JP3748334B2 - Vehicle attitude control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy in attitude control by estimating the slip ratio between a wheel and a road surface in a traveling direction of a vehicle by an arithmetic means to obtain the force in a longitudinal direction and that in a lateral direction to be applied to each wheel. SOLUTION: An attitude control device 1 takes the outputs of a yaw rate sensor 6 and a steering angle sensor 14 when the breaking operation is detected by a brake pressure sensor 12, and determines the wheel speed V' on the basis of the wheel rotating speed sensor 10 of the front and rear wheels 8, 9. Then it takes the detecting output Gx from a longitudinal acceleration sensor 18 to calculate the slip ratio sf in a tire force arithmetic part 2. The actual vehicle speed V is calculated by using the obtained value. Simultaneously, the slip ratio of each wheel is calculated on the basis of the actual speed V and the rotating speed of each wheel to be used as the longitudinal force Fx. Further each angle of side slip βf, βr of the front and rear wheels are determined on the basis of the actual speed V, the acceleration Gy in a lateral direction, the yaw rate ω, the steering angle δ or the like, and the force Fy in the lateral direction is determined on the basis of the braking force or the driving force acting on each wheel.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is used in an automobile. The present invention automatically detects the attitude of a vehicle, and calculates and controls the attitude of the vehicle so as to prevent the side slip when the side slip occurs or when there is a possibility that the side slip occurs. Use as The present invention takes in a value measurable by a running car and performs a calculation in real time, and a driving force or a braking force applied to the wheel so that the wheel does not slip or the slip state of the wheel is controlled. The present invention relates to an apparatus for automatically controlling the above.
[0002]
[Prior art]
If a large driving force is applied to the driving wheel on a slippery road surface, the driving wheel slips. At this time, the vehicle may spin laterally. The same applies to braking. If a large braking force is applied to a wheel on a slippery road surface, the wheel slips and braking cannot be performed. Further, on a slippery road surface, steering may cause the vehicle to slip sideways. In many cases, the steering stability of the vehicle is lost because the driving wheel starts to slip, the braking wheel starts to slip, or sudden steering is performed. Therefore, a driving force below the slip limit is applied so that the driving wheel does not slip during driving, and a braking force below the slip limit is applied so that the braking wheel does not slip during braking. It is desirable to control so as not to steer.
[0003]
Conventionally, an electronic control device for a brake, a vehicle stabilization control device (VSC, Vehicle Stability Control) and the like are known. A typical system of an electronic control device related to a brake is an ABS (Antilock Brake System). This is to detect the wheel rotation by providing a rotation sensor on the wheel, and if the wheel rotation stops when the brake pressure is high, the brake pressure is intermittently controlled as if there was a slip between the wheel and the road surface. . ABS has become widespread in passenger cars and freight cars, and has become widely known as a device that can handle a steering wheel while braking. As a representative device of the vehicle stabilization control device (VSC), a skid prevention device is known. This is because the driver's steering angle (steering wheel angle) that is input by the driver reads the course that the driver is trying to advance, and if the vehicle speed is too high for that course, the driver does not have to step on the brake pedal. In this device, control for deceleration is performed, and control such as distribution of left and right brake pressures is performed so as not to deviate from the course.
[0004]
Further explanation of the already known vehicle posture stabilization device (VSC) (Japanese Patent Laid-Open Nos. 63-279976, 2-112755, etc.) is as follows. The direction of the vehicle changes and the vehicle rolls. At this time, when the tire of the turning inner wheel by steering reaches the grip limit of the road surface, the inner wheel becomes a so-called wheel lift tendency, and the vehicle starts to slide sideways. For example, when the driver steers left from a straight running state, the vehicle tilts to the right. At this time, the vehicle turns according to the steering in a normal state. However, if the steering speed is too large with respect to the traveling speed, the vehicle leans to the right while the left wheel is in a floating state, and the driver Proceed to the right from the direction of. Such a behavior of the vehicle causes a deviation of the driving lane or, in an extreme case, causes the vehicle to roll over.
[0005]
In normal driving conditions, the magnitude and speed of the steering, the speed of the vehicle, the speed of lateral movement of the vehicle, and the speed of change of the direction of the vehicle (yaw rate, vehicle rotational acceleration around the vertical axis at the center of gravity of the vehicle) By detecting and calculating, a device has been developed that predicts the side slip start point of the wheel or the wheel lift start point of the inner ring and controls the brake pressure of the wheel before the side slip or wheel lift starts. This wheel brake pressure control is not necessarily the same brake pressure for all wheels, but applies a large or small brake pressure to one wheel to prevent the vehicle from slipping. Such a device has been studied not only for its basic structure and design, but also for economy and durability, and has reached the stage where it is mounted on commercial products for passenger cars.
[0006]
[Problems to be solved by the invention]
Such a conventional apparatus calculates the yaw rate from the parameters relating to the driving operation including the current steering and braking and the parameters relating to the current behavior of the vehicle, that is, from the current parameters, and this is set and stored in advance for the vehicle. The brake pressure of the vehicle is automatically controlled when it is determined that the yaw rate that may cause the skidding is reached. The possibility of this side slip is determined by executing a calculation in real time from vehicle behavior data as driving operation inputs and various sensor outputs.
[0007]
For example, when the driver steers in the right direction while passing a gentle right curve at a high speed, the vehicle begins to slide sideways, deviating from the lane intended by the driver and entering the left lane. Assuming that The driver performs the braking operation and the braking force is applied to the wheels, but at the same time, the attitude control device does not distribute the braking force evenly to each wheel, but automatically increases the braking force of the right wheel. To control. As a result, a force that is pulled back in the right direction acts on the vehicle.
[0008]
In the above explanation, it was explained that the driver operated the brake, but it was detected that there was still no departure from the driving lane and that the vehicle was likely to start a side slip from the sensor provided on the vehicle. Sometimes, the attitude control device automatically detects this and automatically applies a braking force to some of the wheels in a direction in which the attitude is stabilized.
[0009]
However, when there is a slip between the wheel and the road surface in the traveling direction of the vehicle, the change in the direction of the vehicle with respect to the magnitude of the steering is small, and the force that causes the vehicle to slip is weakened accordingly.
[0010]
The present invention has been carried out against such a background, and it is an object of the present invention to provide an apparatus capable of performing vehicle attitude control with high accuracy. It is an object of the present invention to provide an apparatus for performing vehicle stabilization control that can provide a braking force or a driving force so that a slip limit of a wheel is controlled by predicting and calculating a slip limit of the wheel. . An object of this invention is to provide the automatic control apparatus which stabilizes the driving | running | working state of a vehicle. An object of this invention is to provide the stabilization control apparatus which prevents the dangerous state which leads to vehicle rollover beforehand.
[0011]
[Means for Solving the Problems]
The present invention automatically detects a posture during running of a vehicle, and when a side slip occurs or when a side slip may occur, the vehicle slips to prevent the side slip by estimating the slip of the wheel. It is characterized by controlling the posture of the camera.
[0012]
That is, the present invention provides a constant including the vehicle mass M, the distance Lf from the center of gravity of the vehicle to the front wheel axis, the distance Lr from the center of gravity of the vehicle to the rear wheel axis, and the moment of inertia I around the center of gravity of the vehicle. Means for storing as a model; means for measuring the vehicle speed V ′ obtained from the longitudinal and lateral accelerations Gx, Gy of the vehicle, the rotational speed of the wheels, and the yaw rate ω of the vehicle as electrical signals; A vehicle attitude control device comprising means for calculating the behavior of the vehicle from an electric signal, and means for controlling braking force or driving force applied to each wheel individually and automatically based on the calculation result of the calculating means. The calculating means estimates the slip ratio between the wheel and the road surface in the traveling direction of the vehicle, and applies it to each wheel of the vehicle under the slip ratio. That longitudinal and transverse forces Fx, characterized in that it comprises a wheel force calculating means for calculating a Fy.
[0013]
The relationship between the longitudinal acceleration Gx of the vehicle and the slip ratio s of the wheel that is measuring the vehicle speed V ′ is known, and the wheel force calculation means calculates the slip of the wheel from the measured longitudinal acceleration Gx. The vehicle speed V ′ is corrected using the slip rate s, and the true vehicle speed V is obtained. The slip rate of each wheel is calculated from the true vehicle speed V and the rotational speed of each wheel. It is desirable to include means for obtaining a longitudinal force Fx applied to each wheel.
[0014]
The wheel force calculation means further includes the true vehicle speed V, the lateral acceleration Gy of the vehicle, the yaw rate ω of the vehicle, the distances Lf and Lr from the center of gravity of the vehicle to the front wheel shaft and the rear wheel shaft, and the front wheel from the steering angle δ. The lateral slip angles βf and βr of the rear wheels are obtained, and the lateral force actually acting on each wheel is obtained from the sideslip angles βf and βr and the braking force or driving force actually acting on each wheel. It is desirable to include a means for obtaining.
[0015]
The relationship between the acceleration Gx in the longitudinal direction of the vehicle and the slip ratio s (hereinafter referred to as “wheel characteristics”) varies depending on the friction coefficient between the wheels and the road surface. Therefore, it is preferable to record the wheel characteristics in each case for a plurality of friction coefficients in advance and select and use any of the wheel characteristics according to the road surface condition. In practice, it is sufficient to record the wheel characteristics for three friction coefficients: high, medium and low.
[0016]
To determine the actual road surface condition, the technique disclosed in Japanese Patent Laid-Open No. 4-135923 can be used. That is, when the wheel slips with respect to the road surface from the braking force or driving force applied to the wheel, the state of the road surface is automatically detected in real time. In addition, a method and apparatus for estimating the friction coefficient of the road surface in real time, which was further improved by the inventors of the present application and applied for a patent separately from the present application, can be used. This technique will be described below.
[0017]
For the lateral acceleration Gy generated in the traveling vehicle, the equation Gy = V ((dβ / dt) + ω)
V: Vehicle speed β: Side slip angle of vehicle dβ / dt: Time differential value of side slip angle β ω: Yaw rate has been reached, so lateral acceleration Gy, vehicle speed V and yaw rate ω from lateral acceleration sensor, vehicle speed sensor and yaw rate sensor Is taken as an electrical signal, and the time differential value dβ / dt = (Gy / V) −ω
And the time differential value dβ / dt of the side slip angle β is integrated over time to calculate the side slip angle β. At this stage, the vehicle speed V ′ obtained from the rotational speed of the wheels is actually used as the vehicle speed V. From the obtained side slip angle β and the distance Lf from the center of gravity of the vehicle to the front wheel axis, the front wheel side slip angle βf is βf = β + (Lf / V) ω−δ (δ: front wheel steering angle).
Is required.
[0018]
On the other hand, when the lateral force generated at the front wheel is Ff and the lateral force Fr generated at the rear wheel,
I (dω / dt) = 2Ff · Lf−2Fr · Lr
About the lateral direction of the vehicle
M · Gy = 2Ff + 2Fr
Therefore, the lateral force Ff of the front wheel is calculated from the two formulas and the stored numerical value by the formula Ff = (I (dω / dt) + M · Gy · Lr) / 2 (Lf + Lr)
Calculate by
[0019]
From the thus obtained βf and Ff, the road surface friction coefficient μ of the vehicle front wheel is expressed by the formula μ = Ff / (Kf · βf), where Kf is a cornering power constant determined from the specifications of the tire.
It is calculated by. Note that the above-described friction coefficient estimation method is a desirable example, and the present invention can be similarly implemented by other methods.
[0020]
Thus, according to the present invention, even when there is a slip between the wheel and the road surface in the traveling direction of the vehicle, it is possible to accurately estimate the force that causes the vehicle to slip, and perform posture stabilization control with high accuracy. be able to.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
[0022]
【Example】
Next, an apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a system configuration of an apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view showing an example of mounting the apparatus according to an embodiment of the present invention on a vehicle.
[0023]
The posture control apparatus 1 of the present invention includes a vehicle mass M, a distance Lf from the center of gravity of the vehicle to the front wheel axis, a distance Lr from the center of gravity of the vehicle to the rear wheel axis, and an inertia moment I around the center of gravity of the vehicle. And constants including the vehicle model, and the outputs from the longitudinal acceleration sensor 18, the lateral acceleration sensor 4, the vehicle speed sensor 5 and the yaw rate sensor 6, and the longitudinal acceleration and lateral acceleration Gx, Gy, Means for measuring the vehicle speed V ′ and the yaw rate (ω) of the vehicle obtained from the rotational speed of the wheel as electric signals, means for calculating the behavior of the vehicle from the vehicle model and the electric signals, and calculation results of the means for calculating And a means for controlling braking force or driving force applied to each wheel individually and automatically. Further, as a feature of the present invention, the calculating means estimates the slip ratio between the wheel and the road surface in the traveling direction of the vehicle, and applies the front-rear direction and the lateral direction applied to each wheel of the vehicle under the slip ratio. Wheel force calculation means for determining the direction forces Fx and Fy are included.
[0024]
A tire force calculation unit 2 is provided as a wheel force calculation means, and the relationship between the vehicle longitudinal acceleration Gx and the wheel slip rate s measuring the vehicle speed V ′ is known. Obtains the slip rate s of the wheel from the measured longitudinal acceleration Gx, and corrects the vehicle speed V ′ by using the slip rate s to obtain the true vehicle speed V. Means for calculating the slip ratio of each wheel from the rotational speed of the wheel to obtain the longitudinal force Fx applied to each wheel, the true vehicle speed V, the lateral acceleration Gy of the vehicle, the yaw rate ω of the vehicle, The sideslip angles βf and βr of the front wheels and the rear wheels are obtained from the distances Lf and Lr from the center of gravity to the front wheel axis and the rear wheel axis and the steering angle δ, and the sideslip angles βf and βr and the wheels are actually set. Acting braking force or A drive force, means for obtaining a lateral force actually acting on each wheel is provided.
[0025]
Further, in the posture control apparatus 1 of the present invention, the brake pressure provided in the wheel rotational speed sensor 10 and the brake booster actuator 11 provided on the front wheel 8 and the rear wheel 9 as a part of the control output device. An ABS (automatic braking control device) 3 is included which takes in the detection output of the sensor 12 and intermittently controls the brake pressure when a slip occurs.
[0026]
In the attitude control device 1, as other control information required for attitude stability control, a steering angle sensor 14 for detecting the steering angle of the steering handle 13, a governor sensor 16 provided in the electronic governor 15, and a roll rate of the vehicle Is connected to the output of the roll rate sensor 17. Further, a control signal is sent from the attitude control device 1 to the brake / booster / actuator 11 and the electronic governor 15.
[0027]
In the present embodiment, as shown in FIG. 1, the configuration of the two-axis vehicle is described as an example. However, in the case of a large vehicle, a three-axis or four-axis structure is used. Even if the present invention has a three-axis structure or a four-axis structure, the required control information can be taken in, the slip ratio s is estimated in the same manner, and the automatic braking control is performed using the slip ratio s as control information. Attitude stability control and other controls can be performed in the same manner as a vehicle having a two-axis structure.
[0028]
Next, an attitude control operation by the attitude control apparatus 1 according to the embodiment of the present invention configured as described above will be described.
[0029]
The attitude control device 1 is an electronic device including a computer circuit that is program-controlled, and inputs the driving operation input of the vehicle and the behavior data of the vehicle to calculate and output the movement state of the vehicle, and the driving operation input according to the calculation output Then, a correction input for correcting the disturbance input to the safe side is given to the vehicle to perform stable posture control. In other words, it includes a numerical model that holds the physical characteristics of the vehicle as numerical values, and an observer that takes the driving operation input of the vehicle as data and refers to the numerical model to estimate the response of the vehicle using a transfer function. The function is obtained by the autoregressive method (AR method) in which the data X (k) at the k time point is represented by a value obtained by multiplying the past data until the M time point by the weighting coefficient A (m) at each time point.
[0030]
For example, when the loaded weight changes, when the loaded figure changes, or when the number of passengers changes, the actual behavior of the vehicle does not match the behavior of the numerical model. At this time, the parameters stored in advance in the numerical model of the vehicle are automatically changed to match the behavior. This update is executed when safe traveling is performed in which the behavior of the vehicle with respect to driving operation input or disturbance input is sufficiently smaller than a dangerous level.
[0031]
An example of the control flow of the attitude control device 1 is as shown in FIG. 3 for normal control.
[0032]
Further, when the state of the load changes or the number of passengers changes, the control illustrated in FIG. 4 is performed, and the parameters of the vehicle model are updated. This update is automatically performed by always monitoring whether correction is necessary. The vehicle data is updated based on a transfer function obtained by the autoregressive method (AR method). The update mode process shown in FIG. 4 is executed in step S4 shown in FIG. Thus, control suitable for the present situation can be performed by using the autoregressive method (AR method).
[0033]
FIG. 5 shows an example of input data according to the embodiment of the present invention, where (a) shows the steering angle, (b) shows the yaw rate, and (c) shows the side slip angle. The horizontal axis is time (seconds). The horizontal axis is common to (a), (b), and (c). When the steering handle 13 is operated, the steering angle sensor 14 detects this and sends the operation data shown in (a) to the attitude control device 1. With this steering operation, the yaw rate sensor 6 detects the yaw rate and sends the operation data shown in (b) to the attitude control device 1. At the same time, the lateral acceleration sensor 4 detects the lateral acceleration and sends the operation data shown in (c) to the attitude control device 1. That is, (a) shown in FIG. 5 is an input, and (b) and (c) are responses representing vehicle behavior (behavior).
[0034]
The attitude control device 1 calculates the transfer function of this vehicle based on these data. The transfer function is a complex function, and a practical example can be displayed by displaying the frequency on the horizontal axis and the amplitude and phase on the vertical axis. Considering a relatively simple model, the amplitude characteristic has a gentle downward curve with respect to frequency, and the phase characteristic has a corresponding downward curve. FIGS. 6A and 6B are diagrams illustrating the frequency characteristics of the amplitude and the phase with respect to the yaw rate. FIGS. 7A and 7B are diagrams illustrating frequency characteristics of amplitude and phase with respect to lateral acceleration. These are diagrams showing transfer functions calculated based on actual data.
[0035]
Here, vehicle attitude control and updating will be described. Once the transfer function is determined in this way, the vehicle's dynamic characteristics are calculated using this transfer function, and when an abnormal movement exceeding a predetermined standard is predicted, a different brake pressure is applied to each wheel. Thus, attitude control is performed to suppress abnormal movement of the vehicle. Since this is the same as a method that has been practically used in passenger cars, a detailed description is omitted here. This technology is applied to commercial vehicles (trucks and buses). In commercial vehicles, the transfer function that represents the response of the vehicle fluctuates depending on the status of loading and the number of passengers, so the transfer function is updated. .
[0036]
FIG. 6 is a diagram for explaining this, and it is assumed that the function of the characteristic indicated by the broken line is already accumulated in the numerical model as the transfer function. This is a model in the case of a standard form in which the load is about one third of the maximum load capacity. Assume that an additional load is loaded. Then, the total weight and the position of the center of gravity change. This naturally results in different vehicle responses to the same steering. That is, the transfer function already stored must be changed. Therefore, when the transfer function is calculated again according to the behavior of the vehicle appearing in the sensor, as shown by the solid line, a characteristic different from the already accumulated transfer function appears. This calculation is automatically executed as described with reference to FIG. When the difference, that is, the area to be shaded in FIG. 6 is larger than a preset limit value, the accumulated model itself is updated to a new calculated value indicating the current state as indicated by a solid line. This is automatically performed as described in FIG. By updating the numerical model of such an automatically accumulated transfer function, proper posture control can be performed even when the load fluctuates or the crew changes. .
[0037]
Here, the control operation of braking force or driving force, which is a feature of the present invention, will be described. This operation is executed in step S4 shown in FIG. FIG. 8 is a flowchart showing the flow of the braking force or driving force control operation by the posture control apparatus of the embodiment of the present invention.
[0038]
When the posture control device 1 detects that the brake has been operated from the output of the brake pressure sensor 12, the posture control device 1 takes in the outputs from the yaw rate sensor 6 and the steering angle sensor 14, and the left and right front wheels 8 and the left and right rear wheels 9 The detection output from the wheel rotation speed sensor 10 is taken in, and the vehicle speed V ′ is obtained from the one with the higher wheel rotation speed of the front wheel 8. That is, it is assumed that the vehicle speed V ′ corresponding to a wheel having a high wheel rotation speed is close to the true vehicle speed V.
[0039]
Next, the detection output Gx from the longitudinal acceleration sensor 18 is taken in, and the tire force calculation unit 2 calculates the slip ratio (sf). FIG. 9 is a characteristic diagram showing the relationship between the acceleration Gy generated during braking and the slip ratio sf at a certain road surface friction coefficient. FIG. 4A shows how to determine the slip ratio sf during 1G braking, and FIG. 4B shows how to determine the slip ratio sf during 0.6G braking using the same curve. Such tire characteristics are stored as a map based on the difference in road surface friction coefficient, and the slip ratio sf is obtained from the measured acceleration Gx.
[0040]
The true vehicle speed V is calculated by the following equation using the value of the slip ratio sf.
[0041]
V = V '/ (1-sf)
0 <sf <1
0: Roll, 1: Slip Next, using the calculated true vehicle speed, the detected lateral acceleration Gy, and the yaw rate ω, the true side slip angle β of the vehicle is expressed by the equation β = ∫ ((Gr / V) −ω) dt
Further, the front wheel side slip angle (βf) is calculated using the captured front wheel steering angle δ, the stored distance Lf from the center of gravity of the vehicle to the front wheel axis, and the distance Lr from the center of gravity of the vehicle to the rear wheel axis. And the rear wheel side slip angle (βr) is expressed by the equation βf = β + (Lf / V) ω−δ.
βr = β− (Lr / V) ω
Calculate by
[0042]
At the same time, the slip ratio of each wheel is calculated from the true vehicle speed V and the rotational speed of each wheel to obtain the actual braking force of each wheel, and this is used as the input / output of the vehicle model as the longitudinal force Fx.
[0043]
FIG. 10A is a characteristic curve showing the relationship between the side slip angle β and the side force Fy for each of 0G braking, 0.6G braking and 1G braking, and FIG. 10B shows the characteristic curve during braking at a certain side slip angle. It is a characteristic curve showing the relationship between acceleration Gx and lateral force Fy.
[0044]
A lateral force that takes into account the slip loss caused by the slip from the braking curve obtained from the calculated front wheel side slip angle βf, the rear wheel side slip angle βr, and the longitudinal force Fx (corresponding to the longitudinal acceleration Gx). Fr is obtained and used as the vehicle model input.
[0045]
In order to obtain the slip ratio s from the measured longitudinal acceleration Gx, it is necessary to know the road surface friction coefficient (μ). A method for estimating this in real time will be described below. FIG. 11 is a flowchart showing the flow of the road surface friction coefficient estimation operation.
[0046]
For estimating the road surface friction coefficient, as physical constants related to the vehicle, the mass M of the vehicle, the distance Lf from the center of gravity of the vehicle to the front wheel axis, the distance Lr from the center of gravity of the vehicle to the rear wheel axis, and An inertia moment I around the center of gravity of the vehicle is stored in advance. Further, the detection outputs from the lateral acceleration sensor 4, the vehicle speed sensor 5 and the yaw rate sensor 6 are taken in as electrical signals, and the vehicle lateral acceleration Gy, the vehicle speed V and the vehicle yaw rate ω are measured. Here, as the vehicle speed V, a value obtained from the rotational speed of the wheel is sufficient.
[0047]
Assuming that the side slip angle of the vehicle is β and the time differential value of the side slip angle β is dβ / dt, the lateral acceleration is
Gy = V ((dβ / dt) + ω)
Therefore, the time differential value dβ / dt = (Gy / V) −ω of the side slip angle β using the measured value according to this equation.
And the time differential value of the side slip angle β is integrated over time to calculate the side slip angle β.
[0048]
Inertia moment I around the center of gravity axis of the vehicle, time differential value dω / dt of yaw rate ω, lateral force Ff of the front wheel, distance Lf from the center of gravity to the front wheel axis, lateral force Fr of the rear wheel, distance from the center of gravity to the rear wheel axis Lr, vehicle mass M, and lateral acceleration Gy of the vehicle are as follows:
I (dω / dt) = 2Ff · Lf−2Fr · Lr
In relation to the translation direction of the vehicle,
M · Gy = 2Ff + 2Fr
There is a relationship.
[0049]
From these two relational expressions, the lateral force Ff generated on the front wheel 8 is
Ff = (I (dω / dt) + M · Gy · Lr) / 2 (Lf + Lr)
It is calculated by.
[0050]
Further, as shown in FIG. 12, if the yaw rate generated around the center of gravity of the vehicle is ω while the vehicle is traveling at a speed V, the net side slip angle βf of the front wheel 8 is the center of gravity of the vehicle. Since the distance from the front wheel shaft to the front wheel shaft is Lf, the side slip angle is β + (Lf / V) ω in a state where steering is not performed.
However, when the steering is performed at the steering angle δ, the side slip angle is obtained by subtracting the steering angle δ from a state where the steering is not performed, and βf = β + (Lf / V) ω−δ.
It is shown by the relational expression.
[0051]
Assuming that the cornering power constant Kf obtained from the specifications of the tire is given, the road surface friction coefficient μ of the front wheel 8 is expressed by the formula μ = Ff / (Kf · βf).
Is required.
[0052]
【The invention's effect】
As described above, according to the present invention, the force that causes the vehicle to slip sideways is accurately estimated in consideration of the wheel slip in the traveling direction of the vehicle, and the braking force or driving force is adaptively determined based on the estimation. Since it can be controlled, it is possible to perform highly accurate vehicle attitude stability control.
[Brief description of the drawings]
FIG. 1 is a diagram showing a system configuration of an apparatus according to an embodiment of the present invention.
FIG. 2 is a perspective view showing an example of mounting the embodiment device of the present invention on a vehicle.
FIG. 3 is a flowchart for explaining normal control by the posture control apparatus according to the embodiment of the present invention.
FIG. 4 is a flowchart for explaining parameter update of a vehicle model by the attitude control device according to the embodiment of the present invention.
FIGS. 5A, 5B, and 5C are diagrams showing input data of a steering angle, a yaw rate, and a side slip angle in the control of the posture control apparatus according to the embodiment of the present invention.
FIGS. 6A and 6B are diagrams illustrating an example of a transfer function represented by a gain and a phase in the control of the attitude control device according to the embodiment of the present invention.
7A and 7B are diagrams showing another example of a transfer function represented by a gain and a phase in the control of the attitude control device according to the embodiment of the present invention.
FIG. 8 is a flowchart showing a flow of a braking force or driving force control operation by the posture control apparatus according to the embodiment of the present invention.
9A and 9B are characteristic diagrams showing the relationship between the slip ratio and the longitudinal force.
10A is a characteristic diagram showing a relationship between a side slip angle and a lateral force, and FIG. 10B is a characteristic diagram showing a relationship between [gravity] acceleration and a lateral force.
FIG. 11 is a flowchart showing the flow of a road surface friction coefficient estimation operation by the road surface friction coefficient estimation device of the posture control apparatus according to the embodiment of the present invention.
FIG. 12 is a diagram for explaining a side slip angle used for road surface friction coefficient estimation in the embodiment of the present invention.
[Explanation of symbols]
1 Attitude Control Device 2 Tire Force Calculation Unit 3 ABS (Automatic Braking Control Device)
4 lateral acceleration sensor 5 vehicle speed sensor 6 yaw rate sensor 8 front wheel 9 rear wheel 10 wheel rotational speed sensor 11 brake booster actuator 12 brake pressure sensor 13 steering handle 14 steering angle sensor 15 electronic governor 16 governor sensor 17 roll rate sensor 18 longitudinal direction Acceleration sensor

Claims (2)

Means for storing, as a vehicle model, a constant including a vehicle mass M, a distance Lf from the center of gravity of the vehicle to the front wheel axis, a distance Lr from the center of gravity of the vehicle to the rear wheel axis, and an inertia moment I around the center of gravity of the vehicle; , Means for measuring the vehicle speed V ′ obtained from the longitudinal and lateral accelerations Gx, Gy of the vehicle, the rotational speed of the wheels, and the yaw rate ω of the vehicle as electrical signals, and the vehicle model and the electrical signal In a vehicle attitude control device comprising means for calculating a behavior and means for controlling braking force or driving force applied to each wheel individually and automatically based on a calculation result of the means for calculating,
The calculating means estimates the slip ratio between the wheel and the road surface in the traveling direction of the vehicle, and determines the longitudinal and lateral forces Fx and Fy applied to each wheel of the vehicle under the slip ratio. Including force calculation means ,
A map describing a correspondence relationship between the longitudinal acceleration Gx of the vehicle generated during braking and the slip ratio s of the wheels in the difference in the road surface friction coefficient;
The wheel force calculating means obtains a vehicle speed V ′ corresponding to a wheel having a large wheel rotation speed, obtains a slip ratio s of the wheel with reference to the map from the measured acceleration Gx in the front-rear direction, and this slip ratio. obtains the true vehicle speed V by correcting the vehicle speed V 'with s, to calculate the slip ratio of each wheel from this true vehicle speed V and the rotational speed of each wheel, the front-rear direction applied to the respective wheel A vehicle attitude control device comprising means for obtaining the force Fx of the vehicle. The wheel force calculation means includes the true vehicle speed V, the lateral acceleration Gy of the vehicle, the yaw rate ω of the vehicle, the distances Lf and Lr from the center of gravity of the vehicle to the front wheel shaft and the rear wheel shaft, and the steering wheel δ from the front wheel and The lateral slip angles βf and βr of the rear wheels are obtained, and the lateral force Fr actually acting on each wheel is obtained from the sideslip angles βf and βr and the braking force or driving force actually acting on each wheel. The vehicle attitude control apparatus according to claim 1 , comprising means for obtaining .

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