CN119459871A

CN119459871A - A rear wheel control method, system and vehicle

Info

Publication number: CN119459871A
Application number: CN202411673980.1A
Authority: CN
Inventors: 蔡其书; 赵晓松
Original assignee: Jiangsu Zhiyu Automobile Technology Co ltd
Current assignee: Jiangsu Zhiyu Automobile Technology Co ltd
Priority date: 2024-11-21
Filing date: 2024-11-21
Publication date: 2025-02-18

Abstract

The present application provides a rear wheel control method, system and vehicle, belonging to the field of vehicle technology. The rear wheel control method includes: obtaining the driving condition of the vehicle and the expected yaw torque of the vehicle at the current moment, wherein the driving condition includes a tire blowout condition or a stable condition; determining a target parameter corresponding to the driving condition from a first parameter and a second parameter used to determine the yaw torque; determining the actual yaw torque of the vehicle at the current moment based on the target parameter; and controlling the rear wheel deflection of the vehicle based on the difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment. The present application determines the actual yaw torque through different target parameters under different driving conditions, so that the rear wheel deflection response rate of the vehicle changes with different driving conditions, thereby achieving the technical effect of adapting the rear wheel deflection response rate to different driving conditions of the vehicle.

Description

Rear wheel control method and system and vehicle

Technical Field

The application relates to the technical field of vehicles, in particular to a rear wheel control method and system and a vehicle.

Background

The rear wheels are wheels located on the rear side of the vehicle, and generally do not have an active steering function. However, with the development of technology, in order to improve the steering flexibility and the stability of the vehicle body, the rear wheels can deflect to a certain extent according to different running conditions of the vehicle.

In the related art, when the vehicle turns or a tire burst occurs during normal running, in order to secure the stability of the vehicle, the yaw of the rear wheels is controlled according to the actual yaw torque of the vehicle. However, since the vehicle is steered during normal running and a tire burst occurs, respectively, the required rear wheel yaw response rates are different. Therefore, the rear wheel control method in the related art cannot meet the requirements of the vehicle on the rear wheel deflection response rate under different working conditions.

Disclosure of Invention

Based on the above, the application provides a control method and a control system for rear wheels and a vehicle, so as to solve the problem of how to adapt the yaw response rate of the rear wheels to different working conditions of the vehicle.

In a first aspect of an embodiment of the present application, there is provided a control method of a rear wheel, the method being applied to a rear wheel steering system including a yaw rate sensor, the method including:

Acquiring a running condition of a vehicle and an expected yaw torque of the vehicle at the current moment, wherein the running condition comprises a tire burst condition or a stable condition;

Determining a target parameter corresponding to the driving condition from a first parameter and a second parameter for determining yaw torque, wherein the first parameter comprises driving torque and braking torque of the vehicle, and the second parameter comprises actual yaw rate acquired by the yaw rate sensor;

Determining an actual yaw torque of the vehicle at the current moment based on the target parameter;

and controlling the rear wheel deflection of the vehicle based on the difference between the actual yaw torque at the current time and the expected yaw torque at the current time.

Optionally, the determining a target parameter corresponding to the driving condition from the first parameter and the second parameter for determining the yaw torque includes:

Under the condition that the driving working condition is the tire burst working condition, determining the target parameter as the first parameter;

and under the condition that the driving working condition is the stable working condition, determining the target parameter as the second parameter.

Optionally, the target parameter includes the first parameter, and the determining, based on the target parameter, an actual yaw torque of the vehicle at the current moment includes:

Respectively acquiring state parameters of a plurality of wheels, wherein the state parameters comprise moment of inertia, cornering stiffness and cornering angle;

Determining longitudinal forces respectively applied to the plurality of wheels based on the braking torque, the driving torque and the moment of inertia of the plurality of wheels, and determining lateral forces respectively applied to the plurality of wheels based on the slip angles and the slip stiffness of the plurality of wheels;

And determining the actual yaw torque at the current moment based on the lateral force and the longitudinal force respectively applied to the plurality of wheels.

Optionally, the step of obtaining the moment of inertia and the cornering stiffness includes:

Acquiring the tire pressure of the wheel;

based on the tire pressure of the wheel, the moment of inertia and cornering stiffness of the wheel are determined.

Optionally, the target parameter includes the second parameter, and the determining, based on the target parameter, an actual yaw torque of the vehicle at the current moment includes:

Determining an actual yaw rate acceleration of the vehicle at the current time based on actual yaw rates acquired by the yaw rate sensor at the current time and a plurality of historical times before the current time;

and determining the actual yaw torque at the current moment based on the actual yaw acceleration.

Optionally, the step of obtaining the desired yaw torque at the current moment includes:

Acquiring an actual turning angle of a steering wheel at the current moment and an actual vehicle speed of a vehicle at the current moment;

And determining the expected yaw torque at the current moment based on the actual rotation angle at the current moment and the actual vehicle speed at the current moment.

Optionally, the step of acquiring the driving condition of the vehicle includes:

determining a difference between a desired yaw torque of the vehicle before the current time and an actual yaw torque of the vehicle before the current time;

under the condition that the difference value is smaller than or equal to a preset threshold value, determining the driving working condition as the stable working condition;

and under the condition that the difference value is larger than the preset threshold value, acquiring the rotating speed of the steering wheel, and determining the driving working condition based on the rotating speed of the steering wheel.

Optionally, the controlling the rear wheel yaw of the vehicle based on a difference between the actual yaw torque at the current time and the desired yaw torque at the current time includes:

determining a desired steering angle of the rear wheels based on a difference between the actual yaw torque at the current time and the desired yaw torque at the current time;

controlling the rear wheels to deflect to the desired steering angle.

In a second aspect of the embodiment of the present application, there is provided a control system for rear wheels, the control system being applied to a rear wheel steering system including a yaw rate sensor, the control system including:

the system comprises an acquisition module, a control module and a control module, wherein the acquisition module is used for acquiring the running working condition of a vehicle and the expected yaw torque of the vehicle at the current moment, and the running working condition comprises a tire burst working condition or a stable working condition;

The determining module is used for determining target parameters corresponding to the driving working conditions from first parameters and second parameters used for determining yaw torque, wherein the first parameters comprise driving torque and braking torque of the vehicle, and the second parameters comprise actual yaw rate acquired by the yaw rate sensor;

the decision module is used for determining the actual yaw torque of the vehicle at the current moment based on the target parameter;

and the execution module is used for controlling the rear wheel deflection of the vehicle based on the difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment.

A third aspect of the embodiment of the present application provides a vehicle, which includes the control system for a rear wheel according to the second aspect of the embodiment of the present application, or includes a control module, where the control module is configured to implement the steps of the method for controlling a rear wheel according to the first aspect of the embodiment.

The application provides a control method, a system and a vehicle of rear wheels, wherein the method comprises the steps of obtaining a driving condition of the vehicle and an expected yaw torque of the vehicle at the current moment, determining a target parameter corresponding to the driving condition from first parameters and second parameters used for determining the yaw torque, wherein the first parameters comprise driving torque and braking torque of the vehicle, the second parameters comprise actual yaw rate acquired by a yaw rate sensor, determining the actual yaw torque of the vehicle at the current moment based on the target parameters, and controlling the rear wheel deflection of the vehicle based on the difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment.

According to the application, the target parameter corresponding to the driving condition is determined from the first parameter and the second parameter through the driving condition of the vehicle. And then, according to different target parameters, determining the actual yaw torque of the vehicle at the current moment, and further controlling the rear wheel deflection of the vehicle according to the difference between the actual yaw torque at the current moment and the expected yaw torque. The actual yaw torque is determined based on the driving torque and the braking torque, and can be calculated by only using the driving torque at the current moment and the braking torque at the current moment. But the actual yaw moment is determined based on the actual yaw rate, a plurality of acquisitions by the yaw rate sensor are required. Therefore, the rear wheel yaw response rate when the rear wheel control is performed based on the first parameter is faster than the rear wheel yaw response rate when the rear wheel control is performed based on the second parameter. Therefore, the application determines the actual yaw torque through different target parameters under different driving conditions, so that the yaw response rate of the rear wheels of the vehicle changes along with the different driving conditions, and the technical effect of adapting the yaw response rate of the rear wheels to the different driving conditions of the vehicle is realized.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments of the present application will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a step diagram of a method for controlling a rear wheel according to an embodiment of the present application;

FIG. 2 is a diagram of the steps of a method for determining an actual yaw torque based on a first parameter provided by an embodiment of the present application;

FIG. 3 is a step diagram of a method for determining moment of inertia and yaw stiffness according to an embodiment of the present application;

FIG. 4 is a diagram of steps in a method for determining an actual yaw torque based on a second parameter provided by an embodiment of the present application;

FIG. 5 is a diagram of the steps of a method for obtaining a desired yaw torque provided by an embodiment of the present application;

FIG. 6 is a step diagram of a method for acquiring driving conditions according to an embodiment of the present application;

FIG. 7 is a diagram of the steps of a method for controlling rear wheel deflection based on a desired steering angle provided by an embodiment of the present application;

FIG. 8 is a flowchart of a method for controlling a rear wheel according to an embodiment of the present application;

fig. 9 is a schematic structural diagram of a control system for a rear wheel according to an embodiment of the present application.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Based on the above, in order to solve the problem of adapting the yaw response rate of the rear wheel to different working conditions of the vehicle, the application provides a control method and a control system of the rear wheel and the vehicle. And then, according to different target parameters, determining the actual yaw torque of the vehicle at the current moment, and further controlling the rear wheel deflection of the vehicle according to the difference between the actual yaw torque at the current moment and the expected yaw torque. The actual yaw torque is determined based on the driving torque and the braking torque, and can be calculated by only using the driving torque at the current moment and the braking torque at the current moment. But the actual yaw moment is determined based on the actual yaw rate, a plurality of acquisitions by the yaw rate sensor are required. Therefore, the rear wheel yaw response rate when the rear wheel control is performed based on the first parameter is faster than the rear wheel yaw response rate when the rear wheel control is performed based on the second parameter. Therefore, the application determines the actual yaw torque through different target parameters under different driving conditions, so that the yaw response rate of the rear wheels of the vehicle changes along with the different driving conditions, and the technical effect of adapting the yaw response rate of the rear wheels to the different driving conditions of the vehicle is realized. The specific method comprises the following steps:

The first aspect of the present application proposes an embodiment, as shown in a step chart of a control method of a rear wheel shown in fig. 1, the method being applied to a rear wheel steering system including a yaw rate sensor, and being specifically applied to a controller of the rear wheel steering system. Yaw rate sensors are used to acquire the yaw rate of the vehicle, which is the rate at which the vehicle rotates in a lateral direction about its centroid, typically expressed in degrees per unit of time. The yaw rate sensor may be classified into a gyro type angular rate sensor, a hall type angular rate sensor, a capacitance type angular rate sensor, and the like according to the principle of collection.

The method mainly comprises the following steps:

step S101, acquiring the running condition of a vehicle and the expected yaw torque of the vehicle at the current moment.

The driving conditions include a tire burst condition and a stable condition. The tire burst working condition refers to a working condition that the tire suddenly loses air pressure due to various reasons in the running process of the vehicle, so that air in the tire leaks rapidly, and the tire cannot normally support the weight of the vehicle. The stable working condition can also be called a non-tire burst working condition, namely a working condition that the tire is not damaged and the tire pressure is in a normal range.

The desired yaw torque refers to a yaw torque that meets the driver's desired intention. Yaw torque refers to a moment acting on a vehicle that causes the vehicle to rotate about its vertical axis, and can have an effect on the steering behavior and stability of the vehicle.

In an alternative embodiment, the running condition of the vehicle can be judged by the tire pressure change condition detected by the tire pressure sensor. For example, when the tire pressure sensor detects that the rate of change of the tire pressure is greater than a preset rate, it may be determined that the vehicle is in a flat tire condition, and when the tire pressure sensor detects that the rate of change of the tire pressure is less than or equal to the preset rate, it is determined that the vehicle is in a stable condition.

In an alternative embodiment, the desired yaw torque of the vehicle at the current moment may be determined by the driving speed of the vehicle and the turning radius.

Step S102, determining a target parameter corresponding to the driving working condition from the first parameter and the second parameter for determining the yaw torque.

The different driving conditions correspond to different target parameters, the first parameter comprises driving torque and braking torque of the vehicle, and the second parameter comprises actual yaw rate acquired by the yaw rate sensor.

The drive torque refers to the torque used to drive the wheels in rotation and is typically provided by the drive assembly. The drive assembly may be an engine or a drive motor, depending on the type of energy source. In an alternative embodiment, the drive torque may be obtained by a torque sensor.

Braking torque refers to torque used to retard wheel rotation and is typically produced by a brake. In an alternative embodiment, it may be determined by the brake pedal opening of the vehicle.

The driving condition may be a steady condition or a flat tire condition. In an alternative embodiment, the target parameter may be a first parameter when the driving condition is a steady condition and a second parameter when the driving condition is a flat condition.

Step S103, determining an actual yaw torque of the vehicle at the current time based on the target parameter.

In an alternative embodiment, when the target parameter is the first parameter, the driving torque and the braking torque of the vehicle at the current moment can be collected, and the actual yaw torque of the vehicle at the current moment is determined through the driving torque and the braking torque at the current moment. When the target parameter is the second parameter, the actual yaw moment of the vehicle at the current moment can be determined through the yaw rate of the vehicle at the current moment acquired by the yaw rate sensor and the yaw rates of a plurality of moments after the current moment.

Step S104 of controlling the rear wheel yaw of the vehicle based on a difference between the actual yaw torque at the present moment and the desired yaw torque at the present moment.

During steering, the actual steering process of the vehicle may deviate from the expectations of the driver under the influence of self inertia and ground attachment force, so that a problem of instability of the vehicle body occurs. Among them, excessive or insufficient steering of the vehicle is a major factor causing the problem. Accordingly, the steering radius of the vehicle can be adjusted by controlling the rear wheel deflection of the wheels so that the actual steering process of the vehicle coincides with the expectations of the driver.

On the basis, the deviation degree of the current actual steering process of the vehicle and the steering process expected by a driver is represented due to the difference between the actual yaw torque of the vehicle at the current moment and the expected yaw torque at the current moment, so that the degree of deflection of the rear wheels can be determined through the difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment, and further the control of the deflection of the rear wheels is realized.

According to the embodiment, the target parameter corresponding to the driving condition is determined from the first parameter and the second parameter through the driving condition of the vehicle. And then, according to different target parameters, determining the actual yaw torque of the vehicle at the current moment, and further controlling the rear wheel deflection of the vehicle according to the difference between the actual yaw torque at the current moment and the expected yaw torque. The actual yaw torque is determined based on the driving torque and the braking torque, and can be calculated by only using the driving torque at the current moment and the braking torque at the current moment. But the actual yaw moment is determined based on the actual yaw rate, a plurality of acquisitions by the yaw rate sensor are required. Therefore, the rear wheel yaw response rate when the rear wheel control is performed based on the first parameter is faster than the rear wheel yaw response rate when the rear wheel control is performed based on the second parameter. Therefore, in the embodiment, under different driving conditions, the actual yaw torque is determined through different target parameters, so that the yaw response rate of the rear wheels of the vehicle changes along with different driving conditions, and the technical effect of adapting the yaw response rate of the rear wheels to different driving conditions of the vehicle is achieved.

Optionally, in step S102, from the first parameter and the second parameter for determining the yaw torque, a target parameter corresponding to the driving condition is determined, which specifically includes two cases:

In the first case, the target parameter is determined to be the first parameter under the condition that the driving condition is the tire burst condition.

And secondly, under the condition that the driving working condition is the stable working condition, determining the target parameter as the second parameter.

Based on the above analysis, it is known that the speed of the actual yaw torque is determined by the target parameter in the case where the target parameter is the first parameter, faster than the determination speed in the case where the target parameter is the second parameter. Accordingly, the rear wheel yaw response speed in the case where the target parameter is the first parameter is faster than the response speed in the case where the target parameter is the second parameter, accordingly.

When the running condition of the vehicle is a tire burst condition, the vehicle body can swing severely, so that the running safety of the vehicle is threatened, and the rear wheels should be controlled in a deflection manner at the fastest speed in order to enable the vehicle body to be stabilized as soon as possible. Therefore, in the case where the running condition is a tire burst condition, the target parameter is determined to be the second parameter.

When the running condition of the vehicle is a stable condition, since the various parameters of the vehicle are in a stable state, even if there is a gap between the actual steering process of the vehicle and the expectations of the driver in this case, the gap will not adversely affect the running safety of the vehicle. Meanwhile, taking into account that the rear wheel steering angle adjustment response is too rapid, the riding comfort of the occupant may be reduced. Therefore, in the case where the running condition is a steady condition, the target parameter is determined to be the second parameter.

According to the embodiment, under the condition that the driving working condition is a tire burst working condition, the target parameter is determined to be the first parameter, and under the condition that the driving working condition is a stable working condition, the target parameter is determined to be the second parameter, so that the vehicle has good comfort under the condition of stable driving, and safety measures can be rapidly taken when the vehicle faces danger, and the balance between comfort and safety is realized.

Optionally, the target parameter includes the first parameter, referring to a method step chart of determining an actual yaw torque based on the first parameter shown in fig. 2, the determining, in step S103, the actual yaw torque of the vehicle at the current moment based on the target parameter specifically includes the following steps:

Step S11, state parameters of a plurality of wheels are respectively acquired.

The state parameters include moment of inertia, cornering stiffness, and cornering angle.

And step S12, determining longitudinal forces respectively born by the plurality of wheels based on the braking torque, the driving torque and the rotational inertia of the plurality of wheels, and determining lateral forces respectively born by the plurality of wheels based on the slip angles and the slip rigidities of the plurality of wheels.

And step S13, determining the actual yaw torque at the current moment based on the lateral force and the longitudinal force respectively applied to the wheels.

The plurality of wheels may be all of the wheels of the vehicle, or a number of the wheels of the all of the wheels. The wheels are not limited to the rear wheels, but may include the front wheels.

The moment of inertia and yaw stiffness of the wheels may be measured in advance and stored in a memory module of the controller, from which they are retrieved when calculation of the actual yaw torque is required. The slip angle may be obtained by an angle sensor mounted on the wheel.

Taking the left front wheel of a four-wheeled vehicle as an example, the manner of calculating the longitudinal force is exemplified. Referring to equation (1), the calculation process for determining the longitudinal force to which the left front wheel is subjected based on the braking torque, the driving torque, and the moment of inertia of the left front wheel may be:

Wherein, For the travel of the left front wheel,Is the moment of inertia of the left front wheel,B is the rolling radius of the left front wheel, b is the damping of the rotation of the left front wheel,In order to drive the torque is applied,In order to brake the torque of the vehicle,Is a longitudinal force.

Also taking the left front wheel as an example, the manner of calculating the lateral force is exemplified. Referring to equation (2), the calculation process for determining the lateral force to which the left front wheel is subjected based on the cornering angle and cornering stiffness of the left front wheel may be:

= formula (2)

Wherein, For the lateral force of the left front wheel,Is the slip angle of the left front wheel,Is the cornering stiffness of the left front wheel.

And (3) referring to a calculation formula of the lateral force and the transverse force of the left front wheel, the lateral force and the transverse force of the right front wheel, the left rear wheel and the right rear wheel can be calculated respectively, so that the actual yaw torque of the vehicle at the current moment is calculated.

In an alternative embodiment, the rolling radius of each wheel may be determined from the tire pressure.

According to the embodiment, on the basis of the driving torque and the braking torque, the actual yaw torque of the vehicle is determined by combining the moment of inertia, the cornering stiffness and the cornering angle of each wheel, and the accuracy of the actual yaw torque is improved, so that the accuracy of the control of the deflection of the rear wheels is improved.

Optionally, referring to a method step diagram for determining moment of inertia and cornering stiffness shown in fig. 3, the step of obtaining the moment of inertia and the cornering stiffness includes:

Step S1, tire pressure of the wheels is obtained.

And step S2, determining the moment of inertia and the cornering stiffness of the wheel based on the tire pressure of the wheel.

The cornering stiffness refers to the proportional relation between the lateral deformation of the wheel and the lateral force when the wheel is acted by the lateral force, and is mainly used for measuring the lateral stiffness of the wheel. Moment of inertia refers to a measure of inertia of a wheel as it rotates about its axis of rotation due to the distribution and shape of the wheel material, which measures the degree of resistance of the wheel to changes in rotational motion.

When the tire pressure of the wheel changes, the ground contact footprint half length of the wheel also changes. When the ground contact footprint of the tire is increased, the lateral bending stiffness of the tire body and the torsional stiffness of the tire body are reduced, and the lateral bending stiffness of the tire body and the torsional stiffness of the tire body are reduced, so that the lateral deflection stiffness is reduced. Meanwhile, when the tire pressure of the wheel changes, the mass distribution of the wheel also changes, and the moment of inertia changes. Therefore, the moment of inertia and the cornering stiffness can be determined based on the tire pressure of the wheels, and the accuracy of actual yaw torque calculation is improved.

In an alternative embodiment, the moment of inertia and cornering stiffness of the wheel at standard tyre pressure may be stored in a memory module of the controller. And then, obtaining the tire pressure of the vehicle at the current moment, comparing the tire pressure at the current moment with the standard tire pressure, respectively determining correction parameters of the moment of inertia and the cornering stiffness, and correcting the moment of inertia and the cornering stiffness of the wheel under the standard tire pressure through the correction parameters to finally obtain the moment of inertia and the cornering stiffness of the wheel at the current moment.

According to the embodiment, the rotational inertia and the cornering stiffness of the wheels are determined through the tire pressure of the wheels, and the accuracy of the rotational inertia and the cornering stiffness is improved, so that the accuracy of the vehicle on the control of the rear wheel deflection is improved.

Optionally, referring to a method step diagram for determining an actual yaw torque based on the second parameter shown in fig. 4, the determining an actual yaw torque of the vehicle at the current moment based on the target parameter in step S103 specifically includes the following steps:

Step S21 of determining an actual yaw rate acceleration of the vehicle at the current time based on the actual yaw rates acquired by the yaw rate sensor at the current time and a plurality of historical times before the current time.

And step S22, determining the actual yaw torque at the current moment based on the actual yaw acceleration.

The actual yaw rate acceleration is the amount of change in the actual yaw rate. Therefore, the change amounts of the actual yaw rate between the current moment and the plurality of historical moments can be determined through the actual yaw rates of the current moment and the plurality of historical moments before the current moment, and the actual yaw rate acceleration of the vehicle at the current moment can be further obtained.

And then, according to a calculation formula of the actual yaw torque, calculating the actual yaw torque at the current moment through the moment of inertia of the vehicle and the actual yaw acceleration. The actual yaw moment calculation formula including the moment of inertia and the actual yaw angular acceleration may refer to the related art, and the present application is not repeated.

According to the embodiment, the change amount of the actual yaw rate among the moments is determined through the actual yaw rates at the moments, and the actual yaw torque is determined based on the actual yaw acceleration determined by the change amount, so that the determination process of the actual yaw torque is simplified, and the determination efficiency of the actual yaw torque is improved.

Optionally, referring to a method step diagram for obtaining the desired yaw torque shown in fig. 5, the step of obtaining the desired yaw torque at the current moment specifically includes the following steps:

Step S31, acquiring the actual rotation angle of the steering wheel at the current moment and the actual vehicle speed of the vehicle at the current moment.

And step S32, determining the expected yaw torque at the current moment based on the actual rotation angle at the current moment and the actual vehicle speed at the current moment.

When the driver has a steering intention, the driver will input his steering intention to the vehicle through the steering wheel, so that the vehicle is steered in a manner conforming to the driver's intention. Thus, the actual turning angle of the steering wheel at the present moment characterizes the steering intention of the driver, from which the desired yaw torque of the vehicle should be determined in combination with the actual vehicle speed at the present moment.

In an alternative embodiment, the desired yaw torque at the present moment is determined based on the actual rotation angle at the present moment, by the following formula (3):

Wherein, In order for the yaw torque to be desired,As the actual speed of the vehicle,As the characteristic vehicle speed, the vehicle speed,For the moment of inertia of the vehicle along the z-axis,As the wheelbase of the vehicle,As a transmission ratio between steering wheel angle and wheel angle,Is the actual steering angle of the steering wheel.

According to the embodiment, the intention of the driver is determined through the actual rotation angle of the steering wheel at the current moment, so that the expected yaw torque determined based on the actual rotation angle accords with the expected of the driver, and the running state of the vehicle after the rear wheel deflection control is further enabled to accord with the expected of the driver.

Optionally, referring to a method step diagram of acquiring a driving condition shown in fig. 6, the step of acquiring the driving condition of the vehicle specifically includes the following steps:

Step S41 of determining a difference between a desired yaw torque of the vehicle before the current time and an actual yaw torque of the vehicle before the current time.

And (3) when the difference value is smaller than or equal to a preset threshold value, switching to the step S42, and when the difference value is larger than the preset threshold value, switching to the step S43.

Step S42, determining the driving condition as the stable condition.

And step S43, acquiring the rotating speed of the steering wheel, and determining the driving working condition based on the rotating speed of the steering wheel.

The difference between the desired yaw torque and the actual yaw torque characterizes the yaw torque of the vehicle outside of the driver's expectation, which may typically be caused by a flat tire or some other steering action by the driver. Therefore, the reason for causing the vehicle to generate the unexpected yaw torque can be judged through the difference value between the expected yaw torque of the vehicle before the current moment and the actual yaw torque of the vehicle before the current moment, and the running condition of the vehicle is further determined. The step of determining the desired yaw torque and the actual yaw torque of the vehicle before the current moment may refer to the step of determining the desired yaw torque and the actual yaw torque at the current moment in other embodiments of the present application.

When the difference is smaller than or equal to the preset threshold, the yaw torque of the vehicle beyond the expectation of the driver is smaller, and at the moment, the fact that the vehicle is unlikely to be in a tire burst working condition can be judged, so that the vehicle can be determined to be in a stable working condition. In an alternative embodiment, the preset threshold may be a minimum value of the difference between the desired yaw torque and the actual yaw torque when the vehicle is in a flat tire condition.

When the difference is greater than the preset threshold, it is indicated that the yaw torque of the vehicle is greater beyond the driver's expectation. However, since the difference is large due to the tire burst, the driver can also rotate the steering wheel rapidly, and further judgment is needed based on the rotation speed of the steering wheel.

In an alternative embodiment, step S43 may specifically be determining that the driving condition is a stable condition when the steering wheel rotation speed is greater than the preset rotation speed, and determining that the driving condition is a tire burst condition when the steering wheel rotation speed is less than or equal to the preset rotation speed.

According to the method and the device, the running condition of the vehicle is determined through the difference value between the expected yaw torque and the actual yaw torque of the vehicle before the current moment, so that the types of parameters required by the vehicle in the rear wheel control process are reduced, the number of sensors for acquiring the parameters is reduced, and the production and manufacturing costs of the vehicle are reduced.

Optionally, referring to a method step diagram of controlling rear wheel yaw based on a desired steering angle shown in fig. 7, controlling rear wheel yaw of the vehicle based on a difference between an actual yaw torque at the current time and a desired yaw torque at the current time in step S104 specifically includes the steps of:

Step S51 of determining a desired steering angle of the rear wheels based on a difference between the actual yaw torque at the current time and the desired yaw torque at the current time.

Step S52 of controlling the rear wheels to deflect to the desired steering angle.

The difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment characterizes the correction of the yaw torque required by the vehicle, and the correction which can be realized is different when the steering angles of the rear wheels are different, so that the expected steering angle of the rear wheels can be determined through the difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment, and further, the correction of the yaw torque is realized by controlling the deflection of the rear wheels to the expected steering angle.

In an alternative embodiment, the desired steering angle of the rear wheels may be determined by means of a look-up table. The table stores correspondence between different differences and different steering angles, and the steering angle in the table corresponding to the difference between the actual yaw torque at the current time and the expected yaw torque at the current time is determined as the expected steering angle.

In an alternative embodiment, after the rear wheels are controlled to deflect to the desired steering angle, the desired yaw torque and the actual yaw torque of the vehicle can be acquired again, the desired steering angle can be determined again through the acquired desired yaw torque and the actual yaw torque again, and the steering angle of the rear wheels can be continuously adjusted through proportional-integral control.

According to the embodiment, the expected steering angle of the rear wheels is determined through the difference between the actual yaw torque and the expected yaw torque at the current moment, and the rear wheels are deflected to the expected steering angle, so that the control of the rear wheels is realized. In the process of the rear wheel deflection control, the deflection angle of the rear wheel is quantized through the expected steering angle, so that the accuracy of the rear wheel deflection control is improved.

Based on the above-described embodiments, with reference to a flowchart of a control method of a rear wheel shown in fig. 8, an exemplary description will be made below of a control method of a rear wheel according to the present application:

the control method of the rear wheels is applied to a rear wheel steering system of a vehicle, and is particularly applied to a controller of the rear wheel steering system. The controller includes a storage module in which desired yaw torque and actual yaw torque of the vehicle at a plurality of historical moments, respectively, before a current moment are stored. The rear wheel steering system includes a yaw rate sensor.

The method specifically comprises the following steps:

At the beginning of the method, the actual turning angle of the steering wheel at the current moment and the actual vehicle speed of the vehicle at the current moment are firstly obtained, and the expected yaw torque at the current moment is determined based on the actual turning angle at the current moment and the actual vehicle speed. While determining the expected yaw torque at the current time, determining a difference between the expected yaw torque of the vehicle before the current time and the actual yaw torque before the current time, and judging whether the difference is greater than a preset threshold. And under the condition that the difference value is larger than the preset threshold value, acquiring the steering wheel rotating speed, and determining the running working condition based on the steering wheel rotating speed.

And under the condition that the driving condition is a tire burst condition, determining the target parameters as the driving torque and the braking torque of the vehicle. And the tire pressure and the cornering angle of the wheel are obtained, and further the moment of inertia and the cornering stiffness of the wheel are determined based on the tire pressure of the wheel. After obtaining the cornering angle, moment of inertia, and cornering stiffness of each wheel, determining longitudinal forces to which the plurality of wheels are subjected, respectively, based on the braking torque, the driving torque, and the moment of inertia of the plurality of wheels, and determining lateral forces to which the plurality of wheels are subjected, respectively, based on the cornering angle and the cornering stiffness of the plurality of wheels. And finally, determining the actual yaw torque at the current moment based on the lateral force and the longitudinal force respectively born by the wheels.

And under the condition that the driving working condition is a stable working condition, determining that the target parameter is the actual yaw rate acquired by the yaw rate sensor. Then, an actual yaw rate acceleration of the vehicle at the present moment is determined based on the actual yaw rates acquired by the yaw rate sensor at the present moment and a plurality of history moments before the present moment, and an actual yaw torque at the present moment is determined based on the actual yaw rate acceleration.

After obtaining the actual yaw torque of the vehicle at the current time, a difference between the yaw torque at the current time and the desired yaw torque at the current time is determined, and a desired steering angle of the rear wheels is determined based on the difference at the current time. Finally, the rear wheels are controlled to deflect to a desired steering angle.

Based on the same inventive concept, the present application also provides a control system of a rear wheel applied to a rear wheel steering system including a yaw rate sensor, as shown in a structural schematic diagram of a control system of a rear wheel shown in fig. 9, the control system comprising:

Optionally, the determining module is further configured to determine that the target parameter is the first parameter when the driving condition is the tire burst condition, and determine that the target parameter is the second parameter when the driving condition is the stable condition.

Optionally, the target parameter includes the first parameter, the decision module is further configured to obtain state parameters of a plurality of wheels, where the state parameters include moment of inertia, cornering stiffness, and cornering angle, determine longitudinal forces respectively applied to the plurality of wheels based on the braking torque, the driving torque, and the moment of inertia of the plurality of wheels, determine lateral forces respectively applied to the plurality of wheels based on the cornering angle and the cornering stiffness of the plurality of wheels, and determine actual yaw torque at the current moment based on the lateral forces and the longitudinal forces respectively applied to the plurality of wheels.

Optionally, the decision module is further configured to obtain a tire pressure of the wheel, and determine a moment of inertia and a cornering stiffness of the wheel based on the tire pressure of the wheel.

Optionally, the target parameter includes the second parameter, and the decision module is further configured to determine an actual yaw rate acceleration of the vehicle at the current time based on the actual yaw rates acquired by the yaw rate sensor at the current time and a plurality of historical times before the current time, and determine an actual yaw torque at the current time based on the actual yaw rate acceleration.

Optionally, the acquisition module is further configured to acquire an actual rotation angle of the steering wheel at the current moment and an actual vehicle speed of the vehicle at the current moment, and determine the expected yaw torque at the current moment based on the actual rotation angle at the current moment and the actual vehicle speed at the current moment.

Optionally, the obtaining module is further configured to determine a difference between a desired yaw torque of the vehicle before the current moment and an actual yaw torque of the vehicle before the current moment, determine that the driving condition is the stable condition if the difference is less than or equal to a preset threshold, obtain a steering wheel speed if the difference is greater than the preset threshold, and determine the driving condition based on the steering wheel speed.

Optionally, the execution module is further configured to determine a desired steering angle of the rear wheels based on a difference between the actual yaw torque at the current time and the desired yaw torque at the current time, and control the rear wheels to deflect to the desired steering angle.

The embodiment of the application also provides a computer readable storage medium, on which a computer program/instruction is stored, which when executed by a processor, implements a method for controlling a rear wheel as disclosed in the embodiment of the application.

The embodiment of the application also provides a vehicle, comprising the control system of the rear wheel or a control module, wherein the control module is used for realizing the steps of the control method of the rear wheel.

In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described by differences from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other.

Embodiments of the present application are described with reference to flowchart illustrations and/or block diagrams of methods, systems, electronic devices, and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiment and all such alterations and modifications as fall within the scope of the embodiments of the application.

Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of additional like elements in a process, method, article, or terminal device comprising the element.

The foregoing describes the method, system and vehicle for controlling a rear wheel according to the present application in detail, and specific examples are provided herein to illustrate the principles and embodiments of the present application, and the above examples are provided to assist in understanding the method and core ideas of the present application, and meanwhile, to those skilled in the art, according to the ideas of the present application, there are variations in the specific embodiments and application scope, so that the disclosure should not be construed as limiting the present application.

Claims

1. A control method of a rear wheel, the method being applied to a rear wheel steering system including a yaw rate sensor, the method comprising:

2. The method according to claim 1, wherein the determining a target parameter corresponding to the running condition from the first parameter and the second parameter for determining the yaw torque includes:

3. The method according to claim 1, characterized in that the target parameter includes the first parameter, and the determining the actual yaw torque of the vehicle at the current time based on the target parameter includes:

4. A control method of a rear wheel according to claim 3, wherein the step of obtaining the moment of inertia and the cornering stiffness includes:

Acquiring the tire pressure of the wheel;

5. The method according to claim 1, characterized in that the target parameter includes the second parameter, and the determining the actual yaw torque of the vehicle at the current time based on the target parameter includes:

6. The method according to claim 1, characterized in that the step of obtaining the desired yaw torque at the present moment comprises:

7. The method according to claim 1, characterized in that the step of acquiring the running condition of the vehicle includes:

8. The method according to claim 1, characterized in that the controlling the rear wheel yaw of the vehicle based on a difference between the actual yaw torque at the present time and the desired yaw torque at the present time includes:

controlling the rear wheels to deflect to the desired steering angle.

9. A control system for rear wheels, the control system being applied to a rear wheel steering system including a yaw rate sensor, the control system comprising:

10. A vehicle comprising the rear wheel control system of claim 9 or comprising a control module for implementing the steps of the rear wheel control method of any one of claims 1-8.