Rear wheel steering control method and rear wheel steering system

Abstract

The invention relates to a rear wheel steering control method and a rear wheel steering control system. The rear wheel steering control method comprises the steps that S1, the steering angle and the yaw velocity of a steering wheel are obtained in real time; s2, judging whether the vehicle is in a straight running state or not based on the steering angle and the yaw velocity of the steering wheel; s3, judging whether the vehicle enters the bisection road surface or not in response to the condition that the vehicle is in the straight running state; s4, after the vehicle enters the halving road surface, whether the driver intends to keep the vehicle straight on the halving road surface or not is judged; and S5, in response to the situation that the driver intends to go straight on the bisection road surface, rear wheels are controlled to enable the yaw velocity of the vehicle to be 0. Data can be obtained conveniently, hysteresis is avoided, accuracy is high, the driving state of the vehicle can be reflected accurately, the driving intention of a driver can be judged accurately, the rear wheel turning angle is controlled under the condition that the driver intends to go straight, and the vehicle is made to go straight before and after entering the bisection road surface without additional operation such as steering wheel rotation.

Description

Technical Field

[0001] The present invention relates to the technical field of rear wheel steering, and in particular to a rear wheel steering control method and a rear wheel steering system. Background Art

[0002] A split road means that when a vehicle is driving on a road, the adhesion coefficients of the wheels on the left and right sides of the vehicle are different, such as Figure 1 As shown by the arrow, the adhesion coefficient is larger on the left and smaller on the right. On a split road, if the driver presses the accelerator pedal hard, even if the driver does not turn the steering wheel, the different adhesion coefficients of the left and right wheels will cause the drive torque between the left and right wheels to be inconsistent, which will lead to the generation of yaw torque (or yaw acceleration), thereby causing the vehicle's driving direction to deviate.

[0003] Vehicles with only front-wheel steering, where the driver must turn the steering wheel to keep the vehicle moving in a straight line, because the steering of the front wheels is usually directly controlled by the driver by turning the steering wheel. Vehicles with rear-wheel steering, where the rear wheels can be steered when necessary. The rear-wheel steering can be turned as needed and is not coupled to the steering wheel. If the vehicle has rear-wheel steering, the driver can keep the vehicle moving in a straight line without additional action by automatically steering the rear wheels.

[0004] In the related art, it is disclosed that the rear-wheel steering system can be used on normal roads or split roads, but it does not disclose or involve how to correctly identify the driver's driving intention, that is, whether to go straight or turn, which is crucial to the control of the rear-wheel steering. Summary of the invention

[0005] In order to overcome the problems existing in the related art, the present disclosure provides a rear-wheel steering control method and a rear-wheel steering control system.

[0006] According to a first aspect of an embodiment of the present disclosure, the present disclosure provides a rear-wheel steering control method, step S1: acquiring a steering wheel steering angle and a yaw angular velocity in real time; step S2: judging whether a vehicle is in a straight-ahead state based on the steering wheel steering angle and the yaw angular velocity; step S3: judging whether the vehicle enters a split road surface in response to the vehicle being in a straight-ahead state; step S4: judging whether a driver intends to keep the vehicle going straight on the split road surface in response to the vehicle entering the split road surface; step S5: controlling the rear wheels to make the yaw angular velocity of the vehicle zero in response to the driver intending to keep the vehicle going straight on the split road surface.

[0007] In some embodiments, in step S2, when the steering wheel steering angle and the yaw angular velocity are both 0, it is determined that the vehicle is in a straight-ahead state; if at least one of the steering wheel steering angle and the yaw angular velocity is not equal to 0, it is determined that the vehicle is in a non-straight-ahead state, and the process returns to step S1.

[0008] In some embodiments, in step S3, in response to the vehicle being in a straight-moving state, if it is determined that the vehicle has not entered a bisected road, the process returns to step S1.

[0009] In some embodiments, in step S4, the conditions for judging whether the driver intends to keep the vehicle going straight on a bisected road include: the value of the steering wheel steering angle is 0; or the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle is within a preset range; the conditions for judging whether the driver has no intention to keep the vehicle going straight on a bisected road include: the direction of the steering wheel steering angle is the same as the direction of the yaw angular velocity; or the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle exceeds the preset range.

[0010] In some embodiments, in step S5, controlling the rear wheels to make the yaw velocity of the vehicle 0 specifically includes: a feedforward step S51: obtaining a target rear wheel steering angle based on the yaw velocity and the vehicle speed; a PID closed-loop adjustment step S52: adjusting the target rear wheel steering angle through proportion P, integral I and differential D based on the error value of the yaw velocity, wherein the error value of the yaw velocity = actual yaw velocity - target yaw velocity.

[0011] In some embodiments, step S4 further includes step S41 after step S41, in response to the driver having no intention to keep the vehicle going straight on the bisected road, controlling the rear wheel steering angle to remain unchanged.

[0012] In some embodiments, step S5 also includes step S6, which determines whether the vehicle has exited the divided road surface. In response to the vehicle exiting the divided road surface, the rear wheel steering angle is adjusted according to the normal driving state of the rear wheels of the vehicle, and the process returns to step S1; in response to the vehicle not exiting the divided road surface, the process returns to step S4.

[0013] According to a second aspect of an embodiment of the present disclosure, the present disclosure provides a rear-wheel steering control system, including an acquisition unit configured to acquire a steering wheel steering angle and a yaw angular velocity in real time; a first judgment unit configured to judge whether the vehicle is in a straight-ahead state based on the steering wheel steering angle and the yaw angular velocity; a second judgment unit configured to judge whether the vehicle enters a split road surface in response to the vehicle being in a straight-ahead state; a third judgment unit configured to judge whether the driver intends to keep the vehicle going straight on the split road surface in response to the vehicle entering the split road surface; and a processing control unit configured to control the rear wheels to make the yaw angular velocity of the vehicle zero in response to the driver's intention to keep the vehicle going straight on the split road surface.

[0014] In some embodiments, in the third judgment unit, the conditions for judging whether the driver intends to keep the vehicle going straight on a bisected road include: the value of the steering wheel steering angle is 0; or the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle is within a preset range; the conditions for judging whether the driver has no intention to keep the vehicle going straight on a bisected road include: the direction of the steering wheel steering angle is the same as the direction of the yaw angular velocity; or the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle exceeds the preset range.

[0015] In some embodiments, in the processing control unit, the control of the rear wheels to make the yaw velocity of the vehicle 0 specifically includes: a feedforward unit, configured to obtain a target rear wheel steering angle based on the yaw velocity and the vehicle speed; a PID closed-loop adjustment unit, configured to adjust the target rear wheel steering angle through proportion P, integral I and differential D based on the error value of the yaw velocity, wherein the error value of the yaw velocity = actual yaw velocity - target yaw velocity.

[0016] The technical solution provided by the embodiments of the present disclosure may include the following beneficial effects: before entering the bifurcated road, whether the vehicle is in a straight-ahead state is determined by the steering wheel steering angle and yaw angular velocity obtained in real time; after entering the bifurcated road, whether the driver intends to keep the vehicle going straight is accurately identified by the steering wheel steering angle and yaw angular velocity obtained in real time, thereby controlling the automatic steering of the rear wheels to keep the vehicle going straight. The steering wheel steering angle and yaw angular velocity are easy to obtain in real time, without lag and with high accuracy. Therefore, the method of the present invention can reflect the driving state of the vehicle in real time and accurately, thereby further determining the driver's driving intention, and thus ensuring that the control of the rear wheels is real-time and more accurate. In the case where the driver intends to keep going straight, there is no need for additional operations such as turning the steering wheel, so that the vehicle can keep going straight before and after entering the bifurcated road. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0018] Figure 1 It is a schematic diagram of the adhesion coefficient of the left and right wheels of a vehicle when it is on a bisected road;

[0019] Figure 2 is a schematic diagram showing that the driver intends to keep the vehicle going straight;

[0020] Figure 3 is a schematic diagram showing that the driver has no intention to keep the vehicle going straight;

[0021] Figure 4 It is a flowchart of a rear wheel steering control method according to an exemplary embodiment. DETAILED DESCRIPTION

[0022] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0023] As can be seen from the background technology, in a split road, how to accurately identify the driver's intention to control the rear wheel steering is extremely important. In the known related technologies, the driver's intention can be determined based on navigation and road information, but there are the following problems: First, the road information is not real-time but delayed. Secondly, the driver may not necessarily follow the navigation information; finally, the information provided by the navigation information corresponding to the actual situation is not accurate enough. For example, the current navigation information prompts to go straight, and there is still lane change behavior during the straight process (the yaw angular velocity is not equal to 0 at this time). Therefore, the driver's intention cannot be accurately determined based on navigation and road information, which affects the accuracy of rear wheel steering control. Especially before entering the split road, the driver keeps executing, and after entering the split road, how to accurately judge whether the driver intends to continue to go straight.

[0024] In order to solve the above technical problems, the present disclosure provides a rear wheel steering control method, such as Figure 4As shown, it includes: step S1: real-time acquisition of steering wheel steering angle and yaw angular velocity. Step S2: judging whether the vehicle is in a straight-moving state based on the steering wheel steering angle and yaw angular velocity. Step S3: in response to the vehicle being in a straight-moving state, judging whether the vehicle enters a split road surface. Step S4: in response to the vehicle entering a split road surface, judging whether the driver intends to keep the vehicle going straight on the split road surface. Step S5: in response to the driver intending to keep the vehicle going straight on the split road surface, controlling the rear wheels to make the yaw angular velocity of the vehicle 0.

[0025] Among them, step S1 is the step before entering the bisecting road, that is, the vehicle is driving on a normal road. Therefore, the steering wheel steering angle and yaw angular velocity acquired in real time are all real-time data when driving on a normal road.

[0026] Both the steering wheel angle and the yaw angular velocity can be obtained through sensors and the like. In the present disclosure, no improvement is made to the method of obtaining the steering wheel angle and the yaw angular velocity. Existing devices in the vehicle are used, and data collection is simple and easy, which saves the cost of data collection.

[0027] Furthermore, step S2 is also a step before entering the bifurcated road. In some embodiments, in step S2, when the steering wheel steering angle and the yaw angular velocity are both 0, it is determined that the vehicle is in a straight-ahead state; if at least one of the steering wheel steering angle and the yaw angular velocity is not equal to 0, it is determined that the vehicle is in a non-straight-ahead state, for example, the vehicle is in a turning state, and therefore returns to step S1.

[0028] When the steering wheel steering angle and yaw angular velocity are both 0, it can be assumed that the driver has not turned the steering wheel, the adhesion coefficients of the wheels on both sides of the vehicle are the same, the driving torques of the wheels on both sides are the same, and no yaw torque is generated, so it is recognized that the vehicle is in a straight-ahead state.

[0029] It should be noted that the steering wheel steering angle and the yaw angular velocity are both 0, which does not mean that the actual value of the steering wheel steering angle and the actual value of the yaw angular velocity are 0. The actual values ​​may be values ​​close to 0 or values ​​within a preset range. At this time, it means that the steering wheel steering angle and the yaw angular velocity are 0, so as to determine and identify that the vehicle is in a straight-ahead state.

[0030] The rear wheel steering control method disclosed in the present invention is applied to the following specific situation, that is, before entering the bifurcated road, the vehicle is in a straight-moving state, and after entering the bifurcated road, the vehicle intends to keep moving straight. By identifying whether the driver's intention is to continue moving straight, the rear wheel steering angle is automatically controlled without additional operations such as turning the steering wheel, so that the vehicle keeps moving straight.

[0031] Therefore, when at least one of the steering wheel steering angle and the yaw angular velocity is not equal to 0, it is recognized that the vehicle is turning and the vehicle is in a non-straight state. The vehicle is already in a non-straight state before entering the bisecting road. Therefore, this situation is not within the protection scope of the rear wheel steering control method disclosed in the present invention. It is necessary to return to step S1 and continue to collect the steering wheel steering angle and yaw angular velocity in real time.

[0032] Further, in step S3, in response to the vehicle being in a straight-moving state, if it is determined that the vehicle has not entered a bisected road surface, the process returns to step S1.

[0033] After determining or identifying that the vehicle is in a straight-ahead state, continue to identify whether the vehicle has entered a bifurcated road surface. If the vehicle has not entered a bifurcated road surface, the vehicle itself is in a straight-ahead state, and there will be no different driving torques on the wheels on both sides, and no yaw torque. Therefore, it is not within the protection scope of the present disclosure. Then return to step S1, continue to collect the steering wheel steering angle and yaw angular velocity in real time, and continue to execute step S2.

[0034] It should be noted that how to identify whether a vehicle has entered a divided road is an existing technology in the relevant technology, and the present disclosure does not improve it. Therefore, how to identify whether a vehicle has entered a divided road, even if the present disclosure does not describe it in detail, does not affect the implementation of the method of the present disclosure or the realization of the technical effect.

[0035] In some embodiments, in step S4, the condition for judging that the driver intends to keep the vehicle going straight on the bisected road includes: the value of the steering wheel steering angle is 0; or the direction of the steering wheel steering angle is opposite to the direction of the yaw rate, and the value of the steering wheel steering angle is within a preset range. The condition for judging that the driver does not intend to keep the vehicle going straight on the bisected road includes: the direction of the steering wheel steering angle is the same as the direction of the yaw rate; or the direction of the steering wheel steering angle is opposite to the direction of the yaw rate, and the value of the steering wheel steering angle exceeds the preset range.

[0036] Specifically, after the vehicle in the straight-moving state enters the split road, the method disclosed herein executes step S4 to identify that the driver intends to continue to keep the vehicle moving straight on the split road, including the following two situations.

[0037] In the first case, when the steering wheel angle is detected to be 0, that is, the driver is not detected turning the steering wheel, when the vehicle first enters the divided road, the different adhesion coefficients on the left and right sides of the vehicle affect the left and right wheels, so that the driver fails to react in time in a short period of time. It can be identified that the driver did not intend to change the direction of the vehicle when the vehicle first entered the divided road, but intended to keep the vehicle going straight.

[0038] The second case, such as Figure 2 and Figure 3As shown in , the adhesion coefficient of the left wheel is large, and the adhesion coefficient of the right wheel is small, so the vehicle has a yaw torque (or yaw angular velocity) toward the right direction, as shown in Figure 2 and Figure 3 If the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, that is, when the vehicle first enters the bisected road, the driver has already responded to resist the yaw torque, that is, turning the steering wheel so that the steering wheel Figure 2 If the arrow D2 shown rotates, it means that the driver intends to keep the vehicle going straight.

[0039] Among them, in the second case, the direction of the steering wheel steering angle is opposite to the direction of the yaw torque, but the steering wheel steering angle value is within the preset range, that is, the steering wheel steering angle value cannot be too large. If the steering wheel angle exceeds the preset range, it means that the driver intends to change the direction of the vehicle (such as the fourth case described below).

[0040] In some embodiments, in step S4, identifying that the driver has no intention to continue to keep the vehicle going straight on the split road also includes the following two situations.

[0041] The third case, such as Figure 3 As shown, the direction of the steering wheel steering angle (indicated by arrow D2) is the same as the direction of the yaw angular velocity (or yaw moment) (indicated by arrow D1), which means that the driver turns the steering wheel and makes the vehicle tend to turn right. Therefore, it is recognized that the driver has no intention of keeping the vehicle going straight when entering the divided road.

[0042] In the fourth case, the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle exceeds the preset range, which means that the vehicle driven by the driver has a tendency to turn left. Therefore, it is identified that the driver has no intention to continue to keep the vehicle going straight on the divided road. If the value of the steering wheel steering angle does not exceed the preset range, it is the second case mentioned above, that is, the driver has the intention to continue to keep the vehicle going straight on the divided road.

[0043] In some embodiments, in step S5, the rear wheels are controlled to make the yaw rate of the vehicle 0, which specifically includes: feedforward step S51: based on the yaw rate and the vehicle speed, the target rear wheel angle is obtained; wherein, the greater the yaw rate, the greater the target rear wheel angle; the greater the vehicle speed, the greater the target rear wheel angle. PID closed-loop adjustment step S52: based on the error value of the yaw rate, the target rear wheel angle is adjusted by proportion P, integral I and differential D, wherein the error value of the yaw rate = actual yaw rate - target yaw rate, the actual yaw rate can be measured in real time by the sensor, and when the driver intends to keep the vehicle moving straight, the target yaw rate can be 0.

[0044] From the above content, it can be seen that before the vehicle enters the forked road, the steering wheel steering angle and yaw angular velocity obtained in real time are used to determine whether the vehicle is in a straight-ahead state. After entering the forked road, the steering wheel steering angle and yaw angular velocity obtained in real time are used to accurately identify whether the driver intends to keep the vehicle going straight, thereby controlling the automatic steering of the rear wheels to keep the vehicle going straight. The steering wheel steering angle and yaw angular velocity are easy to obtain in real time, without lag and with high accuracy. Therefore, the method of the present invention can reflect the driving state of the vehicle in real time and accurately, thereby further accurately determining the driver's driving intention, and thus ensuring that the control of the rear wheels is real-time and more accurate. In the case where the driver intends to keep going straight, there is no need to turn the steering wheel or other additional operations, so that the vehicle can keep going straight before and after entering the forked road.

[0045] In some embodiments, step S4 also includes step S41, in response to the driver having no intention of keeping the vehicle going straight on the divided road, the rear wheel steering angle is controlled to remain unchanged, that is, the rear wheel steering control system does not make any change to the rear wheel steering angle, and keeps the rear wheel steering angle detected after entering the divided road unchanged.

[0046] From the above, it can be seen that in step S4, that is, after the vehicle enters the bisected road, there will be four situations. Only when the first and second situations occur, it is recognized that the driver intends to keep the vehicle going straight. When the third and fourth situations occur, it is recognized that the driver has no intention to keep the vehicle going straight. The recognition method is based on the real-time monitoring of the steering wheel steering angle and yaw angular velocity. The data acquisition is reliable and simple, and has good real-time performance and high accuracy.

[0047] In some embodiments, step S5 further includes step S6 to determine whether the vehicle has driven out of the split road.

[0048] In response to the vehicle driving out of the bisected road, the rear wheel steering angle is adjusted according to the normal driving state of the rear wheels of the vehicle, and the process returns to step S1.

[0049] Among them, the normal driving state means that when the vehicle is driving on a normal road, the rear wheel steering angle is not 0, but there is a certain steering angle. For example, when the vehicle is driving slowly, the steering of the front wheels and the steering of the rear wheels are opposite, thereby ensuring that the vehicle has a smaller turning radius; when the vehicle is driving at high speed, the steering of the front wheels and the steering of the rear wheels are the same, thereby improving the driving stability of the vehicle.

[0050] In response to the vehicle not exiting the divided road, the process returns to step S4 to continuously determine whether the driver intends to keep the vehicle going straight on the divided road until the vehicle exits the divided road.

[0051] Based on the same inventive concept, the present disclosure provides a rear-wheel steering control system, including an acquisition unit configured to acquire a steering wheel steering angle and a yaw angular velocity in real time; a first judgment unit configured to judge whether the vehicle is in a straight-ahead state based on the steering wheel steering angle and the yaw angular velocity; a second judgment unit configured to judge whether the vehicle enters a split road surface in response to the vehicle being in a straight-ahead state; a third judgment unit configured to judge whether the driver intends to keep the vehicle going straight on the split road surface in response to the vehicle entering the split road surface; and a first control unit configured to control the rear wheels to make the vehicle's yaw angular velocity 0 in response to the driver's intention to keep the vehicle going straight on the split road surface.

[0052] Further, in the third judgment unit, the conditions for judging whether the driver intends to keep the vehicle going straight on a divided road include: the value of the steering wheel steering angle is 0; or the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle is within a preset range; the conditions for judging whether the driver has no intention to keep the vehicle going straight on a divided road include: the direction of the steering wheel steering angle is the same as the direction of the yaw angular velocity; or the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle exceeds the preset range.

[0053] In some embodiments, in the processing control unit, the rear wheels are controlled to make the yaw velocity of the vehicle 0, and specifically include: a feedforward unit, configured to obtain the target rear wheel angle based on the yaw velocity and the vehicle speed; a PID closed-loop adjustment unit, configured to adjust the target rear wheel angle based on the error value of the yaw velocity through proportion P, integral I and differential D, wherein the error value of the yaw velocity = actual yaw velocity - target yaw velocity.

[0054] In some embodiments, the rear-wheel steering control unit further includes: a fourth judgment unit configured to judge whether the vehicle has driven out of a split road surface.

[0055] The specific manner in which the functions implemented in the rear-wheel steering control system in the above embodiment have been described in detail in the embodiment of the rear-wheel steering control method, and will not be elaborated on here.

[0056] It is to be understood that in the present disclosure, "plurality" refers to two or more than two, and other quantifiers are similar. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. The singular forms "a", "the" and "the" are also intended to include plural forms, unless the context clearly indicates other meanings.

[0057] It is further understood that the terms "first", "second", etc. are used to describe various structures, but these structures should not be limited to these terms. These terms are only used to distinguish structures of the same type from each other, and do not indicate a specific order or importance. In fact, the expressions "first", "second", etc. can be used interchangeably. For example, without departing from the scope of the present disclosure, a first structure can also be referred to as a second structure, and similarly, a second structure can also be referred to as a first structure.

[0058] It will be further understood that the terms “center”, “longitudinal”, “lateral”, “front”, “back”, “up”, “down”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation.

[0059] It can be further understood that, unless otherwise specified, “connection” includes a direct connection without other components between the two, and also includes an indirect connection with other components between the two.

[0060] It is further understood that, although the operations are described in a specific order in the drawings in the embodiments of the present disclosure, it should not be understood as requiring the operations to be performed in the specific order shown or in a serial order, or requiring the execution of all the operations shown to obtain the desired results. In certain environments, multitasking and parallel processing may be advantageous.

[0061] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the following scope of rights.

[0062] It should be understood that the present disclosure is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the scope of the appended claims.

Claims

1. A rear wheel steering control method, characterized in that: Step S1: obtaining the steering wheel steering angle and yaw angular velocity in real time; Step S2: judging whether the vehicle is in a straight-ahead state based on the steering wheel steering angle and the yaw angular velocity; Step S3: In response to the vehicle being in a straight-moving state, determining whether the vehicle enters a bisected road; Step S4: in response to the vehicle entering the bisected road, determining whether the driver intends to keep the vehicle going straight on the bisected road; Step S5: In response to the driver's intention to keep going straight on the bisected road, the rear wheels are controlled to make the yaw rate of the vehicle zero.

2. The rear wheel steering control method according to claim 1, characterized in that: In step S2, when the steering wheel steering angle and the yaw angular velocity are both 0, it is determined that the vehicle is in a straight-ahead state; if at least one of the steering wheel steering angle and the yaw angular velocity is not equal to 0, it is determined that the vehicle is in a non-straight-ahead state, and the process returns to step S1.

3. The rear wheel steering control method according to claim 1, characterized in that: In step S3, in response to the vehicle being in a straight-moving state, if it is determined that the vehicle has not entered a bisected road surface, the process returns to step S1.

4. The rear wheel steering control method according to claim 1, characterized in that: In step S4, The conditions for judging whether the driver intends to keep the vehicle going straight on a bisected road include: the value of the steering wheel steering angle is 0; or the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle is within a preset range; The conditions for judging whether the driver has no intention to keep the vehicle going straight on a divided road include: the direction of the steering wheel steering angle is the same as the direction of the yaw angular velocity; or the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle exceeds a preset range.

5. The rear wheel steering control method according to claim 4, characterized in that: In step S5, controlling the rear wheels to make the yaw rate of the vehicle 0 specifically includes: Feedforward step S51: obtaining a target rear wheel steering angle based on the yaw angular velocity and the vehicle speed; PID closed-loop adjustment step S52: Based on the error value of the yaw rate, the target rear wheel steering angle is adjusted through the proportion P, the integral I and the differential D, wherein the error value of the yaw rate = the actual yaw rate - the target yaw rate.

6. The rear wheel steering control method according to claim 4, characterized in that: The step S4 also includes a step S41 after the step S4, in response to the driver having no intention to keep the vehicle going straight on the bisected road, controlling the rear wheel steering angle to remain unchanged.

7. The rear wheel steering control method according to claim 4, characterized in that: The step S5 further includes a step S6, determining whether the vehicle has driven out of the bisected road surface. In response to the vehicle driving out of the bisected road, adjusting the rear wheel steering angle according to the normal driving state of the rear wheels of the vehicle, and returning to step S1; In response to the vehicle not driving out of the bisected road, the process returns to step S4.

8. A rear wheel steering control system, characterized in that: An acquisition unit configured to acquire a steering wheel steering angle and a yaw angular velocity in real time; A first judgment unit is configured to judge whether the vehicle is in a straight-moving state based on the steering wheel steering angle and the yaw angular velocity; a second determination unit configured to determine whether the vehicle enters a bisected road in response to the vehicle being in a straight-moving state; a third judgment unit configured to judge whether the driver intends to keep the vehicle going straight on the divided road in response to the vehicle entering the divided road; The processing control unit is configured to control the rear wheels to make the yaw rate of the vehicle zero in response to the driver's intention to keep going straight on the bisected road.

9. The rear wheel steering control system according to claim 8, characterized in that: Also includes: In the third judgment unit, The conditions for judging whether the driver intends to keep the vehicle going straight on a bisected road include: the value of the steering wheel steering angle is 0; or the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle is within a preset range; The conditions for judging whether the driver has no intention to keep the vehicle going straight on a divided road include: the direction of the steering wheel steering angle is the same as the direction of the yaw angular velocity; or the direction of the steering wheel steering angle is opposite to the direction of the yaw angular velocity, and the value of the steering wheel steering angle exceeds a preset range.

10. The rear wheel steering control system according to claim 4, characterized in that: In the processing control unit, controlling the rear wheels to make the yaw rate of the vehicle 0 further specifically includes: a feedforward unit configured to obtain a target rear wheel steering angle based on the yaw angular velocity and the vehicle speed; The PID closed-loop adjustment unit is configured to adjust the target rear wheel steering angle through a proportional P, an integral I and a differential D based on an error value of the yaw rate, wherein the error value of the yaw rate=the actual yaw rate-the target yaw rate.

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