Rear wheel control method and system and vehicle

Abstract

The invention provides a rear wheel control method and system and a vehicle, and belongs to the technical field of vehicles, the rear wheel control method comprises the steps that the driving working condition of the vehicle and the expected yaw torque of the vehicle at the current moment are obtained, and the driving working condition comprises the tire burst working condition or the stable working condition; determining a target parameter corresponding to the driving condition from a first parameter and a second parameter which are used for determining a yaw torque; determining the actual yaw torque of the vehicle at the current moment based on the target parameter; and controlling 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. Under different driving conditions, the actual yaw torque is determined through different target parameters, so that the rear wheel deflection response rate of the vehicle changes along with different driving conditions, and the technical effect that the rear wheel deflection response rate is matched with different driving conditions of the vehicle is achieved.

Description

Technical Field

[0001] The present application relates to the field of vehicle technology, and in particular to a rear wheel control method, system and vehicle. Background Art

[0002] Rear wheels refer to the wheels located at the rear of the vehicle, which usually do not have active steering functions. However, with the development of technology, in order to improve the steering flexibility and body stability of the vehicle, the rear wheels can also achieve a certain degree of deflection according to different driving conditions of the vehicle.

[0003] In the related art, when a vehicle turns or has a tire blowout during normal driving, the rear wheel deflection is controlled according to the actual yaw torque of the vehicle to ensure the stability of the vehicle. However, since the required rear wheel deflection response rates are different when the vehicle turns during normal driving and when a tire blowout occurs, the rear wheel control method in the related art cannot meet the rear wheel deflection response rate requirements of the vehicle under different working conditions. Summary of the invention

[0004] Based on this, the present application provides a rear wheel control method, system and vehicle to solve the problem of how to adapt the rear wheel deflection response rate to different working conditions of the vehicle.

[0005] In a first aspect of an embodiment of the present application, a rear wheel control method is provided, the method being applied to a rear wheel steering system, the rear wheel steering system comprising a yaw rate sensor, the method comprising: Acquire a driving condition of a vehicle and an expected yaw torque of the vehicle at a current moment, wherein the driving condition includes a tire blowout condition or a stable condition; Determine a target parameter corresponding to the driving condition from a first parameter and a second parameter used to determine the yaw torque, wherein different driving conditions correspond to different target parameters, the first parameter includes a driving torque and a braking torque of the vehicle, and the second parameter includes an actual yaw angular velocity collected by the yaw angular velocity sensor; determining, based on the target parameter, an actual yaw torque of the vehicle at the current moment; Based on the difference between the actual yaw torque at the current moment and the desired yaw torque at the current moment, the rear wheel yaw of the vehicle is controlled.

[0006] Optionally, determining the target parameter corresponding to the driving condition from the first parameter and the second parameter used to determine the yaw torque includes: When the driving condition is the tire blowout condition, determining the target parameter to be the first parameter; When the driving condition is the stable condition, the target parameter is determined to be the second parameter.

[0007] Optionally, the target parameter includes the first parameter, and determining the actual yaw torque of the vehicle at the current moment based on the target parameter includes: respectively acquiring state parameters of a plurality of wheels, wherein the state parameters include moment of inertia, cornering stiffness, and slip angle; Determine the longitudinal forces respectively applied to the plurality of wheels based on the braking torque, the driving torque and the rotational inertia of the plurality of wheels, and determine the lateral forces respectively applied to the plurality of wheels based on the slip angles and the cornering stiffnesses of the plurality of wheels; The actual yaw torque at the current moment is determined based on the lateral forces and the longitudinal forces respectively exerted on the plurality of wheels.

[0008] Optionally, the step of obtaining the moment of inertia and the cornering stiffness comprises: Obtaining the tire pressure of the wheel; Based on the tire pressure of the wheel, the moment of inertia and the cornering stiffness of the wheel are determined.

[0009] Optionally, the target parameter includes the second parameter, and determining the actual yaw torque of the vehicle at the current moment based on the target parameter includes: Determine the actual yaw acceleration of the vehicle at the current moment based on the actual yaw angular velocity collected by the yaw angular velocity sensor at the current moment and multiple historical moments before the current moment; The actual yaw torque at the current moment is determined based on the actual yaw angular acceleration.

[0010] Optionally, the step of obtaining the expected yaw torque at the current moment includes: Obtaining the actual turning angle of the steering wheel and the actual speed of the vehicle at the current moment; Based on the actual steering angle at the current moment and the actual vehicle speed at the current moment, the expected yaw torque at the current moment is determined.

[0011] Optionally, the step of obtaining the driving condition of the vehicle includes: determining 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; When the difference is less than or equal to a preset threshold, determining that the driving condition is the stable condition; When the difference is greater than the preset threshold, the steering wheel speed is acquired, and the driving condition is determined based on the steering wheel speed.

[0012] Optionally, 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 comprises: determining a desired steering angle of the rear wheels based on a difference between the actual yaw torque at the current moment and the desired yaw torque at the current moment; The rear wheels are controlled to steer to the desired steering angle.

[0013] According to a second aspect of an embodiment of the present application, a rear wheel control system is provided, wherein the control system is applied to a rear wheel steering system, wherein the rear wheel steering system includes a yaw rate sensor, and the control system includes: An acquisition module, used for acquiring a driving condition of a vehicle and an expected yaw torque of the vehicle at a current moment, wherein the driving condition includes a tire blowout condition or a stable condition; a determination module, configured to determine a target parameter corresponding to the driving condition from a first parameter and a second parameter used to determine the yaw torque, wherein different driving conditions correspond to different target parameters, wherein the first parameter includes a driving torque and a braking torque of the vehicle, and the second parameter includes an actual yaw angular velocity collected by the yaw angular velocity sensor; A decision module, configured to determine an actual yaw torque of the vehicle at the current moment based on the target parameter; The execution module is configured to control the rear wheel yaw of the vehicle based on a difference between the actual yaw torque at the current moment and the desired yaw torque at the current moment.

[0014] A third aspect of the embodiments of the present application provides a vehicle, comprising the control system for the rear wheels described in the second aspect of the embodiments of the present application, or comprising a control module, wherein the control module is used to implement the steps of the rear wheel control method described in the first aspect of the embodiments of the present application.

[0015] The present application provides a rear wheel control method, system and vehicle, the method comprising: obtaining a driving condition of a vehicle and an expected yaw torque of the vehicle at a current moment, the driving condition comprising 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, different driving conditions corresponding to different target parameters, the first parameter comprising a driving torque and a braking torque of the vehicle, the second parameter comprising an actual yaw angular velocity acquired by a yaw angular velocity 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 a difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment.

[0016] The present application first determines the target parameter corresponding to the driving condition from the first parameter and the second parameter according to the driving condition of the vehicle. Subsequently, according to different target parameters, the actual yaw torque of the vehicle at the current moment is determined, and then the rear wheel deflection of the vehicle is controlled 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 it can be calculated by the driving torque at the current moment and the braking torque at the current moment. However, the actual yaw torque is determined based on the actual yaw angular velocity, and it is necessary to obtain it multiple times through the yaw angular velocity sensor. Therefore, the rear wheel deflection response rate when the rear wheel is controlled based on the first parameter is faster than the rear wheel deflection response rate when the rear wheel is controlled based on the second parameter. It can be seen from this that 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0018] Figure 1 is a step diagram of a rear wheel control method provided by an embodiment of the present application; Figure 2 is a step diagram of a method for determining an actual yaw torque based on a first parameter provided in an embodiment of the present application; Figure 3 This is a step diagram of a method for determining the moment of inertia and cornering stiffness provided in an embodiment of the present application; Figure 4 is a step diagram of a method for determining an actual yaw torque based on a second parameter provided in an embodiment of the present application; Figure 5 is a step diagram of a method for obtaining a desired yaw torque provided in an embodiment of the present application; Figure 6 This is a step diagram of a method for obtaining driving conditions provided in an embodiment of the present application; Figure 7 is a step diagram of a method for controlling rear wheel deflection based on a desired steering angle provided by an embodiment of the present application; Figure 8 is a flow chart of a rear wheel control method provided by an embodiment of the present application; Fig. 9It is a structural schematic diagram of a rear wheel control system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] Rear wheels refer to the wheels located at the rear of the vehicle, which usually do not have active steering functions. However, with the development of technology, in order to improve the steering flexibility and body stability of the vehicle, the rear wheels can also achieve a certain degree of deflection according to different driving conditions of the vehicle.

[0021] In the related art, when a vehicle turns or has a tire blowout during normal driving, the rear wheel deflection is controlled according to the actual yaw torque of the vehicle to ensure the stability of the vehicle. However, since the required rear wheel deflection response rates are different when the vehicle turns during normal driving and when a tire blowout occurs, the rear wheel control method in the related art cannot meet the rear wheel deflection response rate requirements of the vehicle under different working conditions.

[0022] Based on this, in order to solve the problem of how to make the rear wheel deflection response rate adapt to different working conditions of the vehicle, the present application provides a control method, system and vehicle for the rear wheels. First, through the driving working condition of the vehicle, the target parameter corresponding to the driving working condition is determined from the first parameter and the second parameter. Then, according to different target parameters, the actual yaw torque of the vehicle at the current moment is determined, and then the rear wheel deflection of the vehicle is controlled 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 it can be calculated only by the driving torque at the current moment and the braking torque at the current moment. However, the actual yaw torque is determined based on the actual yaw angular velocity, which needs to be obtained multiple times through the yaw angular velocity sensor. Therefore, the rear wheel deflection response rate when the rear wheel is controlled based on the first parameter is faster than the rear wheel deflection response rate when the rear wheel is controlled based on the second parameter. It can be seen that 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. The specific method is as follows: The first aspect of the present application proposes an embodiment, such as Figure 1As shown in the step diagram of a rear wheel control method, the method is applied to a rear wheel steering system, specifically to a controller of the rear wheel steering system, wherein the rear wheel steering system includes a yaw rate sensor. The yaw rate sensor is used to collect the yaw rate of the vehicle. The yaw rate refers to the speed at which the vehicle rotates laterally around its center of mass, usually expressed in degrees per unit time. According to different collection principles, the yaw rate sensor can be divided into a gyroscopic angular rate sensor, a Hall angular rate sensor, a capacitive angular rate sensor, and the like.

[0023] The main steps of the method described in this application include: Step S101, obtaining the driving condition of the vehicle and the expected yaw torque of the vehicle at the current moment.

[0024] Driving conditions include blowout conditions and stable conditions. Blowout conditions refer to the conditions in which the tire suddenly loses air pressure due to various reasons during driving, causing the internal gas of the tire to leak rapidly and the tire cannot normally support the weight of the vehicle. Stable conditions can also be called non-blowout conditions, which refer to the conditions in which the tire is not damaged and the tire pressure is within the normal range.

[0025] The desired yaw torque is the yaw torque that meets the driver's desired intention. The yaw torque is the moment acting on the vehicle, causing the vehicle to rotate around its vertical axis, which can affect the vehicle's steering behavior and stability.

[0026] In an optional implementation, the driving condition of the vehicle can be determined by the tire pressure change detected by the tire pressure sensor. For example, when the tire pressure sensor detects that the tire pressure change rate is greater than a preset rate, it can be determined that the vehicle is in a tire blowout condition; when the tire pressure sensor detects that the tire pressure change rate is less than or equal to the preset rate, it is determined that the vehicle is in a stable condition.

[0027] In an optional implementation, the expected yaw torque of the vehicle at the current moment may be determined by the vehicle's driving speed and turning radius.

[0028] Step S102: determining a target parameter corresponding to the driving condition from the first parameter and the second parameter used to determine the yaw torque.

[0029] Different driving conditions correspond to different target parameters, the first parameter includes the driving torque and braking torque of the vehicle, and the second parameter includes the actual yaw angular velocity collected by the yaw angular velocity sensor.

[0030] Driving torque refers to the torque used to drive the wheels to rotate, which is usually provided by a drive assembly. Depending on the type of energy, the drive assembly can be an engine or a drive motor. In an optional embodiment, the driving torque can be obtained by a torque sensor.

[0031] Braking torque refers to the torque used to hinder the rotation of the wheel, which is usually generated by the brake. In an optional implementation, it can be determined by the opening of the vehicle's brake pedal.

[0032] The driving condition may be a stable condition or a tire blowout condition. In an optional implementation, when the driving condition is a stable condition, the target parameter may be a first parameter; when the driving condition is a tire blowout condition, the target parameter may be a second parameter.

[0033] Step S103: determining the actual yaw torque of the vehicle at the current moment based on the target parameter.

[0034] In an optional implementation, when the target parameter is the first parameter, the driving torque and braking torque of the vehicle at the current moment may be collected, and the actual yaw torque of the vehicle at the current moment may be determined by the driving torque and braking torque at the current moment. When the target parameter is the second parameter, the actual yaw torque of the vehicle at the current moment may be determined by the yaw angular velocity of the vehicle at the current moment collected by the yaw angular velocity sensor, and the yaw angular velocity at several moments after the current moment.

[0035] Step S104: 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.

[0036] During the steering process, the actual steering process of the vehicle may deviate from the driver's expectations due to its own inertia and ground adhesion, resulting in vehicle body instability. Among them, oversteering or understeering of the vehicle is the main factor causing this problem. Therefore, the steering radius of the vehicle can be adjusted by controlling the rear wheel deflection, so that the actual steering process of the vehicle is consistent with the driver's expectations.

[0037] On this basis, the difference between the actual yaw torque of the vehicle at the current moment and the expected yaw torque at the current moment represents the degree of deviation between the current actual steering process of the vehicle and the steering process expected by the driver. Therefore, the degree of deflection that the rear wheels should make can be determined by the difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment, thereby achieving control of the deflection of the rear wheels.

[0038] In this embodiment, the target parameter corresponding to the driving condition is first determined from the first parameter and the second parameter according to the driving condition of the vehicle. Subsequently, the actual yaw torque of the vehicle at the current moment is determined according to different target parameters, and then the rear wheel deflection of the vehicle is controlled according to the difference between the actual yaw torque at the current moment and the expected yaw torque. The actual yaw torque can be determined based on the driving torque and the braking torque, and can be calculated by the driving torque at the current moment and the braking torque at the current moment. However, the actual yaw torque can be determined based on the actual yaw angular velocity, which needs to be obtained multiple times through the yaw angular velocity sensor. Therefore, the rear wheel deflection response rate when the rear wheel is controlled based on the first parameter is faster than the rear wheel deflection response rate when the rear wheel is controlled based on the second parameter. It can be seen that in this embodiment, the actual yaw torque is determined by 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.

[0039] Optionally, in step S102, determining a target parameter corresponding to the driving condition from the first parameter and the second parameter used to determine the yaw torque specifically includes two cases: In case one, when the driving condition is the tire blowout condition, the target parameter is determined to be the first parameter.

[0040] In case two, when the driving condition is the stable condition, the target parameter is determined to be the second parameter.

[0041] Based on the above analysis, it can be seen that the speed of determining the actual yaw torque by the target parameter when the target parameter is the first parameter is faster than the speed of determining when the target parameter is the second parameter. Therefore, correspondingly, the response speed of the rear wheel deflection when the target parameter is the first parameter is faster than the response speed when the target parameter is the second parameter.

[0042] When the vehicle is in a tire blowout condition, the vehicle body may swing violently, thereby threatening the vehicle's driving safety. At this time, in order to stabilize the vehicle body as quickly as possible, the rear wheel should be deflected at the fastest speed. Therefore, when the vehicle is in a tire blowout condition, the target parameter is determined to be the second parameter.

[0043] When the vehicle is in a stable driving condition, all parameters of the vehicle are in a stable state. Therefore, even if there is a gap between the actual steering process of the vehicle and the driver's expectations, this gap will not have an adverse effect on the driving safety of the vehicle. At the same time, considering that the rear wheel steering angle adjustment response is too fast, it will reduce the riding comfort of the passengers. Therefore, when the driving condition is a stable condition, the target parameter is determined to be the second parameter.

[0044] In this embodiment, when the driving condition is a tire blowout condition, the target parameter is determined to be the first parameter, and when the driving condition is a stable condition, the target parameter is determined to be the second parameter, so that the vehicle has good comfort when driving stably, and can quickly take safety measures when facing danger, thereby achieving a balance between comfort and safety.

[0045] Optionally, the target parameter includes the first parameter, referring to Figure 2 A method step diagram of determining an actual yaw torque based on a first parameter is shown, wherein step S103 determines the actual yaw torque of the vehicle at the current moment based on the target parameter, specifically comprising the following steps: Step S11, respectively obtaining state parameters of a plurality of wheels.

[0046] The state parameters include moment of inertia, cornering stiffness and sideslip angle.

[0047] Step S12, based on the braking torque, the driving torque and the rotational inertia of the multiple wheels, determine the longitudinal forces respectively exerted on the multiple wheels, and based on the slip angles and cornering stiffnesses of the multiple wheels, determine the lateral forces respectively exerted on the multiple wheels.

[0048] Step S13, determining the actual yaw torque at the current moment based on the lateral forces and longitudinal forces respectively exerted on the plurality of wheels.

[0049] A plurality of wheels can be all wheels of the vehicle, or some wheels among all wheels. The wheels are not limited to the rear wheels, and can also include the front wheels.

[0050] The moment of inertia and cornering stiffness of the wheel can be measured in advance and stored in the storage module of the controller, and when the actual yaw torque needs to be calculated, it is obtained from the storage module. The sideslip angle can be obtained by an angle sensor installed on the wheel.

[0051] Taking the left front wheel of a four-wheel vehicle as an example, the calculation method of the longitudinal force is illustrated. Referring to formula (1), based on the braking torque, driving torque and the moment of inertia of the left front wheel, the calculation process of determining the longitudinal force on the left front wheel can be:

[0052] in, is the travel of the left front wheel, is the moment of inertia of the left front wheel, is the rolling radius of the left front wheel, b is the damping of the left front wheel rotation, is the driving torque, is the braking torque, is the longitudinal force.

[0053] Taking the left front wheel as an example, the calculation method of the lateral force is illustrated. Referring to formula (2), based on the sideslip angle and cornering stiffness of the left front wheel, the calculation process of determining the lateral force on the left front wheel can be: = Formula (2) in, is the lateral force on the left front wheel, is the sideslip angle of the left front wheel, is the cornering stiffness of the left front wheel.

[0054] By referring to the calculation formula of the lateral force and transverse force of the left front wheel, the lateral force and transverse force of the right front wheel, the left rear wheel and the right rear wheel can be calculated respectively, and then the actual yaw torque of the vehicle at the current moment can be calculated.

[0055] In an optional embodiment, the rolling radius of each wheel can be determined according to the tire pressure.

[0056] This embodiment determines the actual yaw torque of the vehicle based on the driving torque and the braking torque in combination with the rotational inertia, cornering stiffness and slip angle of each wheel, thereby improving the accuracy of the actual yaw torque and thus improving the precision of the rear wheel deflection control.

[0057] Optionally, refer to Figure 3 A step diagram of a method for determining a moment of inertia and a cornering stiffness is shown, wherein the step of obtaining the moment of inertia and the cornering stiffness comprises: Step S1, obtaining the tire pressure of the wheel.

[0058] Step S2, determining the moment of inertia and cornering stiffness of the wheel based on the tire pressure of the wheel.

[0059] Cornering stiffness refers to the proportional relationship between the lateral deformation of the wheel and the lateral force when the wheel is subjected to a lateral force. It is mainly used to measure the lateral rigidity of the wheel. Moment of inertia refers to the inertia measurement of the wheel due to the distribution and shape of the wheel material when the wheel rotates around its axis of rotation. It is used to measure the resistance of the wheel to changes in rotational motion.

[0060] When the tire pressure of the wheel changes, the half-length of the wheel's contact patch also changes. When the half-length of the tire's contact patch decreases, the lateral bending stiffness and torsional stiffness of the tire carcass increase, which in turn leads to an increase in cornering stiffness; when the half-length of the tire's contact patch increases, the lateral bending stiffness and torsional stiffness of the tire carcass decrease, which in turn leads to a decrease in cornering stiffness. At the same time, when the tire pressure of the wheel changes, the mass distribution of the wheel will also change, which in turn leads to a change in the moment of inertia. Therefore, the moment of inertia and cornering stiffness can be determined based on the tire pressure of the wheel, thereby improving the accuracy of the actual yaw torque calculation.

[0061] In an optional implementation, the moment of inertia and cornering stiffness of the wheel at the standard tire pressure may be stored in the storage module of the controller first. Then, the tire pressure of the vehicle at the current moment is obtained, and the tire pressure at the current moment is compared with the standard tire pressure to determine correction parameters of the moment of inertia and cornering stiffness, respectively, and then the moment of inertia and cornering stiffness of the wheel at the standard tire pressure are corrected by the correction parameters, and finally the moment of inertia and cornering stiffness of the wheel at the current moment are obtained.

[0062] This embodiment determines the moment of inertia and cornering stiffness of the wheel through the tire pressure of the wheel, thereby improving the accuracy of the moment of inertia and cornering stiffness, thereby improving the accuracy of the vehicle's control over rear wheel deflection.

[0063] Optionally, refer to Figure 4 A method step diagram for determining an actual yaw torque based on a second parameter is shown, wherein step S103 determines the actual yaw torque of the vehicle at the current moment based on the target parameter, specifically comprising the following steps: Step S21 , determining the actual yaw acceleration of the vehicle at the current moment based on the actual yaw angular velocity collected by the yaw angular velocity sensor at the current moment and multiple historical moments before the current moment.

[0064] Step S22: determining the actual yaw torque at the current moment based on the actual yaw angular acceleration.

[0065] The actual yaw acceleration is the change in the actual yaw velocity. Therefore, the change in the actual yaw velocity between the current moment and the multiple historical moments before the current moment can be determined by the actual yaw velocity at the current moment and the multiple historical moments before the current moment, and then the actual yaw acceleration of the vehicle at the current moment can be obtained.

[0066] Afterwards, the actual yaw torque at the current moment is calculated according to the calculation formula of the actual yaw torque, through the rotational inertia of the vehicle and the actual yaw angular acceleration. The calculation formula of the actual yaw torque including the rotational inertia and the actual yaw angular acceleration can be referred to in the relevant technology, and will not be described in detail in this application.

[0067] This embodiment determines the change of the actual yaw angular velocity between multiple moments through the actual yaw angular velocity at multiple moments, and determines the actual yaw torque based on the actual yaw angular acceleration determined based on the change, thereby simplifying the determination process of the actual yaw torque and improving the efficiency of determining the actual yaw torque.

[0068] Optionally, refer to Figure 5 A method step diagram for obtaining an expected yaw torque is shown, and the step of obtaining the expected yaw torque at the current moment specifically includes the following steps: Step S31, obtaining the actual turning angle of the steering wheel at the current moment and the actual speed of the vehicle at the current moment.

[0069] Step S32, determining the expected yaw torque at the current moment based on the actual steering angle at the current moment and the actual vehicle speed at the current moment.

[0070] 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 steers in a manner consistent with the driver's intention. Therefore, the actual steering angle of the steering wheel at the current moment represents the driver's steering intention, and the expected yaw torque of the vehicle should be determined based on the actual steering angle of the steering wheel and the actual vehicle speed at the current moment.

[0071] In an optional implementation, based on the actual rotation angle at the current moment, the expected yaw torque at the current moment is determined by the following formula (3):

[0072] in, is the desired yaw torque, is the actual speed of the vehicle, is the characteristic speed, is the moment of inertia of the vehicle along the z-axis, is the vehicle wheelbase, is the transmission ratio between the steering wheel angle and the wheel angle, is the actual steering wheel angle.

[0073] This embodiment determines the driver's intention through the actual steering wheel angle at the current moment, so that the expected yaw torque determined based on the actual steering angle meets the driver's expectations, and further makes the vehicle driving state after rear wheel deflection control more in line with the driver's expectations.

[0074] Optionally, refer to Figure 6 A method step diagram for obtaining a driving condition is shown, and the steps of obtaining the driving condition of the vehicle specifically include the following steps: Step S41 : determining a difference between an expected yaw torque of the vehicle before the current moment and an actual yaw torque of the vehicle before the current moment.

[0075] When the difference is less than or equal to the preset threshold, the process proceeds to step S42; when the difference is greater than the preset threshold, the process proceeds to step S43.

[0076] Step S42, determining that the driving condition is the stable condition.

[0077] Step S43, obtaining the steering wheel speed, and determining the driving condition based on the steering wheel speed.

[0078] The difference between the expected yaw torque and the actual yaw torque represents the yaw torque of the vehicle that is beyond the driver's expectation, and the yaw torque of the vehicle that is beyond the driver's expectation may usually be caused by a tire blowout or some other manipulation actions of the driver. Therefore, the difference between the expected yaw torque of the vehicle before the current moment and the actual yaw torque before the current moment can be used to determine the cause of the vehicle's unexpected yaw torque, and then determine the driving condition of the vehicle. Among them, the step of determining the expected yaw torque and the actual yaw torque of the vehicle before the current moment can refer to the step of determining the expected yaw torque and the actual yaw torque at the current moment in the other embodiments of the present application.

[0079] When the difference is less than or equal to the preset threshold, it indicates that the yaw torque of the vehicle is smaller than the driver's expectation. At this time, it can be determined that the vehicle is unlikely to be in a tire blowout condition, and therefore it can be determined that the vehicle is in a stable condition. In an optional implementation, the preset threshold may be the minimum value of the difference between the expected yaw torque and the actual yaw torque when the vehicle is in a tire blowout condition.

[0080] When the difference is greater than a preset threshold, it indicates that the vehicle has a larger yaw torque than the driver expected. However, since not only a tire blowout can cause a larger difference, but also a driver turning the steering wheel quickly can also cause a larger difference, further judgment based on the steering wheel speed is required.

[0081] In an optional implementation, step S43 may specifically be: when the steering wheel speed is greater than a preset speed, determining the driving condition to be a stable condition; when the steering wheel speed is less than or equal to the preset speed, determining the driving condition to be a tire blowout condition.

[0082] This embodiment determines the driving condition of the vehicle by the difference between the expected yaw torque of the vehicle before the current moment and the actual yaw torque, thereby reducing the types of parameters required for the vehicle during rear wheel control and the number of sensors for parameter acquisition, thereby reducing the production and manufacturing costs of the vehicle.

[0083] Optionally, refer to Figure 7 A method for controlling rear wheel deflection based on a desired steering angle is shown in the step diagram, wherein the rear wheel deflection of the vehicle is controlled based on the difference between the actual yaw torque at the current moment and the desired yaw torque at the current moment in step S104, specifically comprising the following steps: Step S51 : determining the desired steering angle of the rear wheels based on the difference between the actual yaw torque at the current moment and the desired yaw torque at the current moment.

[0084] Step S52, controlling the rear wheels to deflect to the desired steering angle.

[0085] The difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment represents the amount of correction of the yaw torque required for the vehicle, and the achievable correction amounts are different for different steering angles of the rear wheels. Therefore, the expected steering angle of the rear wheels can be determined by the difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment, and then the yaw torque can be corrected by controlling the rear wheels to deflect to the expected steering angle.

[0086] In an optional implementation, the expected steering angle of the rear wheels may be determined by looking up a table. The table stores the correspondence between different differences and different steering angles, and the steering angle corresponding to the difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment in the table is determined as the expected steering angle.

[0087] In an optional embodiment, after controlling the rear wheels to deflect to a desired steering angle, the desired yaw torque and the actual yaw torque of the vehicle can be acquired again, and the desired steering angle can be determined again by the acquired desired yaw torque and the actual yaw torque, and then the steering angle of the rear wheels can be continuously adjusted by proportional-integral control.

[0088] This embodiment first determines the desired steering angle of the rear wheel by the difference between the actual yaw torque at the current moment and the desired yaw torque, and then deflects the rear wheel to the desired steering angle, thereby achieving control of the rear wheel. In the process of rear road deflection control, this embodiment quantifies the deflection angle of the rear wheel by the desired steering angle, thereby improving the accuracy of rear wheel deflection control.

[0089] Based on the above embodiments, reference Figure 8 A flowchart of a rear wheel control method is shown, and the rear wheel control method described in the present application will be exemplarily described below: The rear wheel control method described in the present application is applied to a rear wheel steering system of a vehicle, and is specifically applied to a controller of the rear wheel steering system. The controller includes a storage module, and the storage module stores the expected yaw torque and the actual yaw torque of the vehicle at multiple historical moments before the current moment. The rear wheel steering system includes a yaw angular velocity sensor.

[0090] The specific steps include: At the beginning of the method, the actual steering angle of the steering wheel at the current moment and the actual speed of the vehicle at the current moment are first obtained, and the expected yaw torque at the current moment is determined based on the actual steering angle and the actual speed at the current moment. While determining the expected yaw torque at the current moment, the difference between the expected yaw torque of the vehicle before the current moment and the actual yaw torque before the current moment is determined, and it is determined whether the difference is greater than a preset threshold. If the difference is less than or equal to the preset threshold, the driving condition is determined to be a stable condition; if the difference is greater than the preset threshold, the steering wheel speed is obtained, and the driving condition is determined based on the steering wheel speed.

[0091] When the driving condition is a tire blowout condition, the target parameters are determined to be the driving torque and braking torque of the vehicle. In addition, the tire pressure and slip angle of the wheel are obtained, and then the moment of inertia and cornering stiffness of the wheel are determined based on the tire pressure of the wheel. After obtaining the slip angle, moment of inertia and cornering stiffness of each wheel, the longitudinal forces respectively received by the multiple wheels are determined based on the braking torque, driving torque and the moment of inertia of the multiple wheels, and the lateral forces respectively received by the multiple wheels are determined based on the slip angles and cornering stiffness of the multiple wheels. Finally, the actual yaw torque at the current moment is determined based on the lateral forces and longitudinal forces respectively received by the multiple wheels.

[0092] When the driving condition is a stable condition, the target parameter is determined to be the actual yaw rate collected by the yaw rate sensor. Subsequently, based on the actual yaw rates collected by the yaw rate sensor at the current moment and multiple historical moments before the current moment, the actual yaw acceleration of the vehicle at the current moment is determined, and based on the actual yaw acceleration, the actual yaw torque at the current moment is determined.

[0093] After obtaining the actual yaw torque of the vehicle at the current moment, the difference between the yaw torque at the current moment and the expected yaw torque at the current moment is determined, and based on the difference at the current moment, the expected steering angle of the rear wheels is determined. Finally, the rear wheels are controlled to deflect to the expected steering angle.

[0094] Based on the same inventive concept, the present application also provides a rear wheel control system, the control system is applied to a rear wheel steering system, the rear wheel steering system includes a yaw rate sensor, such as Fig. 9As shown in the structural schematic diagram of a rear wheel control system, the control system includes: An acquisition module, used for acquiring a driving condition of a vehicle and an expected yaw torque of the vehicle at a current moment, wherein the driving condition includes a tire blowout condition or a stable condition; a determination module, configured to determine a target parameter corresponding to the driving condition from a first parameter and a second parameter used to determine the yaw torque, wherein different driving conditions correspond to different target parameters, wherein the first parameter includes a driving torque and a braking torque of the vehicle, and the second parameter includes an actual yaw angular velocity collected by the yaw angular velocity sensor; A decision module, configured to determine an actual yaw torque of the vehicle at the current moment based on the target parameter; The execution module is configured to control the rear wheel yaw of the vehicle based on a difference between the actual yaw torque at the current moment and the desired yaw torque at the current moment.

[0095] Optionally, the determination module is further used to determine the target parameter to be the first parameter when the driving condition is the tire blowout condition; and to determine the target parameter to be the second parameter when the driving condition is the stable condition.

[0096] Optionally, the target parameter includes the first parameter, and the decision module is further used to respectively obtain state parameters of multiple wheels, the state parameters including moment of inertia, cornering stiffness and slip angle; based on the braking torque, the driving torque and the moment of inertia of the multiple wheels, determine the longitudinal forces respectively acted on the multiple wheels, and based on the slip angles and cornering stiffness of the multiple wheels, determine the lateral forces respectively acted on the multiple wheels; based on the lateral forces and longitudinal forces respectively acted on the multiple wheels, determine the actual yaw torque at the current moment.

[0097] Optionally, the decision module is further used to obtain the tire pressure of the wheel; and determine the moment of inertia and cornering stiffness of the wheel based on the tire pressure of the wheel.

[0098] Optionally, the target parameter includes the second parameter, and the decision module is further used to determine the actual yaw angular acceleration of the vehicle at the current moment based on the actual yaw angular velocity collected by the yaw angular velocity sensor at the current moment and multiple historical moments before the current moment; and determine the actual yaw torque at the current moment based on the actual yaw angular acceleration.

[0099] Optionally, the acquisition module is also used to acquire an actual steering angle of the steering wheel at the current moment and an actual vehicle speed at the current moment; and determine the expected yaw torque at the current moment based on the actual steering angle at the current moment and the actual vehicle speed at the current moment.

[0100] Optionally, the acquisition module is also used to determine the difference between the expected yaw torque of the vehicle before the current moment and the actual yaw torque before the current moment; when the difference is less than or equal to a preset threshold, determine that the driving condition is the stable condition; when the difference is greater than the preset threshold, acquire the steering wheel speed, and determine the driving condition based on the steering wheel speed.

[0101] Optionally, the execution module is further used to determine the expected steering angle of the rear wheels based on the difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment; and control the rear wheels to deflect to the expected steering angle.

[0102] The embodiment of the present application also provides a computer-readable storage medium on which a computer program / instruction is stored. When the computer program / instruction is executed by a processor, a rear wheel control method as disclosed in the embodiment of the present application is implemented.

[0103] An embodiment of the present application also provides a vehicle, including a rear wheel control system provided by the present application, or including a control module, wherein the control module is used to implement the steps of the rear wheel control method described in the embodiment of the present application.

[0104] The present application provides a rear wheel control method, system and vehicle, the method comprising: obtaining a driving condition of a vehicle and an expected yaw torque of the vehicle at a current moment, the driving condition comprising 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, different driving conditions corresponding to different target parameters, the first parameter comprising a driving torque and a braking torque of the vehicle, the second parameter comprising an actual yaw angular velocity acquired by a yaw angular velocity 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 a difference between the actual yaw torque at the current moment and the expected yaw torque at the current moment.

[0105] The present application first determines the target parameter corresponding to the driving condition from the first parameter and the second parameter according to the driving condition of the vehicle. Subsequently, according to different target parameters, the actual yaw torque of the vehicle at the current moment is determined, and then the rear wheel deflection of the vehicle is controlled 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 it can be calculated by the driving torque at the current moment and the braking torque at the current moment. However, the actual yaw torque is determined based on the actual yaw angular velocity, and it is necessary to obtain it multiple times through the yaw angular velocity sensor. Therefore, the rear wheel deflection response rate when the rear wheel is controlled based on the first parameter is faster than the rear wheel deflection response rate when the rear wheel is controlled based on the second parameter. It can be seen from this that 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.

[0106] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0107] The embodiments of the present application are described with reference to the flowcharts and / or block diagrams of the methods, systems, electronic devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing terminal device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0108] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing terminal device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0109] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device so that a series of operating steps are executed on the computer or other programmable terminal device to produce a computer-implemented process, thereby providing instructions for executing on the computer or other programmable terminal device to implement the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0110] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0111] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0112] The above is a detailed introduction to a rear wheel control method, system and vehicle provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for general technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for controlling a rear wheel, characterized in that: The method is applied to a rear-wheel steering system, the rear-wheel steering system includes a yaw rate sensor, and the method includes: Acquire a driving condition of a vehicle and an expected yaw torque of the vehicle at a current moment, wherein the driving condition includes a tire blowout condition or a stable condition; Determine a target parameter corresponding to the driving condition from a first parameter and a second parameter used to determine the yaw torque, wherein different driving conditions correspond to different target parameters, the first parameter includes a driving torque and a braking torque of the vehicle, and the second parameter includes an actual yaw angular velocity collected by the yaw angular velocity sensor; determining, based on the target parameter, an actual yaw torque of the vehicle at the current moment; Based on the difference between the actual yaw torque at the current moment and the desired yaw torque at the current moment, the rear wheel yaw of the vehicle is controlled.

2. The rear wheel control method according to claim 1, characterized in that: The step of determining a target parameter corresponding to the driving condition from the first parameter and the second parameter used to determine the yaw torque comprises: When the driving condition is the tire blowout condition, determining the target parameter to be the first parameter; When the driving condition is the stable condition, the target parameter is determined to be the second parameter.

3. The rear wheel control method according to claim 1, characterized in that: The target parameter includes the first parameter, and determining the actual yaw torque of the vehicle at the current moment based on the target parameter includes: respectively acquiring state parameters of a plurality of wheels, wherein the state parameters include moment of inertia, cornering stiffness, and slip angle; Determine the longitudinal forces respectively applied to the plurality of wheels based on the braking torque, the driving torque and the rotational inertia of the plurality of wheels, and determine the lateral forces respectively applied to the plurality of wheels based on the slip angles and the cornering stiffnesses of the plurality of wheels; The actual yaw torque at the current moment is determined based on the lateral forces and the longitudinal forces respectively exerted on the plurality of wheels.

4. The rear wheel control method according to claim 3, characterized in that: The step of obtaining the moment of inertia and the cornering stiffness comprises: Obtaining the tire pressure of the wheel; Based on the tire pressure of the wheel, the moment of inertia and the cornering stiffness of the wheel are determined.

5. The rear wheel control method according to claim 1, characterized in that: The target parameter includes the second parameter, and determining the actual yaw torque of the vehicle at the current moment based on the target parameter includes: Determine the actual yaw acceleration of the vehicle at the current moment based on the actual yaw angular velocity collected by the yaw angular velocity sensor at the current moment and multiple historical moments before the current moment; The actual yaw torque at the current moment is determined based on the actual yaw angular acceleration.

6. The rear wheel control method according to claim 1, characterized in that: The step of obtaining the expected yaw torque at the current moment includes: Obtaining the actual turning angle of the steering wheel and the actual speed of the vehicle at the current moment; Based on the actual steering angle at the current moment and the actual vehicle speed at the current moment, the expected yaw torque at the current moment is determined.

7. The rear wheel control method according to claim 1, characterized in that: The step of obtaining the driving condition of the vehicle comprises: determining 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; When the difference is less than or equal to a preset threshold, determining that the driving condition is the stable condition; When the difference is greater than the preset threshold, the steering wheel speed is acquired, and the driving condition is determined based on the steering wheel speed.

8. The rear wheel control method according to claim 1, characterized in that: The 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 comprises: determining a desired steering angle of the rear wheels based on a difference between the actual yaw torque at the current moment and the desired yaw torque at the current moment; The rear wheels are controlled to steer to the desired steering angle.

9. A rear wheel control system, characterized in that: The control system is applied to a rear-wheel steering system, the rear-wheel steering system includes a yaw rate sensor, and the control system includes: An acquisition module, used for acquiring a driving condition of a vehicle and an expected yaw torque of the vehicle at a current moment, wherein the driving condition includes a tire blowout condition or a stable condition; a determination module, configured to determine a target parameter corresponding to the driving condition from a first parameter and a second parameter used to determine the yaw torque, wherein different driving conditions correspond to different target parameters, wherein the first parameter includes a driving torque and a braking torque of the vehicle, and the second parameter includes an actual yaw angular velocity collected by the yaw angular velocity sensor; A decision module, configured to determine an actual yaw torque of the vehicle at the current moment based on the target parameter; The execution module is configured to control the rear wheel yaw of the vehicle based on a difference between the actual yaw torque at the current moment and the desired yaw torque at the current moment.

10. A vehicle, characterized in that: A control system for the rear wheels comprising the control system of claim 9, or a control module, wherein the control module is used to implement the steps of the rear wheel control method of any one of claims 1-8.

Images