering device 22 through the upper steering shaft 28, the steering angle varying device 14, the lower steering shaft 30, and the universal joint 32. In the illustrated embodiment, the steering angle varying device 14 is connected to the lower end of the upper steering shaft 28 on the housing 14A side and is connected to the upper end of the lower steering shaft 30 on the rotor 14B side. A motor 36 for driving the rudder is included.

  Thus, the steering angle varying device 14 rotationally drives the lower steering shaft 30 relative to the upper steering shaft 28 to drive auxiliary steering of the left and right front wheels 18FL and 18FR relative to the steering wheel 20. Therefore, the steering angle varying device 14 functions as means for correcting the steering angles of the left and right front wheels without depending on the steering operation of the driver, and is controlled by the steering angle control unit of the electronic control device 16.

  In the illustrated embodiment, the electric power steering device 22 is a rack coaxial type electric power steering device, and converts the electric motor 38 and the rotational torque of the electric motor 38 into a force in the reciprocating direction of the rack bar 24. For example, a ball screw type conversion mechanism 40 is included. The electric power steering device 22 is controlled by an electric power steering device (EPS) control unit of the electronic control device 16. The electric power steering device 22 functions as an auxiliary steering force generation device that reduces the steering burden on the driver by generating an auxiliary steering force that drives the rack bar 24 relative to the housing 42. The auxiliary steering force generator may be of any configuration known in the art.

  In the illustrated embodiment, the upper steering shaft 28 is provided with a steering angle sensor 50 that detects the rotation angle of the upper steering shaft as the steering angle θ and a steering torque sensor 52 that detects the steering torque Thd. Signals indicating the steering angle θ and the steering torque Thd are input to the electronic control unit 16. The electronic control unit 16 detects a relative rotation angle θre of the steering angle varying device 14 detected by the rotation angle sensor 54, that is, a signal indicating a relative rotation angle of the lower steering shaft 30 with respect to the upper steering shaft 28, and is detected by the vehicle speed sensor 56. A signal indicating the vehicle speed V is input.

  Further, in the illustrated embodiment, the left and right rear wheels 18RL and 18RR are connected to the tie rod 64L by the electric steering device 62 of the rear wheel steering device 60 irrespective of the steering of the left and right front wheels 18FL and 18FR by the driver. And 64R can be steered. The rear wheel steering device 60 is controlled by a rear wheel steering control unit of the electronic control device 16 as described in detail later. A signal indicating the steering angle δr of the rear wheel detected by the steering angle sensor 66 is input to the rear wheel steering control unit of the electronic control unit 16.

  Each control unit of the electronic control device 16 may include a microcomputer having a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other via a bidirectional common bus. Further, the steering angle sensor 50, the steering torque sensor 52, the rotation angle sensor 54, and the steering angle sensor 66 are respectively the steering angle θ, the steering torque Thd, and the relative rotation angle θre when the steering or turning in the left turn direction of the vehicle is positive. The steering angle δr of the rear wheel is detected.

  As will be described in detail later, the electronic control device 16 controls the steering angle varying device 14, the rear wheel steering device 60, and the electric power steering device 22 in accordance with the flowcharts shown in FIGS. In particular, the electronic control unit 16 determines the necessity of vehicle trajectory control based on the steering angle θ and the vehicle speed V. When the electronic control unit 16 determines that the trajectory control is unnecessary, the electronic control unit 16 calculates a target steering gear ratio Nt for achieving a predetermined steering characteristic based on the vehicle speed V so as to increase as the vehicle speed V increases.

  Further, the electronic control unit 16 calculates a value obtained by dividing the steering angle θ by the product of the target steering gear ratio Nt and the gear ratio coefficient Ks (positive constant) as the target pinion angle θpt. Further, the electronic control unit 16 calculates the target relative rotation angle θret of the rudder angle varying device 14 as a deviation between the target pinion angle θpt and the steering angle θ, and the relative rotation angle θre of the rudder angle varying device 14 becomes the target relative rotation angle θret. The steering angle varying device 14 is controlled so that

  Further, when the electronic control unit 16 determines that the trajectory control is unnecessary, the electronic control device 16 is set to 0 when the steering angle δr of the rear wheel is not 0, and when the steering angle δr of the rear wheel is 0, The rear wheel steering device 60 is controlled so that the steering angle is maintained.

  Further, when the electronic control unit 16 determines that the trajectory control is necessary, the electronic control unit 16 sets the target steering angle δbt of the front wheels for causing the vehicle to travel along the target trajectory of the exponential function based on the steering angle θ and the vehicle speed V at that time. The calculation is performed according to the above formula 62 or 64.

Further, the electronic control unit 16 calculates the estimated yaw rate YRa based on the target steering angle δbt of the front wheels according to the following equation 88 corresponding to the above equation 12. The electronic control unit 16 determines whether or not the yaw rate YR may become excessive in the steering angle control of only the front wheels by determining whether or not the maximum value YRamax of the estimated yaw rate YRa exceeds the reference value YRref. Determine.
YRa = V / WB * δbt (88)

  When the electronic control unit 16 determines that the yaw rate YR is not likely to be excessive, the front wheel target rudder angle δft is set to the front wheel target rudder angle δbt so that the left and right front wheel rudder angles become the target rudder angle δft. The steering angle varying device 14 is controlled in a feed forward manner. Further, the electronic control unit 16 maintains the rear wheel steering angle δr at zero.

  On the other hand, when the electronic control unit 16 determines that the yaw rate YR is likely to be excessive, the electronic control unit 16 determines whether the estimated yaw rate YRa is to be corrected by any of the above-mentioned “restricted by the upper limit value of the turning state amount”. The corrected estimated yaw rate YRaa is calculated by the method. The electronic control unit 16 calculates the front wheel target rudder angle δft and the rear wheel target rudder angle δrt according to the above equations 73 and 74, and steers based on the front wheel target rudder angle δft and the rear wheel target rudder angle δrt, respectively. The angle variable device 14 and the rear wheel steering device 60 are controlled.

  Even when it is determined that the yaw rate YR is likely to be excessive, the electronic control device 16 sets the front wheel target rudder angle δbt to the front wheel target rudder in a region where the estimated yaw rate YRa does not need to be corrected. Set to the angle δft. Then, the electronic control unit 16 controls the steering angle varying device 14 so that the steering angle of the left and right front wheels becomes the target steering angle δft, and maintains the steering angle δr of the rear wheels at zero.

  Further, the electronic control unit 16 calculates the corrected detected steering torque Thdb according to the above equation 84 during execution of the trajectory control, and calculates the driver's steering burden reducing torque Tpad based on the corrected detected steering torque Thdb. . The electronic control unit 16 calculates the steering torque fluctuation amount ΔThbt according to the above equation 83, and sets the sum of the driver's steering burden reduction torque Tpad and the steering torque fluctuation amount ΔThbt as the target assist torque Tpbt. Further, the electronic control device 16 controls the electric power steering device 22 so that the assist torque becomes the target assist torque Tpbt, thereby reducing the steering burden on the driver and reducing the steering torque fluctuation caused by the correction of the steering angle. Reduce.

  It should be noted that control of the steering gear ratio, control of the steering angle of the rear wheels, and control of the assist torque itself when the trajectory control is unnecessary do not form the gist of the present invention, and these controls are in the art. It may be executed in any known manner. The same applies to other embodiments described later.

  Next, the vehicle travel control in the first embodiment will be described with reference to the flowcharts shown in FIGS. The travel control according to the flowchart shown in FIG. 2 is started by closing an ignition switch not shown in the figure, and is repeatedly executed every predetermined time.

  First, in step 50, whether or not the trajectory control is being executed is determined by determining whether or not the flag Fc indicating whether or not the trajectory control of the vehicle is being executed is 1. When it is determined that the trajectory control is not executed, the control proceeds to step 350, and when it is determined that the trajectory control is executed, the control proceeds to step 200. The flag Fc and a flag Fs described later are reset to 0 prior to the start of the travel control according to the flowchart shown in FIG.

  In step 200, it is determined whether or not the end condition of the trajectory control is established in the travel control of the vehicle. When an affirmative determination is made, control proceeds to step 250, and when a negative determination is made, control proceeds to step 450. In this case, when any of the following (1) to (4) is satisfied, it may be determined that the end condition of the trajectory control is satisfied.

(1) A time Ta = 1 [sec] or more required for the vehicle to reach the target arrival point has elapsed since the time when the start condition or update condition (which will be described later) of the trajectory control is satisfied.
(2) The absolute value of the deviation ΔV between the vehicle speed V and the current vehicle speed V when the start condition or the update condition is satisfied is larger than the reference value Ve (positive value).
(3) The absolute value of the deviation Δθ between the steering angle θ and the current steering angle θ when the start condition or the update condition is satisfied is larger than the reference value θe (positive value).
(4) The absolute value of the steering angular velocity, that is, the absolute value of the rate of change θd of the steering angle θ is larger than the reference value θde (positive value).

  The reference values θe and θde may be constants, but may be variably set according to the vehicle speed V, for example, so as to decrease as the vehicle speed V at the time when the start condition or update condition is satisfied.

  In step 250, the control of changing the steering angle δf of the front wheels to the target steering angle δft by the steering angle varying device 14 and the steering angle δr of the rear wheels to the target steering angle δrt by the rear wheel steering device 60 is ended. Thus, the trajectory control is terminated. Further, the flag Fc indicating whether or not the trajectory control is being executed is reset to 0, and then the control proceeds to Step 700.

  In step 350, it is determined whether or not the start condition of the trajectory control is satisfied according to the flowchart shown in FIG. When an affirmative determination is made, control proceeds to step 500, and when a negative determination is made, control proceeds to step 700.

  In step 450, it is determined whether or not the update condition of the trajectory control is satisfied according to the flowchart shown in FIG. When an affirmative determination is made, control proceeds to step 500, and when a negative determination is made, control proceeds to step 600.

  In step 500, the target steering angle δbt of the front wheels is calculated according to the flowchart shown in FIG. 5, and the estimated yaw rate YRa of the vehicle is calculated based on the target steering angle δbt. Further, it is determined whether or not there is a possibility that the yaw rate becomes excessive based on the estimated yaw rate YRa, and the target rudder angle δft of the front wheels and the target rudder angle δrt of the rear wheels are calculated according to the determination result.

  In step 600, the steering angle varying device 14 is controlled in a feedforward manner so that the steering angle δf of the front wheels becomes the target steering angle δft, and the rear wheels so that the steering angle δr of the rear wheels becomes the target steering angle δrt. The steering device 60 is controlled in a feed forward manner.

  In this case, the steering angles of the front wheels and the rear wheels are changed to the target steering angles at a change rate equal to or less than a preset limit value so that the steering angles of the front wheels and the rear wheels do not change suddenly. The same applies to other embodiments described later.

  In step 700, the steering gear ratio is controlled when the trajectory control is not executed. That is, based on the vehicle speed V, the target steering gear ratio Nt is calculated from the map corresponding to the graph shown in FIG. In FIG. 6, N0 represents a standard steering gear ratio, that is, a steering gear ratio when the relative rotation angle of the lower steering shaft 30 with respect to the upper steering shaft 28 is zero.

  A value obtained by dividing the product of the steering angle θ and the gear ratio coefficient Ks (a positive constant corresponding to the ratio of the rotation angle of the pinion 34 to the change amount of the steering angle of the left and right front wheels) by the target steering gear ratio Nt is Calculated as the angle θpt. Further, the target relative rotation angle θret of the rudder angle varying device 14 is calculated as the deviation between the target pinion angle θpt and the steering angle θ, and the rudder angle variable so that the relative rotation angle θre of the rudder angle varying device 14 becomes the target relative rotation angle θret. The device 14 is controlled.

  When the trajectory control is completed and the process proceeds to the control of the steering gear ratio in step 700, the steering gear ratio is not suddenly changed to the target steering gear ratio Nt in order to prevent a sudden change in the steering angle of the front wheels. The variable angle device 14 is controlled. The same applies to other embodiments described later.

  In step 750, the rear wheel steering device is set so that the steering angle δr of the rear wheel is zero when it is not zero, and is maintained when the steering angle δr of the rear wheel is zero. 60 is controlled.

  In step 800, assist torque is controlled when trajectory control is not executed. That is, the basic assist torque Tpab is calculated from the map corresponding to the graph shown in FIG. 7 based on the detected steering torque Thd, and the vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG. Is done. The target assist torque Tpat is calculated as the product of the vehicle speed coefficient Kv and the basic assist torque Tpab, and the electric power steering device 22 is controlled so that the assist torque becomes the target assist torque Tpat.

  The basic assist torque Tpab may be calculated from a map corresponding to the graph shown in FIG. 9 based on the steering torque Thd and the vehicle speed V.

  In step 900, the corrected detected steering torque Thdb is calculated according to the above equation 84, and the basic assist torque Tpab is calculated from the map corresponding to the graph shown in FIG. 7 based on the corrected detected steering torque Thdb. . Further, the vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG. 8 based on the vehicle speed V, and the product of the vehicle speed coefficient Kv and the basic assist torque Tpab is calculated as the steering burden reduction torque Tpad. Then, the steering torque fluctuation amount ΔThbt is calculated according to the above equation 83, and the target assist torque Tpat is calculated as the sum of the driver's steering burden reduction torque Tpad and the steering torque fluctuation amount ΔThat. Further, the electric power steering device 22 is controlled so that the assist torque becomes the target assist torque Tpat.

  Next, with reference to the flowchart shown in FIG. 3, a routine for determining the establishment of the start condition of the trajectory control executed in step 350 will be described in detail.

  First, in step 355, the steering angle θlf after low-pass filter processing is calculated by subjecting the steering angle θ to low-pass filter processing. Then, it is determined whether or not the absolute value of the steering angle θlf after the low-pass filter processing is larger than a reference value θs0 (positive value) for control start determination. When a negative determination is made, control proceeds to step 390, and when an affirmative determination is made, control proceeds to step 360.

  In step 360, the steering angular velocity θd is calculated as a differential value of the steering angle θ, and the steering angular velocity θdlf after low-pass filter processing is calculated by subjecting the steering angular velocity θd to low-pass filter processing.

  In step 365, it is determined whether or not the absolute value of the steering angular velocity θdlf after the low-pass filter process is greater than the first reference value θds1 (positive value) for control start determination. When a negative determination is made, the control proceeds to step 375. When an affirmative determination is made, the flag Fs is set to 1 in step 370 to indicate that the start condition is being determined, and then the control is step 375. Proceed to

  In step 375, it is determined whether or not the flag Fs is 1, that is, whether or not the start condition is being determined. When a negative determination is made, the control proceeds to step 390, and when an affirmative determination is made, the control proceeds to step 380.

  In step 380, it is determined whether or not the absolute value of the steering angular velocity θdlf after the low-pass filter processing is smaller than the second reference value θds2 (positive value less than θds1) for control start determination. When a negative determination is made, control proceeds to step 390, and when an affirmative determination is made, control proceeds to step 385.

  In step 385, the flag Fs is reset to 0 to indicate that the start condition has not been determined, and the flag Fc is set to 1 to indicate that the trajectory control is being executed. Control continues to step 500.

  In step 390, the flag Fs is reset to 0 to indicate that the start condition has not been determined, and the flag Fc is reset to 0 to indicate that the trajectory control is not being performed. Control continues to step 700.

  The reference values θs0, θds1, and θds2 may be constants, but these reference values may also be variably set according to the vehicle speed V, for example, so as to decrease as the vehicle speed V increases.

  Steps 455 to 490 of the locus control update condition establishment determination routine shown in FIG. 4 are basically executed in the same manner as steps 355 to 390 of the locus control start condition establishment determination routine.

  However, the reference value for determination in step 455 is the control update determination reference value θr0 (positive value). The reference value for determination in step 465 is the first reference value θdr1 (positive value) for control update determination, and the reference value for determination in step 480 is the second reference value θdr2 (θdr1 for control update determination). The following positive value). The reference values θr0, θdr1, and θdr2 may be constants, but these reference values may be variably set according to the vehicle speed V, for example, so that the reference values θr0, θdr1, and θdr2 become smaller as the vehicle speed V increases.

  In Steps 470, 475, 485, and 490, the flag Fs is replaced with a flag Fr indicating whether or not an update determination is performed. Further, when step 485 is completed, control proceeds to step 600, and when step 490 is completed, control proceeds to step 500.

  Next, the front and rear wheel target rudder angle calculation routine executed in step 500 will be described in detail with reference to the flowchart shown in FIG.

First in step 505 the front wheel steering angle δf based on the steering angle θ and relative rotation angle θre is determined, the distance x ₀ is calculated according to the equation 46 based on the front wheel steering angle δf and the vehicle speed V. In step 505, the correction coefficient D is calculated in accordance with the above equation 42, with the minimum time ΔT and the Webber ratio k set to positive constants set in advance for general drivers.

  In step 510, the lateral acceleration LAa of the vehicle is calculated according to the above equation 47 based on the steering angle θ and the vehicle speed V when the trajectory control is started or updated.

  In step 515, a component Vx parallel to the coordinate axis related to the distance x is calculated as one of the components of the vehicle speed V based on the steering angle δf and the vehicle speed V of the front wheels when the trajectory control is started or updated according to the above equation 49. Is done.

  In step 520, a component Vy parallel to the coordinate axis with respect to time is calculated as one of the components of the vehicle speed V according to the above equation 50, and an angle σ formed by the component Vx with respect to the vehicle speed V is calculated according to the above equation 52. .

  In step 525, the lateral components Vxx and Vyx of the vehicle are calculated according to the equations 53 and 54, respectively, and the lateral acceleration LAb of the vehicle is calculated according to the equations 55 and 56.

  In step 530, a deviation ΔLA between the lateral acceleration LAb of the vehicle when the vehicle travels along an exponential trajectory Te and the lateral acceleration LAa of the vehicle when the vehicle travels along an arcuate trajectory Tc is obtained. The calculation is performed according to the above equation 57.

  In step 535, based on the steering angle θ, the vehicle speed V, and the lateral acceleration deviation ΔLA when the trajectory control is started or updated, according to the above equation 62 when turning left and according to the above equation 63 when turning right, The target rudder angle δbt of is calculated.

  In step 540, the estimated yaw rate YRa of the vehicle is calculated according to the above equation 88 based on the target steering angle δbt of the front wheels.

  In step 545, the reference value YRref is calculated from the map corresponding to the graph shown in FIG. 31 based on the vehicle speed V so that the reference value YRref becomes smaller as the vehicle speed V increases.

  In step 550, it is determined whether or not the maximum value YRamax of the magnitude of the estimated yaw rate YRa exceeds the reference value YRref, that is, whether or not the yaw rate YR may become excessive in the steering angle control of only the front wheels. A determination is made. When an affirmative determination is made, control proceeds to step 560. When a negative determination is made, at step 555, the target rudder angle δft of the front wheels is set to the target rudder angle δbt, and the target rudder angle δrt of the rear wheels is set. Is set to 0.

  In step 560, a deviation ΔYRa (deviation ΔYRai of each cycle) between the magnitude of the estimated yaw rate YRa and the reference value YRref is calculated for the temporal region where the estimated yaw rate YRa is to be reduced and corrected.

  In step 565, sign (YRa) is used as the sign of the estimated yaw rate YRa, and the corrected estimated yaw rate YRaa is set to sign (YRa) * YRref for the temporal region where the estimated yaw rate YRa is to be reduced and corrected. In addition, in the temporal region where the estimated yaw rate YRa should be corrected to be increased, the corrected estimated yaw rate YRaa is calculated by adding a correction amount based on sign (YRa) * ΔYRa to the estimated yaw rate YRa for each cycle. The increase correction of the estimated yaw rate YRa may be performed by any of the above-mentioned “limitation by the upper limit value of the turning state amount”.

  In step 585, the target rudder angle δft and the rear wheels of the front wheels are calculated in accordance with the above formulas 73 and 74 based on the corrected estimated yaw rate YRaa for the time domain where the estimated yaw rate YRa is to be corrected (decrease correction and increase correction). The target rudder angle δrt is calculated.

  In step 590, for the time domain in which the estimated yaw rate YRa is not corrected, the front wheel target rudder angle δft is set to the front wheel target rudder angle δbt and the rear wheel target rudder angle is the same as in step 555 above. δrt is set to 0.

  In the first embodiment, if the start condition of the trajectory control is satisfied in a situation where the trajectory control is not executed, a negative determination is made in step 50 and an affirmative determination is made in step 350. Is called. In step 500, the target rudder angle δbt of the front wheels and the estimated yaw rate YRa based on the target rudder angle δbt for causing the vehicle to travel along the target locus of the exponential function are calculated. The target rudder angle δrt is calculated. In step 600, the steering angle of the front wheels is controlled to the target steering angle δft by feedforward control, and the steering angle of the rear wheels is controlled to the target steering angle δrt by feedforward control.

  Further, if the update condition of the trajectory control is satisfied in the situation where the trajectory control is being executed, an affirmative determination is made in steps 50 and 450. Steps 500 and 600 are then executed.

  Therefore, according to the first embodiment, in the situation where the trajectory control is to be executed, the steering angle of the front wheels and the rear wheels is controlled to the target steering angle, thereby eliminating the need for the driver's steering operation. It is possible to control the traveling locus of the vehicle so that the vehicle travels along the target locus of the exponential function. The same applies to other embodiments described later.

  In particular, according to the first embodiment, when there is a possibility that the yaw rate YR of the vehicle becomes excessive in the steering angle control of only the front wheels, an affirmative determination is made in step 550. In steps 560 to 590, the target rudder angle δft for the front wheels and the target rudder angle δrt for the rear wheels are calculated for causing the vehicle to travel along the target locus of the exponential function while preventing the yaw rate YR from becoming excessive.

  Note that if there is no possibility that the yaw rate YR of the vehicle will become excessive even with the steering angle control of only the front wheels, a negative determination is made at step 550. In step 555, the target rudder angle δft for the front wheels is set to the target rudder angle δbt, and the target rudder angle δrt for the rear wheels is set to zero. Therefore, since it is not necessary to control the steering angle of the rear wheels to a target steering angle other than 0, the vehicle travel control is compared to the case where the steering angles of both the front wheels and the rear wheels are always controlled to the target steering angle. Can be simplified. The same applies to other embodiments described later.

  Further, according to the first embodiment, the control of the steering angles of the front wheels and the rear wheels is feedforward control performed based on the steering angles of the front wheels and the rear wheels when the trajectory control is started or updated. Therefore, as in the case of the second embodiment described later, the trajectory control with the trajectory of the exponential function as the target trajectory is simply executed as compared with the case where the control of the steering angle of the front wheels and the rear wheels is feedback control. Can do. This effect can also be obtained in the third, fifth, and seventh embodiments described later.

Second Embodiment As shown in Table 1, the second embodiment has the following features.
Rudder angle control device: Semi-by-wire type Target locus: Exponential function Front wheel rudder angle control: Feedback Limiting method of turning state quantity: Limit by upper limit of yaw rate

  The vehicle travel control in the second embodiment is basically executed in the same manner as in the first embodiment described above. However, in the steering angle control in step 600, the front and rear wheels are controlled. The steering angle is feedback controlled.

  That is, for each cycle, the current steering angle δf of the front wheels is obtained based on the steering angle θ and the relative rotation angle θre, and the target relative rotation angle θret is calculated as a deviation between the target steering angle δft of the front wheels and the current steering angle δf. The The steering angle variable device 14 is controlled to rotate the lower steering shaft 30 relative to the upper steering shaft 28 so as to rotate the target relative rotation angle θret, whereby the steering angle of the front wheels is controlled to the target steering angle δft. Further, a deviation between the target steering angle δrt of the rear wheel and the current steering angle δr is calculated, and the rear wheel steering device 60 is controlled so that the deviation becomes zero, so that the steering angle of the rear wheel becomes the target steering angle δrt. Controlled.

  Therefore, according to the second embodiment, when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels, the estimated yaw rate YRa after correction is limited by limiting the estimated yaw rate YRa by the upper limit. Is calculated. The steering angles of the front wheels and the rear wheels are feedback controlled based on the corrected estimated yaw rate YRaa.

  In particular, according to the second embodiment, the target relative rotation angle θret is calculated as a deviation between the target steering angle δft and the current steering angle δf of the front wheels. Therefore, even if the driver performs a steering operation after the start or update of the trajectory control, the steering angle of the front wheels can be reliably controlled to the target steering angle δft. In addition, when the driver performs a steering operation so that the steering angle is suitable for running the vehicle along the target locus of the exponential function, the feedback control amount becomes small. Therefore, when the driver is skilled in driving operation, the control amount of the steering angle varying device 14 can be reduced and the load can be reduced as compared with the case of the first embodiment described above. This effect can also be obtained in the fourth embodiment described later.

Third Embodiment This second embodiment has the following features as shown in Table 1 above.
Steering angle control device: Semi-by-wire type Target locus: Exponential function Front wheel rudder angle control: Feed forward Limiting method of turning state: Limiting by reducing yaw rate peak

  The vehicle travel control in the third embodiment is executed in the same manner as in the first embodiment except for the calculation of the target rudder angle in step 500. Then, the calculation of the target rudder angle in step 500 is executed according to the flowchart shown in FIG. In FIG. 10, steps corresponding to the steps shown in FIG. 5 are assigned the same step numbers as those shown in FIG.

  As shown in FIG. 10, steps 505 to 555 and steps 585 and 590 are executed in the same manner as in the first embodiment described above. If an affirmative determination is made in step 550, control proceeds to step 570.

  In step 570, the predetermined value ΔYRdec is set according to the vehicle speed V so as to increase as the vehicle speed V increases, and the correction determination value YRdec is set to a value smaller than the reference value YRref by the predetermined value ΔYRdec.

  In step 575, a deviation ΔYRamax between the maximum value YRamax of the estimated yaw rate YRa and the reference value YRref is calculated, and a positive correction coefficient Kp for the gain Gp is calculated based on the deviation ΔYRamax. Further, the magnitude is corrected by multiplying the gain Gp by the correction coefficient Kp, and the gain is adapted by correcting the time. In this case, the correction of the time may be any of the both-sides all region correction, the front side one-side region correction, and the rear side one-side all region correction.

  In step 580, the corrected estimated yaw rate YRaa is calculated by multiplying the estimated yaw rate YRa by the adjusted gain Gpa for each cycle in the region where the estimated yaw rate YRa needs to be corrected.

  Therefore, according to the third embodiment, when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels, the estimated yaw rate YRa after correction is limited by limiting the estimated yaw rate YRa by the restriction due to peak reduction. Is calculated. The steering angles of the front and rear wheels are feedforward controlled based on the corrected estimated yaw rate YRaa.

Fourth Embodiment The fourth embodiment has the following features as shown in Table 1 above.
Steering angle control device: Semi-by-wire type Target locus: Exponential function Front wheel rudder angle control: Feedback Limiting method of turning state amount: Limiting by reducing yaw rate peak

  The vehicle travel control in the fourth embodiment is basically executed in the same manner as in the third embodiment described above. However, in the steering angle control in step 600, the front and rear wheels are controlled. The steering angle is feedback controlled as in the second embodiment.

  Therefore, according to the fourth embodiment, when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels, the estimated yaw rate YRa is corrected by limiting the estimated yaw rate YRa by the restriction due to the peak reduction. Is calculated. The steering angles of the front wheels and the rear wheels are feedback controlled based on the corrected estimated yaw rate YRaa.

  According to the first to fourth embodiments described above, in step 900, the corrected detected steering torque Thdb, that is, the steering torque from which the fluctuation of the steering torque due to the steering angle control of the front wheels is eliminated is calculated. Based on the torque Thdb and the vehicle speed V, the steering burden reduction torque Tpad is calculated. Then, the steering torque fluctuation amount ΔThbt resulting from the control of the steering angle of the front wheels is calculated according to the above equation 83, and the target assist torque Tpat is calculated as the sum of the driver's steering burden reduction torque Tpad and the steering torque fluctuation amount ΔThat. The Further, the electric power steering device 22 is controlled so that the assist torque becomes the target assist torque Tpat.

  Therefore, not only the driver's steering burden can be reduced, but also the fluctuation of the steering torque caused by the control of the steering angle of the front wheels associated with the trajectory control is offset, and the driver feels uncomfortable with the steering torque due to the trajectory control. It is possible to effectively prevent learning.

Fifth Embodiment As shown in Table 2, the fifth embodiment has the following features.
Rudder angle control device: By-wire type Target locus: Exponential function Rudder angle control: Feed forward Limiting method of turning state: Limit by upper limit of yaw rate

  FIG. 11 is a schematic configuration diagram showing a fifth embodiment of a vehicle travel control device according to the present invention applied to a vehicle equipped with a by-wire type steering device and a rear wheel steering device.

  In FIG. 11, the code | symbol 80 has shown the driving | running control apparatus of 5th Embodiment generally. When the steering wheel 20 as the steering input means is steered by the driver, the rack and pinion type steering mechanism 82 drives the rack bar 84 and the tie rods 26L and 26R, thereby causing the left and right front wheels 18FL and 18FR to move. Steered.

  The steering shaft 86 connected to the steering wheel 20 and the pinion shaft 88 of the steering mechanism 82 are not connected to each other. An electric motor 90 for applying a steering reaction force torque is connected to the steering shaft 86 via a reduction gear mechanism not shown in FIG. The electric motor 90 is controlled by the steering reaction force control unit of the electronic control unit 92, whereby a required steering reaction force torque is applied to the steering wheel 20. The pinion shaft 88 is connected with an electric motor 94 for turning driving via a reduction gear mechanism not shown in FIG. The electric motor 94 is controlled by the rudder angle control unit of the electronic control unit 92, and thereby the pinion shaft 88 is rotationally driven.

  In the illustrated embodiment, the rotation of the pinion shaft 88 is converted into a linear motion of the rack bar 84 by a rack-and-pinion type steering mechanism 82 as a rotation-linear motion conversion mechanism. However, the steering mechanism may be of any configuration known in the art.

  Thus, the steering wheel 20, the steering mechanism 82, the electric motors 90, 94, etc. steer the left and right front wheels 18FL and 18FR in accordance with the driver's steering operation, and without depending on the driver's steering operation as necessary. A by-wire type steering device 96 for correcting the steering angle of the left and right front wheels is configured.

  The steering shaft 86 is provided with a steering angle sensor 50 that detects the steering angle θ, and a signal indicating the steering angle θ detected by the steering angle sensor 50 is input to the electronic control unit 92. The electronic control unit 92 includes a signal indicating the vehicle speed V detected by the vehicle speed sensor 56, a signal indicating the steering angle δr of the rear wheel detected by the steering angle sensor 66, and the pinion shaft 88 detected by the rotation angle sensor 98. A signal indicating the rotation angle θp is also input.

  Each control unit of the electronic control device 92 may include a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other via a bidirectional common bus. Further, the steering angle sensor 50, the steering angle sensor 66, and the rotation angle sensor 98 detect the steering angle θ, the rear wheel steering angle δr, and the rotation angle θp, respectively, when the vehicle is steered leftward.

  As will be described in detail later, the electronic control device 92 controls the motors 90 and 94 of the steering device 96 according to the flowchart shown in FIG. In particular, the electronic control unit 92 also determines the necessity of vehicle trajectory control based on the steering angle θ and the vehicle speed V. When the electronic control unit 92 determines that the trajectory control is unnecessary, the electronic control unit 92 calculates a target steering gear ratio Nt for achieving a predetermined steering characteristic based on the vehicle speed V so as to increase as the vehicle speed V increases. Further, the electronic control device 92 controls the electric motor 94 of the steering device 96 so that the steering gear ratio becomes the target steering gear ratio Nt.

  When the electronic control unit 92 determines that the trajectory control is necessary, the electronic control device 92 sets the target steering angle δbt of the front wheels for causing the vehicle to travel along the target trajectory of the exponential function based on the steering angle θ and the vehicle speed V at that time. The calculation is performed according to the above formula 62 or 64.

  Further, the electronic control unit 16 calculates the estimated yaw rate YRa based on the target steering angle δbt of the front wheels according to the above equation 88. The electronic control unit 16 determines whether or not the yaw rate YR may become excessive in the steering angle control of only the front wheels by determining whether or not the maximum value YRamax of the estimated yaw rate YRa exceeds the reference value YRref. Determine.

  When the electronic control unit 16 determines that the yaw rate YR is not likely to be excessive, the front wheel target rudder angle δft is set to the front wheel target rudder angle δbt so that the left and right front wheel rudder angles become the target rudder angle δft. The steering device 96 is controlled in a feed forward manner. Further, the electronic control unit 16 maintains the rear wheel steering angle δr at zero.

  On the other hand, when the electronic control unit 16 determines that the yaw rate YR is likely to be excessive, the electronic control unit 16 determines whether the estimated yaw rate YRa is to be corrected by any of the above-mentioned “restricted by the upper limit value of the turning state amount”. The corrected estimated yaw rate YRaa is calculated by the method. Then, the electronic control unit 16 calculates the target rudder angle δft for the front wheels and the target rudder angle δrt for the rear wheels according to the above formulas 73 and 74, and steers based on the target rudder angle δft for the front wheels and the target rudder angle δrt for the rear wheels, respectively. The device 96 and the rear wheel steering device 60 are controlled.

  Even when it is determined that the yaw rate YR is likely to be excessive, the electronic control device 16 sets the front wheel target rudder angle δbt to the front wheel target rudder in a region where the estimated yaw rate YRa does not need to be corrected. Set to the angle δft. The electronic control device 16 controls the steering device 96 so that the steering angle of the left and right front wheels becomes the target steering angle δft, and maintains the steering angle δr of the rear wheels at zero.

  Further, the electronic control unit 92 calculates the corrected detected steering torque Th0 according to the above equation 86 regardless of whether or not the trajectory control is being executed, and steers based on the corrected detected steering torque Th0 and the vehicle speed V. The burden reducing torque Tpad is calculated. Then, the electronic control unit 92 calculates the target steering torque Thbt according to the above equation 87, and controls the electric motor 90 of the steering device 96 so that the steering torque becomes the target steering torque Thbt.

  The vehicle travel control in the fifth embodiment is executed in accordance with the flowchart shown in FIG. The travel control according to the flowchart shown in FIG. 12 is started by closing an ignition switch not shown in the figure, and is repeatedly executed every predetermined time. In FIG. 12, the steps corresponding to the steps shown in FIG. 2 are assigned the same step numbers as those shown in FIG.

  As understood from the comparison between FIG. 12 and FIG. 2, in the fifth embodiment, the step corresponding to step 800 in the first embodiment is not executed, and when step 600 or 750 is completed, the control is completed. Advances to step 950.

In step 505 executed in step 500 of the fifth embodiment, the steering angle δf of the front wheel is obtained based on the rotation angle θp of the pinion shaft 88, and the steering angle δf of the front wheel and the vehicle speed V distance x ₀ is calculated according to the equation 46 based on.

  Therefore, according to the fifth embodiment, when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels, the estimated yaw rate YRa after correction is limited by limiting the estimated yaw rate YRa by the upper limit. Is calculated. The steering angles of the front and rear wheels are feedforward controlled based on the corrected estimated yaw rate YRaa.

  In step 950 corresponding to step 900 in the first to fourth embodiments described above, steering torque that the driver feels as a steering reaction force is controlled. First, the corrected detected steering torque Th0 is calculated according to the above equation 86 based on the steering angle θ. Further, based on the corrected detected steering torque Th0, the basic steering burden reduction torque Tpadb is calculated from the map corresponding to the graph shown in FIG. 13, and based on the vehicle speed V, the map corresponding to the graph shown in FIG. A vehicle speed coefficient Kv is calculated. The steering burden reduction torque Tpad is calculated as the product of the basic steering burden reduction torque Tpadb and the vehicle speed coefficient Kv. The steering burden reduction torque Tpad may be calculated from a map corresponding to the graph shown in FIG.

  Further, the target steering torque Thbt is calculated according to the above equation 87 based on the corrected detected steering torque Th0 and the steering burden reduction torque Tpad, and the electric motor 90 of the steering device 96 is controlled so that the steering torque becomes the target steering torque Thbt.

  The control of the steering torque by the control of the electric motor 90 is similarly performed in the sixth to eighth embodiments described later. That is, when the rudder angle control device is of a by-wire type, the control of the steering torque is the same regardless of whether the limit of the estimated yaw rate YRa is a limit by an upper limit value or a limit by peak reduction. It is performed as follows.

Sixth Embodiment As shown in Table 2 above, this sixth embodiment has the following features.
Rudder angle control device: By-wire type Target locus: Exponential function Rudder angle control: Feedback Limiting method of turning state amount: Limit by upper limit of yaw rate

  The vehicle running control in the sixth embodiment is basically executed in the same manner as in the fifth embodiment described above, but in the steering angle control in step 600, the front and rear wheels are controlled. The steering angle is feedback controlled.

  That is, for each cycle, the current steering angle δf of the front wheels is obtained based on the rotation angle θp of the pinion shaft 88, and a deviation Δδft between the target steering angle δft of the front wheels and the current steering angle δf is calculated. Then, the electric motor 94 of the steering device 96 is controlled so that the magnitude of the steering angle deviation Δδft becomes small. Therefore, the steering angle of the front wheels is controlled to the target steering angle δft by feedback control.

  Therefore, according to the sixth embodiment, when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels, the estimated yaw rate YRa is limited by the upper limit as in the case of the second embodiment. Thus, the corrected estimated yaw rate YRaa is calculated. The steering angles of the front wheels and the rear wheels are feedback controlled based on the corrected estimated yaw rate YRaa.

Seventh Embodiment As shown in Table 2, the seventh embodiment has the following features.
Rudder angle control device: By-wire type Target locus: Exponential function Rudder angle control: Feed forward Limiting the amount of turning state: Limiting by reducing the yaw rate peak

  As shown in FIG. 17, the vehicle travel control in the seventh embodiment is executed in the same manner as in the fifth embodiment except for the calculation of the target rudder angle in step 500. . Then, the calculation of the target rudder angle in step 500 is executed according to the flowchart shown in FIG. 10 as in the third embodiment.

  Therefore, according to the seventh embodiment, when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels, the estimated yaw rate YRa is limited by the restriction due to the peak reduction as in the third embodiment. Thus, the corrected estimated yaw rate YRaa is calculated. The steering angles of the front and rear wheels are feedforward controlled based on the corrected estimated yaw rate YRaa.

Eighth Embodiment The eighth embodiment has the following features as shown in Table 2 above.
Rudder angle control device: By-wire type Target locus: Exponential function Rudder angle control: Feedback Method of limiting the amount of turning state: Limit by peak reduction of yaw rate

  The vehicle travel control in the eighth embodiment is basically executed in the same manner as in the seventh embodiment described above, but the trajectory control in step 600 is the same as that in the sixth embodiment. Similarly, the steering angles of the front and rear wheels are feedback controlled.

  Therefore, according to the seventh embodiment, when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels, the estimated yaw rate YRa is limited by the restriction due to the peak reduction as in the third embodiment. Thus, the corrected estimated yaw rate YRaa is calculated. The steering angles of the front wheels and the rear wheels are feedback controlled based on the corrected estimated yaw rate YRaa.

  According to the fifth to eighth embodiments described above, the steering angle control device is a semi-bias wire type steering angle control device, and a value corresponding to the steering torque when the steering angle of the front wheels is not controlled by the steering angle control device. Then, the corrected detected steering torque Th0 is calculated. Based on the corrected detected steering torque Th0 and the vehicle speed V, the steering burden reducing torque Tpad is calculated. Further, the target steering torque Tpbt is calculated as a value obtained by subtracting the steering burden reduction torque Tpad from the corrected detected steering torque Th0, and the electric motor 90 of the steering device 96 is controlled so that the steering torque becomes the target steering torque Tpbt.

  Therefore, not only can the driver be given a moderate steering burden, but also fluctuations in the steering torque due to the control of the steering angle of the front wheels associated with the trajectory control can be prevented, and the driver feels uncomfortable with the steering torque due to the trajectory control. Can be effectively prevented.

  From the above description, according to each of the above-described embodiments, the vehicle can be driven along a trajectory desired by the driver without requiring acquisition of out-of-vehicle information for obtaining the target trajectory and actual trajectory of the vehicle. Will be understood.

  Further, according to each of the above-described embodiments, since the target locus is an exponential locus, the vehicle locus is controlled to be more favorable for the vehicle occupant than when the target locus is an arcuate locus. be able to. In particular, according to these embodiments, the target locus of the exponential function is set so that the distance x changes according to the above equation 40. Therefore, a trajectory preferable for human perception characteristics can be achieved as compared with a case where the target trajectory is an arc-shaped trajectory.

  Further, according to the first, second, fifth, and sixth embodiments, the estimated yaw rate YRa is limited by the upper limit when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels. Thus, the corrected estimated yaw rate YRaa is calculated. Based on the corrected estimated yaw rate YRaa, the target steering angles of the front wheels and the rear wheels are calculated, and the steering angles of the front wheels and the rear wheels are controlled based on the target steering angles.

  Therefore, the estimated yaw rate YRa is reduced and corrected only in a temporal region exceeding the reference value YRref. Therefore, the amount of increase correction of the estimated yaw rate YRa in other time regions can be reduced or the time region in which the estimated yaw rate YRa is corrected to be increased can be reduced as compared with the case of restriction due to peak reduction.

  Further, according to the third, fourth, seventh, and eighth embodiments, when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels, the estimated yaw rate YRa is limited by the restriction due to the peak reduction. Thus, the corrected estimated yaw rate YRaa is calculated. Based on the corrected estimated yaw rate YRaa, the target steering angles of the front wheels and the rear wheels are calculated, and the steering angles of the front wheels and the rear wheels are controlled based on the target steering angles.

  Therefore, the change in the estimated yaw rate YRaa after the correction can be made closer to the change in the estimated yaw rate YRa before the correction as compared with the case of the restriction due to the peak reduction. Therefore, it is possible to reduce the possibility that the yaw rate of the vehicle changes unnaturally due to the restriction of the estimated yaw rate YRa and that the vehicle occupant feels uncomfortable due to this.

  Each of the above-described embodiments is intended to prevent the yaw rate of the vehicle from becoming excessive due to the limitation of the estimated yaw rate YRa when there is a possibility that the yaw rate YR becomes excessive in the steering angle control of only the front wheels. However, in these embodiments, when there is a possibility that the roll angle Rv of the vehicle becomes excessive in the steering angle control of only the front wheels, the roll angle Rv of the vehicle is prevented from becoming excessive due to the restriction of the estimated yaw rate YRa. May be transformed into

First Modification FIG. 15 shows a target rudder for front and rear wheels in a first modification in which the first embodiment described above is modified to an embodiment in which the roll angle Rv of the vehicle is prevented from becoming excessive. It is a flowchart which shows an angle calculation routine. In FIG. 15, steps corresponding to the steps shown in FIG. 5 are given the same step numbers as those shown in FIG.

  As understood from comparison between FIG. 15 and FIG. 5, steps 505 to 540 and steps 565 to 590 are executed in the same manner as in the first embodiment. Steps 540a and 545a are executed after steps 540 and 545, respectively, and steps 550a and 560a are executed instead of steps 550 and 560, respectively.

In step 540a, the estimated roll angle Rva of the vehicle is calculated according to the following equation xx corresponding to the equation 70 based on the estimated yaw rate YRa and the vehicle speed V.
Rva = M * H * V * YRa / (Kr-Mg * H) (xx)

  In step 545a, the reference value Rvref is calculated from the map corresponding to the graph shown in FIG. 37 based on the vehicle speed V so that the reference value Rvref of the vehicle roll angle becomes smaller as the vehicle speed V increases. The

  In step 550a, it is determined whether or not the maximum value Rvamax of the estimated roll angle Rva of the vehicle exceeds the reference value Rvref, that is, the roll angle Rv may be excessive in the steering angle control of only the front wheels. Whether or not is determined. When an affirmative determination is made, control proceeds to step 560a. When a negative determination is made, at step 555, the target rudder angle δft of the front wheels is set to the target rudder angle δbt, and the target rudder angle δrt of the rear wheels is set. Is set to 0.

  In step 560a, the deviation ΔYRa between the magnitude of the estimated yaw rate YRa and the reference value YRref (for each cycle) is calculated for the temporal region in which the magnitude of the roll angle Rv is to be reduced and corrected by reducing and correcting the estimated yaw rate YRa. Deviation ΔYRai) is calculated.

Second Modification FIG. 16 shows a target rudder for front wheels and rear wheels in a second modification in which the third embodiment described above is modified to an embodiment in which the roll angle Rv of the vehicle is prevented from becoming excessive. It is a flowchart which shows an angle calculation routine. In FIG. 16, steps corresponding to the steps shown in FIG. 10 are assigned the same step numbers as those shown in FIG.

  As understood from comparison between FIG. 16 and FIG. 10, steps 505 to 540 and steps 565 to 590 are executed in the same manner as in the first embodiment. Steps 540a and 545a are executed after steps 540 and 545, respectively, and steps 550a and 560a are executed instead of steps 550 and 560, respectively.

  According to the first and second modified examples, when there is a possibility that the roll angle Rv of the vehicle becomes excessive in the steering angle control of only the front wheels, the roll angle Rv of the vehicle becomes excessive by limiting the estimated yaw rate YRa. Can be prevented. The second, fourth to eighth embodiments can also be modified to modifications that prevent the vehicle roll angle Rv from becoming excessive due to the restriction of the estimated yaw rate YRa, as in the first and second modifications. .

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, when the steering angle of the front wheels is controlled in a feed forward manner, the steering angle of the rear wheels is also controlled in a feed forward manner, and when the steering angle of the front wheels is controlled in a feedback manner, the steering angle of the rear wheels is also fed back. It is controlled by the formula. However, the steering angle of the rear wheels may be controlled by either the feedforward method or the feedback method regardless of the control method of the steering angle of the front wheels.

  In each embodiment, when the control of the steering angle of the front wheels for the trajectory control is not performed, the steering angle of the rear wheels is maintained at 0. It may be controlled based on the steering angle ratio.

  The guide bar extends along the front-rear direction of the front wheel. However, as long as the inclination angle of the guide bar relative to the front-rear direction of the vehicle is set based on the amount of steering operation by the driver, the front-rear direction of the front wheel The direction may be different from the direction along. For example, the inclination angle of the guide rod may be set to the product of the steering angle δ of the front wheels and the direction correction coefficient Kd.

  In each embodiment, the vehicle travel control includes the control of the steering angle of the front wheels and the control of the steering torque. However, the control of the steering torque may be executed in an arbitrary manner.

  In each embodiment, the steering angle of the front wheels is controlled in a feedforward type or a feedback type, but based on the sum of the feedforward control amount multiplied by the gain and the feedback control amount, respectively. May be modified to be controlled.

  DESCRIPTION OF SYMBOLS 10 ... Travel control device, 14 ... Steering angle variable device, 20 ... Steering wheel, 22 ... Electric power steering device, 50 ... Steering angle sensor, 52 ... Steering torque sensor, 54 ... Rotation angle sensor, 56 ... Vehicle speed sensor, 60 ... rear wheel steering device, 66 ... rudder angle sensor, 80 ... travel control device, 82 ... steering mechanism, 90, 94 ... electric motor, 100 ... front wheel, 102 ... rear wheel, 104 ... vehicle, 108 ... target course, 110 ... guidance rod

Claims (15)

Vehicle running control comprising front wheel steering angle control means for changing the steering angle of the front wheels with respect to the amount of steering operation by the driver, and rear wheel steering angle control means for changing the steering angle of the rear wheels independently of the front wheels in the apparatus,
When the starting condition or update condition are set in advance for the control of vehicles trajectory is judged to be satisfied, and determines the target traveling direction based on the steering operation amount of at driver that point, at the time The angle determined based on the amount of steering operation of the driver is a reference angle, and exists on a straight line drawn in a direction inclined by the reference angle with respect to the vehicle front-rear direction from the vehicle position at the time point, and The target arrival position is determined at a position that depends on the vehicle speed from the position of the vehicle at the time,
Based on the driver's steering operation amount and vehicle speed at the time point, the provisional target rudder angle of the front wheels for the vehicle to travel along the target trajectory necessary for the vehicle to reach the target arrival position in the target traveling direction. And based on the provisional target rudder angle, estimate the amount of turning state of the vehicle until the vehicle reaches the target arrival position in the target traveling direction,
When the magnitude of the turning state amount is equal to or less than a reference value, the steering angle of the front wheels is controlled by the front wheel steering angle control means based on the temporary target steering angle,
When the magnitude of the turning state quantity exceeds the reference value, the vehicle is caused to travel along the target locus based on the turning state quantity of the vehicle corrected so that the magnitude of the turning state quantity does not exceed the reference value. And calculating the target steering angle of the front wheels and the rear wheels for controlling the steering angle of the front wheels by the front wheel steering angle control means based on the target steering angle of the front wheels and the rear steering based on the target steering angle of the rear wheels. A vehicle travel control apparatus, wherein a steering angle of a rear wheel is controlled by a wheel steering angle control means.   The corrected amount of turning state of the vehicle is corrected by reducing the amount of turning state amount to the reference value in a region where the amount of turning state amount exceeds the reference value. 2. The region in which the value does not exceed the reference value is obtained by increasing and correcting the magnitude of the turning state quantity so that the magnitude of the turning state quantity does not exceed the reference value. The vehicle travel control apparatus described.   The corrected turning state quantity of the vehicle is corrected to reduce the turning state quantity below the reference value for a region where the magnitude of the turning state quantity exceeds a correction determination value smaller than the reference value, The region where the magnitude of the turning state quantity does not exceed the correction judgment value is obtained by increasing and correcting the magnitude of the turning state quantity so that the magnitude of the turning state quantity does not exceed the correction judgment value. The travel control device for a vehicle according to claim 1.   4. The vehicle according to claim 2, wherein an integral value of the reduction correction amount for the magnitude of the turning state amount and an integral value of the increase correction amount for the magnitude of the turning state amount are substantially equal to each other. Travel control device.   The vehicle travel control apparatus according to any one of claims 1 to 3, wherein the turning state amount of the vehicle is one of a yaw rate and a roll angle of the vehicle.   The target trajectory is a virtual orthogonal coordinate in which a straight line indicating the target traveling direction is a time coordinate axis, and a perpendicular drawn from the vehicle position at the time point to the time coordinate axis is a distance coordinate axis. 4. The vehicle travel control apparatus according to claim 1, wherein the vehicle travel control apparatus is an exponential function curve in which an elapsed time from a time point is an index variable.   The vehicle according to any one of claims 1 to 3, wherein the rudder angle of the front wheels is corrected so that a deviation between the rudder angle of the front wheels and the target rudder angle at the time point becomes small. Travel control device.   The vehicle travel control according to any one of claims 1 to 3, wherein the steering angle of the front wheel is corrected so that a deviation between an actual steering angle of the front wheel and the target steering angle is small. apparatus. A straight line connecting the vehicle position at the time point and the target arrival position is used as a reference line for the direction, and the target traveling direction is in a direction inclined at the reference angle with respect to the reference line of the direction at the target arrival position. The vehicle travel control apparatus according to any one of claims 1 to 8, wherein the vehicle travel control apparatus is determined. In situations not subjected to control of the trajectory, steering operation of the driver after becoming larger than the first reference value for determining the magnitude is opened start condition of the steering operation amount of the rate of change of the driver 1 through claim, characterized in that determining the starting condition for control of the track when it is smaller than the second reference value for determining the magnitude is opened start condition of the amount of change rate is established 4. The vehicle travel control device according to any one of 3 above. In situations having a control of the trajectory, steering operation of the driver after becoming larger than the first reference value for the magnitude of the steering operation amount of the change rate of the driver to determine the update condition 1 through claim, wherein determining that the update condition of control of the trajectory when it becomes smaller than a second reference value for the magnitude of the amount of change rate determining update condition is satisfied 4. The vehicle travel control device according to any one of 3 above.   A target distance is obtained as a product of the reference distance and a natural exponential function having an elapsed time from the time point as an index variable, with the distance from the vehicle to the coordinate axis of the time at the time point being a reference distance. The vehicle travel control apparatus according to claim 6, wherein the trajectory is obtained as a line connecting the position of the target distance from the coordinate axis of the time. ΔT is a general time required for a person to perceive the change in the visual information after the change in the visual information outside the vehicle related to the necessity of the steering operation, and the Weber ratio is −k. an elapsed time as t, the index of the natural exponential function - (k / ΔT) travel control device for a vehicle according to claim 1 2, characterized in that the t. The front wheel rudder angle control unit controls the rudder angle varying unit for correcting the rudder angle of the front wheel by driving the front wheel relative to the steering input unit operated by the driver, and the front wheel rudder angle varying unit. travel control device for a vehicle according to any one of claims 1 to 1 3, characterized in that a steering angle control means Semibaiwaiya type and a control unit. The front wheel steering angle control means is a steering means for changing the steering angle of the front wheels, a means for detecting a steering operation amount of the driver with respect to the steering input means, and a normal operation based on the steering operation amount of the driver. 2. A by-wire type rudder angle control means having a control means for controlling the rudder means and controlling the steer means without depending on the steering operation of the driver as required. 13. The vehicle travel control device according to any one of 1 to 3.

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