CN112550430B - Vehicle stability control method and system - Google Patents
Vehicle stability control method and system Download PDFInfo
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- CN112550430B CN112550430B CN201910852684.0A CN201910852684A CN112550430B CN 112550430 B CN112550430 B CN 112550430B CN 201910852684 A CN201910852684 A CN 201910852684A CN 112550430 B CN112550430 B CN 112550430B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
- B62D5/046—Controlling the motor
- B62D5/0463—Controlling the motor calculating assisting torque from the motor based on driver input
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Abstract
The invention provides a vehicle stability control method and a system, wherein the method comprises the steps of obtaining a first vehicle parameter; judging the current abnormal state type of the vehicle according to the first vehicle parameter; determining an output steering superposition instruction according to the first vehicle parameter and the current abnormal state type of the vehicle; and generating a torque request of the steering motor according to the output steering superposition command. The invention provides a technical scheme for realizing vehicle stability control based on an electric power steering technology, which can obtain more accurate dynamic response, bring better driving experience and improve the vehicle stability before vehicle braking intervention by combining the electric power steering technology and the vehicle dynamic control technology.
Description
Technical Field
The invention relates to the technical field of vehicles, in particular to a vehicle stability control method and system.
Background
Traditional vehicle stability control systems such as ABS (anti-lock braking system), ESC (vehicle body stability control system) are developed relatively well, and mostly control the braking force of different wheels according to the difference between the driver's expected dynamic response and the actual vehicle dynamic response, so as to change the lateral and longitudinal tracks of the vehicle and achieve the purpose of vehicle steady state control.
The existing vehicle stabilizing system controls the transverse track of a vehicle by applying braking force, because the transverse dynamic control of the vehicle is more sensitive relative to the longitudinal direction, the control difficulty is higher by utilizing the difference of the braking force between different wheels, the sudden change of the yaw angular speed is caused, poor driving feeling is often brought to a driver, and the retardation or the overshoot of the system can be brought when the gradient of the built braking pressure is too large or too slow; it is therefore an effective but not perfect way to achieve lateral control of the vehicle using the difference in braking force between the different wheels.
Disclosure of Invention
The invention aims to provide a vehicle stability control method and system, aiming at solving the problems in the prior art, and optimizing the transverse control of a vehicle and realizing the vehicle stability control based on an electric power steering technology.
The embodiment of the invention provides a vehicle stability control method, which comprises the following steps:
acquiring a first vehicle parameter;
judging the current abnormal state type of the vehicle according to the first vehicle parameter;
determining an output steering superposition instruction according to the first vehicle parameter and the current abnormal state type of the vehicle;
and generating a steering motor torque request for driving the electric power steering motor according to the output steering superposition command.
Optionally, the determining the current abnormal state type of the vehicle according to the first vehicle parameter includes the following steps:
calculating to obtain a second vehicle parameter according to the first vehicle parameter;
and acquiring the judging conditions of the abnormal state types, judging the judging conditions met by the first vehicle parameters and the second vehicle parameters, and determining the abnormal state type corresponding to the met judging conditions as the current abnormal state type of the vehicle.
Optionally, the first vehicle parameter includes a wheel speed of each wheel, a yaw rate, a vehicle speed, a lateral acceleration, a vehicle deceleration, a steering wheel angle, and a steering wheel torque.
Optionally, the second vehicle parameter comprises a Yaw-Rate parameter Yaw Rate of the front axle FA And Yaw Rate parameter Yaw Rate of rear axle RA Yaw Rate parameter Yaw Rate of steering wheel angle SA And Yaw Rate parameter Yaw Rate _ Ay of lateral acceleration;
calculating the second vehicle parameter according to the first vehicle parameter by adopting the following formula:
Yaw Rate SA ＝SA×VS×K 1
wherein, the Wheel Speed FL Indicating the left front Wheel Speed, Wheel Speed FR Indicating the wheel speed, Track, of the right front wheel FA Wheel track of front axle, Wheel Speed RL Indicating the left rear Wheel Speed, Wheel Speed RR Indicating the speed of the right rear wheel, Track RA Representing the track of the rear axle, SA the steering wheel angle, VS the vehicle speed, K 1 Indicating a preset first compensationCoefficient, LA represents lateral acceleration, K 2 Representing a preset second compensation factor.
Optionally, the second vehicle parameter further comprises a corrected wheel speed of each wheel;
the second vehicle parameter is calculated according to the first vehicle parameter, and the method further comprises the following steps:
judging whether the vehicle is in straight line running or not according to the steering wheel rotation angle and the steering wheel torque, and acquiring the wheel speed of each wheel when the vehicle is in straight line running;
the corrected wheel speeds of the respective wheels are determined based on the wheel speeds of the respective wheels when the respective wheels are traveling straight so that the corrected wheel speeds of the respective wheels are the same.
Optionally, the abnormal state type comprises a wheel state abnormality;
the determining the determination conditions that the first vehicle parameter and the second vehicle parameter meet includes determining whether the first vehicle parameter and the second vehicle parameter meet the determination conditions that the wheel state is abnormal, using:
judging whether the front axle and the rear axle are abnormal or not according to the yaw angular velocity parameter of the front axle, the yaw angular velocity parameter of the rear axle and the yaw angular velocity;
if the front axle and/or the rear axle is abnormal, comparing the corrected wheel speed of each wheel, and positioning the wheel with abnormal wheel speed;
and if the front axle and/or the rear axle are abnormal, judging that the first vehicle parameter and the second vehicle parameter accord with the judgment condition of the abnormal wheel state.
Optionally, the steering overlay command comprises a steering torque overlay command and/or a steering angle overlay command;
the step of determining the output steering superposition command according to the first vehicle parameter and the current abnormal state type of the vehicle comprises the following steps:
if the current abnormal state type of the vehicle is abnormal wheel state, determining the wheel with abnormal wheel speed, and judging the tire pressure state of the wheel with abnormal wheel speed according to the comparison between the wheel speed of the wheel with abnormal wheel speed and the wheel speeds of other wheels;
judging the vehicle running state according to the value of the vehicle deceleration;
when the vehicle speed is less than a preset vehicle speed threshold value and the steering wheel angle is less than a preset steering angle threshold value, determining an output steering torque superposition instruction;
and when the vehicle speed is greater than or equal to a preset vehicle speed threshold value and the steering wheel angle is greater than or equal to a preset steering angle threshold value, determining an output steering angle superposition instruction.
Optionally, the exception status type comprises an operating status exception;
the determining the determination conditions that the first vehicle parameter and the second vehicle parameter meet comprises determining whether the first vehicle parameter and the second vehicle parameter meet the determination conditions that the operating state is abnormal by adopting the following steps:
judging whether the steering wheel angle is larger than a steering wheel angle threshold value or not, and determining that the driver is in steering operation if the steering wheel torque is larger than a steering wheel torque threshold value;
when a driver is in steering operation, calculating a difference value between a yaw rate parameter of a steering wheel angle and a yaw rate, and if the absolute value of the difference value is greater than a first threshold value, determining that the vehicle meets the judgment condition of abnormal operation state;
and when the driver is in steering operation, calculating the difference value between the yaw rate parameter of the lateral acceleration and the yaw rate, and if the absolute value of the difference value is greater than a second threshold value, determining that the vehicle meets the judgment condition of the abnormal operation state.
Optionally, the steering overlay command comprises a steering torque overlay command and/or a steering angle overlay command;
the step of determining the output steering superposition command according to the first vehicle parameter and the current abnormal state type of the vehicle comprises the following steps:
and if the current abnormal state type of the vehicle is an abnormal operation state, determining an output steering torque superposition command according to the steering wheel angle, the steering wheel moment and the yaw angular velocity.
Optionally, the abnormal state type includes a road surface state abnormality;
the determining the determination conditions that the first vehicle parameter and the second vehicle parameter meet includes determining whether the first vehicle parameter and the second vehicle parameter meet the determination conditions that the road surface state is abnormal by using the following steps:
judging whether the steering wheel angle and the steering wheel torque are unchanged within a preset time range, and if so, determining that a driver is in steering holding operation;
monitoring a change value of a yaw-rate-related parameter, which includes one or more of a yaw rate detected by a yaw-rate sensor, a calculated yaw-rate parameter of a front axle, and a calculated yaw-rate parameter of a rear axle, over a preset period of time while the driver is in the steering-hold operation, and determining that the vehicle meets a determination condition for a road surface state abnormality if the change value exceeds a third threshold value.
Optionally, the steering overlay command comprises a steering torque overlay command and/or a steering angle overlay command;
the step of determining the output steering superposition command according to the first vehicle parameter and the current abnormal state type of the vehicle comprises the following steps:
if the current abnormal state type of the vehicle is abnormal road surface state, judging whether the vehicle speed is greater than a vehicle speed threshold value, and if the vehicle speed is greater than the vehicle speed threshold value, determining an output steering torque superposition command according to the yaw angular speed and the vehicle speed;
and if the vehicle speed is less than or equal to the vehicle speed threshold value, determining the output steering angle superposition instruction according to the yaw angular speed and the vehicle speed.
Optionally, the generating a steering motor torque request according to the output steering superposition command includes:
determining an operation steering command according to the steering wheel angle and the steering wheel torque;
and generating a steering motor torque request according to the steering command obtained by superposing the output steering superposition command and the operation steering command.
Optionally, after the output steering superposition command and the operation steering command are superposed, the method further includes the following steps:
judging whether the corresponding vehicle speed is greater than a fourth threshold value after the output steering superposition command is superposed with the operation steering command;
and if the vehicle speed is greater than a fourth threshold value, judging whether a steering torque superposition value obtained after the output steering superposition instruction and the operation steering instruction are superposed is greater than a preset torque threshold value, if so, generating a steering motor torque request according to the preset torque threshold value, otherwise, generating the steering motor torque request according to the steering torque superposition value.
The embodiment of the invention also provides a vehicle stability control system which is applied to the vehicle stability control method, and the system comprises the following components:
the vehicle dynamic monitoring module is used for acquiring a first vehicle parameter;
the abnormal state type monitoring module is used for judging the current abnormal state type of the vehicle according to the first vehicle parameter;
the vehicle dynamic suppression module is used for determining an output steering superposition instruction according to the first vehicle parameter and the current abnormal state type of the vehicle;
and the steering request generating module is used for generating a steering motor torque request for driving the electric power-assisted steering motor according to the output steering superposition command.
Optionally, the vehicle dynamic monitoring module is further configured to calculate a second vehicle parameter according to the first vehicle parameter;
the abnormal state type monitoring module is used for acquiring the judgment conditions of each abnormal state type, judging the judgment conditions met by the first vehicle parameter and the second vehicle parameter, and determining the abnormal state type corresponding to the met judgment conditions as the current abnormal state type of the vehicle.
Optionally, the steering request generating module is configured to determine an operation steering instruction according to the steering wheel angle and the steering wheel torque, and after the output steering superposition instruction is superposed with the operation steering instruction, determine whether a corresponding vehicle speed is greater than a fourth threshold;
and if the vehicle speed is greater than a fourth threshold value, judging whether a steering torque superposition value obtained after the output steering superposition instruction and the operation steering instruction are superposed is greater than a preset torque threshold value, if so, generating a steering motor torque request according to the preset torque threshold value, otherwise, generating the steering motor torque request according to the steering torque superposition value.
Optionally, the system further comprises a vehicle lateral control module for sending the steering motor torque request to an electric power assisted steering motor.
The vehicle stability control method and the vehicle stability control system provided by the invention have the following advantages:
the invention provides a technical scheme for realizing vehicle stability control based on an electric power steering technology, which can obtain more accurate dynamic response by combining the electric power steering technology and the vehicle dynamic control technology, bring better driving experience, improve the vehicle stability before vehicle braking intervention and is suitable for large-scale popularization and application.
Drawings
Other features, objects and advantages of the present invention will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, with reference to the accompanying drawings.
FIG. 1 is a flow chart of a vehicle stability control method according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a vehicle stability control system according to an embodiment of the present invention;
FIG. 3 is an input/output diagram of a vehicle stability control system according to an embodiment of the present invention
FIG. 4 is a schematic input/output diagram of a vehicle dynamics monitoring module according to an embodiment of the present invention;
fig. 5 is an input/output schematic diagram of an abnormal hit-monitoring module according to an embodiment of the invention.
Fig. 6 is a flowchart of the wheel state abnormality determination according to the embodiment of the invention;
FIG. 7 is a flow chart of an operational state anomaly determination according to an embodiment of the present invention;
fig. 8 is a flowchart of the road surface condition abnormality determination according to the embodiment of the present invention.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their repetitive description will be omitted.
As shown in fig. 1, in order to solve the technical problems in the prior art, the present invention provides a vehicle stability control method, including the steps of:
s100: acquiring a first vehicle parameter;
s200: judging the current abnormal state type of the vehicle according to the first vehicle parameter;
s300: determining an output steering superposition command according to the first vehicle parameter and the current abnormal state type of the vehicle, wherein the steering superposition command comprises a steering torque superposition command and/or a steering angle superposition command;
s400: and generating a steering motor torque request for driving the electric power steering motor according to the output steering superposition command.
Therefore, the vehicle stability control method of the present invention provides a technical solution for realizing vehicle stability control based on an electric power steering technology, and the abnormal state type of the vehicle are identified through the steps S100 and S200, and the steering motor torque request capable of driving the electric power steering motor is generated according to the abnormal state type through the steps S300 and S400, so that a more accurate dynamic response can be obtained by combining the electric power steering technology and the vehicle dynamic control technology, the vehicle stability before vehicle braking intervention is improved, and better driving experience is brought.
As shown in fig. 2, the present invention also provides a vehicle stability control system, the system comprising:
a vehicle dynamic monitoring module M100, configured to obtain a first vehicle parameter, that is, execute the step S100;
an abnormal state type monitoring module M200, configured to determine a current abnormal state type of the vehicle according to the first vehicle parameter, that is, execute the step S200;
the vehicle dynamic suppression module M300 is configured to determine an output steering superposition command according to the first vehicle parameter and a current abnormal state type of the vehicle, where the steering superposition command includes a steering torque superposition command and/or a steering angle superposition command, that is, execute the step S300;
and a steering request generating module M400, configured to generate a steering motor torque request for driving the electric power steering motor according to the output steering superposition command, that is, to execute the step S400.
Further, in this embodiment, the vehicle stability control system may further include a vehicle lateral control module M500 for sending the steering motor torque request to the electric power steering motor.
Therefore, the vehicle stability control system of this embodiment recognizes the abnormal state and the abnormal state type of the vehicle through the vehicle dynamic monitoring module M100 and the abnormal state type monitoring module M200, generates the steering motor torque request that can drive the electric power steering motor according to the abnormal state type through the vehicle dynamic suppression module M300 and the steering request generation module M400, and can transmit the steering motor torque request to the electric power steering motor through the vehicle lateral control module M500, so that it is possible to obtain a more accurate dynamic response in combination with the electric power steering technology and the vehicle dynamic control technology, and improve the vehicle stability before the vehicle brake intervention.
The vehicle stability control system of the present invention may be directly disposed inside the electric power steering system, for example, in an electronic control unit of the electric power steering system, and the first vehicle parameter may be directly obtained from each existing sensor of the vehicle without adding additional hardware devices. However, the present invention is not limited thereto, and in other embodiments, the vehicle stability control system may be provided in other systems, or a single electronic control unit may be provided to perform the functions of the vehicle stability control system, and the like, and all of them fall within the protection scope of the present invention.
As shown in fig. 3, this embodiment is a schematic input/output diagram of the vehicle stability control system. On the left side of the vehicle stability control system, there is a first vehicle parameter, in this embodiment, the first vehicle parameter includes wheel speeds (left front wheel speed, right front wheel speed, left rear wheel speed, and right rear wheel speed) of each wheel, yaw rate, vehicle speed, lateral acceleration, vehicle deceleration, steering wheel angle, and steering wheel torque, and on the right side of the vehicle stability control system, there is a component for receiving an output command, mainly including an electric power steering motor and a vehicle human-computer interaction system, configured to perform a power steering action according to a steering motor torque request. When the vehicle detects an abnormal state, reminding information can be sent to a driver through a vehicle human-machine interaction system (HMI).
In this embodiment, in the step S200, the following steps are adopted to determine the current abnormal state type of the vehicle according to the first vehicle parameter:
the vehicle dynamic monitoring module M100 calculates a second vehicle parameter according to the first vehicle parameter;
the abnormal state type monitoring module M200 obtains the determination conditions of each abnormal state type, determines the determination conditions that the first vehicle parameter and the second vehicle parameter meet, and determines the abnormal state type corresponding to the determination conditions that meet as the current abnormal state type of the vehicle.
As shown in fig. 4, in this embodiment, the second vehicle parameter includes the Yaw-Rate parameter Yaw Rate of the front axle FA And Yaw Rate parameter Yaw Rate of rear axle RA Yaw Rate parameter Yaw Rate of steering wheel angle SA And a Yaw-Rate parameter Yaw Rate _ Ay of lateral acceleration.
Calculating the second vehicle parameter according to the first vehicle parameter by adopting the following formula:
Yaw Rate SA ＝SA×VS×K 1
wherein, the Wheel Speed FL Indicating the left front Wheel Speed, Wheel Speed FR Indicating the right front wheel speed, Track FA Wheel track of front axle, Wheel Speed RL Indicating the left rear Wheel Speed, Wheel Speed RR Indicating the speed of the right rear wheel, Track RA Representing the track of the rear axle, SA the steering wheel angle, VS the vehicle speed, K 1 Representing a preset first compensation factor, LA representing lateral acceleration, K 2 Representing a preset second compensation factor.
Further, the second vehicle parameter further comprises a corrected wheel speed for each wheel: a corrected wheel speed of the left front wheel, a corrected wheel speed of the right front wheel, a corrected wheel speed of the left rear wheel, and a corrected wheel speed of the right rear wheel.
The second vehicle parameter is calculated according to the first vehicle parameter, and the method further comprises the following steps:
judging whether the vehicle is in straight line running or not according to the steering wheel rotation angle and the steering wheel torque, and acquiring the wheel speed of each wheel when the vehicle is in straight line running;
the corrected wheel speeds of the respective wheels are determined based on the wheel speeds of the respective wheels at the time of straight running so that the corrected wheel speeds of the respective wheels are the same.
When the steering wheel angle is 0 degree, namely the middle position, and the driver does not apply force on the steering wheel, the steering wheel torque is smaller than a certain value, the system is defined as straight line driving, and the rotating speeds of all wheels are reasonably the same. Therefore, whether the wheel speeds of all the wheels are consistent or not is judged, if the wheel speeds of all the four wheels are very close, the states of all the wheels are normal, and the corrected wheel speed is determined as the common wheel speed of all the four wheels. If one of the wheels has a wheel speed that is greatly different from the other three wheels, the corrected wheel speed of the wheel having the large difference is also set based on the wheel speeds of the other three wheels.
As shown in fig. 5, in this embodiment, the abnormal state types include a wheel state abnormality, an operation state abnormality, and a road surface state abnormality. The present invention is not limited thereto, and in other alternative embodiments, the abnormal state type may include other types of abnormal states, or include only one or two of the wheel state abnormality, the operation state abnormality, and the road surface state abnormality.
As shown in fig. 6, in this embodiment, the determination of the determination conditions that the first vehicle parameter and the second vehicle parameter meet includes the abnormal state type monitoring module M200 determining whether the first vehicle parameter and the second vehicle parameter meet the determination conditions that the wheel state is abnormal by:
judging whether the front axle and the rear axle are abnormal or not according to the yaw velocity parameter of the front axle, the yaw velocity parameter of the rear axle and the yaw velocity;
according to the Ackerman's corner principle, the yaw velocity of the front and rear axles can be calculated by the left and right wheels of the front and rear axles, and the yaw velocity sensor mounted on the vehicle is compared to judge which axle has a problem in calculation. Specifically, comparing a yaw velocity parameter and a yaw velocity of the front axle, if the difference is greater than a preset yaw difference threshold value, judging that the front axle is abnormal, comparing the yaw velocity parameter and the yaw velocity of the rear axle, and if the difference is greater than the preset yaw difference threshold value, judging that the rear axle is abnormal;
if the front axle and/or the rear axle is abnormal, comparing the corrected wheel speeds of all the wheels, and positioning the wheels with abnormal wheel speeds; specifically, the actual wheel speed and the corrected wheel speed of each wheel may be compared, if the actual wheel speed and the corrected wheel speed of one wheel are greatly different, it is indicated that the wheel is abnormal, when the current axle is abnormal, the wheel speed of the wheel after the corrected wheel speed is determined accurately, when the rear axle is abnormal, the corrected wheel speed of the wheel before the corrected wheel speed is determined accurately, the corrected wheel speeds of the four wheels are all the same, the actual wheel speeds may be different, and the wheel with the actual wheel speed and the corrected wheel speed greatly different is an abnormal wheel;
and if the front axle and/or the rear axle are abnormal, judging that the first vehicle parameter and the second vehicle parameter accord with the judgment condition of the abnormal wheel state.
In this embodiment, the vehicle dynamics suppression module M300 determines the output steering superposition command according to the first vehicle parameter and the current abnormal state type of the vehicle by adopting the following steps:
if the current abnormal state type of the vehicle is abnormal wheel state, determining the wheel with abnormal wheel speed, and judging the tire pressure state of the wheel with abnormal wheel speed according to the comparison between the wheel speed of the wheel with abnormal wheel speed and the wheel speeds of other wheels;
specifically, the tire pressure status of the wheel with abnormal wheel speed can be determined by comparing the wheel with other wheel speeds, for example, calculating the average value of the abnormal speed wheel/normal wheel speed as W, determining the tire pressure of the wheel with abnormal wheel speed according to the magnitude of W, when the W value is in the first range, the tire has a flat tire failure, when the W value is in the second range, the tire has an air leakage failure, etc.
Judging the running state of the vehicle (acceleration running, deceleration running and constant speed running) according to the value of the deceleration of the vehicle;
when the vehicle dynamics is small, determining an output steering torque superposition command, wherein the small vehicle dynamics means that the vehicle speed is less than a set vehicle speed threshold value and the steering wheel steering angle is less than a set steering angle threshold value;
when the vehicle dynamic is large, the output steering angle superposition command is determined, wherein the vehicle dynamic is that the vehicle speed is greater than or equal to a set vehicle speed threshold value or the steering wheel angle is greater than or equal to a set steering angle threshold value.
When the output steering torque superposition command and the output steering angle superposition command are determined, the corresponding output value can be determined according to a preset adaptive model (for example, a PID model with preset model parameters and the like), or a simple table look-up can be carried out, namely a mapping relation table between at least part of preset first vehicle parameters and second vehicle parameters and the steering torque superposition command or a mapping relation table between at least part of preset first vehicle parameters and second vehicle parameters and the steering angle superposition command is looked up. Specifically, when the wheel state is abnormal, a table can be looked up according to the position of the abnormal wheel, the tire pressure condition of the abnormal wheel and the vehicle running state to obtain a corresponding steering torque superposition command or steering angle superposition command.
As shown in fig. 7, in this embodiment, the determination that the first vehicle parameter and the second vehicle parameter meet the determination condition includes the abnormal state monitoring module M200 determining whether the first vehicle parameter and the second vehicle parameter meet the determination condition that the operating state is abnormal by:
judging whether the steering wheel angle is larger than a steering wheel angle threshold value or not, and determining that the driver is in steering operation if the steering wheel torque is larger than a steering wheel torque threshold value;
when a driver is in steering operation, calculating a difference value between a yaw rate parameter of a steering wheel angle and a yaw rate, and if the absolute value of the difference value is greater than a first threshold value, determining that the vehicle meets the judgment condition of abnormal operation state, which indicates that the problem of insufficient steering exists;
and when the driver is in steering operation, calculating the difference value between the yaw rate parameter of the lateral acceleration and the yaw rate, and if the absolute value of the difference value is greater than a second threshold value, determining that the vehicle meets the judgment condition of abnormal operation state, which indicates that the problem of oversteer exists.
The vehicle dynamic suppression module M300 determines the output steering superposition command according to the first vehicle parameter and the current abnormal state type of the vehicle by adopting the following steps:
and if the current abnormal state type of the vehicle is the abnormal operation state, determining an output steering torque superposition command according to the steering wheel rotating angle, the steering wheel moment and the yaw angular velocity.
When the output steering torque superposition command and the output steering angle superposition command are determined, the corresponding output value can be determined according to a preset adaptive model (for example, a PID model with preset model parameters and the like), or a simple table look-up can be carried out, namely a mapping relation table between at least part of preset first vehicle parameters and second vehicle parameters and the steering torque superposition command or a mapping relation table between at least part of preset first vehicle parameters and second vehicle parameters and the steering angle superposition command is looked up. Specifically, when the operation state is abnormal, the steering torque superimposition command or the steering angle superimposition command to be output may be determined by looking up a table according to parameters such as whether the operation state is abnormal or abnormal, a difference between a yaw rate parameter of a steering wheel angle and a yaw rate, a difference between a yaw rate parameter of a lateral acceleration and a yaw rate, and the like.
As shown in fig. 8, the determining the determination conditions that the first vehicle parameter and the second vehicle parameter meet includes the abnormal state type monitoring module M200 determining whether the first vehicle parameter and the second vehicle parameter meet the determination conditions that the road surface state is abnormal by:
judging whether the steering wheel angle and the steering wheel torque are unchanged within a preset time range, and if so, determining that a driver is in steering holding operation;
monitoring a change value of a yaw-rate-related parameter, which includes one or more of a yaw rate detected by a yaw-rate sensor, a calculated yaw-rate parameter of a front axle, and a calculated yaw-rate parameter of a rear axle, over a preset period of time while the driver is in the steering-hold operation, and determining that the vehicle meets a determination condition for a road surface state abnormality if the change value exceeds a third threshold value.
In this embodiment, the vehicle dynamics suppression module M300 determines the output steering superposition command according to the first vehicle parameter and the current abnormal state type of the vehicle by adopting the following steps:
if the current abnormal state type of the vehicle is abnormal road surface state, judging whether the vehicle speed is greater than a vehicle speed threshold value, and if the vehicle speed is greater than the vehicle speed threshold value, determining an output steering torque superposition instruction according to the yaw angular speed and the vehicle speed;
and if the vehicle speed is less than or equal to the vehicle speed threshold value, determining the output steering angle superposition command according to the yaw angular speed and the vehicle speed. The vehicle speed threshold value can be preset according to the chassis structure and characteristics of different vehicles.
When the output steering torque superposition command and the output steering angle superposition command are determined, the corresponding output value can be determined according to a preset adaptive model (for example, a PID model with preset model parameters and the like), or a simple table look-up can be carried out, namely a mapping relation table between at least part of preset first vehicle parameters and second vehicle parameters and the steering torque superposition command or a mapping relation table between at least part of preset first vehicle parameters and second vehicle parameters and the steering angle superposition command is looked up. Specifically, when there is a road surface abnormality, a table may be looked up according to a change value of a yaw rate-related parameter, and a corresponding steering torque superposition command and a corresponding steering angle superposition command may be determined.
In this embodiment, the generating a steering motor torque request according to the output steering superposition command includes:
determining an operation steering command according to the steering wheel angle and the steering wheel torque, wherein the operation steering command can be determined by the electric power steering system according to the input of the steering wheel;
and generating a steering motor torque request according to the steering command obtained by superposing the output steering superposition command and the operation steering command.
In this embodiment, after the outputted steering superposition command is superposed with the operated steering command, the method further includes a step of limiting the maximum value of the steering motor torque according to the vehicle speed, so as to avoid applying an excessive steering motor torque when the vehicle speed is high, specifically including the steps of:
after the output steering superposition command is superposed with the operation steering command, judging whether the corresponding vehicle speed is greater than a fourth threshold value;
if yes, the maximum value of the steering motor torque after superposition is set as a preset steering torque threshold value, and the steering motor torque is limited.
Specifically, under the condition that the vehicle speed is greater than a fourth threshold value, whether a steering torque superposition value obtained after the output steering superposition instruction and the operation steering instruction are superposed is greater than a preset torque threshold value or not is judged, if yes, a steering motor torque request is generated according to the preset torque threshold value, and otherwise, the steering motor torque request is generated according to the steering torque superposition value.
The steering motor torque request is generated according to the preset torque threshold, the steering torque superposition value can be reduced by multiplying the steering torque superposition value by a corresponding coefficient according to the limitation of the preset torque threshold, the coefficient can be obtained by table look-up, and the steering torque value in the steering motor torque request can also be directly set as the preset torque threshold.
In summary, compared with the prior art, the invention provides a technical scheme for realizing vehicle stability control based on an electric power steering technology, and by combining the electric power steering technology and a vehicle dynamic control technology, more accurate dynamic response can be obtained, better driving experience is brought, the vehicle stability before vehicle braking intervention is improved, and the invention is suitable for large-scale popularization and application.
The foregoing is a more detailed description of the present invention in connection with specific preferred embodiments, and it is not to be construed that the specific embodiments of the present invention are limited to those descriptions. It will be apparent to those skilled in the art that various modifications, additions and substitutions can be made without departing from the spirit of the invention.
Claims (14)
1. A vehicle stability control method characterized by comprising the steps of:
acquiring a first vehicle parameter;
judging the current abnormal state type of the vehicle according to the first vehicle parameter;
determining an output steering superposition instruction according to the first vehicle parameter and the current abnormal state type of the vehicle;
generating a steering motor torque request for driving an electric power steering motor according to the output steering superposition command;
the method for generating the torque request of the steering motor according to the output steering superposition command comprises the following steps:
determining an operation steering command according to the steering wheel angle and the steering wheel torque;
generating a steering motor torque request according to the steering instruction after the output steering superposition instruction and the operation steering instruction are superposed;
after the output steering superposition command and the operation steering command are superposed, the method further comprises the following steps:
judging whether the corresponding vehicle speed is greater than a fourth threshold value or not after the output steering superposition instruction is superposed with the operation steering instruction;
and if the vehicle speed is greater than a fourth threshold value, judging whether a steering torque superposition value obtained after the output steering superposition instruction and the operation steering instruction are superposed is greater than a preset torque threshold value, if so, generating a steering motor torque request according to the preset torque threshold value, otherwise, generating the steering motor torque request according to the steering torque superposition value.
2. The vehicle stability control method according to claim 1, wherein the determining a current abnormal state type of the vehicle according to the first vehicle parameter includes the steps of:
calculating to obtain a second vehicle parameter according to the first vehicle parameter;
and acquiring the judging conditions of the abnormal state types, judging the judging conditions met by the first vehicle parameters and the second vehicle parameters, and determining the abnormal state type corresponding to the meeting judging conditions as the current abnormal state type of the vehicle.
3. The vehicle stability control method according to claim 2, characterized in that the first vehicle parameters include wheel speeds of the respective wheels, yaw rate, vehicle speed, lateral acceleration, vehicle deceleration, steering wheel angle, and steering wheel torque.
4. The vehicle stability control method according to claim 3, wherein the second vehicle parameter includes a Yaw-Rate parameter Yaw Rate of a front axle FA And a Yaw Rate parameter Yaw Rate of the rear axle RA Yaw Rate parameter Yaw Rate of steering wheel angle SA And Yaw Rate parameter Yaw Rate _ Ay of lateral acceleration;
calculating the second vehicle parameter according to the first vehicle parameter by adopting the following formula:
Yaw Rate SA ＝SA×VS×K 1
wherein, the Wheel Speed FL Indicating the left front Wheel Speed, Wheel Speed FR Indicating the wheel speed, Track, of the right front wheel FA Wheel track of front axle, Wheel Speed RL Indicating the left rear Wheel Speed, Wheel Speed RR Indicating the speed of the right rear wheel, Track RA Representing the track of the rear axle, SA the steering wheel angle, VS the vehicle speed, K 1 Representing a preset first compensation factor, LA representing lateral acceleration, K 2 Representing a preset second compensation factor.
5. The vehicle stability control method according to claim 4, wherein the second vehicle parameter further includes corrected wheel speeds of the respective wheels;
the second vehicle parameter is calculated according to the first vehicle parameter, and the method further comprises the following steps:
judging whether the vehicle is in straight line running or not according to the steering wheel rotation angle and the steering wheel torque, and acquiring the wheel speed of each wheel when the vehicle is in straight line running;
the corrected wheel speeds of the respective wheels are determined based on the wheel speeds of the respective wheels at the time of straight running so that the corrected wheel speeds of the respective wheels are the same.
6. The vehicle stability control method according to claim 5, characterized in that the abnormal state type includes a wheel state abnormality;
the determining the determination conditions that the first vehicle parameter and the second vehicle parameter meet includes determining whether the first vehicle parameter and the second vehicle parameter meet the determination conditions that the wheel state is abnormal, using:
judging whether the front axle and the rear axle are abnormal or not according to the yaw velocity parameter of the front axle, the yaw velocity parameter of the rear axle and the yaw velocity;
if the front axle and/or the rear axle is abnormal, comparing the corrected wheel speeds of all the wheels, and positioning the wheels with abnormal wheel speeds;
and if the front axle and/or the rear axle are abnormal, determining that the first vehicle parameter and the second vehicle parameter accord with the determination condition of the abnormal wheel state.
7. The vehicle stability control method according to claim 6, characterized in that the steering superimposition command includes a steering torque superimposition command and/or a steering angle superimposition command;
the step of determining the output steering superposition command according to the first vehicle parameter and the current abnormal state type of the vehicle comprises the following steps:
if the current abnormal state type of the vehicle is abnormal wheel state, determining the wheel with abnormal wheel speed, and judging the tire pressure state of the wheel with abnormal wheel speed according to the comparison between the wheel speed of the wheel with abnormal wheel speed and the wheel speeds of other wheels;
judging the vehicle running state according to the value of the vehicle deceleration;
when the vehicle speed is less than a preset vehicle speed threshold and the steering wheel angle is less than a preset steering angle threshold, determining an output steering torque superposition instruction;
and when the vehicle speed is greater than or equal to a preset vehicle speed threshold value and the steering wheel angle is greater than or equal to a preset steering angle threshold value, determining an output steering angle superposition instruction.
8. The vehicle stability control method according to claim 5, characterized in that the abnormal state type includes an operation state abnormality;
the determining the determination conditions that the first vehicle parameter and the second vehicle parameter meet comprises determining whether the first vehicle parameter and the second vehicle parameter meet the determination conditions that the operating state is abnormal by adopting the following steps:
judging whether the steering wheel angle is larger than a steering wheel angle threshold value or not, and determining that the driver is in steering operation if the steering wheel torque is larger than a steering wheel torque threshold value;
when a driver is in steering operation, calculating a difference value between a yaw rate parameter of a steering wheel angle and a yaw rate, and if the absolute value of the difference value is greater than a first threshold value, determining that the vehicle meets the judgment condition of abnormal operation state;
and when the driver is in steering operation, calculating the difference value between the yaw rate parameter of the lateral acceleration and the yaw rate, and if the absolute value of the difference value is greater than a second threshold value, determining that the vehicle meets the judgment condition of the abnormal operation state.
9. The vehicle stability control method according to claim 8, characterized in that the steering superimposition command includes a steering torque superimposition command and/or a steering angle superimposition command;
the step of determining the output steering superposition command according to the first vehicle parameter and the current abnormal state type of the vehicle comprises the following steps:
and if the current abnormal state type of the vehicle is abnormal in the operation state, determining an output steering torque superposition command according to the steering wheel angle, the steering wheel torque and the yaw angular velocity.
10. The vehicle stability control method according to claim 5, characterized in that the abnormal state type includes a road surface state abnormality;
the determination condition that the first vehicle parameter and the second vehicle parameter meet comprises the following steps:
judging whether the steering wheel angle and the steering wheel torque are not changed within a preset time range, and if so, determining that a driver is in steering holding operation;
monitoring a change value of a yaw-rate-related parameter, which includes one or more of a yaw rate detected by a yaw-rate sensor, a calculated yaw-rate parameter of a front axle, and a calculated yaw-rate parameter of a rear axle, over a preset period of time while the driver is in the steering-hold operation, and determining that the vehicle meets a determination condition for a road surface state abnormality if the change value exceeds a third threshold value.
11. The vehicle stability control method according to claim 10, characterized in that the steering superimposition command includes a steering torque superimposition command and/or a steering angle superimposition command;
the step of determining the output steering superposition command according to the first vehicle parameter and the current abnormal state type of the vehicle comprises the following steps:
if the current abnormal state type of the vehicle is abnormal road surface state, judging whether the vehicle speed is greater than a vehicle speed threshold value, and if the vehicle speed is greater than the vehicle speed threshold value, determining an output steering torque superposition command according to the yaw angular speed and the vehicle speed;
and if the vehicle speed is less than or equal to the vehicle speed threshold value, determining the output steering angle superposition instruction according to the yaw angular speed and the vehicle speed.
12. A vehicle stability control system characterized by being applied to the vehicle stability control method according to any one of claims 1 to 11, the system comprising:
the vehicle dynamic monitoring module is used for acquiring a first vehicle parameter;
the abnormal state type monitoring module is used for judging the current abnormal state type of the vehicle according to the first vehicle parameter;
the vehicle dynamic suppression module is used for determining an output steering superposition instruction according to the first vehicle parameter and the current abnormal state type of the vehicle;
the steering request generating module is used for generating a steering motor torque request for driving an electric power-assisted steering motor according to the output steering superposition command;
the steering request generating module is further used for determining an operation steering instruction according to the steering wheel angle and the steering wheel torque, and judging whether the corresponding vehicle speed is greater than a fourth threshold value or not after the output steering superposition instruction and the operation steering instruction are superposed;
and if the vehicle speed is greater than a fourth threshold value, judging whether a steering torque superposition value obtained after the output steering superposition instruction and the operation steering instruction are superposed is greater than a preset torque threshold value, if so, generating a steering motor torque request according to the preset torque threshold value, otherwise, generating the steering motor torque request according to the steering torque superposition value.
13. The vehicle stability control system of claim 12, wherein the vehicle dynamics monitoring module is further configured to calculate a second vehicle parameter from the first vehicle parameter;
the abnormal state type monitoring module is used for acquiring the judgment conditions of each abnormal state type, judging the judgment conditions met by the first vehicle parameter and the second vehicle parameter, and determining the abnormal state type corresponding to the met judgment conditions as the current abnormal state type of the vehicle.
14. The vehicle stability control system of claim 12, further comprising a vehicle lateral control module to send the steering motor torque request to an electric power steering motor.
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