Vehicle steering control method, vehicle and storage medium

Abstract

The embodiment of the invention provides a vehicle steering control method, a vehicle and a storage medium, and the method comprises the steps: determining a target steering angle of a rear wheel when a front wheel steers along a first direction; controlling two rear wheels to steer along the first direction according to the target steering angle of the rear wheels; and a differential torque signal is determined according to the target steering angle of the rear wheels, and differential torque control is conducted on the two rear wheels according to the differential torque signal. Through control intervention of the differential torque signal, the gap between the rear wheel steering angle and the front wheel steering angle in the process that the two rear wheels are controlled to steer in the first direction when the front wheels steer according to the rear wheel target steering angle is made up, and the stability of the vehicle in the high-speed running state is improved.

Description

Technical Field

[0001] This invention relates to the field of vehicle technology, and in particular to a vehicle steering control method, a corresponding vehicle, and a corresponding computer-readable storage medium. Background Technology

[0002] When the rear wheels steer in the same direction as the front wheels, the agile lane change control algorithm needs to reduce the amount of control in the same direction or delay the control function based on the steering state performed by the driver.

[0003] In the related technologies of rear wheel steering control, the main approach is to estimate the lateral slip angle of the vehicle body by receiving vehicle speed, front wheel steering angle, rear wheel steering angle, yaw rate, longitudinal acceleration, and lateral acceleration, and further estimate the tire slip angle. Then, the controller reflects the control weight proportional to the estimated tire slip angle value to the rear wheel directional calculation value, and controls the rear wheel steering based on the final rear wheel steering control value.

[0004] However, while reducing the rear wheel unidirectional control in areas with smaller tire slip angles can improve yaw responsiveness (i.e., the ability to react to steering inputs when the vehicle deviates from the expected course) when the vehicle is traveling at high speeds, and increasing the rear wheel unidirectional control in areas with larger tire slip angles can improve driving stability, the ratio between the rear wheel steering control weight and the estimated tire slip angle is difficult to define in the aforementioned schemes. Furthermore, when the control weight exceeds 1, it means that the rear wheel steering is limited by the geometry and cannot continuously increase the steering angle. Also, since the rear wheel unidirectional control adjustment depends on the size of the tire slip angle, the turning radius of the vehicle will depend on the driver's steering wheel angle loading slope under the same front wheel turning angle, which poses a risk of affecting the driver's steering feel and driving habits. Summary of the Invention

[0005] In view of the above problems, embodiments of the present invention are proposed to provide a vehicle steering control method, a vehicle steering control device, a corresponding vehicle, and a corresponding computer-readable storage medium to overcome or at least partially solve the above problems.

[0006] This invention discloses a vehicle steering control method, the method comprising:

[0007] When the front wheels turn in the first direction, determine the target steering angle of the rear wheels;

[0008] Control the two rear wheels to turn in the first direction according to the target steering angle of the rear wheels;

[0009] The differential torque signal is determined based on the target steering angle of the rear wheels, and differential torque control is performed on the two rear wheels based on the differential torque signal.

[0010] Optionally, determining the differential torque signal based on the target rear wheel steering angle includes:

[0011] Based on the target steering angle of the rear wheels and the torque distribution control weights, a differential torque signal is generated.

[0012] Optionally, generating the differential torque signal based on the target rear wheel steering angle and torque distribution control weights includes:

[0013] The differential torque control target is determined based on the torque distribution control weight and the target steering angle of the rear wheels; the differential torque control target is used to constrain the differential torque to obtain the differential torque signal.

[0014] Optionally, determining the differential torque control target based on the torque distribution control weights and the target rear wheel steering angle includes:

[0015] If the target steering angle of the rear wheel is less than or equal to a preset second angle threshold, the torque distribution control weight is determined based on the estimated tire slip angle.

[0016] The differential torque control target is determined based on the torque distribution control weights and the estimated tire slip angle.

[0017] Optionally, determining the differential torque control target based on the torque distribution control weights and the target rear wheel steering angle includes:

[0018] If the target steering angle of the rear wheel is greater than the preset second angle threshold, the torque distribution control weight is determined based on the estimated value of the vehicle yaw rate.

[0019] The differential torque control target is determined based on the torque distribution control weight and the estimated vehicle yaw rate.

[0020] Optionally, generating the differential torque signal based on the target rear wheel steering angle and torque distribution control weights includes:

[0021] If the target steering angle of the rear wheel is less than or equal to a preset second angle threshold, the torque distribution control weight is determined based on the estimated tire slip angle.

[0022] A differential torque signal is generated based on the torque distribution control weights.

[0023] Optionally, generating the differential torque signal based on the target rear wheel steering angle and torque distribution control weights includes:

[0024] If the target steering angle of the rear wheel is greater than the preset second angle threshold, the torque distribution control weight is determined based on the estimated value of the vehicle yaw rate.

[0025] A differential torque signal is generated based on the torque distribution control weights.

[0026] Optionally, determining the torque distribution control weights based on the estimated tire slip angle includes:

[0027] Determine the torque distribution control weight based on the current estimated tire slip angle from the second preset table;

[0028] The second preset table is used to indicate different torque distribution control weights corresponding to different tire slip angle estimates, and the tire slip angle estimates are positively correlated with the torque distribution control weights.

[0029] Optionally, determining the torque distribution control weights based on the estimated vehicle yaw rate includes:

[0030] From the third preset table, determine the torque distribution control weights based on the current estimated vehicle yaw rate;

[0031] The third preset table is used to indicate the different torque distribution control weights corresponding to different estimated values ​​of vehicle yaw rate, and the estimated value of vehicle yaw rate is positively correlated with the torque distribution control weight.

[0032] Optionally, during the process of controlling the two rear wheels to turn in the first direction according to the target rear wheel steering angle, the method further includes:

[0033] When the target steering angle of the rear wheels is greater than a preset second angle threshold, the two rear wheels are controlled to steer according to the preset second angle threshold.

[0034] Optionally, the differential torque control of the two rear wheels based on the differential torque signal includes:

[0035] In response to the differential torque signal, the two rear wheel drive units are controlled to output differential torque, thereby driving the two rear wheels to rotate.

[0036] Optionally, when the current wheel turns in the first direction, determining the target steering angle of the rear wheel includes:

[0037] When the front wheels turn in the first direction, the target steering angle of the rear wheels is determined based on the front wheel steering information and the vehicle speed; the front wheel steering information includes either the front wheel steering angle or the steering wheel angle.

[0038] Optionally, determining the target rear wheel steering angle based on the front wheel steering information and vehicle speed includes:

[0039] The rear wheel steering angle follow-up ratio is determined based on the front wheel steering information and vehicle speed, and the target rear wheel steering angle is determined based on the rear wheel steering angle follow-up ratio.

[0040] Optionally, determining the rear wheel steering angle follow-up ratio based on front wheel steering information and vehicle speed includes:

[0041] From the first preset table, determine the following ratio of the rear wheel steering angle corresponding to the steering wheel angle at the current driving speed of the vehicle;

[0042] The first preset table is used to indicate the different rear wheel steering angle follow-up ratios corresponding to different steering wheel angles at the same vehicle speed.

[0043] Optionally, determining the target rear wheel steering angle based on the rear wheel steering angle follow-up ratio includes:

[0044] The target rear wheel steering angle is calculated by using the rear wheel steering angle follow-up ratio and the steering wheel angle.

[0045] Optionally, controlling the two rear wheels to turn in the first direction according to the target rear wheel steering angle includes:

[0046] Activate the rear wheel and front wheel synchronous steering function, and control the two rear wheels to turn in the first direction according to the target steering angle of the rear wheels.

[0047] Optionally, activating the rear-wheel and front-wheel synchronized steering function includes:

[0048] After the rear wheel and front wheel synchronous steering function is activated, the current driving speed of the vehicle is detected;

[0049] If the current driving speed of the vehicle is greater than or equal to a preset speed threshold, the rear wheel and front wheel synchronous steering function is activated based on the steering wheel angle.

[0050] Optionally, the function of activating the synchronous steering of the rear and front wheels based on the steering wheel angle includes:

[0051] If the steering wheel angle is greater than or equal to a preset first angle threshold, the rear wheel and front wheel synchronous steering function is activated.

[0052] Optionally, controlling the two rear wheels to turn in the first direction according to the target rear wheel steering angle includes:

[0053] Based on the target rear wheel steering angle, control the two rear wheel steering actuators to drive the two rear wheels to turn in the first direction.

[0054] Optionally, controlling the two rear wheel steering actuators to drive the two rear wheels to turn in the first direction according to the target rear wheel steering angle includes:

[0055] Based on the target rear wheel steering angle and the first direction, corresponding control signals are sent to the two rear wheel steering actuators; the two rear wheel steering actuators are used to drive the two rear wheels to turn along the first direction according to the control signals.

[0056] This invention also discloses a vehicle, including: a processor, a memory, and a computer program stored in the memory and capable of running on the processor, wherein the computer program, when executed by the processor, implements any of the vehicle steering control methods described above.

[0057] This invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, implements any of the vehicle steering control methods described above.

[0058] The embodiments of the present invention have the following advantages:

[0059] In this embodiment of the invention, when the front wheel turns in the first direction, the two rear wheels can be controlled to turn in the first direction according to the determined target steering angle of the rear wheels. At this time, a differential torque signal can be determined according to the target steering angle of the rear wheels, and differential torque control can be performed on the two rear wheels according to the differential torque signal. This allows the differential torque signal to intervene during the process of controlling the rear wheels to turn in the first direction that is the same as the front wheels, thereby compensating for the difference between the steering angle of the rear wheels and the steering angle of the front wheels during the turning process and increasing the stability of the vehicle at high speed. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of the vehicle transmission system provided in an embodiment of the present invention;

[0061] Figure 2 This is a schematic diagram of the framework of the vehicle control system provided in an embodiment of the present invention;

[0062] Figure 3 This is a schematic diagram of the rear wheel steering control strategy provided in an embodiment of the present invention;

[0063] Figure 4 This is a flowchart illustrating the steps of an embodiment of the vehicle steering control method of the present invention;

[0064] Figure 5 This is a flowchart illustrating a control program based on a control strategy provided in an embodiment of the present invention;

[0065] Figure 6 This is a flowchart illustrating another control program based on a control strategy provided in an embodiment of the present invention;

[0066] Figure 7 This is a structural block diagram of an embodiment of a vehicle steering control device according to the present invention.

[0067] The attached figures are labeled as follows:

[0068] 11-Front wheel; 12-Left and right front half-shafts; 13-Front drive motor integrated with front differential; 15-Steering wheel; 20-Rear wheel steering actuator motor; 21-Rear wheel; 22-Left and right rear wheel end drive motors; 30-Left front wheel speed sensor; 31-Right front wheel speed sensor; 32-Left rear wheel speed sensor; 33-Right rear wheel speed sensor; 34-Steering wheel angle sensor; 35-Yaw rate sensor; 36-Lateral acceleration sensor; 37-CAN bus; 38-4WS controller; 39-Differential torque signal distribution controller; 40-Rear wheel steering actuator; 41-Left rear drive motor controller; 42-Right rear drive motor controller; 51-Rear wheel follow-up angle calculation module; 52-Rear wheel steering control module; 53-Vehicle state estimator; 54-Yaw rate estimation module; 55-Center of gravity sideslip angle estimation module; 56-Tire slip angle estimation module; 57-Distribution controller. Detailed Implementation

[0069] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0070] Compared to two-wheel steering systems (2WS), four-wheel steering systems (4WS), which use both front and rear wheels for steering, can reduce the vehicle's turning radius by controlling the rear wheels' steering angle at low speeds and in the opposite direction to the front wheels' steering angle. While 4WS can suppress lateral drift and increase vehicle stability when the rear wheels steer in the same direction as the front wheels at high speeds, the increased turning radius degrades yaw response and reduces cornering ability. Therefore, when the rear wheels steer in the same direction as the front wheels, the agile lane change control algorithm needs to reduce or delay the same-direction control based on the driver's steering state.

[0071] In this embodiment of the invention, during the process of controlling the rear wheels to turn in the first direction that is the same as the front wheels, a differential torque signal can be determined based on the target steering angle of the rear wheels. Differential torque control is then performed on the two rear wheels based on the differential torque signal, so that the difference between the steering angle of the rear wheels and the steering angle of the front wheels can be compensated through the intervention of the differential torque signal, thereby increasing the stability of the vehicle at high speeds. Specifically, when the rear-wheel and front-wheel synchronous steering function is activated, the rear-wheel steering angle follow-up ratio can be determined based on the front-wheel steering angle. Based on this determined ratio, the rear wheels can be controlled to steer synchronously with the front wheels. This allows the rear-wheel steering angle to follow the front-wheel steering angle input based on predetermined control weights. This addresses the issue of inconsistent steering feel and driving habits caused by the ratio of rear-wheel steering angle to driver steering wheel angle input changing with tire slip angle at high speeds. Furthermore, during the process of controlling the rear wheels and front wheels to steer synchronously, differential torque signals can be responded to, enabling differential torque control of the two rear wheels. This compensates for the increased stability at high speeds after the actual rear-wheel steering angle reaches its limit, overcoming the problem that once the actual rear-wheel steering angle reaches its geometrically permissible steering limit, the vehicle's high-speed stability cannot be further improved. In particular, when adding rear wheel differential torque control, the control weights corresponding to the estimated values ​​of the center of gravity sideslip angle and yaw rate under the current state of the vehicle can be reflected in the control quantity of the rear wheel differential torque to output differential torque.

[0072] Reference Figure 1 This diagram illustrates a framework of a vehicle transmission system provided in an embodiment of the present invention. The vehicle transmission system may include a front-wheel steering system, a rear-wheel steering system, and a drive system. The dashed line indicates the neutral position of the rear wheels when rear-wheel steering is not engaged.

[0073] The front wheel steering system may include front wheels 11, a steering wheel 15, and a front steering assembly. The steering wheel 15 serves as the driver's interface, controlling the vehicle's steering by rotating it, which facilitates the pivoting of the front wheels 11 and rear wheels 21, thereby steering the vehicle. The front steering assembly may include a rack and pinion mechanism mechanically connected to the steering wheel 15. When the steering wheel 15 rotates clockwise or counterclockwise, it mechanically actuates the rack and pinion mechanism, causing the front wheels 11 to pivot to the right and left, respectively.

[0074] The rear-wheel steering system may include rear wheels 21 and a rear steering assembly associated with the rear wheels 21. The rear steering assembly may include a rear-wheel steering actuation motor 20 and a linear servo motor. The target steering angle of the rear wheels 21 depends primarily on the steering wheel angle of the steering wheel 15 and the vehicle speed. Each rear wheel 21 has an independent rear-wheel steering actuation motor 20, which can be operated independently. This design allows the steering angle of each rear wheel to be selected independently to provide an effective Ackermann angle, which helps to improve the handling and stability of the vehicle. The rear-wheel steering actuation motor 20 may be a linear servo motor containing a movable piston, which can pivot the respective steering knuckle about the kingpin axis, thereby helping to control the steering of the rear wheels 21.

[0075] The drive system may include front left and right half-shafts 12, a front drive motor integrated with a front differential 13, and left and right rear wheel-end drive motors 22. The front left and right half-shafts 12 primarily connect the front wheels and the drive shaft of the front differential. The design of the front drive motor integrated with the front differential 13 allows for torque distribution adjustment via the differential when either of the vehicle's front wheels 11 slips, reducing the torque distributed to the slipping wheel and thus improving traction, handling performance, and / or stability. Since each rear wheel has an independent rear-wheel drive unit, which can be a rear-wheel drive motor, such as the configuration of the left and right rear wheel-end drive motors 22, it can provide better power distribution and handling performance, driving the two rear wheels to rotate separately.

[0076] like Figure 1 The vehicle drivetrain design shown combines independent steering mechanisms for the front and rear wheels with a highly efficient drive system, aiming to improve vehicle handling, stability, and traction. By independently controlling the steering and power of each wheel, more precise vehicle dynamic control can be achieved, enhancing the driving experience and safety.

[0077] Furthermore, referring to Figure 2 The diagram illustrates a framework of a vehicle control system provided in an embodiment of the present invention. It shows the various components of the vehicle control system, which consist of multiple sensors and controllers, including a left front wheel speed sensor 30, a right front wheel speed sensor 31, a left rear wheel speed sensor 32, a right rear wheel speed sensor 33, a steering wheel angle sensor 34, a yaw rate sensor 35, a lateral acceleration sensor 36, a CAN bus 37, a four-wheel steering system (i.e., a 4WS controller) 38, a differential torque signal distribution controller 39, a rear wheel steering actuator 40, a left rear drive motor controller 41, and a right rear drive motor controller 42.

[0078] Among them, the left front wheel speed sensor 30 and the right front wheel speed sensor 31 are mainly used to measure the speed of the left and right front wheels of the vehicle, providing the control system with information to calculate the actual speed and direction of the vehicle; the left rear wheel speed sensor 32 and the right rear wheel speed sensor 33 are mainly used to measure the speed of the left and right rear wheels of the vehicle, also used to calculate the actual speed and direction of the vehicle, and for the control of the four-wheel drive and four-wheel steering systems; the steering wheel angle sensor 34 can detect the rotation angle of the steering wheel through a potentiometer, thereby determining the driver's steering intention; the yaw rate sensor 35 can be mainly used to measure the rotational speed of the vehicle about the vertical axis, i.e., the yaw rate of the vehicle, which is beneficial to the stability and handling of the vehicle; the lateral acceleration sensor 36 can be mainly used to measure the lateral (lateral) acceleration of the vehicle, to help the control system evaluate the dynamic response and stability of the vehicle; the CAN bus 37 is a Controller Area Network (CAN) bus, allowing different control groups The system facilitates data exchange between components and sensors. The 4WS controller 38 coordinates the steering of the front and rear wheels, primarily controlling the steering angle of the rear wheels based on vehicle speed, steering wheel angle, and other sensor data to improve vehicle handling and stability. The differential torque signal distribution controller 39 receives data via the CAN bus based on the vehicle's driving status and driver operation, determining how to distribute torque to the left and right rear wheel drive units. The rear wheel steering actuator 40 is primarily responsible for actually executing the steering action of the rear wheels. The rear wheel drive unit may include a rear wheel drive motor, or a rear wheel drive motor and a reducer. The left rear drive motor controller 41 and the right rear drive motor controller 42 can respectively control the drive motors of the left and right rear wheels, and / or respectively control the reducers of the left and right rear wheels, adjusting the differential torque output by the two rear wheel drive units according to the instructions of the differential torque signal distribution controller 39 to drive the two rear wheels to rotate.

[0079] In practical applications, the 4WS controller 38 assists in the operation of the rear wheel steering actuator 40 to rotate the rear wheels 21. Specifically, the rear wheel steering actuator 40 is a device used to change the direction of the rear wheels of a vehicle. It is typically controlled by an electric or hydraulic system. By transmitting torque to the wheels, it causes the rear wheels to turn in the desired direction. Usually, each rear wheel steering actuator 40 can be associated with one of the rear wheels 21. The 4WS controller 38 is responsible for controlling the rear wheel steering actuator 40 to achieve independent pivoting of the rear wheels 21. Specifically, when the steering wheel 15 is turned to steer the vehicle, the 4WS controller 38 can operate the rear wheel steering actuator 40 to control the steering of the rear wheels 21 in the same phase and proportionally as the steering angle of the front wheels. That is, the steering direction of the rear wheels is the same as that of the front wheels, but the steering angle may be adjusted according to the vehicle speed and steering wheel position, thereby improving the vehicle's cornering stability and sideslip control.

[0080] For the functional control of the four-wheel steering system (i.e., the 4WS controller) 38, specifically, the 4WS controller 38 can collect vehicle data indirectly (i.e., via the CAN bus 37) or directly from various suitable data sources. Specifically, the steering wheel angle sensor 34 can indicate the position of the steering wheel 15 when the steering wheel 15 moves and the potentiometer resistance changes via a potentiometer connected to the steering wheel 15; the left front wheel speed sensor 30, the right front wheel speed sensor 31, the left rear wheel speed sensor 32, and the right rear wheel speed sensor 33 can be connected to the CAN bus 37 and collect the speed data of the left and right front wheels 11 and the rear wheels 21 via Hall effect sensors; then the 4WS controller 38 can comprehensively estimate the current vehicle speed and center of gravity sideslip angle through speedometers, GPS output, other data from the CAN bus 37, or other suitable vehicle speed detection devices; at the same time, the 4WS controller 38 can also obtain the angular velocity measured by the yaw rate sensor 35 via the CAN bus 37, which can be specifically measured by a piezoelectric or micro-mechanical gyroscope sensor around the vertical axis.

[0081] Specifically, the differential torque signal distribution controller 39 transmits steering angle input (e.g., from steering wheel 15), throttle position input, vehicle speed, and vehicle acceleration to the left and right rear wheel drive motors 22 via the CAN bus 37. Upon receiving the aforementioned inputs, the left and right rear wheel drive motors 22 can distribute torque to the left rear drive motor controller 41 and the right rear drive motor controller 42 based on the aforementioned information and control weights, thereby distributing torque between the rear wheels 21, which means controlling the differential torque output by the two rear wheel drive units, such as the rear wheel drive motors.

[0082] The rear-wheel steering control strategy provided in this embodiment of the invention can be as follows: Figure 3 As shown, the rear wheel steering angle calculation module 51 can receive input signals of vehicle speed, steering wheel angle and front wheel angle, and output a rear wheel angle signal carrying the rear wheel steering angle. The rear wheel angle signal can generate a corresponding motor control signal through the rear wheel steering control module 52, and transmit the motor control signal to the rear wheel steering actuator 40 so that the rear wheel steering actuator 40 can respond to the motor control signal to perform corresponding steering control on the rear wheels.

[0083] The vehicle state estimator 53 receives inputs including vehicle speed, front wheel steering angle (based on real-time feedback from front wheel steering angle signals), rear wheel steering angle (based on real-time feedback from rear wheel steering angle signals), yaw rate, longitudinal acceleration, and lateral acceleration. It then uses the yaw rate estimation module 54 to estimate the yaw rate and the center of gravity sideslip angle estimation module 55 to estimate the center of gravity sideslip angle. Based on these estimates, the tire slip angle estimation module 56 further estimates the tire slip angle. Finally, when the actual rear wheel steering angle reaches a preset threshold value... If the preset threshold for the rear wheel steering angle is not reached, the torque distribution control weight is calculated by the distribution controller 57 based on the estimated tire slip angle or yaw rate obtained above, and then the differential torque signal is obtained. Taking the rear wheel drive unit as a rear wheel drive motor as an example, the differential torque signal can be represented as the rear wheel motor differential torque signal. At this time, the calculated rear wheel motor differential torque signal can be transmitted to the left rear wheel drive motor controller 41 and the right rear wheel drive motor controller 42 so that the left rear wheel drive motor controller 41 and the right rear wheel drive motor controller 42 can perform corresponding rotation control on the left rear wheel and the right rear wheel respectively.

[0084] Reference Figure 4 The diagram illustrates a flowchart of an embodiment of the vehicle steering control method of the present invention, which may specifically include the following steps:

[0085] Step S401: When the front wheel turns in the first direction, determine the target steering angle of the rear wheel;

[0086] When the front wheel turns in the first direction, the target steering angle of the rear wheel can be determined so that the two rear wheels can be controlled to turn synchronously with the front wheel according to the determined target steering angle of the rear wheel.

[0087] Specifically, the target steering angle of the rear wheels can be determined based on the front wheel steering information and the vehicle speed.

[0088] Optionally, the front wheel steering information may include either the front wheel steering angle or the steering wheel angle, that is, the target steering angle of the rear wheels can be determined based on the front wheel steering angle or the steering wheel angle.

[0089] In a four-wheel steering system (4WS), the target steering angle of the rear wheels can be dynamically adjusted based on the steering information of the front wheels and the vehicle speed. The rear wheel steering angle usually follows the changes in the steering angle of the front wheels in real time. During the follow-up control process, the rear wheel steering control weights can be preset according to different driving conditions (such as vehicle speed, steering angle, vehicle load, etc.) so that the target steering angle of the rear wheels can follow the input of the front wheel steering angle based on the predetermined rear wheel steering control weights.

[0090] Rear wheel steering control weights can be used to indicate the relationship between the target rear wheel steering angle and the front wheel steering angle. Typically, the target rear wheel steering angle is adjusted according to a certain proportional relationship when it dynamically adjusts to follow the front wheel steering angle. In order to determine the aforementioned proportional relationship, the rear wheel steering angle following ratio can be determined based on the front wheel steering angle. A rear wheel steering control strategy that follows the front wheel steering angle input based on the predetermined rear wheel steering angle following ratio can ensure that the steering feel remains unchanged after the rear wheel and front wheel synchronous steering function is activated, while achieving synchronous steering of the rear and front wheels.

[0091] In one embodiment of the present invention, the rear wheel steering angle following ratio can be determined based on the front wheel steering information and the vehicle speed, and the target rear wheel steering angle can be determined based on the rear wheel steering angle following ratio.

[0092] The specific steps for determining the follow-up ratio of the rear wheel steering angle may include the following:

[0093] From the first preset table, determine the following ratio of the rear wheel steering angle corresponding to the steering wheel angle at the current vehicle speed.

[0094] The first preset table can be a two-dimensional table. The first preset table can be used to indicate the different rear wheel steering angle follow-up ratios corresponding to different steering wheel angles at the same vehicle speed. For example, assuming the vehicle speed v = 80, there can be corresponding rear wheel steering angle follow-up ratios at different steering wheel angles.

[0095] After obtaining the rear wheel steering angle tracking ratio, the target rear wheel steering angle can be calculated using the rear wheel steering angle tracking ratio and the steering wheel angle. Specifically, this can be represented by calculating the weighted rear wheel steering angle using the rear wheel steering angle tracking ratio and the steering wheel angle.

[0096] Step S402: Control the two rear wheels to turn in the first direction according to the target steering angle of the rear wheels;

[0097] After calculating the target steering angle of the rear wheels, the rear wheels can be controlled to steer synchronously with the front wheels. Specifically, synchronous steering can be expressed as controlling the two rear wheels to steer in the first direction.

[0098] In some embodiments of the present invention, synchronous steering of the rear wheels is achieved when the rear wheel steering function is activated in the same direction as the front wheel steering function.

[0099] The rear-wheel synchronous steering function, which is used when the rear wheels sometimes turn with the front wheels, can also mean that the rear wheels turn in the same direction as the front wheels. That is, the rear wheels turn in the same direction as the front wheels. This function can be called same-phase rotation or four-wheel same-direction steering. By generating a steering angle in the same direction as the front wheels, the rear wheels can compensate for the tendency of oversteer. This helps to improve the stability and handling of the vehicle at high speeds, and thus ensures the consistency of vehicle steering and handling when the function is activated.

[0100] It should be noted that the synchronous steering of the rear wheels and the front wheels does not strictly require the rear wheels to be in the same direction as the front wheels. Rather, during the steering of the front wheels, the rear wheels may sometimes turn with the front wheels. The specific direction can be determined according to the vehicle's condition at the time, but it usually manifests as the rear wheels and the front wheels turning in the same direction. This embodiment of the invention does not impose any restrictions on this.

[0101] Specifically, the rear wheel and front wheel synchronous steering function can be activated, and the two rear wheels can be controlled to turn in the first direction according to the target steering angle of the rear wheels. In order to achieve the synchronous steering of the rear wheels and front wheels based on the determined target steering angle of the rear wheels by using the activated rear wheel and front wheel synchronous steering function.

[0102] First, the functional status of the rear wheel and front wheel synchronous steering function can be determined.

[0103] Optionally, after the rear-wheel and front-wheel synchronous steering function is activated, the current driving speed of the vehicle can be detected. If the current driving speed of the vehicle is greater than or equal to a preset speed threshold, the rear-wheel and front-wheel synchronous steering function can be activated based on the steering wheel angle.

[0104] For example, in S501 or S601, after a function is enabled, such as the rear-wheel and front-wheel synchronized steering function, the enabled rear-wheel and front-wheel synchronized steering function still needs to meet activation conditions. After the rear-wheel and front-wheel synchronized steering function is activated, it is allowed to be used. In practical applications, the 4WS controller can execute S502 or S602 to detect the vehicle's current driving speed v. In one case, if the vehicle's current driving speed v is less than a preset speed threshold, such as 60 kph, it can be determined that the rear-wheel and front-wheel synchronized steering function has entered a standby state. The standby state can refer to the aforementioned function being enabled but not yet activated, or it can be understood as the aforementioned function being in a state awaiting activation. In another case, if the vehicle's current driving speed v is greater than or equal to the preset speed threshold, such as 60 kph, S503 or S603 can be executed to detect the current steering wheel angle α and steering direction, and activate the rear-wheel and front-wheel synchronized steering function based on the detected current steering wheel angle.

[0105] In practical applications, this can be manifested as determining the current state of the synchronous steering function of the rear and front wheels based on the current steering wheel angle.

[0106] Optionally, if the current steering wheel angle is less than a preset first angle threshold, the rear-wheel and front-wheel synchronized steering function can be determined to be in standby mode, i.e., awaiting activation; if the steering wheel angle is greater than or equal to the preset first angle threshold, the rear-wheel and front-wheel synchronized steering function can be activated. That is, when the function is enabled, if the vehicle is traveling at high speed (e.g., the current vehicle speed reaches 60 kph) and the steering wheel angle is greater than or equal to the preset first angle threshold, the activated rear-wheel and front-wheel synchronized steering function can be in an active state.

[0107] Understandably, when the vehicle's current speed is greater than or equal to a preset speed threshold, and the current steering wheel angle is greater than or equal to a preset first angle threshold, the rear-wheel and front-wheel synchronized steering function can be activated. It should be noted that during high-speed driving, minute changes in the steering wheel angle typically do not significantly affect the vehicle's steering. In this case, there is usually a calibrated value for the steering wheel. When the steering wheel angle is less than this calibrated value, the power steering system will not significantly increase the steering force; that is, the preset first angle threshold can be the aforementioned calibrated value for the steering wheel.

[0108] The activated rear-wheel-to-front-wheel steering function can include the meaning of the rear wheels steering in the same direction as the front wheels, such as... Figure 1 As shown, when the rear wheel 21 rotates in the same phase as the front wheel 11, compared to the case where only the front wheel 11 rotates when the function is off, as indicated by the dashed line, the vehicle is less likely to become unstable and / or lose traction, and can experience less yaw.

[0109] In practical applications, the front wheel steering angle can be determined based on the steering wheel angle α. The rear wheel steering angle follow-up ratio A can be determined by executing S504 or S604 through the 4WS controller, based on the vehicle speed v and the steering wheel angle α.

[0110] After obtaining the rear wheel steering angle follow-up ratio A, you can execute S505 or S605 to determine the weighted rear wheel steering angle, i.e., the target rear wheel steering angle. Let's assume the target rear wheel steering angle is θ. 21 &θ 22 Specifically, the following formula can be used for calculation:

[0111]

[0112] Among them, the weighted rear wheel steering angle is beneficial to the driver's steering intention. The weighted steering wheel angle can make the rear wheel steering angle rotate in the same direction as the front wheel steering angle according to a certain proportional relationship, thus ensuring the stability of the vehicle body.

[0113] In this embodiment of the invention, the rear wheel is a holistic concept and may include the rear wheel, the rear wheel drive unit, and the rear wheel steering actuator. This embodiment of the invention does not limit this.

[0114] In controlling the rear wheels to steer synchronously with the front wheels, that is, controlling the two rear wheels to steer along the first direction, the two rear wheel steering actuators can be controlled to drive the two rear wheels to steer along the first direction based on the target rear wheel steering angle. Specifically, based on the target rear wheel steering angle and the first direction, corresponding control signals can be sent to the two rear wheel steering actuators so that the two rear wheel steering actuators can drive the two rear wheels to steer along the first direction according to the control signals.

[0115] For example, it can be executed Figure 5 As shown in S506, a control signal is sent to the rear wheel steering actuator 40 based on the weighted rear steering angle value, so that the rear wheel steering actuator can perform corresponding same-direction steering control on the rear wheels according to the control signal. The control signal sent to the rear wheel steering actuator can refer to the steering motor control signal. Specifically, in S507, a steering motor control signal can be sent to the rear wheel steering actuator to turn the rear wheels. Specifically, the rear wheel steering actuator 40 controls the rear wheel steering actuator motor 20 to turn the rear wheels 21 in the first direction according to the steering motor control signal sent by the 4WS controller 38, so that the rear wheels turn in the same direction as the front wheels.

[0116] It should be noted that the target steering angle of the rear wheels is a calculated theoretical value, and the actual steering angle of the rear wheels will not exceed the preset threshold for the rear wheel steering angle.

[0117] Step S403: Determine the differential torque signal based on the target steering angle of the rear wheels, and perform differential torque control on the two rear wheels based on the differential torque signal.

[0118] In one embodiment of the present invention, during the process of controlling the steering of the rear wheels and the front wheels, especially controlling the synchronous steering of the rear wheels and the front wheels, there may be an increase in the center of gravity offset angle (i.e., the angle between the actual speed direction of the vehicle and the axle direction) due to the increase in the actual steering angle of the rear wheels. At this time, the rear wheel differential torque control can be intervened to increase the stability of the vehicle at high speed.

[0119] Furthermore, in practical applications, in a four-wheel steering system (4WS), when the actual steering angle of the rear wheels reaches the preset maximum or minimum limit value, the rear wheel steering system will no longer continue to adjust the steering angle of the rear wheels. Because the actual steering angle of the rear wheels is limited by its geometry and space, there is a limit to the steering angle. When the actual steering angle of the rear wheels follows the input of the steering angle of the front wheels, the actual steering angle of the rear wheels will stop following when it reaches the preset threshold of the rear wheel steering angle, and will maintain this angle until the following value of the actual steering angle of the rear wheels is lower than the set angle. However, continuously maintaining the maximum actual steering angle of the rear wheels puts a large load on the rear wheel steering actuator. When the actual steering angle of the rear wheels reaches the extreme value, it is impossible to continue to improve the stability of the vehicle at high speed. At this time, the difference between the actual steering angle of the rear wheels and the steering angle of the front wheels after the rear wheel steering angle reaches the limit can be made up by increasing the rear wheel differential torque control. This allows the stability of the vehicle at high speed to be increased through the intervention of the rear wheel differential torque control, without involving the additional vehicle stability control compensation schemes mentioned in the background section when the rear wheel steering control weight calculated based on the tire slip angle estimation value exceeds 1.

[0120] In this embodiment of the invention, in order to ensure the stability of the vehicle at high speed when the center of gravity offset angle increases due to the increase in the rear wheel steering angle, and to overcome the problem that the stability of the vehicle at high speed cannot be further improved after the actual steering angle of the rear wheel reaches the steering limit allowed by its geometry, during the process of controlling the rear wheel to steer synchronously with the front wheel, regardless of whether the actual steering angle of the following rear wheel reaches the preset threshold of the rear wheel steering angle, the stability of the vehicle at high speed can be increased by the intervention of the rear wheel differential torque control.

[0121] By controlling the differential torque of the rear wheels, the final torque of the rear wheel drive motor can be output based on the differential torque of the rear wheels. Specifically, this can be manifested as responding to the differential torque signal, controlling the two rear wheel drive units to output differential torque, and driving the two rear wheels to rotate.

[0122] The intervention of rear wheel differential torque control can be manifested by first determining the differential torque signal based on the target steering angle of the rear wheels.

[0123] Differential torque refers to the difference in torque distribution caused by the difference in rotational speed between the left and right wheels or different parts in a vehicle or mechanical system with a differential. In controlling the differential torque of the rear wheels, this can be represented by reflecting the torque distribution control weights to the control quantity of the rear wheel differential torque, thus calculating the final rear wheel drive torque.

[0124] Specifically, differential torque signals can be generated based on the target steering angle of the rear wheels and the torque distribution control weights.

[0125] Optionally, the differential torque signal can be obtained by constraining the differential torque control target. Specifically, the differential torque control target can be used to constrain the rear wheel differential torque to obtain the rear wheel differential torque signal. Specifically, this can be manifested as determining the differential torque control target based on the torque distribution control weight and the target steering angle of the rear wheels.

[0126] In this embodiment of the invention, to ensure the stability of the vehicle at high speeds when the center of gravity offset angle increases due to the increase in the actual steering angle of the rear wheels, and to overcome the problem that the stability of the vehicle at high speeds cannot be further improved after the actual steering angle of the rear wheels reaches the steering limit allowed by its geometry, during the process of controlling the rear wheels to steer in the same direction as the front wheels, regardless of whether the steering angle of the following rear wheels reaches a preset second angle threshold, the rear wheel differential torque control can intervene to increase the stability of the vehicle at high speeds. It should be noted that the preset second angle threshold can refer to the preset maximum limit value reached by the rear wheel steering angle, i.e., the preset threshold value for the rear wheel steering angle.

[0127] In practical applications, during the process of controlling the rear wheels to steer synchronously with the front wheels, the differential torque signal distribution controller 39 can execute S508 to detect the rear wheel steering angle signal output in the current state of the vehicle. At this time, the rear wheel steering angle signal can be used to indicate the calculated theoretical value, i.e., the target rear wheel steering angle. This target rear wheel steering angle is the theoretical rear wheel steering angle calculated based on the front wheel steering angle, rather than the actual rear wheel steering angle. In practice, the actual rear wheel steering angle will not be greater than the preset threshold for the rear wheel steering angle.

[0128] In one scenario, if the target steering angle of the rear wheel is less than or equal to a preset second angle threshold, the estimated value of the tire slip angle can be obtained, and the torque distribution control weight can be obtained based on the estimated value of the tire slip angle. Then, based on the torque distribution control weight and the estimated value of the tire slip angle, the differential torque control target used to constrain the differential torque of the rear wheel can be determined.

[0129] Taking the rear-wheel drive unit as a rear-wheel drive motor as an example, the rear wheel differential torque signal can be represented as the rear wheel motor differential torque signal. At this time, the differential torque control target used to constrain the differential torque of the rear wheel motor can be determined based on the distribution control weight of the differential torque of the rear wheel motor and the estimated value of the tire slip angle.

[0130] For example, if the target steering angle of the rear wheel is less than or equal to a preset second angle threshold (e.g., 6 degrees), S509 can be executed to estimate the estimated value of the vehicle's center of gravity sideslip angle β and the estimated value of the tire slip angle δ. Here, the center of gravity sideslip angle can refer to the angle between the vehicle's actual velocity direction and the axle direction, and the tire slip angle can refer to the angle between the vehicle's actual radial velocity direction and the tire's radial velocity direction. In actual calculations, the center of gravity sideslip angle can be used as a process value for calculating the tire slip angle. This embodiment of the invention does not limit the specific estimation process. Then, the differential torque signal distribution controller 39 can execute S510 to determine the differential torque T of the rear wheel motor based on the estimated value of the vehicle's tire slip angle δ. 21 &T 22 Assign control weight B.

[0131] In another case, if the target steering angle of the rear wheel is greater than the preset second angle threshold, the estimated value of the vehicle yaw rate can be obtained, and the torque distribution control weight can be obtained based on the estimated value of the vehicle yaw rate. Then, based on the torque distribution control weight and the estimated value of the vehicle yaw rate, the differential torque control target used to constrain the differential torque of the rear wheel can be determined.

[0132] Taking the rear-wheel drive unit as a rear-wheel drive motor as an example, the rear wheel differential torque signal can be represented as the rear wheel motor differential torque signal. At this time, the differential torque control target used to constrain the differential torque of the rear wheel motor can be determined based on the distribution control weight of the differential torque of the rear wheel motor and the estimated value of the tire slip angle.

[0133] For example, such as Figure 5 As shown, if the target steering angle of the rear wheel is greater than a preset second angle threshold (e.g., 6 degrees), S511 can be executed to estimate the vehicle yaw rate γ; then, the differential torque signal distribution controller 39 can execute S512 to determine the differential torque T of the rear wheel motor based on the estimated vehicle yaw rate γ. 21 &T 22 Assign control weight B.

[0134] Specifically, the differential torque T of the rear wheel motor 21 &T 22 The formula can be followed as follows:

[0135]

[0136] Optionally, when the target rear wheel steering angle is lower than a certain preset second angle threshold, the controller may set the control target of the differential torque to minimize the tire slip angle; when the target rear wheel steering angle is higher than a certain second preset angle threshold, the controller may set the control target of the differential torque to control the vehicle's yaw rate.

[0137] In the above formula, the judgment value of the rear wheel target steering angle being less than or equal to the preset angle threshold, and the judgment value of the rear wheel target steering angle reaching the preset angle threshold, are considered state values. For example, when the rear wheel target steering angle is less than or equal to the preset second angle threshold, the judgment value of the rear wheel target steering angle being less than or equal to the preset angle threshold can be 1, and the judgment value of the rear wheel target steering angle being greater than the preset angle threshold can be 0; when the rear wheel target steering angle is greater than the preset second angle threshold, the judgment value of the rear wheel target steering angle being less than or equal to the preset angle threshold can be 0, and the judgment value of the rear wheel target steering angle being greater than the preset angle threshold can be 1. As for the control weight B that actually participates in the calculation, the allocated control weight corresponding to the state value of 1 can be selected.

[0138] In practical applications, the control weights corresponding to the estimated sideslip angle and yaw rate of the vehicle under its current state can be reflected in the control quantity of the rear wheel differential torque. The differential torque T between the motors on both sides of the rear wheels is determined based on the estimated tire slip angle. 21 &T 22 After assigning weight B, S513 can be executed to combine the differential torque distribution control weight based on the motors on both sides of the rear wheel and the target steering angle of the rear wheel to determine the differential torque target as the tire slip angle δ / yaw rate γ.

[0139] In practical applications, such as Figure 5 As shown in S514, the left and right rear wheel drive motors 22 can output the drive torque of the left and right rear wheel motors according to the differential torque signals obtained from the left rear drive motor controller 41 and the right rear drive motor controller 42, so as to control the auxiliary rear wheel steering actuator through the differential torque of the rear wheel motors, thereby further increasing the stability of the vehicle at high speed.

[0140] Furthermore, the function determination can also return to the vehicle speed determination status. It should be noted that for the 4WS controller 38 and the differential torque signal distribution controller 39, in situations such as... Figure 5 The execution order of certain steps in the control program shown may alternate or run in parallel, and the embodiments of the present invention do not impose any restrictions on this.

[0141] Optionally, the differential torque signal can be realized by reflecting the control weights corresponding to the estimated values ​​of the center of gravity sideslip angle and yaw rate under the current state of the vehicle to the control quantity of the rear wheel differential torque, and calculating the final rear wheel drive torque.

[0142] In practical applications, during the process of controlling the rear wheels to steer synchronously with the front wheels, the differential torque signal distribution controller 39 can execute S606 to detect the rear wheel steering angle signal output in the current state of the vehicle. The rear wheel steering angle signal can be used to indicate the calculated theoretical value, i.e., the target rear wheel steering angle. This target rear wheel steering angle is the theoretical rear wheel steering angle calculated based on the front wheel steering angle, rather than the actual rear wheel steering angle. In practice, the actual rear wheel steering angle will not be greater than the preset threshold for the rear wheel steering angle.

[0143] In one scenario, if the target steering angle of the rear wheel is less than or equal to a preset second angle threshold, the estimated value of the tire slip angle can be obtained, and the torque distribution control weight can be obtained based on the estimated value of the tire slip angle. Then, a differential torque signal can be generated based on the torque distribution control weight.

[0144] Taking the rear-wheel drive unit as the rear-wheel drive motor as an example, the rear-wheel differential torque signal can be represented as the rear-wheel motor differential torque signal. At this time, the weighting of the distribution control of the rear-wheel motor differential torque can be added to the original drive motor output torque to obtain the final rear-wheel drive torque.

[0145] For example, if the target steering angle of the rear wheel is less than or equal to a preset second angle threshold (e.g., 6 degrees), step S607 can be executed to estimate the estimated value of the vehicle's center of gravity sideslip angle β and the estimated value of the tire slip angle δ. The center of gravity sideslip angle can refer to the angle between the vehicle's actual velocity direction and the axle direction, and the tire slip angle can refer to the angle between the vehicle's actual radial velocity direction and the tire's radial velocity direction. In actual calculations, the center of gravity sideslip angle can be used as a process value for calculating the tire slip angle. This embodiment of the invention does not limit the specific estimation process. Then, the differential torque signal distribution controller 39 can execute step S611 to determine the differential torque T of the rear wheel motor based on the estimated value of the vehicle's tire slip angle δ. 21 &T 22 Assign control weight B.

[0146] In another scenario, if the target steering angle of the rear wheels is greater than a preset second angle threshold, the estimated value of the vehicle yaw rate can be obtained, and the torque distribution control weight can be obtained based on the estimated value of the vehicle yaw rate. Then, the torque distribution control weight generates a differential torque signal.

[0147] Taking the rear-wheel drive unit as the rear-wheel drive motor as an example, the rear-wheel differential torque signal can be represented as the rear-wheel motor differential torque signal. At this time, the weighting of the distribution control of the rear-wheel motor differential torque can be added to the original drive motor output torque to obtain the final rear-wheel drive torque.

[0148] For example, such as Figure 6As shown, if the target steering angle of the rear wheel is greater than a preset second angle threshold (e.g., 6 degrees), S609 can be executed to estimate the vehicle yaw rate γ; then, the differential torque signal distribution controller 39 can execute S610 to determine the differential torque T of the rear wheel motor based on the estimated vehicle yaw rate γ. 21 &T 22 Assign control weight B. It should be noted that the differential torque T of the rear wheel motor... 21 &T 22 The specific formula can be found in the above content, and the embodiments of the present invention are not limited here.

[0149] In practical applications, such as Figure 6 As shown in S611, the differential torque distribution control weight B of the motors on both sides of the rear wheel can be weighted to the output torque of the original drive motor. Then, the left and right rear wheel end drive motors 22 can output the drive torque of the left and right rear wheel motors according to the differential torque signals obtained from the left rear drive motor controller 41 and the right rear drive motor controller 42. This allows the differential torque control of the rear wheel motors to assist the rear wheel steering actuator, further increasing the stability of the vehicle at high speeds.

[0150] Optionally, the aforementioned allocation of control weights can be obtained primarily through a lookup table based on state changes.

[0151] For example, the second preset table can be used to indicate different torque distribution control weights corresponding to different estimated tire slip angles. The torque distribution control weight under the current estimated tire slip angle can be determined from the second preset table. The third preset table can be used to indicate different torque distribution control weights corresponding to different estimated vehicle yaw rates. The torque distribution control weight under the current estimated vehicle yaw rate can be determined from the third preset table. It should be noted that the estimated tire slip angle and the torque distribution control weight are positively correlated; that is, the larger the tire slip angle, the larger the differential torque distribution control weight. Similarly, the estimated vehicle yaw rate and the torque distribution control weight are positively correlated; that is, the larger the vehicle yaw rate, the larger the differential torque distribution control weight. The embodiments of the present invention do not limit the specific second and third preset tables.

[0152] Preferably, during the process of controlling the two rear wheels to turn in the first direction according to the target rear wheel steering angle, if the target rear wheel steering angle is less than or equal to a preset second angle threshold, then the two rear wheels can be controlled to turn according to the target rear wheel steering angle. For example, such as... Figure 6 As shown, S612 can be executed to output the weighted rear wheel steering angle value of the rear wheel steering motor controller, so that S614 can be executed, causing the rear wheel steering motor controller to steer the vehicle's rear wheels according to the rear wheel steering angle signal.

[0153] Preferably, during the process of controlling the two rear wheels to turn in the first direction based on the target rear wheel steering angle, if the target rear wheel steering angle is greater than a preset second angle threshold, then the two rear wheels can be controlled to turn according to the preset second angle threshold. For example, such as... Figure 6 As shown, S613 can be executed to output the preset threshold of the rear wheel steering angle to the rear wheel steering control motor controller, so that S614 can be executed, causing the rear steering motor controller to steer the rear wheels of the vehicle according to the rear wheel steering angle signal.

[0154] That is, during the process of controlling the rear wheels to turn synchronously with the front wheels, when the actual steering angle of the rear wheels reaches the preset maximum limit value, i.e. the preset second angle threshold, the following of the rear wheels can be stopped and the angle can be maintained until the following value of the actual steering angle of the rear wheels is lower than the preset second angle threshold.

[0155] Furthermore, the function determination can also return to the vehicle speed determination status. It should be noted that for the 4WS controller 38 and the differential torque signal distribution controller 39, in situations such as... Figure 6 The execution order of certain steps in the control program shown may alternate or run in parallel, and the embodiments of the present invention do not impose any restrictions on this.

[0156] In this embodiment of the invention, by activating the rear-wheel and front-wheel synchronous steering function, the rear-wheel steering angle follow-up ratio is determined based on the front-wheel steering angle, and the rear wheels are controlled to steer synchronously with the front wheels based on the determined rear-wheel steering angle follow-up ratio. This allows the actual rear-wheel steering angle to follow the front-wheel steering angle input based on a predetermined control weight, thus solving the problem of inconsistent steering feel and driving habits caused by the ratio of the actual rear-wheel steering angle to the driver's steering wheel angle input changing with the tire slip angle when the vehicle is traveling at high speed. Furthermore, during the process of controlling the synchronous steering of the rear wheels and front wheels, the differential torque signal of the rear wheels can be responded to, and differential torque control can be performed on the two rear wheels. This compensates for the fact that after the actual rear-wheel steering angle reaches the limit, the intervention of the differential torque control of the rear wheels increases the stability of the vehicle at high speed, overcoming the problem that the stability of the vehicle at high speed cannot be further improved after the actual rear-wheel steering angle reaches the steering limit allowed by its geometry.

[0157] It should be noted that, for the sake of simplicity, the method embodiments are all described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.

[0158] Reference Figure 7 The diagram illustrates a structural block diagram of an embodiment of a torque control device for vehicle steering according to the present invention, which may specifically include the following modules:

[0159] The target steering angle determination module 701 is used to determine the target steering angle of the rear wheels when the current wheel turns in the first direction;

[0160] Steering control module 702 is used to control the two rear wheels to steer along the first direction according to the target steering angle of the rear wheels;

[0161] The differential torque control module 703 is used to determine the differential torque signal based on the target steering angle of the rear wheels, and to perform differential torque control on the two rear wheels based on the differential torque signal.

[0162] In one embodiment of the present invention, the target steering angle determination module 701 may include the following sub-modules:

[0163] The target steering angle determination submodule is used to determine the target steering angle of the rear wheels based on the front wheel steering information and the vehicle speed when the front wheels are turning in the first direction; the front wheel steering information includes either the front wheel steering angle or the steering wheel angle.

[0164] In one embodiment of the present invention, the target steering angle determination submodule may include the following units:

[0165] The target steering angle determination unit is used to determine the rear wheel steering angle follow-up ratio based on the front wheel steering information and the vehicle speed, and to determine the rear wheel target steering angle according to the rear wheel steering angle follow-up ratio.

[0166] In one embodiment of the present invention, the target steering angle determination unit may include the following sub-units:

[0167] The follow-up ratio determination subunit is used to determine, from a first preset table, the follow-up ratio of the rear wheel steering angle corresponding to the steering wheel angle at the current driving speed of the vehicle; wherein, the first preset table is used to indicate different follow-up ratios of the rear wheel steering angle corresponding to different steering wheel angles at the same vehicle driving speed.

[0168] In one embodiment of the present invention, the target steering angle determination unit may include the following sub-units:

[0169] The target steering angle determination subunit is used to calculate the target steering angle of the rear wheels by using the rear wheel steering angle follow-up ratio and the steering wheel angle.

[0170] In one embodiment of the present invention, the steering control module 702 may include the following sub-modules:

[0171] The steering control submodule is used to activate the synchronous steering function of the rear wheels and the front wheels, and to control the two rear wheels to turn in the first direction according to the target steering angle of the rear wheels.

[0172] In one embodiment of the present invention, the steering control submodule may include the following units:

[0173] The synchronous steering function activation unit is used to detect the current driving speed of the vehicle after the synchronous steering function of the rear wheels and front wheels is activated; if the current driving speed of the vehicle is greater than or equal to a preset speed threshold, the synchronous steering function of the rear wheels and front wheels is activated based on the steering wheel angle.

[0174] In one embodiment of the present invention, the synchronous steering function activation unit may include the following sub-units:

[0175] The synchronous steering function activation subunit is used to activate the synchronous steering function of the rear wheels and front wheels when the steering wheel angle is greater than or equal to a preset first angle threshold.

[0176] In one embodiment of the present invention, the steering control submodule may include the following units:

[0177] A steering control unit is used to control two rear wheel steering actuators to drive two rear wheels to steer in the first direction according to the target rear wheel steering angle.

[0178] In one embodiment of the present invention, the differential torque control module 703 may include the following sub-modules:

[0179] The differential torque signal generation submodule is used to generate a differential torque signal based on the target steering angle of the rear wheels and the torque distribution control weight.

[0180] In one embodiment of the present invention, the differential torque signal generation submodule may include the following units:

[0181] The first differential torque signal generation unit is used to determine the differential torque control target based on the torque distribution control weight and the target steering angle of the rear wheel; the differential torque control target is used to constrain the differential torque to obtain the differential torque signal.

[0182] In one embodiment of the present invention, the first differential torque signal generation unit may include the following sub-units:

[0183] The differential torque signal generation subunit is used to determine the torque distribution control weight based on the tire slip angle estimation value when the target steering angle of the rear wheel is less than or equal to a preset second angle threshold; and to determine the differential torque control target according to the torque distribution control weight and the tire slip angle estimation value.

[0184] In one embodiment of the present invention, the differential torque signal generation subunit is further configured to determine the torque distribution control weight based on the estimated value of the vehicle yaw rate when the target steering angle of the rear wheel is greater than a preset second angle threshold; and to determine the differential torque control target according to the torque distribution control weight and the estimated value of the vehicle yaw rate.

[0185] In one embodiment of the present invention, the differential torque signal generation submodule may include the following units:

[0186] The second differential torque signal generation unit is used to determine the torque distribution control weight based on the tire slip angle estimation value when the target steering angle of the rear wheel is less than or equal to a preset second angle threshold; and to generate a differential torque signal according to the torque distribution control weight.

[0187] In one embodiment of the present invention, the second differential torque signal generation unit is further configured to determine the torque distribution control weight based on the estimated value of the vehicle yaw rate when the target steering angle of the rear wheel is greater than a preset second angle threshold; and generate a differential torque signal according to the torque distribution control weight.

[0188] In one embodiment of the present invention, the step of determining the torque distribution control weight based on the estimated tire slip angle may include:

[0189] From the second preset table, the torque distribution control weight under the current estimated tire slip angle is determined; wherein, the second preset table is used to indicate different torque distribution control weights corresponding to different estimated tire slip angles, and the estimated tire slip angle is positively correlated with the torque distribution control weight.

[0190] In one embodiment of the present invention, the step of determining the torque distribution control weight based on the estimated vehicle yaw rate may include:

[0191] From the third preset table, the torque distribution control weight under the current estimated vehicle yaw rate is determined; wherein, the third preset table is used to indicate different torque distribution control weights corresponding to different estimated vehicle yaw rates, and the estimated vehicle yaw rate is positively correlated with the torque distribution control weight.

[0192] In one embodiment of the present invention, the steering control submodule is further configured to control the two rear wheels to steer according to the preset second angle threshold when the target steering angle of the rear wheels is greater than the preset second angle threshold. In one embodiment of the present invention, the differential torque control module 703 may include the following submodules:

[0193] The differential torque control submodule is used to respond to the differential torque signal and control the two rear wheel drive units to output differential torque, thereby driving the two rear wheels to rotate.

[0194] In this embodiment of the invention, when the front wheels turn in the first direction, the vehicle steering control device provided by this embodiment can control the two rear wheels to turn in the first direction according to the determined target steering angle of the rear wheels. At this time, a differential torque signal can be determined according to the target steering angle of the rear wheels, and differential torque control can be performed on the two rear wheels according to the differential torque signal. This allows the differential torque signal to intervene during the process of controlling the rear wheels to turn in the first direction that is the same as the front wheels, thereby compensating for the difference between the steering angle of the rear wheels and the steering angle of the front wheels during the steering process and increasing the stability of the vehicle at high speed.

[0195] As the device embodiment is basically similar to the method embodiment, the description is relatively simple, and relevant parts can be found in the description of the method embodiment.

[0196] This invention also provides a vehicle, comprising:

[0197] It includes a processor, a memory, and a computer program stored in the memory and capable of running on the processor. When the computer program is executed by the processor, it implements the various processes of the above-described embodiment of the torque control method for vehicle steering and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0198] This invention also provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the various processes of the above-described vehicle steering torque control method embodiment and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0199] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0200] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, apparatus, or computer program products. Therefore, embodiments of the present invention can take the form of entirely hardware embodiments, entirely software embodiments, or embodiments combining software and hardware aspects. Furthermore, embodiments of the present invention can take the form of computer program products implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0201] Embodiments of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, terminal vehicles (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal vehicle to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal vehicle, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0202] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal vehicle to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0203] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal vehicle, causing a series of operational steps to be executed on the computer or other programmable terminal vehicle to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal vehicle for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0204] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0205] Finally, it should be noted that the user information (including but not limited to user vehicle information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties. Furthermore, the collection, use and processing of the relevant data must comply with the relevant laws, regulations and standards of the relevant countries and regions, and corresponding operation portals are provided for users to choose to authorize or refuse.

[0206] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or end vehicle that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or end vehicle. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or end vehicle that includes said element.

[0207] The present invention has provided a detailed description of a vehicle steering control method, a corresponding vehicle, and a corresponding computer-readable storage medium. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A vehicle steering control method, characterized in that, The method includes: When the front wheels turn in the first direction, determine the target steering angle of the rear wheels; Control the two rear wheels to turn in the first direction according to the target steering angle of the rear wheels; The differential torque signal is determined based on the target steering angle of the rear wheels, and differential torque control is performed on the two rear wheels based on the differential torque signal.

2. The method according to claim 1, characterized in that, The step of determining the differential torque signal based on the target steering angle of the rear wheels includes: Based on the target steering angle of the rear wheels and the torque distribution control weights, a differential torque signal is generated.

3. The method according to claim 2, characterized in that, The generation of differential torque signals based on the target rear wheel steering angle and torque distribution control weights includes: The differential torque control target is determined based on the torque distribution control weight and the target steering angle of the rear wheels; the differential torque control target is used to constrain the differential torque to obtain the differential torque signal.

4. The method according to claim 3, characterized in that, The step of determining the differential torque control target based on the torque distribution control weights and the target rear wheel steering angle includes: If the target steering angle of the rear wheel is less than or equal to a preset second angle threshold, the torque distribution control weight is determined based on the estimated tire slip angle. The differential torque control target is determined based on the torque distribution control weights and the estimated tire slip angle.

5. The method according to claim 3, characterized in that, The step of determining the differential torque control target based on the torque distribution control weights and the target rear wheel steering angle includes: If the target steering angle of the rear wheel is greater than the preset second angle threshold, the torque distribution control weight is determined based on the estimated value of the vehicle yaw rate. The differential torque control target is determined based on the torque distribution control weight and the estimated vehicle yaw rate.

6. The method according to claim 2, characterized in that, The generation of differential torque signals based on the target rear wheel steering angle and torque distribution control weights includes: If the target steering angle of the rear wheel is less than or equal to a preset second angle threshold, the torque distribution control weight is determined based on the estimated tire slip angle. A differential torque signal is generated based on the torque distribution control weights.

7. The method according to claim 2, characterized in that, The generation of differential torque signals based on the target rear wheel steering angle and torque distribution control weights includes: If the target steering angle of the rear wheel is greater than the preset second angle threshold, the torque distribution control weight is determined based on the estimated value of the vehicle yaw rate. A differential torque signal is generated based on the torque distribution control weights.

8. The method according to claim 4 or 6, characterized in that, The determination of torque distribution control weights based on tire slip angle estimation includes: Determine the torque distribution control weight based on the current estimated tire slip angle from the second preset table; The second preset table is used to indicate different torque distribution control weights corresponding to different tire slip angle estimates, and the tire slip angle estimates are positively correlated with the torque distribution control weights.

9. The method according to claim 5 or 7, characterized in that, The determination of torque distribution control weights based on the estimated vehicle yaw rate includes: From the third preset table, determine the torque distribution control weights based on the current estimated vehicle yaw rate; The third preset table is used to indicate the different torque distribution control weights corresponding to different estimated values ​​of vehicle yaw rate, and the estimated value of vehicle yaw rate is positively correlated with the torque distribution control weight.

10. The method according to claim 1, characterized in that, In the process of controlling the two rear wheels to turn in the first direction according to the target steering angle of the rear wheels, the method further includes: When the target steering angle of the rear wheels is greater than a preset second angle threshold, the two rear wheels are controlled to steer according to the preset second angle threshold.

11. The method according to claim 1, characterized in that, The differential torque control of the two rear wheels based on the differential torque signal includes: In response to the differential torque signal, the two rear wheel drive units are controlled to output differential torque, thereby driving the two rear wheels to rotate.

12. The method according to claim 1, characterized in that, When the current wheel turns in the first direction, the target steering angle of the rear wheel is determined, including: When the front wheels turn in the first direction, the target steering angle of the rear wheels is determined based on the front wheel steering information and the vehicle speed; the front wheel steering information includes either the front wheel steering angle or the steering wheel angle.

13. The method according to claim 12, characterized in that, The process of determining the target rear wheel steering angle based on front wheel steering information and vehicle speed includes: The rear wheel steering angle follow-up ratio is determined based on the front wheel steering information and vehicle speed, and the target rear wheel steering angle is determined based on the rear wheel steering angle follow-up ratio.

14. The method according to claim 13, characterized in that, The determination of the rear wheel steering angle follow-up ratio based on front wheel steering information and vehicle speed includes: From the first preset table, determine the following ratio of the rear wheel steering angle corresponding to the steering wheel angle at the current driving speed of the vehicle; The first preset table is used to indicate the different rear wheel steering angle follow-up ratios corresponding to different steering wheel angles at the same vehicle speed.

15. The method according to claim 13, characterized in that, The step of determining the target rear wheel steering angle based on the rear wheel steering angle follow-up ratio includes: The target rear wheel steering angle is calculated by using the rear wheel steering angle follow-up ratio and the steering wheel angle.

16. The method according to claim 1, characterized in that, The step of controlling the two rear wheels to turn in the first direction according to the target steering angle of the rear wheels includes: Activate the rear wheel and front wheel synchronous steering function, and control the two rear wheels to turn in the first direction according to the target steering angle of the rear wheels.

17. The method according to claim 16, characterized in that, The activation of the rear-wheel and front-wheel synchronized steering function includes: After the rear wheel and front wheel synchronous steering function is activated, the current driving speed of the vehicle is detected; If the current driving speed of the vehicle is greater than or equal to a preset speed threshold, the rear wheel and front wheel synchronous steering function is activated based on the steering wheel angle.

18. The method according to claim 17, characterized in that, The function of activating the synchronous steering of the rear and front wheels based on the steering wheel angle includes: If the steering wheel angle is greater than or equal to a preset first angle threshold, the rear wheel and front wheel synchronous steering function is activated.

19. The method according to claim 16, characterized in that, The step of controlling the two rear wheels to turn in the first direction according to the target steering angle of the rear wheels includes: Based on the target rear wheel steering angle, control the two rear wheel steering actuators to drive the two rear wheels to turn in the first direction.

20. The method according to claim 19, characterized in that, The step of controlling the two rear wheel steering actuators to drive the two rear wheels to turn in the first direction according to the target rear wheel steering angle includes: Based on the target rear wheel steering angle and the first direction, corresponding control signals are sent to the two rear wheel steering actuators; the two rear wheel steering actuators are used to drive the two rear wheels to turn along the first direction according to the control signals.

21. A vehicle, characterized in that, include: A processor, a memory, and a computer program stored in the memory and capable of running on the processor, wherein the computer program, when executed by the processor, implements the vehicle steering control method as described in any one of claims 1 to 20.

22. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium, which, when executed by a processor, implements the vehicle steering control method as described in any one of claims 1 to 20.

Images