Brake control method and system for U-shaped turning of vehicle with rear wheel steering

Abstract

A braking control method and system for U-shaped turning of a rear wheel steering vehicle belongs to the field of vehicle control, and comprises the following steps: when the vehicle is judged to enter a turning working condition at a high speed, judging whether a longitudinal acceleration is smaller than a preset negative value, and if so, adopting a curve braking control strategy; if not, adopting a proportional control strategy; the curve braking control strategy comprises the steps that when the real-time vehicle speed is reduced to be not larger than a switching threshold value, the rear wheel turning angle is controlled to be reduced to 0 degree; the proportional control strategy comprises the steps that when the real-time vehicle speed is larger than a switching threshold value, the rear wheel turning angle and the front wheel turning angle are controlled to deflect in the same direction, and when the real-time vehicle speed is not larger than the switching threshold value, the rear wheel turning angle and the front wheel turning angle are controlled to deflect in the opposite direction. Aiming at the rear wheel control problem when the vehicle with the rear turning function performs a rapid curve braking scene, the problem of sudden change of the rear wheel turning angle under the working condition is solved by limiting sudden turning of the rear wheels, and the safety and comfort of the vehicle are improved.

Description

Technical Field

[0001] The present application relates to the field of vehicle control, and in particular to a braking control method and system for a vehicle with rear-wheel steering that performs a U-turn. Background Art

[0002] Nowadays, more and more new energy vehicles have rear-wheel steering function, which can control the rear wheel angle to be opposite to the front wheel angle at low speed, reduce the turning radius, and increase the maneuverability of the vehicle. At high speed, the rear wheel angle can be controlled to be in the same direction as the front wheel angle to increase stability.

[0003] Generally, the rear wheel steering angle control uses a proportional control strategy, that is, when the vehicle enters a curve at a higher speed, the rear wheels will turn in the same direction as the front wheel angle due to the high speed. Subsequently, the driver brakes to reduce the speed of the vehicle to ensure the safety of the vehicle. When the speed reaches the low-speed area, the rotation direction of the rear wheels will be opposite to the front wheel angle, and since the curvature of the curve is small, the greater the front wheel angle, the greater the angle of reverse rotation of the rear wheels will also be. The time for the rear wheel angle to change is related to the speed of the vehicle. If the driver brakes in a hurry, the process will change faster. Since the rear wheel angle changes from the same direction to a larger angle in the opposite direction, the vehicle's driving trajectory exceeds expectations, and the driver has no time to adjust the steering wheel, resulting in the risk of the front of the vehicle hitting the guardrail on the curve.

[0004] Among the existing rear-wheel steering control methods, there is no control method for the scenario of fast entering a curve and braking. Summary of the invention

[0005] The present application provides a braking control method and system for a rear-wheel steering vehicle during a U-turn, which can solve the technical problem in the prior art of sudden rear wheel angle changes when the rear-wheel steering vehicle performs rapid cornering braking.

[0006] In a first aspect, an embodiment of the present application provides a braking control method for a U-turn of a vehicle with rear-wheel steering, the method comprising:

[0007] When determining that the vehicle enters a turning condition at a high speed, determining whether the longitudinal acceleration is not greater than a preset negative value, if so, adopting a cornering braking control strategy; if not, adopting a proportional control strategy;

[0008] The cornering braking control strategy includes controlling the rear wheel steering angle to decrease to 0° when the real-time vehicle speed decreases to a value not greater than a switching threshold;

[0009] The proportional control strategy includes controlling the rear wheel steering angle to deflect in the same direction as the front wheel steering angle when the real-time vehicle speed is greater than the switching threshold, and controlling the rear wheel steering angle to deflect in the opposite direction as the front wheel steering angle when the real-time vehicle speed is not greater than the switching threshold.

[0010] In combination with the first aspect, in one implementation, the method further includes:

[0011] The turning radius of the vehicle is calculated by combining the front wheel turning angle, the rear wheel turning angle, and the vehicle wheelbase;

[0012] When the vehicle's turning radius is greater than a preset radius threshold for a period of time greater than a preset period of time, it is determined that the vehicle enters a turning condition.

[0013] In combination with the first aspect, in one implementation, the vehicle turning radius is calculated using the following formula:

[0014] R=[tan(AgF)-tan(AgR)] / L

[0015] Among them, R represents the turning radius of the vehicle, AgF represents the front wheel turning angle, AgR represents the rear wheel turning angle, and L represents the vehicle wheelbase.

[0016] In combination with the first aspect, in one implementation, the method further includes:

[0017] After determining that the vehicle enters a turning condition, determine whether the real-time vehicle speed is greater than the switching threshold. If so, it is determined that the vehicle enters the turning condition at a high speed and a proportional control strategy is adopted; if not, it is determined that the vehicle enters the turning condition at a low speed and a proportional control strategy is adopted.

[0018] In combination with the first aspect, in one implementation, the method further includes:

[0019] After adopting the curve braking control strategy, determine whether the real-time vehicle speed is not greater than the exit threshold and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than the preset acceleration threshold. If so, exit the curve braking control strategy and adopt the proportional control strategy; if not, continue to adopt the curve braking control strategy.

[0020] In combination with the first aspect, in one implementation, the method further includes:

[0021] When exiting the cornering braking control strategy and adopting the proportional control strategy, the slope of the rear wheel turning angle changing with the front wheel turning angle is limited. The greater the vehicle speed, the smaller the slope.

[0022] In a second aspect, an embodiment of the present application provides a braking control system for a U-turn of a vehicle with rear-wheel steering, the system comprising:

[0023] A control module, which is used to determine whether the longitudinal acceleration is less than a preset negative value when determining that the vehicle enters a turning condition at a high speed, and if so, adopt a cornering braking control strategy; if not, adopt a proportional control strategy;

[0024] The cornering braking control strategy includes controlling the rear wheel steering angle to decrease to 0° when the real-time vehicle speed decreases to a value not greater than a switching threshold;

[0025] The proportional control strategy includes controlling the rear wheel steering angle to deflect in the same direction as the front wheel steering angle when the real-time vehicle speed is greater than the switching threshold, and controlling the rear wheel steering angle to deflect in the opposite direction as the front wheel steering angle when the real-time vehicle speed is not greater than the switching threshold.

[0026] In combination with the second aspect, in one embodiment, the control module is also used to determine whether the real-time vehicle speed is greater than the switching threshold after determining that the vehicle enters a turning condition. If so, it is determined that the vehicle enters the turning condition at a high speed and a proportional control strategy is adopted; if not, it is determined that the vehicle enters the turning condition at a low speed and a proportional control strategy is adopted.

[0027] In combination with the second aspect, in one embodiment, the control module is also used to determine whether the real-time vehicle speed is not greater than the exit threshold and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than the square sum threshold after adopting the curve braking control strategy. If so, exit the curve braking control strategy and adopt the proportional control strategy; if not, continue to adopt the curve braking control strategy.

[0028] In combination with the second aspect, in one implementation, the control module is also used to limit the slope of the rear wheel angle changing with the front wheel angle when exiting the cornering braking control strategy and adopting the proportional control strategy, and the greater the vehicle speed, the smaller the slope.

[0029] The beneficial effects brought by the technical solution provided in the embodiments of the present application include:

[0030] To solve the rear wheel control problem when a vehicle with rear steering performs fast cornering braking, the sudden steering of the rear wheels is limited to solve the problem of sudden rear wheel angle changes under such conditions, thereby increasing the safety and comfort of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of a first embodiment of a braking control method for a U-turn of a vehicle with rear-wheel steering according to the present application;

[0032] Figure 2 This is a functional module diagram of an embodiment of a braking control system for a U-turn of a vehicle with rear-wheel steering according to the present application. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0035] In a first aspect, an embodiment of the present application provides a braking control method when a vehicle with rear-wheel steering makes a U-turn.

[0036] In one embodiment, referring to Figure 1 , Figure 1 This is a flow chart of the first embodiment of the braking control method for a U-turn of a rear-wheel steering vehicle of the present application. Figure 1 As shown, the braking control method for a U-turn of a vehicle with rear wheel steering includes:

[0037] Step S1: Determine whether the real-time vehicle speed under the turning condition is greater than the switching threshold:

[0038] If yes, go to step S2.

[0039] If not, go to step S3.

[0040] Step S2: The vehicle does not enter a high-speed turning condition, and a proportional control strategy is adopted, and then the process goes to step S1.

[0041] Step S3: The vehicle enters a high-speed turning condition and adopts a proportional control strategy, and then proceeds to step S4.

[0042] Step S4: Whether the longitudinal acceleration is less than a preset negative value:

[0043] If yes, go to step S5.

[0044] If not, go to step S6.

[0045] Step S5: The vehicle does not enter a high-speed turning braking condition and a proportional control strategy is adopted.

[0046] Step S6: The vehicle enters a high-speed turning braking condition and adopts a cornering braking control strategy.

[0047] Step S7: Whether the real-time vehicle speed is less than the preset vehicle speed threshold, and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than the preset acceleration:

[0048] If yes, go to step S8.

[0049] If not, go to step S6.

[0050] Step S8: The vehicle exits the high-speed turning braking condition and adopts a proportional control strategy.

[0051] Among them, the traditional proportional control strategy is divided into two parts. One part is that when the real-time vehicle speed is greater than the switching threshold, the rear wheel angle changes with the change of the front wheel angle. Specifically, the rear wheel angle deflects in the same direction as the front wheel angle, and the front wheel angle gradually increases when it deflects to the left, then the rear wheel angle gradually increases when it deflects to the left, and the front wheel angle decreases when it deflects to the left, then the rear wheel angle decreases when it deflects to the left. The other part is that when the real-time vehicle speed is less than or equal to the switching threshold, the rear wheel angle changes with the change of the front wheel angle. Specifically, the rear wheel angle deflects in the same direction as the front wheel angle, and the front wheel angle gradually increases when it deflects to the left, then the rear wheel angle gradually increases when it deflects to the right, and the front wheel angle decreases when it deflects to the left, then the rear wheel angle decreases when it deflects to the right. During actual driving, when the vehicle initially enters a turning road at high speed, the rear wheel angle deflects in the same direction as the front wheel angle. When the vehicle speed decreases, the rear wheel angle deflects in the opposite direction of the front wheel angle. When switching from the same direction deflection to the opposite direction deflection, the rear wheel first returns to the center to 0°, and then continues to deflect in the opposite direction of the front wheel.

[0052] The turning braking strategy is to control the rear wheel angle to change in the same direction as the front wheel angle when the real-time vehicle speed is greater than the switching threshold. If the front wheel angle deflects to the left and gradually increases, the rear wheel angle will also deflect to the left and gradually increase. If the front wheel angle deflects to the left and decreases, the rear wheel angle will also deflect to the left and decrease. That is, when the real-time vehicle speed is greater than the switching threshold, the control method for the high-speed stage in the proportional control strategy is still used. When it is judged that the longitudinal acceleration is less than or equal to the preset negative value, even if the real-time vehicle speed drops to less than or equal to the switching threshold, the rear wheel angle will not change from deflecting in the same direction as the front wheel to deflecting in the opposite direction of the front wheel. The rear wheel angle can only return to the center to 0° and cannot continue to deflect to the opposite direction of the front wheel angle.

[0053] In this embodiment, when the cornering braking control strategy is activated, the normal proportional angle control is no longer used, and the requested angle of the rear wheel steering angle is limited so that it cannot be opposite to the front wheel steering angle and can only change to 0° to ensure the normal vehicle trajectory. In view of the rear wheel control problem in the fast cornering braking scenario of a vehicle with rear steering, the sudden steering of the rear wheels is limited to solve the problem of sudden rear wheel steering angle changes under this condition, thereby increasing the safety and comfort of the vehicle.

[0054] Furthermore, in one embodiment, the above method further includes:

[0055] The vehicle turning radius is calculated by combining the front wheel turning angle, rear wheel turning angle, and vehicle wheelbase.

[0056] When the vehicle's turning radius is greater than a preset radius threshold for a period of time greater than a preset period of time, it is determined that the vehicle enters a turning condition.

[0057] The turning radius of the above vehicle is calculated using the following formula (1):

[0058] R = [tan(AgF) - tan(AgR)] / L (1)

[0059] Among them, R represents the turning radius of the vehicle, AgF represents the front wheel turning angle, AgR represents the rear wheel turning angle, and L represents the vehicle wheelbase.

[0060] In this embodiment, AgF is the front wheel turning angle, AgR is the rear wheel turning angle, and L is the vehicle wheelbase. When the vehicle turning radius R is greater than the turning radius threshold Rth for 2 seconds, and the front and rear wheel turning angles are in the same direction, that is, AgF*AgR>0, at this time, if the monitored vehicle longitudinal acceleration Lgt value is less than a certain threshold such as -0.6g, it means that the driver has stepped on the brake and the braking force is relatively large. At this time, the vehicle speed drops relatively quickly, and the cornering braking control strategy is activated.

[0061] Furthermore, in one embodiment, the above method further includes:

[0062] After determining that the vehicle enters a turning condition, determine whether the real-time vehicle speed is greater than the switching threshold. If so, it is determined that the vehicle enters a turning condition at a high speed and a proportional control strategy is adopted. If not, it is determined that the vehicle enters a turning condition at a low speed and a proportional control strategy is adopted.

[0063] In this embodiment, after determining that the vehicle enters a turning condition, it is determined whether the real-time vehicle speed is greater than the switching threshold. If the real-time vehicle speed is less than or equal to the switching threshold, the traditional proportional control strategy is adopted. If the real-time vehicle speed is greater than the switching threshold, it is necessary to start detecting whether the longitudinal acceleration is less than or equal to a preset negative value such as -0.6g. If so, it is considered that the current vehicle is in a high-speed turning braking condition, and the cornering braking strategy needs to be activated to avoid sudden rear wheel angle changes under this condition and increase the safety and comfort of the vehicle.

[0064] Furthermore, in one embodiment, the above method further includes:

[0065] After adopting the curve braking control strategy, it is determined whether the real-time vehicle speed is not greater than the exit threshold and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than the preset acceleration threshold. If so, the curve braking control strategy is exited and the proportional control strategy is adopted. If not, the curve braking control strategy is continued.

[0066] In this embodiment, after adopting the curve braking strategy, it is necessary to start detecting whether the real-time vehicle speed is less than or equal to the exit threshold and whether the sum of the squares of the longitudinal acceleration and the lateral acceleration is less than or equal to the preset acceleration threshold (Lgt 2 +Lat2 < a certain threshold, Lgt is the longitudinal acceleration, Lat is the lateral acceleration), the real-time vehicle speed is less than or equal to the exit threshold, indicating that the vehicle speed has dropped and the vehicle is no longer in a high-speed turning braking condition. The sum of the squares of the longitudinal acceleration and the lateral acceleration is less than or equal to the preset acceleration threshold, indicating that the vehicle is overall stable. Therefore, after judging based on the vehicle speed and acceleration, you can exit the cornering braking strategy and switch back to the proportional control strategy.

[0067] Furthermore, in one embodiment, the above method further includes:

[0068] When exiting the cornering braking control strategy and adopting the proportional control strategy, the slope of the rear wheel turning angle changing with the front wheel turning angle is limited. The greater the vehicle speed, the smaller the slope.

[0069] In this embodiment, in the proportional control strategy, a certain proportional relationship is always maintained between the rear wheel angle and the front wheel angle, and the difference is only whether the rear wheel angle follows the front wheel angle in the same direction at high speed or the opposite direction at low speed. If the real-time vehicle speed is less than or equal to the switching threshold value after the vehicle just enters the turning condition, the traditional proportional control strategy is adopted. However, if the real-time vehicle speed is greater than the switching threshold value after the vehicle just enters the turning condition, it is necessary to detect whether the real-time vehicle speed is not greater than the exit threshold value and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than the preset acceleration threshold value while adopting the traditional proportional control strategy. If so, the improved proportional control strategy is switched to be used. The improved proportional control strategy still follows the traditional proportional control strategy. A certain proportional relationship is always maintained between the rear wheel angle and the front wheel angle, and the difference is only whether the rear wheel angle follows the front wheel angle in the same direction at high speed or the opposite direction at low speed. The additional content is that the proportional relationship between the rear wheel angle and the front wheel angle is different from the traditional proportional control strategy. The proportional relationship between the rear wheel angle and the front wheel angle changes with the vehicle speed. The ratio is small when the vehicle speed is high and large when the vehicle speed is low.

[0070] In a specific embodiment, when the cornering braking control strategy is activated, the normal proportional angle control is no longer used. The requested angle of the rear wheel steering angle is limited so that it cannot be opposite to the front wheel steering angle and can only change to 0° to ensure the normal vehicle trajectory.

[0071] Exit the cornering braking control strategy. As the vehicle speed decreases, the vehicle gradually returns to a steady state. When the lateral acceleration and lateral acceleration of the vehicle meet the steady-state requirements, the cornering braking control strategy is exited. When Lgt2+Lat2<a certain threshold, the cornering braking strategy is exited.

[0072] The rear turning angle responds to proportional control. At this time, the proportional control angle is relatively large, and the actual rear wheel turning angle is 0°. In order to prevent the rear wheel angle from jumping, this scheme limits the slope of the requested rear wheel turning angle change after exiting the cornering braking control strategy. The size of the slope is related to the vehicle speed. The greater the speed, the smaller the slope. This can prevent the rear wheel turning angle from changing too quickly when the vehicle speed is fast, causing the rear axle of the vehicle to yaw too quickly. It can also ensure that the rear wheel turning angle quickly follows the target angle when the vehicle speed is slow, thereby ensuring the maneuverability of the vehicle.

[0073] In a second aspect, an embodiment of the present application also provides a braking control system for a vehicle with rear-wheel steering making a U-turn.

[0074] In one embodiment, referring to Figure 2 , Figure 2 This is a functional module diagram of an embodiment of a braking control system for a U-turn of a rear-wheel steering vehicle of the present application. Figure 2 As shown, the braking control system for a U-turn of a vehicle with rear-wheel steering includes:

[0075] The control module 2 is used to determine whether the longitudinal acceleration is less than a preset negative value when the vehicle enters a turning condition at a high speed, and if so, adopt a cornering braking control strategy. If not, adopt a proportional control strategy.

[0076] The above-mentioned cornering braking control strategy includes controlling the rear wheel steering angle to decrease to 0° when the real-time vehicle speed decreases to a value not greater than the switching threshold.

[0077] The above-mentioned proportional control strategy includes controlling the rear wheel steering angle to deflect in the same direction as the front wheel steering angle when the real-time vehicle speed is greater than the switching threshold, and controlling the rear wheel steering angle to deflect in the opposite direction as the front wheel steering angle when the real-time vehicle speed is not greater than the switching threshold.

[0078] Among them, the traditional proportional control strategy is divided into two parts. One part is that when the real-time vehicle speed is greater than the switching threshold, the rear wheel angle changes with the change of the front wheel angle. Specifically, the rear wheel angle deflects in the same direction as the front wheel angle, and the front wheel angle gradually increases when it deflects to the left, then the rear wheel angle gradually increases when it deflects to the left, and the front wheel angle decreases when it deflects to the left, then the rear wheel angle decreases when it deflects to the left. The other part is that when the real-time vehicle speed is less than or equal to the switching threshold, the rear wheel angle changes with the change of the front wheel angle. Specifically, the rear wheel angle deflects in the same direction as the front wheel angle, and the front wheel angle gradually increases when it deflects to the left, then the rear wheel angle gradually increases when it deflects to the right, and the front wheel angle decreases when it deflects to the left, then the rear wheel angle decreases when it deflects to the right. During actual driving, when the vehicle initially enters a turning road at high speed, the rear wheel angle deflects in the same direction as the front wheel angle. When the vehicle speed decreases, the rear wheel angle deflects in the opposite direction of the front wheel angle. When switching from the same direction deflection to the opposite direction deflection, the rear wheel first returns to the center to 0°, and then continues to deflect in the opposite direction of the front wheel.

[0079] The turning braking strategy is to control the rear wheel angle to change in the same direction as the front wheel angle when the real-time vehicle speed is greater than the switching threshold. If the front wheel angle deflects to the left and gradually increases, the rear wheel angle will also deflect to the left and gradually increase. If the front wheel angle deflects to the left and decreases, the rear wheel angle will also deflect to the left and decrease. That is, when the real-time vehicle speed is greater than the switching threshold, the control method for the high-speed stage in the proportional control strategy is still used. When it is judged that the longitudinal acceleration is less than or equal to the preset negative value, even if the real-time vehicle speed drops to less than or equal to the switching threshold, the rear wheel angle will not change from deflecting in the same direction as the front wheel to deflecting in the opposite direction of the front wheel. The rear wheel angle can only return to the center to 0° and cannot continue to deflect to the opposite direction of the front wheel angle.

[0080] Furthermore, the system also includes a collection module 1 for collecting real-time vehicle speed, longitudinal acceleration and lateral acceleration, and transmitting the collected data to the control module 2.

[0081] In this embodiment, when the cornering braking control strategy is activated, the normal proportional angle control is no longer used, and the requested angle of the rear wheel steering angle is limited so that it cannot be opposite to the front wheel steering angle and can only change to 0° to ensure the normal vehicle trajectory. In view of the rear wheel control problem in the fast cornering braking scenario of a vehicle with rear steering, the sudden steering of the rear wheels is limited to solve the problem of sudden rear wheel steering angle changes under this condition, thereby increasing the safety and comfort of the vehicle.

[0082] Furthermore, in one embodiment, the above method further includes:

[0083] The vehicle turning radius is calculated by combining the front wheel turning angle, rear wheel turning angle, and vehicle wheelbase.

[0084] When the vehicle's turning radius is greater than a preset radius threshold for a period of time greater than a preset period of time, it is determined that the vehicle enters a turning condition.

[0085] The turning radius of the above vehicle is calculated using the following formula (1):

[0086] R=[tan(AgF)-tan(AgR)] / L (1)

[0087] Among them, R represents the turning radius of the vehicle, AgF represents the front wheel turning angle, AgR represents the rear wheel turning angle, and L represents the vehicle wheelbase.

[0088] In this embodiment, AgF is the front wheel turning angle, AgR is the rear wheel turning angle, and L is the vehicle wheelbase. When the vehicle turning radius R is greater than the turning radius threshold Rth for 2 seconds, and the front and rear wheel turning angles are in the same direction, that is, AgF*AgR>0, at this time, if the monitored vehicle longitudinal acceleration Lgt value is less than a certain threshold such as -0.6g, it means that the driver has stepped on the brake and the braking force is relatively large. At this time, the vehicle speed drops relatively quickly, and the cornering braking control strategy is activated.

[0089] Furthermore, in one embodiment, the control module 2 is further configured to determine whether the real-time vehicle speed is greater than the switching threshold after determining that the vehicle enters a turning condition, and if so, determine that the vehicle enters a turning condition at a high speed and adopt a proportional control strategy. If not, determine that the vehicle enters a turning condition at a low speed and adopt a proportional control strategy.

[0090] In this embodiment, after determining that the vehicle enters a turning condition, it is determined whether the real-time vehicle speed is greater than the switching threshold. If the real-time vehicle speed is less than or equal to the switching threshold, the traditional proportional control strategy is adopted. If the real-time vehicle speed is greater than the switching threshold, it is necessary to start detecting whether the longitudinal acceleration is less than or equal to a preset negative value such as -0.6g. If so, it is considered that the current vehicle is in a high-speed turning braking condition, and the cornering braking strategy needs to be activated to avoid sudden rear wheel angle changes under this condition and increase the safety and comfort of the vehicle.

[0091] Furthermore, in one embodiment, the control module 2 is further used to determine whether the real-time vehicle speed is not greater than the exit threshold and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than the preset acceleration threshold after the curve braking control strategy is adopted, and if so, the curve braking control strategy is exited and the proportional control strategy is adopted. If not, the curve braking control strategy is continued.

[0092] In this embodiment, after adopting the curve braking strategy, it is necessary to start detecting whether the real-time vehicle speed is less than or equal to the exit threshold and whether the sum of the squares of the longitudinal acceleration and the lateral acceleration is less than or equal to the preset acceleration threshold (Lgt 2 +Lat 2 < a certain threshold, Lgt is the longitudinal acceleration, Lat is the lateral acceleration), the real-time vehicle speed is less than or equal to the exit threshold, indicating that the vehicle speed has dropped and the vehicle is no longer in a high-speed turning braking condition. The sum of the squares of the longitudinal acceleration and the lateral acceleration is less than or equal to the preset acceleration threshold, indicating that the vehicle is overall stable. Therefore, after judging based on the vehicle speed and acceleration, you can exit the cornering braking strategy and switch back to the proportional control strategy.

[0093] Furthermore, in one embodiment, the control module 2 is also used to limit the slope of the rear wheel angle changing with the front wheel angle when exiting the curve braking control strategy and adopting the proportional control strategy. The greater the vehicle speed, the smaller the slope.

[0094] In this embodiment, in the proportional control strategy, a certain proportional relationship is always maintained between the rear wheel angle and the front wheel angle, and the difference is only whether the rear wheel angle follows the front wheel angle in the same direction at high speed or the opposite direction at low speed. If the real-time vehicle speed is less than or equal to the switching threshold value after the vehicle just enters the turning condition, the traditional proportional control strategy is adopted. However, if the real-time vehicle speed is greater than the switching threshold value after the vehicle just enters the turning condition, it is necessary to detect whether the real-time vehicle speed is not greater than the exit threshold value and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than the preset acceleration threshold value while adopting the traditional proportional control strategy. If so, the improved proportional control strategy is switched to be used. The improved proportional control strategy still follows the traditional proportional control strategy. A certain proportional relationship is always maintained between the rear wheel angle and the front wheel angle, and the difference is only whether the rear wheel angle follows the front wheel angle in the same direction at high speed or the opposite direction at low speed. The additional content is that the proportional relationship between the rear wheel angle and the front wheel angle is different from the traditional proportional control strategy. The proportional relationship between the rear wheel angle and the front wheel angle changes with the vehicle speed. The ratio is small when the vehicle speed is high and large when the vehicle speed is low.

[0095] Among them, the functional implementation of each module in the braking control system when the vehicle with rear-wheel steering makes a U-turn corresponds to the steps in the braking control method embodiment when the vehicle with rear-wheel steering makes a U-turn, and its functions and implementation processes will not be repeated here one by one.

[0096] On the third aspect, an embodiment of the present application provides a braking control device for a vehicle with rear-wheel steering making a U-turn. The braking control device for a vehicle with rear-wheel steering making a U-turn can be a personal computer (PC), a laptop computer, a server, or other device with data processing capabilities.

[0097] In an embodiment of the application, a brake control device for a U-turn of a vehicle with rear-wheel steering may include a processor, a memory, a communication interface, and a communication bus.

[0098] The communication bus may be of any type and is used to interconnect the processor, the memory, and the communication interface.

[0099] The communication interface includes an input / output (I / O) interface, a physical interface, and a logical interface, etc., which are used to interconnect the components inside the brake control device when the rear-wheel steering vehicle makes a U-turn, and an interface used to interconnect the brake control device when the rear-wheel steering vehicle makes a U-turn with other devices (such as other computing devices or user devices). The physical interface can be an Ethernet interface, an optical fiber interface, an ATM interface, etc. The user device can be a display, a keyboard, etc.

[0100] The memory can be various types of storage media, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), flash memory, optical storage, hard disk, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), etc.

[0101] The processor may be a general-purpose processor, which may call the braking control program for a U-turn of a vehicle with rear-wheel steering stored in the memory, and execute the braking control method for a U-turn of a vehicle with rear-wheel steering provided in the embodiment of the present application. For example, the general-purpose processor may be a central processing unit (CPU). The method executed when the braking control program for a U-turn of a vehicle with rear-wheel steering is called may refer to the various embodiments of the braking control method for a U-turn of a vehicle with rear-wheel steering in the present application, which will not be described in detail here.

[0102] In a fourth aspect, an embodiment of the present application also provides a computer-readable storage medium.

[0103] The computer-readable storage medium of the present application stores a braking control program for a U-turn of a vehicle with rear-wheel steering. When the braking control program for a U-turn of a vehicle with rear-wheel steering is executed by a processor, the steps of the braking control method for a U-turn of a vehicle with rear-wheel steering as described above are implemented.

[0104] Among them, the method implemented when the braking control program for a rear-wheel steering vehicle making a U-turn is executed can refer to the various embodiments of the braking control method for a rear-wheel steering vehicle making a U-turn in the present application, and will not be repeated here.

[0105] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are only for description and do not represent the advantages or disadvantages of the embodiments.

[0106] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit "first", "second" and "third" to different types.

[0107] In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

[0108] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; the “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0109] In some processes described in the embodiments of the present application, multiple operations or steps that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0110] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, disk, CD) as described above, and includes a number of instructions for a terminal device to execute the methods described in each embodiment of the present application.

[0111] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A braking control method for a rear-wheel steering vehicle when making a U-turn, characterized in that: The method comprises: When determining that the vehicle enters a turning condition at a high speed, determining whether the longitudinal acceleration is not greater than a preset negative value, if so, adopting a cornering braking control strategy; if not, adopting a proportional control strategy; The cornering braking control strategy includes controlling the rear wheel steering angle to decrease to 0° when the real-time vehicle speed decreases to a value not greater than a switching threshold; The proportional control strategy includes controlling the rear wheel steering angle to deflect in the same direction as the front wheel steering angle when the real-time vehicle speed is greater than the switching threshold, and controlling the rear wheel steering angle to deflect in the opposite direction as the front wheel steering angle when the real-time vehicle speed is not greater than the switching threshold.

2. The braking control method for a U-turn of a vehicle with rear-wheel steering according to claim 1, characterized in that: The method further comprises: The turning radius of the vehicle is calculated by combining the front wheel turning angle, the rear wheel turning angle, and the vehicle wheelbase; When the vehicle's turning radius is greater than a preset radius threshold for a period of time greater than a preset period of time, it is determined that the vehicle enters a turning condition.

3. The braking control method for a U-turn of a vehicle with rear-wheel steering according to claim 2, characterized in that: The vehicle turning radius is calculated using the following formula: R=[tan(AgF)-tan(AgR)] / L Among them, R represents the turning radius of the vehicle, AgF represents the front wheel turning angle, AgR represents the rear wheel turning angle, and L represents the vehicle wheelbase.

4. The braking control method for a U-turn of a vehicle with rear-wheel steering according to claim 1, characterized in that: The method further comprises: After determining that the vehicle enters a turning condition, determine whether the real-time vehicle speed is greater than the switching threshold. If so, it is determined that the vehicle enters the turning condition at a high speed and a proportional control strategy is adopted; if not, it is determined that the vehicle enters the turning condition at a low speed and a proportional control strategy is adopted.

5. The braking control method for a U-turn of a rear-wheel steering vehicle according to claim 1, characterized in that: The method further comprises: After adopting the curve braking control strategy, determine whether the real-time vehicle speed is not greater than the exit threshold and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than the preset acceleration threshold. If so, exit the curve braking control strategy and adopt the proportional control strategy; if not, continue to adopt the curve braking control strategy.

6. The braking control method for a U-turn of a vehicle with rear-wheel steering according to claim 5, characterized in that: The method further comprises: When exiting the cornering braking control strategy and adopting the proportional control strategy, the slope of the rear wheel turning angle changing with the front wheel turning angle is limited. The greater the vehicle speed, the smaller the slope.

7. A braking control system for a U-turn of a vehicle with rear-wheel steering, characterized in that: The system comprises: A control module, which is used to determine whether the longitudinal acceleration is less than a preset negative value when determining that the vehicle enters a turning condition at a high speed, and if so, adopt a cornering braking control strategy; if not, adopt a proportional control strategy; The cornering braking control strategy includes controlling the rear wheel steering angle to decrease to 0° when the real-time vehicle speed decreases to a value not greater than a switching threshold; The proportional control strategy includes controlling the rear wheel steering angle to deflect in the same direction as the front wheel steering angle when the real-time vehicle speed is greater than the switching threshold, and controlling the rear wheel steering angle to deflect in the opposite direction as the front wheel steering angle when the real-time vehicle speed is not greater than the switching threshold.

8. The braking control system for a U-turn of a rear-wheel steering vehicle as claimed in claim 7, characterized in that: The control module is also used to determine whether the real-time vehicle speed is greater than a switching threshold after determining that the vehicle enters a turning condition. If so, it is determined that the vehicle enters the turning condition at a high speed and a proportional control strategy is adopted; if not, it is determined that the vehicle enters the turning condition at a low speed and a proportional control strategy is adopted.

9. The braking control system for a U-turn of a rear-wheel steering vehicle as claimed in claim 7, characterized in that: The control module is also used to determine whether the real-time vehicle speed is not greater than the exit threshold and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than the square sum threshold after adopting the curve braking control strategy. If so, exit the curve braking control strategy and adopt the proportional control strategy; if not, continue to adopt the curve braking control strategy.

10. The braking control system for a U-turn of a rear-wheel steering vehicle according to claim 9, characterized in that: The control module is also used to limit the slope of the rear wheel turning angle changing with the front wheel turning angle when exiting the curve braking control strategy and adopting the proportional control strategy. The greater the vehicle speed, the smaller the slope.

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