Braking control method and system for a vehicle with rear wheel steering during a u-turn

Abstract

The application discloses a brake control method and system for a U-turn of a vehicle with rear wheel steering, and belongs to the field of vehicle control. When it is determined that the vehicle enters a turning working condition at a high speed, it is determined whether the longitudinal acceleration is less than a preset negative value. If yes, a curve braking control strategy is adopted. If no, a proportional control strategy is adopted. The curve braking control strategy comprises controlling the rear wheel turning angle to reduce to 0 DEG during the process that the real-time vehicle speed reduces to not more than a switching threshold. The proportional control strategy comprises controlling the rear wheel turning angle to deflect in the same direction as the front wheel turning angle when the real-time vehicle speed is greater than the switching threshold, and controlling the rear wheel turning angle to deflect in the opposite direction of the front wheel turning angle after the real-time vehicle speed is not greater than the switching threshold. The application aims at the rear wheel control problem of the vehicle with rear wheel steering in a fast curve braking scene, solves the problem of sudden rear wheel turning angle change in the working condition by limiting the sudden steering of the rear wheel, and increases the safety and comfort of the vehicle.

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 during a U-turn. Background Art

[0002] Nowadays, more and more new energy vehicles have rear-wheel steering functions. This function can control the rear wheel angle to be opposite to the front wheel angle at low speeds, reduce the turning radius, and increase the vehicle's maneuverability. At high speeds, it can control the rear wheel angle 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, due to the high speed, the rear wheels will produce an angle in the same direction as the front wheel angle. Subsequently, the driver brakes and reduces the speed to ensure the safety of the vehicle. When the speed reaches the low-speed area, the direction of rotation of the rear wheels will be opposite to the front wheel angle, and because 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 too quickly, 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 currently no control method for the scenario of quickly entering a corner 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 a 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 vehicle with rear-wheel steering during a U-turn, the method comprising:

[0007] When determining that the vehicle enters a turning condition at high speed, determine whether the longitudinal acceleration is not greater than a preset negative value. If so, adopt the cornering braking control strategy; if not, adopt the 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 and the front wheel steering angle to deflect in the same direction when the real-time vehicle speed is greater than the switching threshold, and controlling the rear wheel steering angle and the front wheel steering angle to deflect in the opposite direction after the real-time vehicle speed is no greater than the switching threshold.

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

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

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

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

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

[0015] Among them, R represents the vehicle turning radius, 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 embodiment, 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 embodiment, 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 embodiment, 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 vehicle with rear-wheel steering during a U-turn, the system comprising:

[0023] a control module configured to determine whether the longitudinal acceleration is less than a preset negative value when the vehicle enters a turning condition at high speed, and if so, to adopt a cornering braking control strategy; if not, to 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 and the front wheel steering angle to deflect in the same direction when the real-time vehicle speed is greater than the switching threshold, and controlling the rear wheel steering angle and the front wheel steering angle to deflect in the opposite direction after the real-time vehicle speed is no 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 embodiment, the control module is further 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. The greater the vehicle speed, the smaller the slope.

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

[0030] To address the rear wheel control issues of vehicles with rear-wheel steering during rapid cornering braking scenarios, this system limits sudden rear wheel steering, solves the problem of sudden rear wheel angle changes under such conditions, and increases vehicle safety and comfort. 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 rear-wheel steering vehicle according to the present invention;

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

[0033] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, 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 this application clearer, the implementation methods of this 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 for a vehicle with rear-wheel steering making 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 in this application. Figure 1 As shown, the braking control method for a rear-wheel steering vehicle during a U-turn 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: Is the longitudinal acceleration 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 a preset vehicle speed threshold, and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than a preset acceleration:

[0048] If yes, go to step S8.

[0049] If no, go to step S6.

[0050] Step S8, the vehicle exits the high-speed corner braking working condition, and a proportional control strategy is adopted.

[0051] In the traditional proportional control strategy, when the real-time vehicle speed is greater than the switching threshold, the rear wheel angle changes with the front wheel angle, specifically, the rear wheel angle and the front wheel angle deflect in the same direction, the front wheel angle deflects to the left side and gradually increases, and the rear wheel angle deflects to the left side and gradually increases; the front wheel angle deflects to the left side and gradually decreases, and the rear wheel angle deflects to the left side and gradually decreases; when the real-time vehicle speed is less than or equal to the switching threshold, the rear wheel angle changes with the front wheel angle, specifically, the rear wheel angle and the front wheel angle deflect in opposite directions, the front wheel angle deflects to the left side and gradually increases, and the rear wheel angle deflects to the right side and gradually increases; the front wheel angle deflects to the left side and gradually decreases, and the rear wheel angle deflects to the right side and gradually decreases. In the actual driving process, when the vehicle initially enters the corner 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 0°, and then continues to deflect in the opposite direction of the front wheel angle.

[0052] When the real-time vehicle speed is greater than the switching threshold, the rear wheel angle changes with the front wheel angle in the same direction, the front wheel angle deflects to the left side and gradually increases, and the rear wheel angle also deflects to the left side and gradually increases; the front wheel angle deflects to the left side and gradually decreases, and the rear wheel angle also deflects to the left side and gradually decreases, 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 adopted. When the longitudinal acceleration is less than or equal to the preset negative value, even if the real-time vehicle speed decreases to be less than or equal to the switching threshold, the rear wheel angle will not change from the same direction deflection to the opposite direction deflection of the front wheel, and the rear wheel angle can only return to 0° and cannot continue to deflect to the opposite direction of the front wheel angle.

[0053] In this embodiment, when the corner braking control strategy is activated, the normal proportional angle control is no longer used, the request angle of the rear wheel angle is limited, so that the rear wheel angle cannot be opposite to the front wheel angle and can only change to 0°, so as to ensure the normal vehicle trajectory. For the rear wheel control problem of the vehicle with rear steering in the rapid corner braking scene, the sudden steering of the rear wheel is limited, the problem of sudden change of the rear wheel angle in this working condition is solved, and the safety and comfort of the vehicle are increased.

[0054] Further, in an embodiment, the method further includes:

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

[0056] When the turning radius of the vehicle is greater than the preset radius threshold for a duration greater than a preset duration, it is determined that the vehicle enters a turning working condition.

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

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

[0059] Wherein, 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 the embodiment, AgF is the front wheel turning angle, AgR is the rear wheel turning angle, and L is the vehicle wheelbase. When the turning radius R of the vehicle is greater than the turning radius threshold Rth for 2s, and the front and rear wheel turning angles are in the same direction, i.e. AgF*AgR>0, if the longitudinal acceleration Lgt of the vehicle is less than a certain threshold such as -0.6g, it indicates that the driver steps on the brake and the braking force is relatively large, at this time the vehicle speed decreases relatively fast, and the curve braking control strategy is activated.

[0061] Further, in an embodiment, the method further comprises:

[0062] After determining that the vehicle enters the turning working condition, it is determined whether the real-time vehicle speed is greater than a switching threshold. If yes, it is determined that the vehicle enters the turning working condition at high speed, and a proportional control strategy is adopted. If no, it is determined that the vehicle enters the turning working condition at low speed, and the proportional control strategy is adopted.

[0063] In the embodiment, after determining that the vehicle enters the turning working condition, it is determined whether the real-time vehicle speed is greater than a switching threshold. If the real-time vehicle speed is less than or equal to the switching threshold, a 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 yes, it is considered that the current vehicle is in a high-speed turning braking working condition, and the curve braking strategy needs to be activated to avoid sudden rear wheel turning angle change in the working condition, thereby increasing the safety and comfort of the vehicle.

[0064] Further, in an embodiment, the method further comprises:

[0065] After adopting the curve braking control strategy, it is determined whether the real-time vehicle speed is not greater than an exit threshold and the sum of the squares of the longitudinal acceleration and the lateral acceleration is not greater than a preset acceleration threshold. If yes, the curve braking control strategy is exited, and the proportional control strategy is adopted. If no, the curve braking control strategy is continued to be adopted.

[0066] In the 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 an exit threshold and the sum of the squares of the longitudinal acceleration and the lateral acceleration is less than or equal to a preset acceleration threshold (Lgt 2+Lat 2 < a certain threshold, where Lgt is the longitudinal acceleration and Lat is the lateral acceleration). If the real-time vehicle speed is less than or equal to the exit threshold, it means that the vehicle speed has dropped and the vehicle is no longer in a high-speed cornering braking condition. If the sum of the squares of the longitudinal acceleration and the lateral acceleration is less than or equal to the preset acceleration threshold, it means that the vehicle is overall stable. Therefore, after making a judgment 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, the proportional control strategy maintains a constant proportional relationship between the rear wheel angles and the front wheel angles, differing only in whether they rotate in the same direction at high speeds or in opposite directions at low speeds. If the vehicle's real-time speed is less than or equal to a switching threshold immediately after entering a turn, the conventional proportional control strategy is employed. However, if the vehicle's real-time speed exceeds the switching threshold immediately after entering a turn, the conventional proportional control strategy is also tested to determine whether the real-time speed is less than an exit threshold and the sum of the squares of the longitudinal and lateral accelerations is less than a preset acceleration threshold. If these conditions are met, the improved proportional control strategy is employed. This improved proportional control strategy still follows the conventional proportional control strategy, maintaining a constant proportional relationship between the rear wheel angles and the front wheel angles, differing only in whether they rotate in the same direction at high speeds or in opposite directions at low speeds. However, unlike the conventional proportional control strategy, the proportional relationship between the rear and front wheel angles varies with vehicle speed, with a smaller ratio at higher speeds and a larger ratio at lower speeds.

[0070] In one specific embodiment, when the cornering braking control strategy is activated, the normal proportional angle control is no longer followed. 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, it gradually returns to a steady state. When the vehicle's lateral acceleration and side acceleration 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 wheel steering angle responds to proportional control. At this time, the proportional control angle is relatively large, and the actual rear wheel steering angle is 0°. In order to prevent the rear wheel angle from jumping, this solution limits the slope of the requested rear wheel steering 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 steering 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 steering 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 in this application. Figure 2 As shown, the braking control system for a U-turn on 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 high speed. If so, a cornering braking control strategy is adopted. If not, a proportional control strategy is adopted.

[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 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 to the front wheel steering angle when the real-time vehicle speed is no 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 deflects to the left gradually increases, then the rear wheel angle deflects to the left gradually increases, and the front wheel angle deflects to the left decreases, then the rear wheel angle deflects to the left decreases. 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 deflects to the left gradually increases, then the rear wheel angle deflects to the right gradually increases, and the front wheel angle deflects to the left decreases, then the rear wheel angle deflects to the right decreases. 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 that when the real-time vehicle speed is greater than the switching threshold, the rear wheel angle changes in the same direction as the front wheel angle, the front wheel angle gradually increases to the left side, and the rear wheel angle also gradually increases to the left side, the front wheel angle gradually decreases to the left side, and the rear wheel angle also gradually decreases to the left side, 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 adopted. When the longitudinal acceleration is less than or equal to the preset negative value, even if the real-time vehicle speed is less than or equal to the switching threshold, the rear wheel angle will not change from the same direction as the front wheel to the opposite direction of the front wheel, and the rear wheel angle can only return to 0° and cannot continue to deflect to the opposite direction of the front wheel angle.

[0080] Further, the system further comprises a collection module 1 for collecting real-time vehicle speed, longitudinal acceleration and transverse acceleration, and transmitting the collected data to the control module 2.

[0081] In the embodiment, when the turning braking control strategy is activated, the normal proportional angle control is no longer used, the request angle of the rear wheel angle is limited, the rear wheel angle cannot be opposite to the front wheel angle, and can only change to 0°, so as to ensure the normal vehicle trajectory. For the rear wheel control problem of the vehicle with rear turning steering in the rapid turning braking scene, the sudden turning of the rear wheel is limited, the problem of sudden change of the rear wheel angle in this working condition is solved, and the safety and comfort of the vehicle are increased.

[0082] Further, in an embodiment, the above method further comprises:

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

[0084] When the turning radius of the vehicle is greater than the preset radius threshold for a duration greater than the preset duration, it is determined that the vehicle enters the turning working condition.

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

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

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

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

[0089] Further, in an embodiment, the control module 2 is further configured to, after determining that the vehicle enters the turning working condition, determine whether the real-time vehicle speed is greater than a switching threshold value, and if yes, determine that the vehicle enters the turning working condition at a high speed, and adopt the proportional control strategy. If no, determine that the vehicle enters the turning working condition at a low speed, and adopt the proportional control strategy.

[0090] In the embodiment, after determining that the vehicle enters the turning working condition, it is determined whether the real-time vehicle speed is greater than a switching threshold value. If the real-time vehicle speed is less than or equal to the switching threshold value, the traditional proportional control strategy is adopted. If the real-time vehicle speed is greater than the switching threshold value, 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 yes, it is considered that the current vehicle is in a high-speed turning braking working condition, and the curve braking strategy needs to be activated to avoid sudden rear wheel turning angle change in the working condition, and increase the safety and comfort of the vehicle.

[0091] Further, in an embodiment, the control module 2 is further configured to, after adopting the curve braking control strategy, determine whether the real-time vehicle speed is not greater than an exit threshold value and the sum of squares of the longitudinal acceleration and the lateral acceleration is not greater than a preset acceleration threshold value, and if yes, exit the curve braking control strategy and adopt the proportional control strategy. If no, continue to adopt the curve braking control strategy.

[0092] In the 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 an exit threshold value and the sum of squares of the longitudinal acceleration and the lateral acceleration is less than or equal to a preset acceleration threshold value (Lgt 2 +Lat 2 < a certain threshold value, Lgt is the longitudinal acceleration, Lat is the lateral acceleration), the real-time vehicle speed less than or equal to the exit threshold value indicates that the vehicle speed has been reduced and the vehicle is no longer in a high-speed turning braking working condition, and the sum of squares of the longitudinal acceleration and the lateral acceleration less than or equal to the preset acceleration threshold value indicates that the vehicle is overall stable. Therefore, after the vehicle speed and acceleration are determined, the curve braking strategy can be exited and the proportional control strategy can be switched again.

[0093] Further, in an embodiment, the control module 2 is further configured to, when the curve braking control strategy is exited and the proportional control strategy is adopted, limit the slope of the rear wheel turning angle with respect to the change of the front wheel turning angle. 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 steering angle and the front wheel steering angle, and the only difference is whether the rear wheel turns in the same direction as the front wheel at high speed or reversely at low speed. If the real-time vehicle speed is less than or equal to the switching threshold value when the vehicle enters the turning working condition, the traditional proportional control strategy is adopted, but if the real-time vehicle speed is greater than the switching threshold value when the vehicle enters the turning working condition, while the traditional proportional control strategy is adopted, it is detected whether the two conditions that the real-time vehicle speed is not greater than the exit threshold value and the sum of the longitudinal acceleration and the lateral acceleration is not greater than the preset acceleration threshold value are met, and if so, the improved proportional control strategy is switched to. The improved proportional control strategy still imitates the traditional proportional control strategy, a certain proportional relationship is always maintained between the rear wheel steering angle and the front wheel steering angle, and the only difference is whether the rear wheel turns in the same direction as the front wheel at high speed or reversely at low speed, and the additional content is that the proportional relationship between the rear wheel steering angle and the front wheel steering angle is different from the traditional proportional control strategy, and the proportional relationship between the rear wheel steering angle and the front wheel steering angle changes with the vehicle speed, and the proportion is small at high speed, and the proportion is large at low speed.

[0095] The functions of each module in the brake control system for a rear-wheel-steering vehicle during U-turn are implemented in the steps of the brake control method for a rear-wheel-steering vehicle during U-turn, and the functions and implementation processes will not be repeated here.

[0096] In a third aspect, the embodiments of the present application provide a brake control device for a rear-wheel-steering vehicle during U-turn. The brake control device for a rear-wheel-steering vehicle during U-turn can be a personal computer (PC), a notebook computer, a server, or other devices with data processing functions.

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

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

[0099] The communication interface includes input / output (I / O) interfaces, physical interfaces, and logical interfaces, and other interfaces for interconnecting devices inside the brake control device for a rear-wheel-steering vehicle during U-turn, and interfaces for interconnecting the brake control device for a rear-wheel-steering vehicle during U-turn with other devices (such as other computing devices or user devices). The physical interface can be an Ethernet interface, a fiber interface, an ATM interface, etc. The user device can be a display (Display), a keyboard (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), and the like.

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

[0102] In a fourth aspect, the embodiments of the present application further provide a computer readable storage medium.

[0103] The computer readable storage medium of the present application stores the braking control program for the rear-wheel-steering vehicle during U-turn, wherein the braking control program for the rear-wheel-steering vehicle during U-turn is executed by the processor to implement the steps of the braking control method for the rear-wheel-steering vehicle during U-turn as described above.

[0104] The method implemented when the braking control program for the rear-wheel-steering vehicle during U-turn is executed can refer to each embodiment of the braking control method for the rear-wheel-steering vehicle during U-turn, and will not be described here.

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

[0106] The terms “include,” “comprise,” “have,” and any variations thereof, in the Specification and in the Claims of the present application, and the above-mentioned drawings, are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or device that includes a list of steps or units is not limited to the listed steps or units, but can optionally further include steps or units not listed, or can optionally further include other steps or units inherent to such processes, methods, products, or devices. The terms “first”, “second”, and “third” and the like descriptions are used to distinguish different objects, and do not represent the order or limit the types of “first”, “second”, and “third”.

[0107] In the description of the embodiments of the present application, “exemplary”, “for example”, or “for instance” is used to represent an example, illustration, or description. Any embodiment or design scheme described as “exemplary”, “for example”, or “for instance” in the embodiments of the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the words “exemplary”, “for example”, or “for instance” are intended to present the relevant concept in a specific manner.

[0108] In the description of the embodiments of the present application, unless otherwise specified, “ / ” represents the meaning of or, for example, A / B can represent A or B; “and / or” in the text only represents a description of the relationship between the associated objects, which means that there can be three relationships, for example, A and / or B can represent the three cases of A alone, A and B together, and B alone. In addition, in the description of the embodiments of the present application, “multiple” means two or more than two.

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

[0110] From the above description of the embodiments, those skilled in the art can clearly understand that the above-mentioned embodiment method can be realized by means of software and a general hardware platform as required, of course, it can also be realized by hardware, but in many cases the former is a better embodiment. Based on such understanding, the technical solutions of the present application can be embodied in the form of a software product, which is stored in a storage medium (such as a ROM / RAM, a magnetic disk, an optical disk) as described above, and includes a plurality of instructions for causing a terminal device to execute the methods described in the embodiments of the present application.

[0111] The preferred embodiments of the present application have been described above with the illustrated embodiments, and are not intended to limit the scope of patent protection for the present application, and any equivalent structures or equivalent processes transformed by the contents of the specification and drawings of the present application, or directly or indirectly applied to other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A braking control method for a vehicle with rear-wheel steering during a U-turn, characterized in that: The method comprises: When determining that the vehicle enters a turning condition at high speed, determine whether the longitudinal acceleration is not greater than a preset negative value. If so, adopt the cornering braking control strategy; if not, adopt the 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 and the front wheel steering angle to deflect in the same direction when the real-time vehicle speed is greater than the switching threshold, and controlling the rear wheel steering angle and the front wheel steering angle to deflect in the opposite direction after the real-time vehicle speed is no greater than the switching threshold.

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

3. The braking control method for a rear-wheel steering vehicle during a U-turn according to claim 2, wherein: The vehicle turning radius is calculated using the following formula: R= L / [tan(AgF)-tan(AgR)] Among them, R represents the vehicle turning radius, 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 rear-wheel steering vehicle during a U-turn according to claim 1, wherein: 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 when the longitudinal acceleration is not greater than the preset negative value, the cornering braking control strategy is adopted; if not, it is determined that the vehicle enters the turning condition at a low speed, and the proportional control strategy is adopted.

5. The braking control method for a rear-wheel steering vehicle during a U-turn according to claim 1, wherein: 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 rear-wheel steering vehicle during a U-turn according to claim 5, wherein: 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 rear-wheel steering vehicle making a U-turn, characterized in that: The system comprises: a control module configured to determine whether the longitudinal acceleration is less than a preset negative value when the vehicle enters a turning condition at high speed, and if so, to adopt a cornering braking control strategy; if not, to 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 and the front wheel steering angle to deflect in the same direction when the real-time vehicle speed is greater than the switching threshold, and controlling the rear wheel steering angle and the front wheel steering angle to deflect in the opposite direction after the real-time vehicle speed is no greater than the switching threshold.

8. The U-turn braking control system for a rear-wheel steering vehicle according to claim 7, wherein: 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 cornering braking control strategy is adopted when the longitudinal acceleration is not greater than a preset negative value; 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 according to 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 preset acceleration threshold after adopting the curve braking control strategy. 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 to be adopted.

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 further configured to limit the slope of the rear wheel steering angle as it changes with the front wheel steering angle when exiting the cornering braking control strategy and adopting the proportional control strategy. The greater the vehicle speed, the smaller the slope.

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