Rear wheel steering control method, device, control apparatus, and vehicle

Abstract

This application discloses a rear-wheel steering control method, device, control equipment, and vehicle. The method includes: determining a first target rear-wheel steering angle and a first target rear-wheel steering rate based on vehicle speed and steering wheel angle; determining a rear-wheel steering angle limit and a rear-wheel steering rate limit based on vehicle speed and current vehicle parameters; determining a second target rear-wheel steering angle based on the first target rear-wheel steering angle and the rear-wheel steering angle limit; determining a second target rear-wheel steering rate based on the first target rear-wheel steering rate and the rear-wheel steering rate limit; and controlling rear-wheel steering based on the second target rear-wheel steering angle and the second target rear-wheel steering rate. The scheme disclosed in this application determines the rear-wheel steering angle limit and the rear-wheel steering rate limit based on vehicle speed and current vehicle parameters, and restricts the first target rear-wheel steering angle and the first target rear-wheel steering rate based on these two limits. The restricted data is used to control rear-wheel steering, thereby improving the rationality of rear-wheel steering intervention and enhancing vehicle driving safety.

Description

Technical Field

[0001] This application relates to the field of vehicle steering control technology, and in particular to a rear-wheel steering control method, device, control equipment, and vehicle. Background Technology

[0002] The advent of rear-wheel steering solved the problem of difficulty in turning at low speeds, significantly reducing the turning radius of the vehicle and improving its agility.

[0003] However, improper rear-wheel steering intervention can lead to vehicle instability or even lane departure, endangering the driver and passengers.

[0004] In conclusion, how to improve the rationality of rear-wheel steering intervention in order to enhance vehicle driving safety is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a rear-wheel steering control method, device, control equipment and vehicle to improve the rationality of rear-wheel steering intervention, thereby improving vehicle driving safety.

[0006] To achieve the above objectives, this application provides the following technical solution: A rear-wheel steering control method includes: determining a first target rear-wheel steering angle and a first target rear-wheel steering rate based on vehicle speed and steering wheel angle; determining a rear-wheel steering angle limit and a rear-wheel steering rate limit based on the vehicle speed and current vehicle parameters; determining a second target rear-wheel steering angle based on the first target rear-wheel steering angle and the rear-wheel steering angle limit; determining a second target rear-wheel steering rate based on the first target rear-wheel steering rate and the rear-wheel steering rate limit; and controlling rear-wheel steering based on the second target rear-wheel steering angle and the second target rear-wheel steering rate.

[0007] Optionally, determining the first target rear wheel angle and the first target rear wheel steering rate based on the vehicle speed and steering wheel angle includes: determining the first target rear wheel angle based on the vehicle speed, the steering wheel angle, the steering wheel angular velocity and the coefficient of adhesion, and determining the first target rear wheel steering rate based on the first target rear wheel angle.

[0008] Optionally, determining the first target rear wheel steering angle based on the vehicle speed, the steering wheel angle, the steering wheel angular velocity, and the coefficient of adhesion includes: determining a base rear wheel steering coefficient based on the vehicle speed and the steering wheel angle; determining a first correction coefficient based on the steering wheel angular velocity; determining a second correction coefficient based on the coefficient of adhesion; and determining the front wheel steering angle based on the steering wheel angle. Wherein, if the vehicle speed does not exceed a speed threshold, the vehicle speed and the base rear wheel steering coefficient are negatively correlated; if the vehicle speed exceeds the speed threshold, the base rear wheel steering coefficient is equal to 0; the steering wheel angular velocity is negatively correlated with the first correction coefficient; the coefficient of adhesion is positively correlated with the second correction coefficient; and the first target rear wheel steering angle is determined based on the base rear wheel steering coefficient, the first correction coefficient, the second correction coefficient, and the front wheel steering angle.

[0009] Optionally, determining a base rear wheel steering coefficient based on the vehicle speed and the steering wheel angle, determining a first correction coefficient based on the steering wheel angular velocity, and determining a second correction coefficient based on the adhesion coefficient includes: determining the base rear wheel steering coefficient based on the vehicle speed, the steering wheel angle, and the driving mode; determining the first correction coefficient based on the steering wheel angular velocity and the driving mode; and determining the second correction coefficient based on the adhesion coefficient and the driving mode.

[0010] Optionally, before controlling the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate, the method further includes: if the vehicle speed does not exceed a vehicle speed threshold, determining that the steering direction of the rear wheels is opposite to the steering direction of the front wheels; controlling the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate includes: controlling the rear wheel steering based on the steering direction of the rear wheels, the second target rear wheel steering angle, and the second target rear wheel steering rate.

[0011] Optionally, it further includes: if the number of zero crossings of the front wheel steering angle within a first preset time period is greater than 1, then after the steering direction of the current wheel is maintained in the current direction for a second preset time period, the steering direction of the rear wheel is updated according to the steering direction of the front wheel and the vehicle speed.

[0012] Optionally, the current vehicle parameters include suspension height, rear wheel steering motor torque and speed. Determining rear wheel steering angle limits and rear wheel steering rate limits based on the vehicle speed and current vehicle parameters includes: determining a first rear wheel steering angle limit based on the suspension height; determining a first rear wheel steering rate limit based on the torque and speed of the rear wheel steering motor; determining a second rear wheel steering angle limit and a second rear wheel steering rate limit based on the vehicle speed; determining a second target rear wheel steering angle based on the first target rear wheel steering angle and the rear wheel steering angle limits; and determining a second target rear wheel steering rate limit based on the first target rear wheel steering angle and the rear wheel steering angle limits. Determining a second target rear wheel steering rate based on the first rear wheel angle limit and the first target rear wheel angle includes: determining a target rear wheel angle after a limit based on the first rear wheel angle limit and the first target rear wheel angle; determining a target rear wheel steering rate after a limit based on the first rear wheel steering rate limit and the first target rear wheel steering rate, wherein the target rear wheel angle after the limit is not greater than the first rear wheel angle limit, and the target rear wheel steering rate after the limit is not greater than the first rear wheel steering rate limit; determining a second target rear wheel steering rate based on the second rear wheel angle limit and the target rear wheel steering rate after the limit. The target rear wheel steering angle is determined by: 1) a second target rear wheel steering rate determined based on a second rear wheel steering rate limit and a rear wheel steering rate after the limit, wherein the second target rear wheel steering angle is not greater than the second rear wheel steering angle limit and the second target rear wheel steering rate is not greater than the second rear wheel steering rate limit; or 2) a second target rear wheel steering angle is determined based on a first rear wheel steering angle limit and a first target rear wheel steering angle, and the second target rear wheel steering rate is determined based on the first rear wheel steering rate limit and the first target rear wheel steering rate; wherein the second target rear wheel steering angle is not greater than the first rear wheel steering angle limit and the second target rear wheel steering rate is not greater than the first rear wheel steering rate limit; or 3) a second target rear wheel steering angle is determined based on a second rear wheel steering angle limit and a first target rear wheel steering angle, and the second target rear wheel steering rate is determined based on the second rear wheel steering rate limit and the first target rear wheel steering rate; wherein the second target rear wheel steering angle is not greater than the second rear wheel steering angle limit and the second target rear wheel steering rate is not greater than the second rear wheel steering rate limit.

[0013] Optionally, determining the first rear wheel steering rate limit based on the torque and speed of the rear wheel steering motor includes: determining the rack force based on the torque of the rear wheel steering motor; determining the maximum rack speed based on the rack force; determining the theoretical rack speed based on the speed of the rear wheel steering motor; determining the target rack speed based on the maximum rack speed and the theoretical rack speed; and determining the first rear wheel steering rate limit based on the target rack speed.

[0014] Optionally, it further includes: if the suspension height changes, the first rear wheel steering angle limit corresponding to the suspension height before the change changes at a preset rate of change to the first rear wheel steering angle limit corresponding to the suspension height after the change.

[0015] Optionally, before controlling the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate, the method further includes: determining whether the parameters used to determine the first target rear wheel steering angle or the state of the rear wheel steering system are abnormal; if so, determining the third target rear wheel steering rate and controlling the rear wheel steering based on the third target rear wheel steering rate.

[0016] Optionally, after controlling the rear wheel steering according to the third target rear wheel steering rate, the method further includes: if the abnormal parameter occurs or the state of the rear wheel steering system returns to normal, determining whether the vehicle speed exceeds a first preset safe speed; if the vehicle speed exceeds the first preset safe speed, controlling the rear wheels to remain in the neutral position; if the vehicle speed does not exceed the first preset safe speed, determining a new second target rear wheel angle and a new second target rear wheel steering rate, and controlling the rear wheel steering according to the new second target rear wheel angle and the new second target rear wheel steering rate.

[0017] Optionally, before controlling the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate, the method further includes: if the steering wheel angle crosses zero and the rate of change of the vehicle speed is greater than a preset rate of change, then determining a fourth target rear wheel steering rate, and controlling the rear wheel steering based on the fourth target rear wheel steering rate; after the rear wheel steering rate is in the center position, if the vehicle speed exceeds a second preset safe speed, then controlling the rear wheels to remain in the center position; if the vehicle speed does not exceed the second preset safe speed, then determining a new second target rear wheel steering angle and a new second target rear wheel steering rate, and controlling the rear wheel steering based on the new second target rear wheel steering angle and the new second target rear wheel steering rate.

[0018] A rear-wheel steering control device includes: a first determining module, configured to determine a first target rear wheel angle and a first target rear wheel steering rate based on vehicle speed and steering wheel angle, and to determine a rear wheel angle limit and a rear wheel steering rate limit based on current vehicle parameters; a second determining module, configured to determine a second target rear wheel angle based on the first target rear wheel angle and the rear wheel angle limit, and to determine a second target rear wheel steering rate based on the first target rear wheel steering rate and the rear wheel steering rate limit; and a first controlling module, configured to control rear wheel steering based on the second target rear wheel angle and the second target rear wheel steering rate.

[0019] A control device includes: a memory for storing a computer program; and a processor for executing the computer program to implement the steps of the rear wheel steering control method described above.

[0020] A vehicle including the control device as described above.

[0021] This application provides a rear-wheel steering control method, device, control equipment, and vehicle. The method includes: determining a first target rear-wheel steering angle and a first target rear-wheel steering rate based on vehicle speed and steering wheel angle; determining a rear-wheel steering angle limit and a rear-wheel steering rate limit based on vehicle speed and current vehicle parameters; determining a second target rear-wheel steering angle based on the first target rear-wheel steering angle and the rear-wheel steering angle limit; determining a second target rear-wheel steering rate based on the first target rear-wheel steering rate and the rear-wheel steering rate limit; and controlling rear-wheel steering based on the second target rear-wheel steering angle and the second target rear-wheel steering rate.

[0022] The technical solution disclosed in this application determines the rear wheel angle limit and the rear wheel steering rate limit based on vehicle speed and current vehicle parameters. Based on the rear wheel angle limit and the rear wheel steering rate limit, it restricts the first target rear wheel angle and the first target rear wheel steering rate determined by vehicle speed and steering wheel angle. Based on the second target rear wheel angle and the second target rear wheel steering rate obtained by the restriction, it performs rear wheel steering control to improve the rationality of rear wheel steering intervention, thereby improving the rationality of steering, reducing the risk of vehicle instability and lane departure, and improving vehicle driving safety.

[0023] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0024] Figure 1 A flowchart illustrating a rear-wheel steering control method provided in some embodiments of this application; Figure 2 A flowchart for determining the target rear wheel angle after setting a limit based on a first target rear wheel angle and a first rear wheel angle limit, provided for some embodiments of this application; Figure 3 A flowchart for determining a second target rear wheel steering angle is provided for some embodiments of this application; Figure 4 A flowchart for determining a second target rear wheel steering angle is provided for some embodiments of this application; Figure 5 A diagram showing the relationship between the modules implementing rear wheel steering control provided in some embodiments of this application; Figure 6 A schematic diagram of the structure of a rear wheel steering control device provided in some embodiments of this application; Figure 7 This is a schematic diagram of the structure of a control device provided in some embodiments of this application. Detailed Implementation

[0025] Rear-wheel steering is a chassis technology that improves vehicle handling, stability, and maneuverability. Its core lies in actively controlling the rear wheels to generate a certain steering angle, working in conjunction with the front-wheel steering to optimize the vehicle's dynamic response.

[0026] As passenger car sizes generally increase, the increased wheelbase leads to a larger turning radius, posing a significant challenge for drivers. Rear-wheel steering addresses this difficulty in low-speed cornering, significantly reducing the turning radius and improving vehicle agility. However, at high speeds, improper rear-wheel steering intervention can lead to vehicle instability and even lane departure, endangering the driver and passengers.

[0027] Therefore, this application provides a rear-wheel steering control method, device, control equipment, and vehicle. The method determines a first target rear-wheel steering angle and a first target rear-wheel steering rate based on vehicle speed and steering wheel angle. It then determines rear-wheel steering angle limits and rear-wheel steering rate limits based on vehicle speed and current vehicle parameters. These limits are used to restrict the first target rear-wheel steering angle and the first target rear-wheel steering rate, respectively, to improve the rationality and reliability of the resulting second target rear-wheel steering angle and second target rear-wheel steering rate. Finally, the method controls rear-wheel steering based on the restricted second target rear-wheel steering angle and second target rear-wheel steering rate to improve the rationality of rear-wheel steering intervention, thereby improving steering rationality, reducing the probability of vehicle instability, lane departure, and other dangerous situations, and improving vehicle driving safety.

[0028] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0029] See Figure 1 This is a flowchart illustrating a rear-wheel steering control method provided in some embodiments of this application. The rear-wheel steering control method provided in some embodiments of this application may include: S11: Determine the first target rear wheel angle and the first target rear wheel steering rate based on vehicle speed and steering wheel angle, and determine the rear wheel angle limit and rear wheel steering rate limit based on vehicle speed and current vehicle parameters.

[0030] It should be noted that the execution subject of the rear wheel steering control method provided in some embodiments of this application can be a control device in a vehicle.

[0031] In some embodiments of this application, the control device can acquire current frame data collected by sensors related to rear wheel steering control (such as vehicle speed sensors, steering wheel angle sensors, etc.). The current frame data includes, but is not limited to, the vehicle's current speed, the vehicle's current steering wheel angle, and current vehicle parameters. The control device can determine a first target rear wheel angle and a first target rear wheel steering rate based on the vehicle's current speed and steering wheel angle. The vehicle speed and the first target rear wheel angle are negatively correlated; that is, the higher the vehicle speed, the smaller the first target rear wheel angle. This ensures agility during low-speed steering and safety at high speeds, reducing the risk of the vehicle deviating from its speed limit or fishtailing at high speeds.

[0032] For example, the method for determining the first target rear wheel steering rate can be as follows: while determining the first target rear wheel steering angle corresponding to the current frame data based on the current frame data, simultaneously obtain the first target rear wheel steering angle corresponding to the previous frame data adjacent to the current frame data; and determine the first target rear wheel steering rate based on the first target rear wheel steering angle corresponding to the previous frame data, the first target rear wheel steering angle corresponding to the current frame data, and the time between the two adjacent frames. In other words, the first target rear wheel steering rate can be determined based on the first target rear wheel steering angle of the current frame and the first target rear wheel steering angle of the previous frame.

[0033] In addition, the control equipment can determine the rear wheel steering angle limit and the rear wheel steering rate limit based on the current vehicle speed and current vehicle parameters. This process can improve the rationality, reliability and effectiveness of the determination of the rear wheel steering angle limit and the rear wheel steering rate limit, so as to limit the rear wheel steering from the two dimensions of rear wheel steering angle and rear wheel steering rate, thereby improving the safety of rear wheel steering.

[0034] S12: Determine the second target rear wheel angle based on the first target rear wheel angle and the rear wheel angle limit, and determine the second target rear wheel steering rate based on the first target rear wheel steering rate and the rear wheel steering rate limit.

[0035] Based on step S11, a second target rear wheel angle can be determined according to the first target rear wheel angle and the rear wheel angle limit, so as to limit the first target rear wheel angle using the determined rear wheel angle limit. Furthermore, a second target rear wheel steering rate can be determined according to the first target rear wheel steering rate and the rear wheel steering rate limit, so as to limit the first target rear wheel steering rate from the determined rear wheel steering rate limit.

[0036] The above process allows for the restriction of rear-wheel steering from two dimensions: rear-wheel angle and rear-wheel steering rate. This prevents unreasonable rear-wheel steering intervention, improves the rationality of rear-wheel steering intervention and the effectiveness of steering, thereby enhancing vehicle driving safety.

[0037] It should be noted that before executing step S11, it can be determined whether the vehicle's rear-wheel steering function is activated. If the vehicle's rear-wheel steering function is activated, step S11 and related steps can be executed to perform rear-wheel steering control. If the vehicle's rear-wheel steering function is not activated, step S11 can be refused. Alternatively, the first target rear-wheel angle or rear-wheel angle limit can be determined to be 0, so that the determined second target rear-wheel angle is 0, thus not performing rear-wheel steering control. Alternatively, after determining the rear-wheel angle limit based on the vehicle speed and current vehicle parameters, it can be determined whether the vehicle's rear-wheel steering function is activated. If the vehicle's rear-wheel steering function is activated, the rear-wheel angle limit can maintain the determined original value (i.e., the value determined based on the vehicle speed and current vehicle parameters). If the vehicle's rear-wheel steering function is not activated, the determined rear-wheel angle limit can be updated to 0, so that the determined second target rear-wheel angle is 0, thus not performing rear-wheel steering control. For example, determining whether the rear-wheel steering function of the vehicle is activated can be done by: determining whether the driver has turned on the rear-wheel steering switch; if the driver has turned on the rear-wheel steering switch, the vehicle is determined to have the rear-wheel steering function activated; if the driver has not turned on the rear-wheel steering switch, the vehicle is determined not to have the rear-wheel steering function activated. Alternatively, the rear-wheel steering function can be activated by default after the vehicle is started.

[0038] S13: Control the rear wheel steering based on the rear wheel angle and rear wheel steering rate of the second target.

[0039] After determining the second target rear wheel steering angle and the second target rear wheel steering rate, the rear wheel steering can be controlled based on these parameters. Specifically, the rear steering actuator in the rear wheel steering system can be controlled based on the second target rear wheel steering angle and the second target rear wheel steering rate to drive the rear wheels to turn to the second target rear wheel steering angle according to the second target rear wheel steering rate.

[0040] As can be seen from the above process, some embodiments of this application provide a rear-wheel steering safety strategy, which determines a first target rear-wheel steering angle and a first target rear-wheel steering rate based on vehicle speed and steering wheel angle, and Based on vehicle speed and current vehicle parameters, the rear wheel steering angle limit and rear wheel steering rate limit are determined. Based on these two limits, the first target rear wheel steering angle and the first target rear wheel steering rate are restricted, and the rationality and reliability of the obtained second target rear wheel steering angle and the second target rear wheel steering rate are improved. This improves the rationality of rear wheel steering intervention, thereby reducing the probability of dangerous situations such as vehicle instability and lane departure, and improving vehicle driving safety.

[0041] This application provides a rear-wheel steering control method, which determines a first target rear-wheel steering angle and a first target rear-wheel steering rate based on vehicle speed and steering wheel angle, and may include: The first target rear wheel angle is determined based on vehicle speed, steering wheel angle, steering wheel angular velocity, and adhesion coefficient. The first target rear wheel steering rate is then determined based on the first target rear wheel angle.

[0042] In some embodiments of this application, the first target rear wheel steering angle can be determined based on vehicle speed, steering wheel angle, steering wheel angular velocity, and adhesion coefficient (vehicle speed, steering wheel angle, steering wheel angular velocity, and adhesion coefficient can all be included in the current frame data). This is to comprehensively consider the impact of vehicle speed, steering wheel angle, steering wheel angular velocity, and adhesion coefficient on the rear wheel steering requirements, thereby improving the rationality, reliability, and accuracy of determining the first target rear wheel steering angle and thus improving the safety of rear wheel steering control.

[0043] Of course, in some embodiments, the first target rear wheel angle can be determined solely based on vehicle speed and steering wheel angle. For example, the specific implementation can be as follows: determine the basic rear wheel steering coefficient based on vehicle speed and steering wheel angle, determine the front wheel angle based on steering wheel angle, and calculate the first target rear wheel angle based on the basic rear wheel steering coefficient and front wheel angle using the formula: first target rear wheel angle = basic rear wheel steering coefficient × front wheel angle.

[0044] Furthermore, while determining the first target rear wheel steering angle corresponding to the current frame data in the manner described above, the first target rear wheel steering rate can be determined based on the first target rear wheel steering angle corresponding to the current frame data and the first target rear wheel steering angle corresponding to the previous frame data. Specifically, while determining the first target rear wheel steering angle corresponding to the current frame data in the manner described above, the first target rear wheel steering angle corresponding to the previous frame data adjacent to the current frame data can be obtained. The first target rear wheel steering rate is determined based on the first target rear wheel steering angle corresponding to the current frame data, the first target rear wheel steering angle corresponding to the previous frame data, and the time between two adjacent frames, thereby improving the rationality, reliability, and accuracy of the determination of the first target rear wheel steering rate, and thus improving the safety of rear wheel steering control.

[0045] This application provides a rear-wheel steering control method in some embodiments, which determines a first target rear-wheel steering angle based on vehicle speed, steering wheel angle, steering wheel angular velocity, and coefficient of friction. The method may include: The base rear wheel steering coefficient is determined based on vehicle speed and steering wheel angle. A first correction coefficient is determined based on steering wheel angular velocity, and a second correction coefficient is determined based on the adhesion coefficient. The front wheel angle is determined based on the steering wheel angle. Specifically, if the vehicle speed does not exceed a speed threshold, the vehicle speed and the base rear wheel steering coefficient are negatively correlated; if the speed exceeds the speed threshold, the base rear wheel steering coefficient is equal to 0. The steering wheel angular velocity is negatively correlated with the first correction coefficient, and the adhesion coefficient is positively correlated with the second correction coefficient. The first target rear wheel steering angle is determined based on the basic rear wheel steering coefficient, the first correction coefficient, the second correction coefficient, and the front wheel steering angle.

[0046] In some embodiments of this application, the specific method for determining the first target rear wheel steering angle based on vehicle speed, steering wheel angle, steering wheel angular velocity, and adhesion coefficient can be as follows: Step 101: Determine the basic rear wheel steering coefficient based on vehicle speed and steering wheel angle.

[0047] For example, a first correspondence between vehicle speed and maximum steering wheel angle can be established in advance through calibration, etc., and a second correspondence between the two independent variables (also called input quantities) of vehicle speed, steering wheel angle and the ratio of the maximum steering wheel angle at the current vehicle speed (i.e., the relative steering wheel angle) and the basic rear wheel steering coefficient can be established. Based on this, the maximum steering wheel angle corresponding to the vehicle speed can be determined according to the vehicle speed and the first correspondence, and the relative steering wheel angle can be determined by comparing the steering wheel angle with the maximum steering wheel angle corresponding to the vehicle speed. The basic rear wheel steering coefficient can be determined according to the vehicle speed, the relative steering wheel angle and the second correspondence. It should be noted that the vehicle state can be determined as forward or backward according to the wheel speed direction. Forward and backward can each have their own corresponding first and second correspondences.

[0048] Specifically, if the vehicle speed does not exceed the speed threshold (i.e., the preset high-speed threshold), there is a negative correlation between vehicle speed and the basic rear-wheel steering coefficient; that is, the higher the speed, the smaller the basic rear-wheel steering coefficient. If the vehicle speed exceeds the speed threshold, the basic rear-wheel steering coefficient equals 0 (at this time, the first target rear-wheel steering angle determined based on the basic rear-wheel steering coefficient also equals 0). This achieves high rear-wheel steering following accuracy at low speeds, ensuring vehicle agility at low speeds. At medium and high speeds, considering the lower demand for rear-wheel steering, the following accuracy of rear-wheel steering decreases as vehicle speed increases. If the speed exceeds the speed threshold, the rear-wheel steering remains at zero degrees to ensure the driving safety of high-speed vehicles. Through the aforementioned process, the following accuracy of the rear-wheel steering angle differs from that of the front-wheel steering angle as vehicle speed changes, but if the speed is greater than the speed threshold, the rear-wheel steering remains at zero degrees. This not only ensures agility at low speeds but also ensures safety at high speeds.

[0049] Furthermore, there is a negative correlation between the relative steering wheel angle and the base rear wheel steering coefficient. That is, the larger the relative steering wheel angle, the smaller the base rear wheel steering coefficient. This results in a larger relative steering wheel angle and a smaller target rear wheel angle, which in turn leads to a larger steering wheel rotation ratio and a smaller steering amplitude. This reduces the probability of the vehicle deviating from its lane or fishtailing at high speeds, improves vehicle handling stability, enhances steering linearity, improves vehicle handling precision, and ultimately enhances vehicle driving safety.

[0050] Step 102: Determine the first correction coefficient based on the steering wheel angular velocity. This first correction coefficient can be considered either a correction coefficient for the rear wheel steering coefficient or a correction coefficient for the base target rear wheel steering angle determined based on the base rear wheel steering coefficient and the front wheel steering angle.

[0051] For example, a third correspondence between the steering wheel angular velocity and the first correction coefficient can be pre-established. Based on this, the first correction coefficient can be determined according to the steering wheel angular velocity and the pre-established third correspondence.

[0052] Among them, there is a negative correlation between the steering wheel angular velocity and the first correction coefficient, so that the larger the steering wheel angular velocity, the smaller the first correction coefficient, which in turn makes the steering wheel angular velocity larger and the first target rear wheel turning angle smaller, thereby suppressing drastic changes in vehicle posture and making the vehicle less prone to sideslip or fishtailing at higher speeds, thus improving the dynamic stability of the vehicle at higher speeds.

[0053] Step 103: Determine the second correction coefficient based on the adhesion coefficient. Similar to the first correction coefficient, the second correction coefficient can be regarded as a correction coefficient for the rear wheel steering coefficient, or as a correction coefficient for the base target rear wheel steering angle determined based on the base rear wheel steering coefficient and the front wheel steering angle.

[0054] For example, a fourth correspondence between the adhesion coefficient and the second correction coefficient can be pre-established, and the second correction coefficient can be determined based on the adhesion coefficient and the pre-established fourth correspondence.

[0055] The adhesion coefficient and the second correction coefficient are positively correlated, so that the smaller the adhesion coefficient, the smaller the second correction coefficient, and thus the smaller the adhesion coefficient and the smaller the first target rear wheel turning angle, thereby improving the lateral stability of the vehicle and reducing the risk of loss of control, and improving the driving safety of the vehicle.

[0056] Step 104: Determine the front wheel angle based on the steering wheel angle.

[0057] For example, a fifth correspondence between the steering wheel angle and the front left and front right wheel angles can be pre-established. Based on this, the front left and front right wheel angles can be determined according to the steering wheel angle and the pre-established fifth correspondence, and then averaged to obtain the front wheel angle. Alternatively, the steering wheel angle can be first gradient-limited (i.e., the rate of change of the steering wheel angle can be limited) to prevent vehicle instability and improve ride comfort. The gradient-limited steering wheel angle is then low-pass filtered, and the front left and front right wheel angles are determined according to the low-pass filtered steering wheel angle and the pre-established fifth correspondence, and the front wheel angle is determined accordingly. Of course, a sixth correspondence between the steering wheel angle and the front wheel angles can also be pre-established, and the front wheel angle can be determined according to the steering wheel angle and the pre-established sixth correspondence.

[0058] It should be noted that the execution order of steps 101 to 104 is not limited; for example, steps 101 to 104 can be executed in parallel. Furthermore, the pre-built correspondences can be stored in tabular form to facilitate efficient and rapid determination of the corresponding parameters.

[0059] Step 105: Determine the first target rear wheel steering angle based on the base rear wheel steering coefficient, the first correction coefficient, the second correction coefficient, and the front wheel steering angle. For example, the rear wheel steering coefficient can be calculated first using: Rear wheel steering coefficient = Base rear wheel steering coefficient × First correction coefficient × Second correction coefficient. Then, the first target rear wheel steering angle can be calculated using: First target rear wheel steering angle = Rear wheel steering coefficient × Front wheel steering angle. Alternatively, the base target rear wheel steering angle can be calculated first using: Base target rear wheel steering angle = Base rear wheel steering coefficient × Front wheel steering angle. Then, the first target rear wheel steering angle can be calculated using: First target rear wheel steering angle = Base target rear wheel steering angle × First correction coefficient × Second correction coefficient.

[0060] The above method can achieve the following when calculating the first target rear wheel turning angle: not only the influence of vehicle speed and steering wheel angle are comprehensively considered, but also the steering wheel angular velocity and adhesion coefficient are introduced to correct the target rear wheel turning angle. This improves the rationality, reliability and accuracy of the determination of the first target rear wheel turning angle, thereby facilitating the improvement of vehicle driving stability and safety, and ensuring agility in low-speed steering.

[0061] This application provides a rear-wheel steering control method that, according to some embodiments, determines a basic rear-wheel steering coefficient based on vehicle speed and steering wheel angle, determines a first correction coefficient based on steering wheel angular velocity, and determines a second correction coefficient based on adhesion coefficient. The method may include: The basic rear wheel steering coefficient is determined based on vehicle speed, steering wheel angle, and driving mode. The first correction coefficient is determined based on steering wheel angular velocity and driving mode. The second correction coefficient is determined based on adhesion coefficient and driving mode.

[0062] In some embodiments of this application, the driving mode can also be taken into account when determining the first target rear wheel steering angle, so as to meet the differentiated needs of the driver for rear steering when selecting different driving modes, and improve the matching between rear steering control and vehicle status, thereby further improving the rationality of rear steering intervention.

[0063] Different driving modes can be matched with different base rear wheel steering coefficients, first correction coefficients, and second correction coefficients. It should be noted that the driving modes mentioned in some embodiments of this application can be determined according to needs. For example, the driving modes may include sport mode, standard mode, comfort mode, low-fly mode, etc. The driving mode can be selected by the driver according to needs, or it can be determined according to the current state of the vehicle, etc.

[0064] Specifically, when determining the base rear-wheel steering coefficient, it can be based on vehicle speed, steering wheel angle, and the vehicle's current driving mode. For example, a pre-established correspondence between vehicle speed, steering wheel angle, and the base rear-wheel steering coefficient for each driving mode can be constructed (see the first and second correspondences mentioned above). Based on this, the corresponding correspondence for the current driving mode can be obtained first, and then the base rear-wheel steering coefficient can be determined based on the corresponding correspondence, the vehicle's current speed, and the steering wheel angle.

[0065] When determining the first correction coefficient, it can be specifically determined based on the steering wheel angular velocity and the driving mode. For example, a correspondence between the steering wheel angle and the first correction coefficient for each driving mode can be pre-established (see the third correspondence mentioned above for details). Based on this, the corresponding correspondence for the current driving mode can be obtained first, and then the first correction coefficient can be determined based on the corresponding correspondence and the current steering wheel angle of the vehicle.

[0066] When determining the second correction coefficient, it can be based on the adhesion coefficient and the driving mode. For example, a correspondence between the adhesion coefficient and the second correction coefficient for each driving mode can be pre-established (see the fourth correspondence mentioned above). Based on this, the corresponding correspondence in the current driving mode can be obtained first, and then the second correction coefficient can be determined based on the corresponding correspondence and the current adhesion coefficient.

[0067] Based on this, if the driving mode changes during vehicle operation, the rear wheel steering angle will switch from the previous second target rear wheel steering angle to the new second target rear wheel steering angle. During this switching process, a new first target rear wheel steering angle and a new first target rear wheel steering rate can be determined based on the new driving mode, along with new rear wheel steering angle limits and new rear wheel steering rate limits. These two limits are used to apply safety limits to the new first target rear wheel steering angle and the new first target rear wheel steering rate, thus obtaining the second target rear wheel steering angle and the second target rear wheel steering rate after the driving mode change. Based on this, the rear wheel steering is controlled to achieve a smooth switch from the previous second target rear wheel steering angle to the new second target rear wheel steering angle, preventing the second target rear wheel steering angle from changing too quickly and causing excessive yaw rate, which could affect driving safety.

[0068] By taking into account the different requirements of rear-wheel steering for different driving modes, the rear-wheel steering is matched with different driving modes to improve the matching between the first target rear wheel steering angle and the driving mode, thereby improving vehicle stability, safety and passenger comfort.

[0069] A rear-wheel steering control method provided in some embodiments of this application may further include, before controlling the rear-wheel steering according to a second target rear-wheel steering angle and a second target rear-wheel steering rate: If the vehicle speed does not exceed the speed threshold, then the steering direction of the rear wheels is determined to be opposite to that of the front wheels. Controlling rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate includes: The rear wheel steering is controlled based on the steering direction of the rear wheels, the steering angle of the second target's rear wheels, and the steering rate of the second target's rear wheels.

[0070] Considering that traditional rear-wheel steering involves the rear wheels steering in the opposite direction to the front wheels at low speeds and in the same direction as the front wheels at high speeds, while this simultaneous front and rear steering at high speeds can reduce vehicle yaw, it also presents the following problems: increased understeer makes turning more difficult, and improper control of rear wheel steering may lead to lane departure; on low-friction surfaces, the rear wheels reach saturation of grip first, especially in rear-wheel-drive vehicles, easily leading to high-speed fishtailing; during cornering braking, the front wheels bear greater lateral forces, easily causing understeer, which can lead to front axle lock-up and loss of steering ability. Furthermore, due to the rear wheels' yaw rate at both low and high speeds... The opposite direction of steering gives the driver a non-linear driving experience, which can easily lead to misjudgment and cause safety accidents. Therefore, in some embodiments of this application, the rear wheel steering is opposite to the front wheel steering in both medium and high speed conditions and low speed conditions. After the vehicle speed exceeds the speed threshold, the rear wheel steering remains at zero degrees. This not only ensures the agility of low-speed steering, but also improves safety at high speeds. Furthermore, it ensures that the driver has a linear driving experience at both low and high speeds, reduces the learning cost for drivers of vehicles with rear wheels, reduces misjudgment during driving, and improves driving safety.

[0071] Specifically, before controlling the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate, for example, when determining the first target rear wheel steering angle and the first target rear wheel steering rate based on vehicle speed and steering wheel angle, it can be determined whether the vehicle speed exceeds a speed threshold. If the vehicle speed exceeds the speed threshold, the basic rear wheel steering coefficient can be determined to be 0, that is, the first target rear wheel steering angle can be determined to be 0. If the vehicle speed does not exceed the speed threshold, the steering direction of the rear wheels is determined to be opposite to the steering direction of the front wheels. In this case, controlling the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate can specifically be: controlling the rear wheel steering based on the steering direction of the rear wheels (or the steering direction of the front wheels), the second target rear wheel steering angle, and the second target rear wheel steering rate.

[0072] As can be seen from the above, through some embodiments of this application, it is possible to achieve that the rear wheel steering is always opposite to the front wheel steering, regardless of low speed or medium-high speed. The degree of following of the rear wheel steering angle and the front wheel steering angle varies with the vehicle speed. However, if the vehicle speed is greater than the vehicle speed threshold, the rear wheel maintains zero degrees. This not only ensures the agility of low-speed steering, but also ensures the effectiveness of steering when the driver is driving on a narrow road at high speed. It avoids the risk of understeering at high speeds due to the rear wheel steering being the same as the front wheel steering, which would increase the risk of lane departure. This improves the safety of driving at high speeds and ensures a linear change in the driver's driving experience at low and high speeds.

[0073] A rear-wheel steering control method provided in some embodiments of this application may further include: If the number of zero crossings of the front wheel steering angle within the first preset time period is greater than 1, then after the current steering direction is maintained in the current direction for more than the second preset time period, the steering direction of the rear wheels is updated according to the steering direction of the front wheels and the vehicle speed.

[0074] In some embodiments of this application, in rear-wheel steering control, for example, before determining that the steering direction of the rear wheels is opposite to that of the front wheels, or while controlling the rear-wheel steering, it can be determined whether the number of zero-crossings (i.e., changes in positive or negative direction, i.e., from positive to negative or from negative to positive) of the front wheel steering angle (or steering wheel angle) within a first preset time period is greater than 1. The magnitude of the first preset time period can be determined in advance through calibration or other methods.

[0075] If the number of zero-crossings of the front wheel angle within the first preset time period is not greater than 1, it indicates that the front wheel direction has not changed rapidly. At this time, if the vehicle speed does not exceed the vehicle speed threshold, it can be determined that the steering direction of the rear wheels is opposite to that of the front wheels, and the rear wheel steering can be controlled accordingly. If the vehicle speed exceeds the vehicle speed threshold, it can be determined that the first target rear wheel angle is equal to 0. At this time, the rear wheels can be controlled to return to center. For example, the return-to-center rate can be determined according to the vehicle speed (the return-to-center rate can be relatively small to achieve slow return to center), and the rear wheels can be controlled to return to center according to the return-to-center rate.

[0076] If the number of zero-crossings of the front wheel steering angle within a first preset time period is greater than 1, it indicates a rapid change in front wheel direction. To prevent the rear wheel steering direction from also oscillating rapidly and dramatically, the rear wheel steering direction can be updated based on the front wheel steering direction and vehicle speed after the front wheel steering direction has been maintained in its current position for a second preset time period. Specifically, if the vehicle speed does not exceed a speed threshold, the rear wheel steering direction is determined to be opposite to the front wheel steering direction; if the vehicle speed exceeds the speed threshold, the rear wheel steering direction is determined to be in the center position. This avoids changing the rear wheel steering direction when the front wheel steering direction changes frequently, thus preventing vehicle skidding or loss of control and improving vehicle safety.

[0077] This application provides a rear-wheel steering control method in some embodiments. Current vehicle parameters may include suspension height, rear-wheel steering motor torque and speed. Determining rear-wheel steering angle limits and rear-wheel steering rate limits based on vehicle speed and current vehicle parameters may include: The first rear wheel steering angle limit is determined based on the suspension height, the first rear wheel steering rate limit is determined based on the torque and speed of the rear wheel steering motor, and the second rear wheel steering angle limit and the second rear wheel steering rate limit are determined based on the vehicle speed. Determining the second target rear wheel steering angle based on the first target rear wheel steering angle and the rear wheel steering angle limit, and determining the second target rear wheel steering rate based on the first target rear wheel steering rate and the rear wheel steering rate limit, may include: The target rear wheel angle is determined based on the first rear wheel angle limit and the first target rear wheel angle. The rear wheel steering rate is determined based on the first rear wheel steering rate limit and the first target rear wheel steering rate. The target rear wheel angle and the rear wheel steering rate are both not greater than the first rear wheel angle limit. Similarly, the second target rear wheel angle and the target rear wheel angle are determined based on the second rear wheel angle limit and the target rear wheel angle. The second target rear wheel steering rate and the rear wheel steering rate are both determined based on the second rear wheel steering rate limit and the rear wheel steering rate. The second target rear wheel angle and the second target rear wheel steering rate are both not greater than the second rear wheel angle limit. or, The second target rear wheel angle is determined based on the first rear wheel angle limit and the first target rear wheel angle, and the second target rear wheel steering rate is determined based on the first rear wheel steering rate limit and the first target rear wheel steering rate; wherein, the second target rear wheel angle is not greater than the first rear wheel angle limit, and the second target rear wheel steering rate is not greater than the first rear wheel steering rate limit; or, The second target rear wheel angle is determined based on the second rear wheel angle limit and the first target rear wheel angle, and the second target rear wheel steering rate is determined based on the second rear wheel steering rate limit and the first target rear wheel steering rate; wherein, the second target rear wheel angle is not greater than the second rear wheel angle limit, and the second target rear wheel steering rate is not greater than the second rear wheel steering rate limit.

[0078] In some embodiments of this application, the current vehicle parameters may specifically include suspension height, rear wheel steering motor torque, and rotational speed. Based on this, the specific implementation method for determining the rear wheel steering angle limit and rear wheel steering rate limit according to vehicle speed and current vehicle parameters can be as follows: Step 201: Determine the first rear wheel steering angle limit based on the vehicle's current suspension height. The first rear wheel steering angle limit is determined according to the current suspension height. Suspension height can be represented by a suspension height value or suspension height level, which can be selected based on the suspension configuration of different vehicle models.

[0079] For example, the suspension height and the first rear wheel steering angle limit can be determined in advance based on the physical parameters of different vehicle models. The first rear wheel steering angle limit is then determined based on this correspondence and the current suspension height of the vehicle.

[0080] There is a negative correlation between suspension height and the first rear wheel steering angle limit. Generally, the higher the suspension height, the smaller the first rear wheel steering angle limit. This is primarily because, at the same vehicle speed, front wheel steering angle, and rear wheel steering coefficient, a higher suspension height results in a higher center of gravity, leading to a greater yaw rate and a higher risk of safety hazards. Additionally, this design ensures that there is no physical interference between the suspension and the rear wheel steering angle.

[0081] Step 202: Determine the first rear wheel steering rate limit based on the torque and speed of the rear wheel steering motor.

[0082] For example, a maximum rack speed can be determined based on the torque and speed of the rear wheel steering motor, and a first rear wheel steering rate limit can be determined based on this maximum rack speed.

[0083] As can be seen from steps 201 and 202, the first rear wheel steering angle limit and the first rear wheel steering rate limit are both safety boundaries set based on the vehicle's physical limits, in order to ensure vehicle safety and improve fault tolerance.

[0084] Step 203: Determine the second rear wheel steering angle limit and the second rear wheel steering rate limit based on the vehicle speed.

[0085] In other words, the second rear wheel steering angle limit is primarily based on vehicle speed, and there can be a negative correlation between vehicle speed and the second rear wheel steering angle limit. Generally, the higher the vehicle speed, the smaller the rear wheel steering angle. This limit mainly considers the boundary rear turn angle corresponding to the yaw rate that may endanger the overall vehicle safety under different vehicle speed conditions. The relationship between vehicle speed and the second rear wheel steering angle limit can be determined through simulation calculations or through real-vehicle verification, and is related to specific vehicle parameters.

[0086] Regarding the second rear wheel steering rate limit, considering that if the rear wheel steering angle changes too quickly with the front wheel, it will generate a large yaw rate, which will affect driving safety, the second rear wheel steering rate limit is determined based on the vehicle speed. This limit restricts the rear wheel steering rate, thereby limiting the second target rear wheel steering rate to a certain range as the vehicle speed changes, serving as the rear wheel steering rate boundary to improve driving safety.

[0087] As can be seen from step 203, the second rear wheel steering angle limit and the second rear wheel steering rate limit are both determined based on the current vehicle speed. These two limits are updated in real time to prevent the vehicle from losing control, overturning, etc., and to improve vehicle safety.

[0088] It should be noted that the execution order of steps 201-203 above is not limited. For example, a first rear wheel steering angle limit and a first rear wheel steering rate limit can be determined first, and a first target rear wheel steering angle and a first target rear wheel steering rate can be limited based on these limits. Then, a second rear wheel steering angle limit and a second rear wheel steering rate limit can be determined, and further restrictions can be imposed based on these limits. Alternatively, the first rear wheel steering angle limit, the first rear wheel steering rate limit, and the second rear wheel steering angle limit and the second rear wheel steering rate limit can be determined in parallel.

[0089] Based on the above, the second target rear wheel steering angle is determined according to the first target rear wheel steering angle and the rear wheel steering angle limit. The specific implementation method for determining the second target rear wheel steering rate according to the first target rear wheel steering rate and the rear wheel steering rate limit can be as follows: Step 301: Determine the target rear wheel angle after the limit is set based on the first rear wheel angle limit and the first target rear wheel angle. Specifically, the first rear wheel angle limit can be compared with the first target rear wheel angle. If the first target rear wheel angle is greater than or equal to the first rear wheel angle limit, then the target rear wheel angle after the limit is set is output, i.e., the first rear wheel angle limit is determined as the target rear wheel angle after the limit is set. If the first target rear wheel angle is less than the first rear wheel angle limit, then the first target rear wheel angle is maintained, i.e., the target rear wheel angle after the limit is equal to the first target rear wheel angle. This method ensures that the target rear wheel angle after the limit is not greater than the first rear wheel angle limit.

[0090] In some embodiments, see Figure 2 This document describes a flowchart illustrating the process of determining a target rear wheel angle based on a first target rear wheel angle and a limit value for the first rear wheel angle, as provided in some embodiments of this application. The flowchart first determines the first rear wheel angle limit value based on the suspension height, uses this limit value for restriction, and then determines whether the vehicle's rear wheel steering function is activated. If the rear wheel steering function is not activated, the first rear wheel angle limit value can be set to zero, and the target rear wheel angle after the limit value is switched and maintained at zero degrees. Alternatively, the target rear wheel angle after the limit value can be directly switched and maintained at zero degrees. If the rear wheel steering function is activated, the target rear wheel angle after the limit value is determined using the first rear wheel angle limit value based on the suspension height is output. Alternatively, it is possible to first determine whether the vehicle's rear wheel steering function is activated.

[0091] Step 302: Determine the rear wheel steering rate after the limit is set based on the first rear wheel steering rate limit and the first target rear wheel steering rate. Specifically, the first rear wheel steering rate limit can be compared with the first target rear wheel steering rate. If the first target rear wheel steering rate is greater than or equal to the first rear wheel steering rate limit, then the first rear wheel steering rate limit is determined as the rear wheel steering rate after the limit is set. If the first target rear wheel steering rate is less than the first rear wheel steering rate limit, then the first target rear wheel steering rate is determined as the rear wheel steering rate after the limit is set. This method ensures that the rear wheel steering rate after the limit is not greater than the first rear wheel steering rate limit.

[0092] It should be noted that the execution order of steps 301 and 302 is not limited, and they can be performed simultaneously. After the first rear wheel steering angle limit and the first rear wheel steering rate limit are applied, the second rear wheel steering angle limit and the second rear wheel steering rate limit can be used for further restriction, specifically by executing steps 303 and 304.

[0093] Step 303: Determine the second target rear wheel angle based on the second rear wheel angle limit and the target rear wheel angle after the limit. Specifically, if the target rear wheel angle after the limit obtained after the first rear wheel angle limit is greater than or equal to the second rear wheel angle limit, then output the second target rear wheel angle after the limit obtained, that is, determine the second rear wheel angle limit as the second target rear wheel angle. If the target rear wheel angle after the limit obtained after the first rear wheel angle limit is less than the second rear wheel angle limit, then directly output the target rear wheel angle after the limit, that is, determine the target rear wheel angle after the limit as the second target rear wheel angle. Through the above process, the second target rear wheel angle is ensured to be no greater than the second rear wheel angle limit.

[0094] Step 304: Determine the second target rear wheel steering rate based on the second rear wheel steering rate limit and the rear wheel steering rate after the limit. Specifically, if the rear wheel steering rate after the limit obtained after the first rear wheel steering rate limit is greater than or equal to the second rear wheel steering rate limit, then the second rear wheel steering rate limit is determined as the second target rear wheel steering rate. If the rear wheel steering rate after the limit is less than the second target rear wheel steering rate, then the rear wheel steering rate after the limit is determined as the second target rear wheel steering rate. Through the aforementioned process, the second target rear wheel steering rate is ensured to be no greater than the second rear wheel steering rate limit.

[0095] It should be noted that there is no restriction on the execution order between steps 303 and 304.

[0096] As can be seen from the above, some embodiments of this application first use the first rear wheel steering angle limit and the first rear wheel steering rate limit for restriction, and then use the second rear wheel steering angle limit and the second rear wheel steering rate limit for restriction, thereby achieving restriction in a serial manner to ensure that the vehicle hardware is not damaged, prevent loss of control, and improve vehicle driving safety.

[0097] Alternatively, the implementation method of determining the second target rear wheel steering angle based on the first target rear wheel steering angle and the rear wheel steering angle limit, and determining the second target rear wheel steering rate based on the first target rear wheel steering rate and the rear wheel steering rate limit, can be as follows: Step 401: Determine the second target rear wheel steering angle based on the first rear wheel steering angle limit and the first target rear wheel steering angle. Specifically, the first rear wheel steering angle limit can be compared with the first target rear wheel steering angle. If the first target rear wheel steering angle is greater than or equal to the first rear wheel steering angle limit, then the first rear wheel steering angle limit is determined as the second target rear wheel steering angle. If the first target rear wheel steering angle is less than the first rear wheel steering angle limit, then the first target rear wheel steering angle is determined as the second target rear wheel steering angle. This method ensures that the second target rear wheel steering angle is not greater than the first rear wheel steering angle limit.

[0098] Step 402: Determine the second target rear wheel steering rate based on the first rear wheel steering rate limit and the first target rear wheel steering rate. Specifically, the first rear wheel steering rate limit can be compared with the first target rear wheel steering rate. If the first target rear wheel steering rate is greater than or equal to the first rear wheel steering rate limit, then the first rear wheel steering rate limit is determined as the second target rear wheel steering rate. If the first target rear wheel steering rate is less than the first rear wheel steering rate limit, then the first target rear wheel steering rate is determined as the second target rear wheel steering rate. This method ensures that the second target rear wheel steering rate is not greater than the first rear wheel steering rate limit.

[0099] It should be noted that there is no restriction on the execution order between steps 401 and 402. By limiting the first rear wheel steering angle and the first rear wheel steering rate, unreasonable rear wheel steering intervention is avoided, thereby improving the rationality of rear wheel steering intervention and the effectiveness of steering, and thus improving vehicle driving safety.

[0100] Alternatively, the implementation method of determining the second target rear wheel steering angle based on the first target rear wheel steering angle and the rear wheel steering angle limit, and determining the second target rear wheel steering rate based on the first target rear wheel steering rate and the rear wheel steering rate limit, can be as follows: Step 501: Determine the second target rear wheel steering angle based on the second rear wheel steering angle limit and the first target rear wheel steering angle. Specifically, the second rear wheel steering angle limit can be compared with the first target rear wheel steering angle. If the first target rear wheel steering angle is greater than or equal to the second rear wheel steering angle limit, then the second rear wheel steering angle limit is determined as the second target rear wheel steering angle. If the first target rear wheel steering angle is less than the second rear wheel steering angle limit, then the first target rear wheel steering angle is determined as the second target rear wheel steering angle. This method ensures that the second target rear wheel steering angle is not greater than the second rear wheel steering angle limit.

[0101] Step 502: Determine the second target rear wheel steering rate based on the second rear wheel steering rate limit and the first target rear wheel steering rate. Specifically, the second rear wheel steering rate limit can be compared with the first target rear wheel steering rate. If the first target rear wheel steering rate is greater than or equal to the second rear wheel steering rate limit, then the second rear wheel steering rate limit is determined as the second target rear wheel steering rate. If the first target rear wheel steering rate is less than the second rear wheel steering rate limit, then the first target rear wheel steering rate is determined as the second target rear wheel steering rate. This method ensures that the second target rear wheel steering rate is not greater than the second rear wheel steering rate limit.

[0102] It should be noted that there is no restriction on the execution order between steps 501 and 502. By limiting the second rear wheel steering angle and the second rear wheel steering rate, unreasonable rear wheel steering intervention is avoided, the rationality of rear wheel steering intervention and the effectiveness of steering are improved, thereby enhancing vehicle driving safety.

[0103] This application provides a rear-wheel steering control method in some embodiments, which determines a first rear-wheel steering rate limit based on the torque and speed of the rear-wheel steering motor, and may include: The rack force is determined based on the torque of the rear wheel steering motor, and the maximum rack speed is determined based on the rack force. The theoretical rack speed is determined based on the rotational speed of the rear wheel steering motor; The target rack speed is determined based on the maximum rack speed and the theoretical rack speed, and the first rear wheel steering rate limit is determined based on the target rack speed.

[0104] In some embodiments of this application, the method for determining the first rear wheel steering rate limit based on the torque and speed of the rear wheel steering motor can be as follows: Step 601: Calculate the rack force based on the current torque of the rear wheel steering motor (i.e., the current actual torque), and finally obtain a maximum rack speed based on the rack force.

[0105] Step 602: Calculate the theoretical rack speed based on the current speed of the rear wheel steering motor (i.e., the current actual speed).

[0106] Step 603: Take the maximum value between the maximum rack speed in Step 601 and the theoretical rack speed in Step 602 to obtain the target rack speed. That is, determine the rack speed with the largest value between the maximum rack speed in Step 601 and the theoretical rack speed in Step 602 as the target rack speed. Determine the first rear wheel steering rate limit based on the target rack speed to improve the rationality and reliability of the determination of the first rear wheel steering rate limit.

[0107] A rear-wheel steering control method provided in some embodiments of this application may further include: If the suspension height changes, the first rear wheel steering angle limit corresponding to the original suspension height will change at a preset rate to the first rear wheel steering angle limit corresponding to the new suspension height.

[0108] In some embodiments of this application, if the suspension height of the vehicle changes, the first rear wheel steering angle limit will change. In order to avoid abrupt changes in the first rear wheel steering angle limit and improve the stability of the vehicle, when the suspension height changes, the first rear wheel steering angle limit corresponding to the suspension height before the change can be changed at a preset rate to the first rear wheel steering angle limit corresponding to the changed suspension height. The preset rate of change can be obtained in advance through calibration, etc.

[0109] In some embodiments, see Figure 3 This document describes a flowchart for determining a second target rear wheel steering angle, provided in some embodiments of this application. After obtaining the first target rear wheel steering angle and the first target rear wheel steering rate, if the driving mode changes, a new first target rear wheel steering angle and a new first target rear wheel steering rate can be determined. If the driving mode does not change, the original first target rear wheel steering angle and the first target rear wheel steering rate are maintained. It is determined whether the first rear wheel steering angle limit has changed. If it has not changed, the original first rear wheel steering angle limit is maintained; if it has changed, it is changed to the new first rear wheel steering angle limit at a preset rate. The first target rear wheel steering angle and the first target rear wheel steering rate are sequentially constrained by the first rear wheel steering angle limit and the first rear wheel steering rate limit, and then by the second rear wheel steering angle limit and the second rear wheel steering rate limit, outputting the final second target rear wheel steering angle and the second target rear wheel steering rate.

[0110] A rear-wheel steering control method provided in some embodiments of this application may further include, before controlling the rear-wheel steering according to a second target rear-wheel steering angle and a second target rear-wheel steering rate: Determine if the parameters used to determine the rear wheel steering angle of the first target or the state of the rear wheel steering system are abnormal; If so, determine the third target rear wheel steering rate and control the rear wheel rotation based on the third target rear wheel steering rate.

[0111] In some embodiments of this application, before controlling the rear wheel steering according to the second target rear wheel steering angle and the second target rear wheel steering rate, it can be determined whether the parameters used to determine the first target rear wheel steering angle or the state of the rear wheel steering system are abnormal. Specifically, the determination can be made at any stage before controlling the rear wheel steering.

[0112] If the parameters used to determine the first target rear wheel angle and the state of the rear wheel steering system are not abnormal, the rear wheel steering control can be performed normally according to the logic in some of the above embodiments.

[0113] If the parameters used to determine the first target rear wheel steering angle are abnormal, the calculated first target rear wheel steering angle is considered unreliable. In this case, a third target rear wheel steering rate can be determined. For example, the third target rear wheel steering rate can be determined based on the vehicle speed. If the vehicle speed is abnormal, the third target rear wheel steering rate can be determined based on the normal vehicle speed in the previous frame of data. Then, the rear wheels can be controlled to return to center based on the third target rear wheel steering rate, where the third target rear wheel steering rate is a relatively small value to allow the rear wheels to slowly return to center and remain in the center position after returning to center. Alternatively, if the state of the rear wheel steering system is abnormal (i.e., the state parameters are abnormal, such as a problem with a parameter, position deviation, abnormal response speed, etc.), a third target rear wheel steering rate can also be determined to ensure safety (the process is the same as the aforementioned process for determining the third target rear wheel steering rate), and the rear wheels can be controlled to return to center based on the third target rear wheel steering rate and remain in the center position after returning to center.

[0114] The above process enables the monitoring and handling of parameters for determining the first target rear wheel steering angle and abnormal situations during the execution of the target rear wheel steering process, thereby improving the safety of rear wheel steering control and thus enhancing vehicle driving safety.

[0115] A rear-wheel steering control method provided in some embodiments of this application, after controlling the rear wheel steering speed according to a third target rear wheel steering rate, may further include: If abnormal parameters are detected or the rear wheel steering system returns to normal, determine whether the vehicle speed exceeds the first preset safe speed. If the vehicle speed exceeds the first preset safe speed, control the rear wheels to keep them in the center position; If the vehicle speed does not exceed the first preset safe speed, a new second target rear wheel steering angle and a new second target rear wheel steering rate are determined, and the rear wheel steering is controlled according to the new second target rear wheel steering angle and the new second target rear wheel steering rate.

[0116] In some embodiments of this application, after controlling the rear wheel steering according to the third target rear wheel steering rate, if abnormal parameters occur or the state of the rear wheel steering system returns to normal, it can be determined whether the current vehicle speed exceeds the first preset safe speed. For example, see... Figure 4 This is a flowchart of determining the second target rear wheel angle provided in some embodiments of this application.

[0117] If the vehicle's current speed exceeds the first preset safe speed, the rear wheels can be controlled to remain in the center position.

[0118] If the vehicle's current speed does not exceed the first preset safe speed, a new second target rear wheel steering angle and a new second target rear wheel steering rate can be determined based on the vehicle's current speed according to some of the above embodiments. The rear wheel steering is then controlled based on these new second target rear wheel steering angles and rates. This ensures that, after an anomaly recovery, during the process of the rear wheels moving from the neutral position to executing the new target rear wheel steering angle, the change in rear wheel steering angle is processed by rear wheel steering angle limits and rear wheel steering rate limits, preventing excessively rapid changes in rear wheel steering angle that could result in excessive yaw rate, thereby improving driving safety.

[0119] The above methods can prevent additional yaw rate from being generated due to the sudden intervention of abnormal recovery after high vehicle speed, which would affect driving safety.

[0120] A rear-wheel steering control method provided in some embodiments of this application may further include, before controlling the rear-wheel steering according to a second target rear-wheel steering angle and a second target rear-wheel steering rate: If the steering wheel angle passes zero and the rate of change of vehicle speed is greater than the preset rate of change, then the fourth target rear wheel steering rate is determined, and the rear wheel rotation is controlled according to the fourth target rear wheel steering rate. If the vehicle speed exceeds the second preset safe speed during the rear wheel rotation, the rear wheels are controlled to remain in the neutral position; if the vehicle speed does not exceed the second preset safe speed, a new second target rear wheel steering angle and a new second target rear wheel steering rate are determined, and the rear wheel steering is controlled according to the new second target rear wheel steering angle and the new second target rear wheel steering rate.

[0121] In some embodiments of this application, before controlling the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate, if the steering wheel angle crosses zero (i.e., the positive or negative direction of the steering wheel angle changes, i.e., the front wheel angle changes positive or negative) and the rate of change of vehicle speed is greater than a preset rate of change (indicating that the vehicle speed changes too quickly), it may cause a sudden and significant change in rear wheel steering, affecting the stability of the entire vehicle. Therefore, if the steering wheel angle crosses zero and the rate of change of vehicle speed is greater than the preset rate of change, a fourth target rear wheel steering rate can be determined. For example, the fourth target rear wheel steering rate can be determined based on the vehicle speed. Then, the rear wheels can be controlled to return to center based on the fourth target rear wheel steering rate, wherein the fourth target rear wheel steering rate is a relatively small value, so that the rear wheels can slowly return to center.

[0122] After the rear wheels return to their neutral position, if the vehicle's current speed exceeds the second preset safe speed, the rear wheels can be controlled to remain in the neutral position. If the vehicle's current speed does not exceed the first preset safe speed, a new second target rear wheel steering angle and a new second target rear wheel steering rate can be determined based on the vehicle's current speed, according to some of the embodiments described above. The rear wheel steering is then controlled based on these new second target rear wheel steering angles and rates. This ensures that during the process of the rear wheels moving from the neutral position to the execution of the new target rear wheel steering angle, the change in rear wheel steering angle is processed by rear wheel steering angle limits and rear wheel steering rate limits, preventing excessively rapid changes in rear wheel steering angle that could result in excessive yaw rate, thereby improving driving safety.

[0123] If the steering wheel angle does not cross zero and the rate of change of vehicle speed is greater than the preset rate of change, then the step of controlling the rear wheel steering based on the second target rear wheel angle and the second target rear wheel steering rate can be executed.

[0124] In some embodiments of this application, a rear wheel target steering angle value calculation module, a rear wheel target steering angle and rate monitoring module, an abnormal situation handling module, and a rear wheel steering angle execution module can be utilized. See details in [link to relevant documentation]. Figure 5 This is a diagram showing the relationship between the modules implementing rear wheel steering control provided in some embodiments of this application.

[0125] The rear wheel target steering angle calculation module is used to calculate the first target rear wheel steering angle and can also be used to calculate the first rear wheel steering rate limit. In some embodiments, the rear wheel target steering angle calculation module can calculate the first target rear wheel steering angle based on the rear wheel steering coefficient and the front wheel steering angle. Furthermore, in some embodiments, the rear wheel target steering angle calculation module can recalculate after a change in driving mode.

[0126] The rear wheel target steering angle and rate monitoring module is used to determine the first rear wheel steering angle limit, the second rear wheel steering angle limit, the first rear wheel steering rate limit, and the second rear wheel steering rate limit, and based on these, as well as the first target rear wheel steering angle and the first rear wheel steering rate limit, to determine the second target rear wheel steering angle and the second target rear wheel steering rate.

[0127] The anomaly handling module primarily monitors and handles anomalies in the parameters used to calculate the first rear wheel steering angle limit and in the state of the rear wheel steering system. In the event of an anomaly, the rear wheel steering angle execution module restores the centering; after the anomaly is resolved, the rear wheel target steering angle value calculation module recalculates the new first target rear wheel steering angle.

[0128] The rear wheel steering angle execution module is used to drive the rear wheel steering according to the second target rear wheel steering angle and the second target rear wheel steering rate.

[0129] Some embodiments of this application also provide a rear-wheel steering control device, see [link to relevant documentation]. Figure 6 This is a schematic diagram of the structure of a rear wheel steering control device provided in some embodiments of this application. It may include: a first determining module 61, used to determine a first target rear wheel angle and a first target rear wheel steering rate based on vehicle speed and steering wheel angle, and to determine a rear wheel angle limit and a rear wheel steering rate limit based on current vehicle parameters; a second determining module 62, used to determine a second target rear wheel angle based on the first target rear wheel angle and the rear wheel angle limit, and to determine a second target rear wheel steering rate based on the first target rear wheel steering rate and the rear wheel steering rate limit; and a first control module 63, used to control the rear wheel steering based on the second target rear wheel angle and the second target rear wheel steering rate.

[0130] Some embodiments of this application provide a rear wheel steering control device, wherein the first determining module 61 may include: a first determining submodule, used to determine a first target rear wheel turning angle based on vehicle speed, steering wheel angle, steering wheel angular velocity and adhesion coefficient, and to determine a first target rear wheel steering rate based on the first target rear wheel turning angle.

[0131] This application provides a rear-wheel steering control device in some embodiments. A first determining submodule may include: a first determining unit, configured to determine a base rear-wheel steering coefficient based on vehicle speed and steering wheel angle; determine a first correction coefficient based on steering wheel angular velocity; determine a second correction coefficient based on adhesion coefficient; and determine the front wheel angle based on steering wheel angle. Wherein, if the vehicle speed does not exceed a vehicle speed threshold, the vehicle speed and the base rear-wheel steering coefficient are negatively correlated; if the vehicle speed exceeds the vehicle speed threshold, the base rear-wheel steering coefficient is equal to 0; the steering wheel angular velocity is negatively correlated with the first correction coefficient; and the adhesion coefficient is positively correlated with the second correction coefficient. A second determining unit is configured to determine a first target rear-wheel angle based on the base rear-wheel steering coefficient, the first correction coefficient, the second correction coefficient, and the front wheel angle.

[0132] Some embodiments of this application provide a rear wheel steering control device, wherein the first determining unit may include: a first determining subunit, used to determine a basic rear wheel steering coefficient based on vehicle speed, steering wheel angle and driving mode, determine a first correction coefficient based on steering wheel angular velocity and driving mode, and determine a second correction coefficient based on adhesion coefficient and driving mode.

[0133] The rear wheel steering control device provided in some embodiments of this application may further include: a third determining module, used to determine that the steering direction of the rear wheels is opposite to the steering direction of the front wheels if the vehicle speed does not exceed a vehicle speed threshold before controlling the rear wheel steering according to the second target rear wheel steering angle and the second target rear wheel steering rate; the first control module 63 may include: a control submodule, used to control the rear wheel steering according to the rear wheel steering direction, the second target rear wheel steering angle and the second target rear wheel steering rate.

[0134] The rear wheel steering control device provided in some embodiments of this application may further include: an update module, configured to update the steering direction of the rear wheels according to the steering direction of the front wheels and the vehicle speed if the number of zero crossings of the front wheel steering angle within a first preset time period is greater than 1.

[0135] This application provides a rear wheel steering control device in some embodiments. The current vehicle parameters may include suspension height, torque and speed of the rear wheel steering motor. The first determining module 61 may include: a second determining submodule, used to determine a first rear wheel steering angle limit based on the suspension height, a first rear wheel steering rate limit based on the torque and speed of the rear wheel steering motor, and a second rear wheel steering angle limit and a second rear wheel steering rate limit based on the vehicle speed. The second determining module 62 may include: a third determining submodule, configured to determine a target rear wheel angle after the limit is set based on a first rear wheel angle limit and a first target rear wheel angle; and to determine a target rear wheel steering rate after the limit is set based on a first rear wheel steering rate limit and a first target rear wheel steering rate, wherein the target rear wheel angle after the limit is not greater than the first rear wheel angle limit, and the target rear wheel steering rate after the limit is not greater than the first rear wheel steering rate limit; and to determine a second target rear wheel angle based on a second rear wheel angle limit and a target rear wheel angle after the limit is set; and to determine a second target rear wheel steering rate based on a second rear wheel steering rate limit and a target rear wheel steering rate after the limit is set, wherein the second target rear wheel angle is not greater than the second rear wheel angle limit, and the target rear wheel steering rate after the limit is not greater than the second rear wheel steering rate limit; or The fourth determining submodule is used to determine the second target rear wheel angle based on the first rear wheel angle limit and the first target rear wheel angle, and to determine the second target rear wheel steering rate based on the first rear wheel steering rate limit and the first target rear wheel steering rate; wherein the second target rear wheel angle is not greater than the first rear wheel angle limit, and the second target rear wheel steering rate is not greater than the first rear wheel steering rate limit; or, the fifth determining submodule is used to determine the second target rear wheel angle based on the second rear wheel angle limit and the first target rear wheel angle, and to determine the second target rear wheel steering rate based on the second rear wheel steering rate limit and the first target rear wheel steering rate; wherein the second target rear wheel angle is not greater than the second rear wheel angle limit, and the second target rear wheel steering rate is not greater than the second rear wheel steering rate limit.

[0136] Some embodiments of this application provide a rear wheel steering control device, wherein the second determining submodule may include: a third determining unit, used to determine the rack force based on the torque of the rear wheel steering motor, and to determine the maximum rack speed based on the rack force; a fourth determining unit, used to determine the theoretical rack speed based on the rotational speed of the rear wheel steering motor; and a fifth determining unit, used to determine the target rack speed based on the maximum rack speed and the theoretical rack speed, and to determine a first rear wheel steering rate limit based on the target rack speed.

[0137] Some embodiments of this application provide a rear wheel steering control device, wherein the first determining module 61 may further include: a sixth determining submodule, used to, if the suspension height changes, change the first rear wheel steering angle limit corresponding to the suspension height before the change to the first rear wheel steering angle limit corresponding to the suspension height after the change at a preset change rate.

[0138] The rear wheel steering control device provided in some embodiments of this application may further include: a first judgment module, used to determine whether the parameters used to determine the first target rear wheel angle or the state of the rear wheel steering system are abnormal before controlling the rear wheel steering according to the second target rear wheel angle and the second target rear wheel steering rate; and a fourth determination module, used to determine a third target rear wheel steering rate if the parameters or the state of the rear wheel steering system are abnormal, and control the rear wheel steering according to the third target rear wheel steering rate.

[0139] The rear-wheel steering control device provided in some embodiments of this application may further include: a second judgment module, used to determine whether the vehicle speed exceeds a first preset safe vehicle speed if abnormal parameters occur or the state of the rear-wheel steering system returns to normal after controlling the rear wheel steering according to a third target rear-wheel steering rate; a second control module, used to control the rear wheels to remain in the neutral position if the vehicle speed exceeds the first preset safe vehicle speed; and a third control module, used to determine a new second target rear-wheel steering angle and a new second target rear-wheel steering rate if the vehicle speed does not exceed the first preset safe vehicle speed, and control the rear wheel steering according to the new second target rear-wheel steering angle and the new second target rear-wheel steering rate.

[0140] A rear-wheel steering control device provided in some embodiments of this application may further include: a fifth determining module, configured to, before controlling rear-wheel steering according to a second target rear-wheel steering angle and a second target rear-wheel steering rate, determine a fourth target rear-wheel steering rate if the steering wheel angle crosses zero and the rate of change of vehicle speed is greater than a preset rate of change, and control rear-wheel steering according to the fourth target rear-wheel steering rate; and a fourth controlling module, configured to, after rear-wheel steering has returned to center, control the rear wheels to remain in the center position if the vehicle speed exceeds a second preset safe vehicle speed; and if the vehicle speed does not exceed the second preset safe vehicle speed, determine a new second target rear-wheel steering angle and a new second target rear-wheel steering rate, and control rear-wheel steering according to the new second target rear-wheel steering angle and the new second target rear-wheel steering rate.

[0141] Some embodiments of this application also provide a control device, see [link to relevant documentation]. Figure 7 This is a schematic diagram of the structure of a control device provided in some embodiments of this application, which may include: Memory 71 is used to store computer programs; The processor 72, when executing the computer program stored in the memory 71, can implement the steps of any of the above-described rear wheel steering control methods.

[0142] Some embodiments of this application also provide a vehicle that may include the control device described above.

[0143] For a description of the rear wheel steering control device, control equipment, and related parts in a vehicle provided in some embodiments of this application, please refer to the detailed description of the corresponding parts in a rear wheel steering control method provided in some embodiments of this application, which will not be repeated here.

[0144] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0145] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0146] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0147] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0148] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0149] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A rear-wheel steering control method, characterized in that, include: The first target rear wheel angle and the first target rear wheel steering rate are determined based on the vehicle speed and steering wheel angle. The rear wheel angle limit and the rear wheel steering rate limit are determined based on the vehicle speed and current vehicle parameters. The second target rear wheel angle is determined based on the first target rear wheel angle and the rear wheel angle limit, and the second target rear wheel steering rate is determined based on the first target rear wheel steering rate and the rear wheel steering rate limit. Control the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate.

2. The rear-wheel steering control method according to claim 1, characterized in that, Determine the first target rear wheel steering angle and the first target rear wheel steering rate based on vehicle speed and steering wheel angle, including: The first target rear wheel steering angle is determined based on the vehicle speed, the steering wheel angle, the steering wheel angular velocity, and the coefficient of adhesion; the first target rear wheel steering rate is determined based on the first target rear wheel steering angle.

3. The rear-wheel steering control method according to claim 2, characterized in that, Determining the first target rear wheel steering angle based on the vehicle speed, steering wheel angle, steering wheel angular velocity, and coefficient of friction includes: A base rear wheel steering coefficient is determined based on the vehicle speed and the steering wheel angle. A first correction coefficient is determined based on the steering wheel angular velocity. A second correction coefficient is determined based on the adhesion coefficient. The front wheel angle is determined based on the steering wheel angle. Wherein, if the vehicle speed does not exceed a speed threshold, the vehicle speed and the base rear wheel steering coefficient are negatively correlated; if the vehicle speed exceeds the speed threshold, the base rear wheel steering coefficient is equal to 0. The steering wheel angular velocity is negatively correlated with the first correction coefficient. The adhesion coefficient is positively correlated with the second correction coefficient. The first target rear wheel steering angle is determined based on the basic rear wheel steering coefficient, the first correction coefficient, the second correction coefficient, and the front wheel steering angle.

4. The rear-wheel steering control method according to claim 3, characterized in that, The base rear wheel steering coefficient is determined based on the vehicle speed and the steering wheel angle. A first correction coefficient is determined based on the steering wheel angular velocity. A second correction coefficient is determined based on the adhesion coefficient, including: The base rear wheel steering coefficient is determined based on the vehicle speed, the steering wheel angle, and the driving mode; the first correction coefficient is determined based on the steering wheel angular velocity and the driving mode; and the second correction coefficient is determined based on the adhesion coefficient and the driving mode.

5. The rear-wheel steering control method according to claim 3, characterized in that, Before controlling the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate, the method further includes: If the vehicle speed does not exceed the vehicle speed threshold, then the steering direction of the rear wheels is determined to be opposite to the steering direction of the front wheels; Controlling rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate includes: The rear wheel steering is controlled based on the steering direction of the rear wheel, the steering angle of the second target rear wheel, and the steering rate of the second target rear wheel.

6. The rear-wheel steering control method according to claim 5, characterized in that, Also includes: If the number of zero crossings of the front wheel steering angle within a first preset time period is greater than 1, then after the steering direction of the front wheel is maintained in the current direction for a second preset time period, the steering direction of the rear wheel is updated according to the steering direction of the front wheel and the vehicle speed.

7. The rear-wheel steering control method according to claim 1, characterized in that, The current vehicle parameters include suspension height, rear wheel steering motor torque and speed. Based on the vehicle speed and current vehicle parameters, the rear wheel steering angle limit and rear wheel steering rate limit are determined, including: The first rear wheel steering angle limit is determined based on the suspension height, the first rear wheel steering rate limit is determined based on the torque and speed of the rear wheel steering motor, and the second rear wheel steering angle limit and the second rear wheel steering rate limit are determined based on the vehicle speed. Determining a second target rear wheel angle based on the first target rear wheel steering angle and the rear wheel steering angle limit, and determining a second target rear wheel steering rate based on the first target rear wheel steering rate and the rear wheel steering rate limit, includes: The target rear wheel angle after the limit is determined based on the first rear wheel steering angle limit and the first target rear wheel steering angle; the rear wheel steering rate after the limit is determined based on the first rear wheel steering rate limit and the first target rear wheel steering rate, wherein the target rear wheel steering angle after the limit is not greater than the first rear wheel steering angle limit, and the rear wheel steering rate after the limit is not greater than the first rear wheel steering rate limit; the second target rear wheel steering angle is determined based on the second rear wheel steering angle limit and the target rear wheel steering angle after the limit; the second target rear wheel steering rate is determined based on the second rear wheel steering rate limit and the rear wheel steering rate after the limit, wherein the second target rear wheel steering angle is not greater than the second rear wheel steering angle limit, and the second target rear wheel steering rate is not greater than the second rear wheel steering rate limit. or, The second target rear wheel angle is determined based on the first rear wheel angle limit and the first target rear wheel angle, and the second target rear wheel steering rate is determined based on the first rear wheel steering rate limit and the first target rear wheel steering rate; wherein, the second target rear wheel angle is not greater than the first rear wheel angle limit, and the second target rear wheel steering rate is not greater than the first rear wheel steering rate limit; or, The second target rear wheel angle is determined based on the second rear wheel angle limit and the first target rear wheel angle, and the second target rear wheel steering rate is determined based on the second rear wheel steering rate limit and the first target rear wheel steering rate; wherein, the second target rear wheel angle is not greater than the second rear wheel angle limit, and the second target rear wheel steering rate is not greater than the second rear wheel steering rate limit.

8. The rear-wheel steering control method according to claim 7, characterized in that, Determining the first rear wheel steering rate limit based on the torque and speed of the rear wheel steering motor includes: The rack force is determined based on the torque of the rear wheel steering motor, and the maximum rack speed is determined based on the rack force. The theoretical rack speed is determined based on the rotational speed of the rear wheel steering motor; The target rack speed is determined based on the maximum rack speed and the theoretical rack speed, and the first rear wheel steering rate limit is determined based on the target rack speed.

9. The rear-wheel steering control method according to claim 7, characterized in that, Also includes: If the suspension height changes, the first rear wheel steering angle limit corresponding to the suspension height before the change changes at a preset rate to the first rear wheel steering angle limit corresponding to the suspension height after the change.

10. The rear-wheel steering control method according to any one of claims 1 to 9, characterized in that, Before controlling the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate, the method further includes: Determine whether the parameters used to determine the rear wheel angle of the first target or the state of the rear wheel steering system are abnormal; If so, then determine the third target rear wheel steering rate, and control the rear wheel rotation according to the third target rear wheel steering rate.

11. The rear-wheel steering control method according to claim 10, characterized in that, Following the control of the rear wheel steering rate based on the third target, the process also includes: If the abnormal parameter occurs or the state of the rear wheel steering system returns to normal, then determine whether the vehicle speed exceeds the first preset safe speed. If the vehicle speed exceeds the first preset safe speed, the rear wheels are controlled to remain in the neutral position. If the vehicle speed does not exceed the first preset safe vehicle speed, then a new second target rear wheel steering angle and a new second target rear wheel steering rate are determined, and the rear wheel steering is controlled according to the new second target rear wheel steering angle and the new second target rear wheel steering rate.

12. The rear wheel steering control method according to claim 1, characterized in that, Before controlling the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate, the method further includes: If the steering wheel angle passes zero and the rate of change of the vehicle speed is greater than the preset rate of change, then the fourth target rear wheel steering rate is determined, and the rear wheel rotation is controlled according to the fourth target rear wheel steering rate. In the subsequent rear wheel rotation, if the vehicle speed exceeds the second preset safe speed, the rear wheels are controlled to remain in the neutral position; if the vehicle speed does not exceed the second preset safe speed, a new second target rear wheel steering angle and a new second target rear wheel steering rate are determined, and the rear wheel steering is controlled according to the new second target rear wheel steering angle and the new second target rear wheel steering rate.

13. A rear-wheel steering control device, characterized in that, include: The first determining module is used to determine the first target rear wheel angle and the first target rear wheel steering rate based on the vehicle speed and steering wheel angle, and to determine the rear wheel angle limit and the rear wheel steering rate limit based on the current vehicle parameters. The second determining module is used to determine the second target rear wheel angle based on the first target rear wheel angle and the rear wheel angle limit, and to determine the second target rear wheel steering rate based on the first target rear wheel steering rate and the rear wheel steering rate limit; The first control module is used to control the rear wheel steering based on the second target rear wheel steering angle and the second target rear wheel steering rate.

14. A control device, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the steps of the rear wheel steering control method as described in any one of claims 1 to 12 when executing the computer program.

15. A vehicle, characterized in that, Includes the control device as described in claim 14.

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