Vehicle steering control method, vehicle steering system, and vehicle

Abstract

This invention discloses a vehicle steering control method, a vehicle steering system, and a vehicle. The vehicle includes a distributed drive system. The vehicle steering control method includes: determining a steering wheel angle error based on a target steering wheel angle and an actual steering wheel angle; determining a target differential torque of the steering wheels based on the steering wheel angle error; and controlling the drive motors of the corresponding steering wheels in the distributed drive system according to the target differential torque of the steering wheels to distribute the target differential torque to the steering wheels. The method and system of this invention can solve the problem of inaccurate steering that may occur in vehicle steering systems under fault conditions. Furthermore, it requires no additional hardware, has low manufacturing costs, simplifies vehicle structure and control design, and saves space.

Description

Technical Field

[0001] This invention relates to the field of driver assistance technology, and in particular to a vehicle steering control method, a vehicle steering system, and a vehicle. Background Technology

[0002] The reliability and accuracy of a vehicle's steering system are crucial for driving safety and handling. For vehicles with distributed drive systems, a malfunction in the steering system can prevent accurate steering, posing a serious safety hazard. While some related technologies can improve steering accuracy, they are often complex and expensive. Therefore, a new steering control method is urgently needed to address this problem. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. Therefore, the first objective of this invention is to propose a vehicle steering control method that can solve the problem of steering inaccuracy that may occur when the vehicle steering system malfunctions, without requiring additional hardware, resulting in low manufacturing costs, simple vehicle structure and control design, and space savings.

[0004] The second objective of this invention is to provide a vehicle steering system.

[0005] The third objective of this invention is to provide a vehicle.

[0006] To achieve the above objectives, a vehicle steering control method according to a first aspect of the present invention is provided. The vehicle includes a distributed drive system. The vehicle steering control method includes: determining a steering wheel angle error based on a target steering wheel angle and an actual steering wheel angle; determining a target differential torque of the steering wheels based on the steering wheel angle error; and controlling the drive motors of the corresponding steering wheels in the distributed drive system according to the target differential torque of the steering wheels to distribute the target differential torque of the steering wheels to the steering wheels.

[0007] According to the vehicle steering control method of the present invention, based on the vehicle's distributed drive system, the distributed drive system has the characteristic that each drive motor of the corresponding wheel can work independently, and controls the target differential torque of the steering wheel. It can realize the tracking and closed-loop control of the steering wheel angle, thereby solving the problem of inaccurate steering that may occur in the vehicle steering system under fault conditions. Moreover, the steering control function is realized without adding extra hardware, the manufacturing cost is low, the vehicle structure and control design are simplified, the space occupied is saved, and it is conducive to the actual vehicle layout.

[0008] To achieve the above objectives, a vehicle steering system according to a second aspect of the present invention includes: a distributed drive system for driving each wheel of a vehicle; a sensor system for collecting steering sensing information; and a controller communicatively connected to the distributed drive system and the sensor system for executing the vehicle steering control method described in the above embodiment.

[0009] According to the vehicle steering system of the present invention, the distributed drive system uses multiple drive motors to drive each wheel of the vehicle, and each drive motor has the characteristic of independent operation. By adopting the vehicle steering control method described in the above embodiment, the distribution of target differential torque of the steering wheels and steering control are realized, thereby realizing the steering control function without adding additional hardware. Moreover, multiple drive motors control different steering wheels. This distributed configuration allows each steering wheel to be controlled independently, realizing the redundancy of steering control, with low manufacturing cost, simple vehicle structure and control design, space saving, and convenient for actual vehicle layout.

[0010] To achieve the above objectives, a third aspect of the present invention also provides a vehicle including the vehicle steering system described in the above embodiments.

[0011] According to the vehicle of the present invention, by adopting the vehicle steering control method described in the above embodiments, the steering control function is realized based on the vehicle's distributed drive system without adding additional hardware. Moreover, multiple drive motors control different steering wheels. This distributed configuration allows each steering wheel to be controlled independently, thereby achieving redundancy in steering control. It can solve the problem of inaccurate steering that may occur in the event of a vehicle steering system failure. It has low manufacturing cost, simple vehicle structure and control design, saves space, and is conducive to actual vehicle layout.

[0012] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0013] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0014] Figure 1 This is a schematic diagram of a vehicle steering system according to an embodiment of the present invention;

[0015] Figure 2 This is a flowchart of a vehicle steering control method according to an embodiment of the present invention;

[0016] Figure 3 This is a flowchart of a vehicle steering control method according to an embodiment of the present invention;

[0017] Figure 4 This is a block diagram of a vehicle according to an embodiment of the present invention.

[0018] Figure label:

[0019] 100 vehicles;

[0020] Vehicle steering system 1;

[0021] 11. Left front drive motor; 12. Left rear drive motor; 13. Right rear drive motor; 14. Right front drive motor; 21. Steering wheel angle sensor; 22. IMU sensor; 31. Steering drive and control device; 32. Vehicle controller; 41. Steering wheel; 42. Steering column; 43. Universal joint; 44. Worm gear and rack steering gear; 45. Left front steering tie rod; 46. Right front steering tie rod; 51. Left front brake assembly; 52. Left rear brake assembly; 53. Right rear brake assembly; 54. Right front brake assembly; 55. Left rear brake fluid transmission pipe; 56. Right rear brake fluid transmission pipe; 57. Right front brake fluid transmission pipe; 58. Brake fluid supply and control device; 59. Left front brake fluid transmission pipe; 61. Left rear wheel assembly; 62. Right rear wheel assembly; 63. Right front wheel assembly; 64.

[0022] First controller 331; second controller 332. Detailed Implementation

[0023] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. The embodiments of the present invention are described in detail below.

[0024] To address the problems of complex structure, high cost, and large space occupation of vehicle steering systems in related technologies, this invention proposes a vehicle steering control method. This vehicle steering control method can be based on the vehicle's distributed drive system without adding additional hardware; that is, it achieves vehicle steering control based on a four-wheel independently controlled drive system.

[0025] To facilitate the explanation of the technical solution, the vehicle steering system of the present invention will be described first below.

[0026] Figure 1 This is a schematic diagram of a vehicle steering system according to an embodiment of the present invention, such as... Figure 1 As shown, the vehicle steering system 1 includes: a distributed drive system, a sensor system, and a controller.

[0027] A distributed drive system refers to a vehicle powertrain system in which multiple drive motors are distributed across different wheels of the vehicle to provide independent control and power output for driving each wheel. This type of system is commonly used in electric or hybrid vehicles to achieve more flexible power distribution and enhanced performance. The primary goal of a distributed drive system is to improve traction, suspension control, and steering precision.

[0028] In some embodiments, different types of vehicles have different distributed drive system configurations. For example, for vehicles with steering wheels at the front, such vehicles are typically equipped with at least two drive motors: a left front motor and a right front motor. These two drive motors can be controlled independently to provide driving force to the front wheels, thereby propelling the vehicle forward or backward. When steering is required, the left front motor and the right front motor can operate at different speeds to achieve the steering operation.

[0029] For vehicles with rear-wheel steering, they are typically equipped with at least two drive motors: a left rear motor and a right rear motor. These two drive motors can be controlled independently to provide driving force to the rear wheels, thus propelling the vehicle forward or backward. When steering is required, the left and right rear drive motors can operate at different speeds to achieve the steering operation.

[0030] Furthermore, for four-wheel drive vehicles, a drive motor can be installed on each wheel to achieve optimal traction and dynamic performance. During differential steering, all four motors can be controlled differently to change the speed of the wheels, helping the vehicle achieve more agile steering maneuvers.

[0031] The sensor system is used to collect sensing information required during vehicle steering, including but not limited to longitudinal acceleration, yaw rate, vehicle speed, steering wheel angle, and angular velocity. The sensor system may include various sensors, such as an IMU (Inertial Measurement Unit) sensor 22, a steering wheel angle sensor 21, and a vehicle speed sensor. These sensors can monitor the vehicle's status and motion parameters in real time and transmit the collected information to the controller.

[0032] The controller is the core component of the vehicle steering system 1, and it communicates with the distributed drive system and sensor system. The controller processes and analyzes data collected by the sensor system and executes corresponding control strategies according to the vehicle steering control method described in the following embodiments. Based on the vehicle's operating status and steering requirements, the controller applies different torques to each drive motor of the distributed drive system to achieve steering control. Simultaneously, the controller can also adjust the steering control process in real time based on data collected by the sensors to ensure vehicle stability and safety.

[0033] According to the vehicle steering system 1 of the present invention, the distributed drive system uses multiple drive motors to drive each wheel of the vehicle respectively. The sensor system is responsible for monitoring parameters such as steering wheel angle, wheel angle, and vehicle speed. The controller receives real-time data from the sensor system and executes the vehicle steering control method described below to realize the distribution of target differential torque of the steering wheels and steering control. Thus, the steering control function is realized without adding extra hardware. Moreover, multiple drive motors control different steering wheels. This distributed configuration allows each steering wheel to be controlled independently, realizing redundancy in steering control, reducing manufacturing costs, simplifying the vehicle's structure and control design, and saving space.

[0034] In some embodiments, the distributed drive system includes a left front drive motor 11, a left rear drive motor 12, a right rear drive motor 13, and a right front drive motor 14. Each drive motor has independent control capabilities and can generate forward driving torque, reverse driving torque, and regenerative braking torque. This means that each drive motor can control the movement of its corresponding wheel, including forward driving, rearward driving, and regenerative braking. With this design, the vehicle steering system 1 can control the torque output of each wheel as needed, thereby achieving more precise and flexible vehicle steering and motion control. Such a system design helps improve the vehicle's handling performance and stability, while also enhancing the vehicle's energy efficiency and energy recovery capabilities.

[0035] The left front drive motor 11 is responsible for driving the movement of the vehicle's left front wheel. The left front drive motor transmits its output torque to the left front wheel through a reduction gear, thereby controlling the rotation of the vehicle's left front wheel. The left rear drive motor 12 is responsible for driving the movement of the vehicle's left rear wheel. The left rear drive motor transmits its output torque to the left rear wheel through a reduction gear, thereby controlling the vehicle's left rear wheel.

[0036] The right front drive motor 14 is responsible for driving the movement of the right front wheel. The right front drive motor transmits its output torque to the right front wheel through a reduction gear, thus controlling the right front wheel of the vehicle. The right rear drive motor 13 is responsible for driving the movement of the right rear wheel of the vehicle. The right rear drive motor transmits its output torque to the right rear wheel through a reduction gear, thus controlling the right rear wheel of the vehicle.

[0037] In some embodiments, the controller includes: an autonomous driving controller, a steering drive and control device 31, and a vehicle controller 32.

[0038] The autonomous driving controller is a crucial component of the vehicle steering system 1, responsible for issuing steering control commands in autonomous driving mode. The autonomous driving controller can be based on advanced algorithms and artificial intelligence technologies, using real-time analysis and processing of sensor data and prediction of vehicle dynamic characteristics to formulate corresponding steering control strategies. For example, in advanced autonomous driving mode, the controller can autonomously plan the vehicle's route based on map and sensor data, and generate steering control commands accordingly to achieve autonomous navigation and steering control of the vehicle.

[0039] The steering drive and control device 31 is connected in communication with the automatic driving controller to execute steering control commands in automatic driving mode. In automatic driving mode, the steering drive and control device 31 can control the output torque of each drive motor and adjust the steering angle of each wheel according to the received commands, thereby realizing the control of vehicle turning, steering or automatic driving path.

[0040] The vehicle controller 32 is communicatively connected to the autonomous driving controller and can monitor the status of the steering drive and control device 31. Once an abnormality is detected, it immediately takes over the steering control and executes the steering commands issued by the autonomous driving controller to ensure the safety and stability of the vehicle. The vehicle controller 32 may include a conventional hydraulic power steering system or other backup steering system to ensure that the vehicle can still perform safe and stable steering control in autonomous driving mode.

[0041] In some embodiments, the autonomous driving controller includes a first controller 331 and a second controller 332.

[0042] In this design, one of the first controllers 331 and the other of the second controller 332 is the master controller and the other is the slave controller. These two controllers are redundant, meaning they have the same functions. Under normal circumstances, the master controller is responsible for executing steering control commands and controlling the steering drive and control device 31 to achieve vehicle steering control. At the same time, the slave controller acts as a backup, receiving information from the master controller and maintaining communication with the vehicle.

[0043] In the vehicle steering system 1, a redundancy mechanism is implemented between the master controller and the slave controller. If the master controller malfunctions, such as failing or malfunctioning, and cannot continue to execute steering control commands, the slave controller will detect the malfunction and automatically take over the master controller's authority. Once the slave controller gains master control authority, it will immediately begin issuing steering control commands and control the steering drive and control device 31 to ensure that the vehicle continues to steer along the predetermined path, thereby ensuring the vehicle's safety and stability. This dual-controller design improves the system's reliability and redundancy to cope with possible malfunctions or abnormal situations, thus ensuring the safe operation of the vehicle in autonomous driving mode.

[0044] In some embodiments, the vehicle steering system 1 further includes an Ackermann steering system and a steer-by-wire system.

[0045] Ackermann steering is a traditional steering system suitable for conventional wheeled vehicles. This system achieves vehicle cornering by giving the steering wheels different steering angles. When the vehicle turns, the inner steering wheel rotates at a larger angle to ensure the vehicle's trajectory more closely follows the intended curve, while reducing lateral slip between the inner and outer tires and improving vehicle stability.

[0046] A steer-by-wire system is an electronic steering system used in electric or hybrid vehicles. This system uses electronics and an electric motor to achieve vehicle steering, rather than a traditional mechanical steering linkage. Controlling the vehicle's steering via electronic signals allows for more precise and flexible steering control. In autonomous driving mode, the steer-by-wire system can execute steering control commands through communication with a first controller 331 and a second controller 332. After the autonomous driving controller issues a steering command, the steer-by-wire system can adjust the vehicle's steering angle and torque according to the command to achieve vehicle steering control.

[0047] In short, the vehicle steering system 1 of this invention can combine an Ackermann steering system and a steer-by-wire system, selecting the appropriate steering method according to different situations. In conventional driving mode, the Ackermann steering system may be used to achieve vehicle steering control. However, in autonomous driving mode, especially in advanced autonomous driving mode, a steer-by-wire system may be used to achieve more precise and flexible steering control.

[0048] In some embodiments, the Ackermann steering system includes a steering wheel 41, a steering column 42, a universal joint 43, a rack and pinion steering gear 44, a left front steering tie rod 45, a right front steering tie rod 46, and a steering drive and control device 31.

[0049] The steering wheel 41 can be a manual input device used by the driver to control the vehicle's steering. The driver applies torque by turning the steering wheel 41, indicating the direction of vehicle steering. The steering column 42 can be a structure connecting the steering wheel 41 and the steering gear, transmitting the torque applied to the steering wheel 41 to the steering gear. The universal joint 43 can be a connecting device that allows the steering column 42 to transmit steering torque at different angles, ensuring the vehicle's agility during steering. The worm gear and rack steering gear 44 converts the torque from the steering wheel 41 into linear motion, driving the steering tie rods through the movement of the rack. The left front steering tie rod 45 and the right front steering tie rod 46 are respectively connected to the rack of the worm gear and rack steering gear 44, used to transmit steering torque to the left and right front wheels of the vehicle, achieving vehicle steering. The steering drive and control device 31 is connected to the worm gear and rack steering gear 44 and controls the movement of the rack. This control device can be an electric drive device or other types of drive devices, used to automatically control the steering torque output of the steering system.

[0050] In some embodiments, the steering wheel 41, steering column 42, universal joint 43, and rack and pinion steering gear 44 are connected in sequence to transmit the torque and steering angle applied to the steering wheel 41 to the worm portion of the rack and pinion steering gear 44. Driving the rack of the rack and pinion steering gear 44 controls the movement of the left front steering tie rod 45 and the right front steering tie rod 46, transmitting steering force to the left and right front wheels of the vehicle, thereby achieving vehicle steering control. Furthermore, in certain situations, such as certain autonomous driving modes or emergency situations, steering commands can be transmitted in reverse to the steering wheel 41. This ensures that in the event of system malfunction or when manual vehicle control is required, the driver can control the vehicle's steering through the steering wheel 41, guaranteeing the driver's control and safety.

[0051] Simultaneously, the steering drive and control device 31 is connected to the worm rack steering gear 44. The steering drive and control device 31 can precisely control the movement of the rack of the worm rack steering gear 44 to adjust the vehicle's steering angle and torque, thereby making the steering more precise and stable. The torque on the steering drive and control device 31 and the steering wheel 41 can be superimposed on the rack of the worm rack steering gear 44. The steering wheel angle sensor 21 is fixed to the steering column 42 and is used to measure the steering angle and angular velocity of the steering wheel 41, thereby providing the steering input signal required by the vehicle steering system 1.

[0052] In some embodiments, the steer-by-wire system includes: a left front brake assembly 51, a left rear brake assembly 52, a right rear brake assembly 53, a right front brake assembly 54, a left rear brake fluid transmission pipe 55, a right rear brake fluid transmission pipe 56, a right front brake fluid transmission pipe 57, a brake fluid supply and control device 58, and a left front brake fluid transmission pipe 59.

[0053] The left front brake assembly 51, left rear brake assembly 52, right rear brake assembly 53, and right front brake assembly 54 are located on each wheel of the vehicle and are used to achieve the vehicle's braking function. They consist of brake discs (or brake drums) and brake calipers. The brake discs are located on the rotating wheel hubs, while the brake calipers are located on both sides of the brake discs. When the brake assemblies are controlled, the brake calipers clamp the brake discs, thereby generating braking torque, slowing wheel rotation, and achieving the vehicle's braking effect.

[0054] The left rear brake fluid transmission pipe 55, right rear brake fluid transmission pipe 56, right front brake fluid transmission pipe 57 and left front brake fluid transmission pipe 59 can respectively connect the left rear brake assembly 52, right rear brake assembly 53, right front brake assembly 54 and left front brake assembly 51 to the brake fluid supply and control device 58 to realize the transmission of brake fluid.

[0055] The brake fluid supply and control device 58 is the core component controlling the entire braking system. It may include a brake fluid reservoir and a brake fluid control unit. The brake fluid reservoir stores brake fluid, while the brake fluid control unit controls the braking torque of the brake assembly according to the vehicle's braking commands. When the driver presses the brake pedal or the automatic driving system requires braking, the brake fluid supply and control device 58 transmits brake fluid to the corresponding brake assembly via the brake fluid transmission pipe, generating the required braking torque to achieve vehicle braking.

[0056] In short, the function of a steer-by-wire system is to steer the vehicle by controlling the braking torque of the brake assembly. In autonomous driving mode, the controller calculates the required braking torque based on the vehicle's steering commands and controls the braking torque of the brake assembly through the brake fluid supply and control device 58 to achieve vehicle steering. By controlling the distribution of braking torque, the steer-by-wire system enables precise steering control of the vehicle, thereby ensuring the stability and safety of the vehicle when driving in autonomous driving mode.

[0057] In some embodiments, the vehicle steering system 1 further includes a wheel system. This wheel system may include a left front wheel assembly 61, a left rear wheel assembly 62, a right rear wheel assembly 63, and a right front wheel assembly 64. These four wheel assemblies together form the vehicle's chassis system, providing necessary support and stability through contact with the ground. Simultaneously, they can provide corresponding braking and driving torques according to the driver's driving commands or the control of the autonomous driving system, thereby controlling the vehicle's speed and steering to achieve safe and stable driving.

[0058] In some embodiments, under normal circumstances, the steering drive and control device 31 executes the steering control command. However, when the steering drive and control device 31 malfunctions and cannot function properly, the vehicle controller 32 will execute the steering control command. During the execution of the steering control command by the vehicle controller 32, steering angular acceleration can be generated by the torques of the left front wheel assembly 61 and the right front wheel assembly 64 around the kingpin. First, the left front wheel assembly 61 and the right front wheel assembly 64 transmit torques through the left front steering tie rod 45 and the right front steering tie rod 46, and these torques are synthesized on the rack of the worm gear steering gear 44. The difference in the synthesized result drives the rack of the worm gear steering gear 44 to move, thereby causing the left front wheel assembly 61 and the right front wheel assembly 64 to produce a steering angle, thus achieving steering control.

[0059] Simultaneously, the rack movement of the worm rack steering gear 44 can also drive the steering column 42 and steering wheel 41 to rotate via the worm of the worm rack steering gear 44. This rotation can be measured by the steering wheel angle sensor 21, and the measurement result is transmitted to the vehicle controller 32 to provide real-time steering wheel angle information.

[0060] In short, redundant backup steering control is achieved by utilizing the torque of the left front wheel assembly 61 and the right front wheel assembly 64. When the main steering drive and control device 31 fails, the vehicle controller 32 can maintain the vehicle's steering function by using the power transmission of the left front wheel assembly 61 and the right front wheel assembly 64, and ensure safe steering control can still be performed in autonomous driving mode.

[0061] In summary, the vehicle steering control method of this invention is based on a four-wheel independent drive vehicle steering system. In the embodiments, when the electronic control part of the Ackerman steering system fails, redundant steering function can be achieved by the fusion of the distributed drive system and the brake-by-wire system. No additional hardware structure is required, resulting in low cost, small space occupation, and practical vehicle layout.

[0062] The following is for reference. Figure 2 and Figure 3 A vehicle steering control method according to an embodiment of the present invention is described.

[0063] In this embodiment, the vehicle steering control method of the present invention is applicable to autonomous driving mode. When the steering drive and control device cannot function properly, the vehicle controller can execute backup steering control to achieve the vehicle steering control required for autonomous driving. Of course, in some embodiments, it can also be applied to driver working mode.

[0064] Figure 2 This is a flowchart of a vehicle steering control method according to an embodiment of the present invention, such as... Figure 2As shown, the vehicle steering control method includes at least steps S1-S3, as detailed below. The vehicle includes a distributed drive system, which has the characteristic of independent drive control for each wheel.

[0065] S1, determine the steering wheel angle error based on the target steering wheel angle and the actual steering wheel angle.

[0066] In some embodiments, the target steering wheel angle can be the expected vehicle steering angle input by the driver or the expected steering angle calculated by the autonomous driving system based on the vehicle's current navigation and driving path. The actual steering wheel angle can be the actual steering wheel angle measured by the vehicle's sensor system, representing the vehicle's current steering angle. Both angle values ​​are important input parameters for subsequent steering control.

[0067] Steering wheel angle error is the difference between the target steering wheel angle and the actual steering wheel angle. The magnitude of the steering wheel angle error reflects the degree of deviation between the driver's expected steering angle and the actual steering angle. A larger steering wheel angle error means the vehicle needs a greater degree of steering adjustment, while a smaller error indicates more accurate steering control. By calculating the steering wheel angle error, the system can understand the deviation between the driver's expected vehicle steering angle and the actual steering angle. The steering wheel angle error will be used in subsequent calculations to achieve precise correction of steering control.

[0068] S2, determine the target differential torque of the steering wheel based on the steering wheel angle error.

[0069] The target differential torque of the steering wheels can be the desired differential torque used for steering control. It determines the torque that the drive motor of the steering wheels in the distributed drive system should output to achieve vehicle steering control. In this embodiment, the target differential torque of the steering wheels can be calculated using a vehicle dynamics model and a control algorithm.

[0070] Therefore, the vehicle steering system can determine the target differential torque required for each steering wheel and convert it into the output torque of the drive motor to achieve steering control. Different target differential torque calculation methods and parameter configurations may be used under different driving scenarios and control requirements to achieve the best steering control effect. Therefore, the calculation of the target differential torque is a flexible and crucial step that needs to be adjusted and optimized according to the specific vehicle steering system design and performance requirements.

[0071] S3 controls the drive motor of the corresponding steering wheel in the distributed drive system according to the target differential torque of the steering wheel, so as to distribute the target differential torque of the steering wheel to the steering wheel.

[0072] Specifically, in a distributed drive system, each wheel can be controlled by a separate drive motor. Based on the independent control of each drive motor in a distributed drive system, the output torque of each drive motor can be controlled to generate a corresponding steering torque in the wheel, thereby achieving vehicle steering. Therefore, in step S4, the target differential torque needs to be distributed to the drive motors of each steering wheel based on the calculated result. In this way, each steering wheel will be driven accordingly according to the requirements of the target differential torque, thus achieving vehicle steering control. Furthermore, because a distributed drive system is used, each drive motor independently controls one steering wheel. Even if one steering motor fails, the other steering motors can continue to operate, ensuring the redundancy and stability of vehicle steering control.

[0073] In some embodiments, if the target differential torque is δT, the distributed drive system has four drive motors, corresponding to four steering wheels. To achieve the steering effect of the target differential torque, the motors can be allocated as follows:

[0074] Left front drive motor: Output torque is -δT / 2;

[0075] Right front drive motor: Output torque is δT / 2;

[0076] Left rear drive motor: Output torque is -δT / 2;

[0077] Right rear drive motor: Output torque is δT / 2;

[0078] In general, this distribution means that the left front wheel and the right rear wheel will generate opposite steering torques to achieve vehicle steering, while the right front wheel and the left rear wheel will also generate opposite steering torques to ensure vehicle balance and stability.

[0079] According to the vehicle steering control method of this invention, the steering wheel angle error is calculated by acquiring the target steering wheel angle and the actual steering wheel angle. Based on the steering wheel angle error and the reference vehicle speed, the target differential torque of the steering wheels is obtained, and the system controls the drive motors of the corresponding steering wheels in the distributed drive system. By controlling the output torque of each drive motor, the target differential torque of the steering wheels is distributed to each steering wheel. Through the control of the differential torque of the steering wheels, steering wheel angle tracking and closed-loop control can be achieved. Furthermore, this method, based on existing distributed drive systems, achieves steering control functions without adding additional hardware. Multiple drive motors control different steering wheels, and this distributed configuration allows each steering wheel to be controlled independently, thereby achieving redundant steering functions. It has low manufacturing costs, simplifies vehicle structure and control design, saves space, and facilitates practical vehicle layout.

[0080] In some embodiments, the vehicle steering control method further includes: determining a yaw control compensation torque. The yaw control compensation torque is distributed to the non-steering wheels. Yaw can refer to the rotational motion of the vehicle during cornering, typically the rotational motion between the front and rear of the vehicle. The yaw control compensation torque can be an additional torque used to counteract or adjust the vehicle's yaw motion. This yaw control compensation torque can be determined based on the vehicle's yaw motion and other factors. The yaw control compensation torque is not applied directly to the steering wheels but is distributed to the non-steering wheels. This means that this additional torque is used to influence the vehicle's non-steering wheels, which may be the front or rear wheels, to control yaw motion. By applying a torque to the non-steering wheels, the vehicle's yaw characteristics can be altered to better control its behavior during cornering.

[0081] The purpose of this method is to enhance a vehicle's yaw stability and handling performance. In situations such as high-speed driving or emergency cornering, vehicles may experience yaw problems, which can lead to loss of control. By introducing a yaw control compensation torque and applying it to the non-steering wheels, the vehicle can better cope with these situations, ensuring it remains stable and drives as the driver intends.

[0082] In some embodiments, determining the yaw control compensation torque includes: obtaining an ideal yaw rate based on a target steering wheel angle and a reference vehicle speed; obtaining the yaw rate deviation based on the ideal yaw rate and the actual yaw rate; and obtaining the yaw control compensation torque based on the yaw rate deviation.

[0083] Specifically, based on the target steering wheel angle and the reference vehicle speed, the yaw rate of the vehicle under ideal conditions is calculated using a two-degree-of-freedom model. This ideal yaw rate can be the yaw rate that the vehicle is expected to achieve under a given target steering wheel angle and current reference vehicle speed.

[0084] Furthermore, the actual yaw rate information is obtained through the vehicle's IMU sensors and compared with the calculated ideal yaw rate to obtain the yaw rate deviation. The yaw rate deviation represents the difference between the vehicle's actual yaw motion and the ideal state.

[0085] Furthermore, the required yaw control compensation torque is calculated based on the yaw rate deviation and the vehicle's moment of inertia. Moment of inertia is the inertial characteristic of the vehicle about its center of mass; considering the vehicle's moment of inertia allows for a more accurate calculation of the compensation torque required for yaw control. In this embodiment, the yaw control compensation torque is an auxiliary torque applied to the vehicle to achieve stable lateral movement. During steering, if the vehicle experiences yaw instability or oversteering, the yaw control compensation torque helps adjust the vehicle's lateral movement, allowing the vehicle to better follow the intended steering path.

[0086] In some embodiments, in addition to calculating the compensation torque using the vehicle's inertia around its center of mass, a two-dimensional lookup table can be constructed based on the reference vehicle speed and yaw rate deviation. This lookup table can be calibrated beforehand to determine the required yaw control compensation torque under different vehicle speed and angular velocity deviation conditions. Obtaining the compensation torque through a lookup table simplifies the calculation and also helps in optimization for different vehicle types and driving conditions.

[0087] Furthermore, after obtaining the yaw control compensation torque, the calculated yaw control compensation torque is distributed to the non-steering wheels according to the activation state of the vehicle's yaw control system. The yaw control system can be activated or deactivated based on the vehicle's motion state and the driver's needs. When the yaw control system is activated, the vehicle's steering system distributes the yaw control compensation torque according to the activation state. This means that the magnitude of the yaw control compensation torque can be adjusted as needed under different driving conditions to adapt to different handling requirements. In steering control, typically only the non-steering wheels are subjected to lateral forces; therefore, in this step, the yaw control compensation torque is evenly distributed to the non-steering wheels and executed by the corresponding wheels to achieve vehicle stability control.

[0088] By incorporating calculations of yaw rate deviation and yaw control compensation torque, and by distributing torque appropriately based on the activation state of the yaw control system, the vehicle steering system can more precisely control the vehicle's lateral movement, thereby improving handling performance and stability. This vehicle steering control method enables more flexible and safer steering control under various driving conditions.

[0089] In some embodiments, distributing yaw control compensation torque to non-steering wheels includes distributing yaw control compensation torque to non-steering wheels when the vehicle's yaw control system (ESC, Electronic Stability Controller) is not activated. This means that even when the vehicle's yaw control system is off, yaw control compensation torque can still be distributed to non-steering wheels to improve yaw stability. This is an additional safety measure to ensure that the vehicle remains stable in the event of yaw.

[0090] The purpose of this method is to enhance the vehicle's yaw stability and handling performance, regardless of whether the yaw control system is activated. Even when the yaw control system is off, the vehicle can still benefit from the yaw control compensation torque to ensure that the vehicle remains stable in potential yaw situations.

[0091] In some embodiments, the vehicle steering control method further includes: acquiring a reference vehicle speed; and determining a target differential torque of the steering wheels based on the steering wheel angle error and the reference vehicle speed.

[0092] The reference speed can be the vehicle's current target speed or desired speed, typically set by the driver via the accelerator pedal. This speed can be used to help calculate the target differential torque of the steering wheels.

[0093] In some embodiments, determining the target differential torque of the steering wheels based on the steering wheel angle error and the vehicle's reference speed includes: obtaining the target differential torque of the steering wheels by querying a mapping relationship based on the steering wheel angle error and the reference speed, wherein the mapping relationship is the correspondence between the steering wheel angle error, the reference speed, and the differential torque of the steering wheels. The mapping relationship can be a function or a table that maps the steering wheel angle error and the reference speed to the required target differential torque of the steering wheels. This function can be obtained through experimentation and calibration to ensure that it accurately reflects the dynamic characteristics and handling requirements of the vehicle.

[0094] For example, the target differential torque of the steering wheels can be calibrated and confirmed using a two-dimensional lookup table. This method takes the steering wheel angle error and reference vehicle speed as inputs and retrieves the corresponding target differential torque value from the table. This target differential torque value is then converted into the actual output torque of the drive motor, which is used to control the drive motor of the corresponding steering wheel in the distributed drive system.

[0095] In some embodiments, the target differential torque of the steering wheels can also be calculated based on the steering wheel angle error, the reference vehicle speed, and the vehicle's steering component parameters. The vehicle's steering component parameters may include physical characteristics related to the vehicle's steering system, such as the equivalent inertia of the steering column and the parameters of the kingpin.

[0096] In some embodiments, controlling the drive motors of the corresponding steering wheels in the distributed drive system according to the target differential torque of the steering wheels to distribute the target differential torque to the steering wheels includes: controlling two drive motors of the two corresponding steering wheels in the distributed drive system according to the target differential torque of the steering wheels to distribute the target differential torque of the steering wheels evenly to the two steering wheels. Through this distribution, the left and right steering wheels will generate opposite steering torques, thereby achieving the vehicle's steering action. Furthermore, because the target differential torque of the two steering wheels is evenly distributed, the vehicle maintains balance and stability during steering.

[0097] In some embodiments, when the target differential torque of the steering wheels is distributed between the two wheels on the same axle, the torque is distributed according to a certain strategy to ensure that the torque of each wheel meets the execution limit and achieves effective steering control.

[0098] Specifically, when distributing the target differential torque of the steering wheels between the two wheels on the same axle, the target differential torque of the steering wheels is first evenly distributed between the two wheels on the same axle. This ensures that the two wheels receive equal target differential torque, thereby achieving a balanced steering effect.

[0099] Furthermore, check whether the torque of the first wheel of the two coaxial wheels, after vector superposition, exceeds the first execution limit of that wheel. The first execution limit can refer to the maximum torque that the first wheel can withstand. If the torque of the first wheel after vector superposition does not exceed the first execution limit, then keep the torque of the first wheel unchanged and continue to control the drive motors corresponding to the two wheels according to the evenly distributed torque.

[0100] If the combined torque of the first wheel exceeds the first execution limit, the torque needs to be redistributed. The torque at the first execution limit is allocated to the first wheel to ensure its torque does not exceed the limit. The difference between the combined torque of the first wheel and the torque at the first execution limit is allocated to the second wheel on the same axle. This gives the second wheel additional torque, resulting in stronger steering performance.

[0101] Furthermore, it is checked whether the total torque distributed to the second wheel exceeds the second execution limit. The second execution limit may refer to the maximum torque that the second wheel can withstand. If the total torque distributed to the second wheel does not exceed the second execution limit, the drive motors corresponding to the two coaxial wheels are controlled according to the distributed torque. If the total torque distributed to the second wheel exceeds the second execution limit, the drive motor corresponding to the second wheel is controlled according to the second execution limit to ensure that its torque does not exceed the limit.

[0102] Through the above steps, this vehicle steering control method can effectively handle the distribution of differential torque between the two wheels on the same axle, ensuring that the torque of each wheel is controlled within a safe range. This vehicle steering control method improves vehicle stability and handling, and ensures the reliability of the steering system.

[0103] In some embodiments, the distributed drive system includes a left front drive motor, a left rear drive motor, a right rear drive motor, and a right front drive motor. This distributed configuration enables each drive motor to drive the corresponding steering wheel of the vehicle, achieving steering and drive control.

[0104] To achieve steering control, a reference vehicle speed is required for calculating and executing the steering control strategy. In this embodiment, the reference speed can be obtained based on the rotational speeds of the left front drive motor, left rear drive motor, right rear drive motor, and right front drive motor, as well as the vehicle's inertia information.

[0105] The rotational speed information refers to the change in the drive motor's rotational speed, which can be acquired through devices such as sensors or encoders to monitor the drive motor's operating status. Simultaneously, vehicle inertial information is also required, such as vehicle acceleration, angular velocity, and rate of change of velocity. Inertial information can be obtained through sensors such as the vehicle's inertial measurement unit.

[0106] Furthermore, by inputting rotational speed and inertia information into the Kalman filter algorithm, the vehicle's current speed can be estimated and filtered to obtain a more accurate reference speed. The Kalman filter is a state estimation algorithm that optimizes the estimation of the system state based on the system's dynamic model and measurement data, thereby reducing the impact of errors and noise and obtaining more reliable results. When estimating the reference speed, the current braking or driving state of the wheels also needs to be considered to more accurately reflect the vehicle's current speed.

[0107] In some embodiments, other fusion algorithms and sensors can be considered to further improve the accuracy of vehicle speed estimation for obtaining the reference vehicle speed. For example, in addition to the Kalman filter algorithm, advanced filtering algorithms such as the Extended Kalman Filter (EKF) and the Unscented Kalman Filter (UKF) can be used. Furthermore, the vehicle can also be equipped with wheel speed sensors, GPS, and other devices, and this information can also be used for estimating the reference vehicle speed.

[0108] In some embodiments, the vehicle steering control method further includes: calculating the slip ratio of each wheel based on a reference vehicle speed; obtaining a slip limiting compensation torque based on the reference vehicle speed and slip ratio, or obtaining the slip limiting compensation torque based on the slip ratio and the moment of inertia of each wheel; and applying torque limiting to each wheel based on the slip limiting compensation torque.

[0109] Specifically, the rotational speed and reference vehicle speed of each wheel are acquired through a sensor system, and the slip ratio of each wheel is calculated based on this data. The slip ratio is the proportion of slippage or rotation that occurs during vehicle operation. These parameters reflect the vehicle's motion state during cornering or braking and are important indicators for evaluating vehicle handling and stability.

[0110] Furthermore, the slip limiting compensation torque can be calculated based on the vehicle's reference speed and wheel slip ratio, or based on the slip ratio and the moment of inertia of each wheel. The slip limiting compensation torque can be an auxiliary torque applied to the wheels to limit tire slippage or rotation. Under certain driving conditions, excessive wheel slip can lead to loss of vehicle control or poor handling. The role of the slip limiting compensation torque is to counteract the instability caused by slippage during steering control, thereby improving the accuracy and stability of steering control.

[0111] Furthermore, a two-dimensional lookup table can be established based on the reference vehicle speed and slip ratio. Using the reference vehicle speed and slip ratio as input parameters, the corresponding slip limiting compensation torque value can be obtained by looking up the table. Such a two-dimensional lookup table can be established through experiments and calibration to obtain accurate slip limiting compensation torque values.

[0112] Furthermore, the distribution of slip-limiting compensation torque is determined by whether the vehicle's traction control system (TSS) is activated. The STS can be activated or deactivated based on the vehicle's motion and the driver's needs. When the STS is activated, the vehicle's steering system will distribute the slip-limiting compensation torque according to the activation status. Specifically, the slip-limiting compensation torque may be increased or decreased to adapt to the current driving conditions. For example, activating the STS may require increasing the slip-limiting compensation torque to improve vehicle stability when driving on a wet or curved road.

[0113] By considering the vehicle's reference speed and slip ratio, calculating the slip-limiting compensation torque based on these parameters, and distributing the torque appropriately according to the activation state of the anti-slip system, the vehicle steering system can respond more accurately to the vehicle's steering needs, thereby improving steering control performance and safety. This vehicle steering control method allows the vehicle to maintain stable and flexible steering performance under various driving conditions.

[0114] In some embodiments, torque limitation on each wheel based on slip limiting compensation torque includes: limiting torque on each wheel based on slip limiting compensation torque when the vehicle's traction control system (ASR / TCS, Acceleration Slip Regulation) is not activated. This means that even when the vehicle's traction control system is off, torque limitation on each wheel can still be applied based on slip limiting compensation torque. For example, in situations involving emergency braking, rapid steering, or sudden road surface changes, the vehicle may slip or spin, potentially leading to loss of control. If the traction control system is not activated or malfunctions, limiting wheel torque based on slip limiting compensation torque helps stabilize the vehicle and prevent uncontrolled spinning. This approach can be considered a safety mechanism that helps address potentially dangerous situations and improves overall vehicle performance.

[0115] In some embodiments, the vehicle steering control method further includes: when the vehicle is in braking condition, distributing the braking torque demand to the front and rear axles of the vehicle. The braking torque distributed to the front and rear axles is then evenly distributed to the corresponding wheels, wherein the braking torque includes regenerative braking torque from the motor and braking torque from the braking system.

[0116] Specifically, during vehicle operation, when the driver or autonomous driving system triggers a braking request, the vehicle steering system receives the request and prepares to brake the vehicle. The system distributes the required braking torque proportionally to the front and rear axles according to a pre-set ideal braking force distribution curve. This braking force distribution optimizes braking performance based on the vehicle's dynamic characteristics and suspension arrangement, ensuring vehicle stability and balance during braking. Building upon the front-to-rear axle braking torque distribution, the braking torque is further evenly distributed among the wheels on each axle, ensuring that each wheel receives a corresponding braking force during braking.

[0117] In some embodiments, the braking torque may include regenerative braking torque from an electric motor and braking torque from a braking system. Regenerative braking from an electric motor refers to converting the vehicle's kinetic energy into electrical energy and storing it during braking, which helps improve energy efficiency and reduce brake wear. Braking torque from a braking system refers to the torque applied to the wheels through conventional braking components such as brake discs and brake pads to decelerate or stop the vehicle.

[0118] Specifically, based on the vehicle's battery SOC (State of Charge) and the motor's capabilities, a portion of the braking energy is converted into regenerative braking torque. Regenerative braking can be an energy recovery technology that converts kinetic energy into electrical energy and stores it in the battery by having the motor work in reverse, thereby extending battery life and improving energy utilization efficiency. If the regenerative braking torque meets the braking torque requirement, it will be directly applied during braking. However, if the regenerative braking torque is insufficient to meet the braking torque requirement, the vehicle's steering system can compensate for the shortfall using the braking torque of the braking system (such as hydraulic braking torque) to ensure braking performance.

[0119] In some embodiments, if the vehicle is equipped with a regenerative braking controller, the system will directly execute the allocation scheme of the regenerative braking controller and output the allocation value. The regenerative braking controller can optimize the allocation and utilization of regenerative braking force according to the vehicle status and energy recovery strategy.

[0120] In some embodiments, the drive motors of the corresponding steering wheels in the distributed drive system are controlled according to the target differential torque of the steering wheels to distribute the target differential torque to the steering wheels. This includes: while keeping the total braking torque of the steering shaft constant, the target differential torque of the steering wheels is evenly distributed and then vector-superimposed onto the two steering wheels. The total braking torque of the steering shaft can refer to the sum of the braking torques of the drive motors related to steering in the distributed drive system. Through reasonable vector superposition, it is ensured that the two steering wheels receive the same steering torque during braking, enabling the vehicle to stably complete steering maneuvers.

[0121] It is important to note that when performing vector superposition, the total braking torque of the steering axis must remain constant. This means that even while steering control is in progress, the braking torque distribution to the non-steering wheels must maintain its original stable state. This is done to avoid interfering with the braking of the non-steering wheels and to ensure the vehicle's stability and balance during steering.

[0122] In some embodiments, if both the vehicle's yaw control system and traction control system are activated, the vehicle steering system will directly transmit the target differential torque of the steering wheels to the left front drive motor, left rear drive motor, right rear drive motor, right front drive motor, and brake fluid supply and control device for execution, based on the previous calculation results.

[0123] In some embodiments, if the vehicle's yaw control system and anti-slip system are not activated, it means that the vehicle does not require slip control, but only yaw control. In this case, the torque allocated to the steering wheels remains unchanged; that is, the steering wheels continue to execute the previously allocated target differential torque. Then, yaw control is achieved by vectoring the yaw control compensation torque onto the non-steering wheels. Through this vector superposition, the non-steering wheels will experience additional torque, thereby assisting the steering wheels in yaw control of the vehicle.

[0124] In some embodiments, if the vehicle's yaw control system is not activated but the anti-slip system is activated, it indicates that the vehicle does not require yaw control, only slip control. In this case, the slip limiting compensation torque and the steering wheel target differential torque are vector-superimposed. The slip limiting compensation torque is a compensation torque previously calculated based on the reference vehicle speed and slip ratio; its function is to control the wheel slip ratio, prevent tire slippage, and improve traction and braking performance. The steering wheel target differential torque is previously calculated based on the steering wheel angle error and the reference vehicle speed, and is used to achieve steering control. After vector superimposing these two torques, they are sent to the respective drive motors and reduction gears, as well as the vehicle's brake fluid supply and control devices for execution. The drive motors will adjust their drive torque accordingly based on this synthesized torque value, while the brake fluid supply and control devices will adjust the braking torque distribution based on the synthesized torque value.

[0125] In some embodiments, if neither the vehicle's yaw control system nor its traction control system is activated, it indicates that the vehicle requires neither yaw control nor slip control. In this case, the slip limiting compensation torque, yaw control compensation torque, and steering wheel target differential torque are vector-superimposed. The slip limiting compensation torque is used to control the wheel slip ratio, the yaw control compensation torque is used to achieve lateral stability of the vehicle, and the steering wheel target differential torque can be used for steering control.

[0126] By vectoring and superimposing these three torques, a composite torque value is obtained. This composite torque value is then sent to the left front drive motor, left rear drive motor, right rear drive motor, and right front drive motor, as well as the vehicle's brake fluid supply and control system. The drive motors will adjust their drive torque accordingly based on this composite torque value, while the brake fluid supply and control system will adjust the braking torque distribution based on the composite torque value.

[0127] In some embodiments, the vehicle steering control method further includes: when the vehicle is in a non-braking condition, maintaining the driving torque of the front and rear axles unchanged, and distributing the target differential torque of the steering wheels evenly and then superimposing it on the two steering wheels.

[0128] Specifically, when the vehicle is in a non-braking condition, meaning there is no need for braking, the vehicle steering control method will focus on steering control and will not adjust the braking torque. That is, the driving torque of the front and rear axles will remain constant. This is because no braking request has been triggered, the vehicle does not need to decelerate or stop, and maintaining constant driving torque on the front and rear axles helps maintain the vehicle's motion.

[0129] Furthermore, during steering control, the driving torque of the front and rear axles remains constant, meaning that steering control does not affect the vehicle's acceleration or deceleration. Only the drive motors of the steering wheels are controlled by the target differential torque of the steering wheels, and while maintaining the constant driving torque of the front and rear axles, the target differential torque of the steering wheels is evenly distributed and superimposed on the two steering wheels. This ensures that the two steering wheels receive the same target differential torque during steering. This target differential torque value is then converted into the actual output torque of the drive motor and superimposed on the drive motor of the steering wheel to achieve steering control.

[0130] In some embodiments, when the vehicle is not braking, if both the yaw control system and the traction control system are activated, the vehicle steering system needs to simultaneously perform yaw stability control and slip control. The yaw control system is used to adjust the lateral movement of the vehicle to maintain a stable yaw rate. The traction control system is used to monitor the slippage of each wheel to ensure that the wheels do not slip excessively or slip during braking or acceleration. In this case, the target differential torque of the steering wheels allocated to each wheel is directly transmitted to the left front drive motor, left rear drive motor, right rear drive motor, and right front drive motor to execute the corresponding steering control and slip control.

[0131] In some embodiments, if the vehicle's yaw control system is activated while the drive anti-slip system is not activated, the steering wheel torque distribution remains unchanged, and the yaw control compensation torque vector is superimposed on the non-steering wheels and sent to the left front drive motor, left rear drive motor, right rear drive motor, and right front drive motor for execution.

[0132] Specifically, since the traction control system is not activated, the vehicle does not need to adjust the braking torque of each wheel to control slippage; therefore, the torque distribution on the steering wheels remains unchanged. However, the vehicle's yaw control function is activated, and to achieve yaw stability control, yaw control compensation torque is superimposed on the non-steering wheels. The purpose of this is to control the vehicle's yaw motion by adjusting the driving torque of the non-steering wheels, thereby enhancing the vehicle's lateral stability.

[0133] In some embodiments, if the vehicle's yaw control system is not activated but the anti-slip system is activated, the slip limiting compensation torque and the steering wheel target differential torque are vector-superimposed and transmitted to the left front drive motor, left rear drive motor, right rear drive motor and right front drive motor for execution.

[0134] Specifically, when the yaw control system is not activated but the anti-slip system is activated, the slip limiting compensation torque and the target differential torque of the steering wheels will be vector-superimposed. After vector superposition of these two torques, they will be transmitted to the left front drive motor, left rear drive motor, right rear drive motor, and right front drive motor.

[0135] In some embodiments, if neither the vehicle's yaw control system nor the traction control system is activated, the slip limiting compensation torque, the yaw control compensation torque, and the target differential torque of the steering wheels are vector-superimposed. By vector-superimposing these three torques, a composite torque value is obtained, which is then transmitted to the left front drive motor, left rear drive motor, right rear drive motor, and right front drive motor. Executing these drive motors controls the wheels, thereby achieving steering control.

[0136] In summary, on the one hand, by controlling the target differential torque of the steering wheels, the vehicle steering system can achieve steering wheel angle tracking and closed-loop control. This means that the system can calculate the steering wheel angle error based on the driver's steering wheel input (target steering wheel angle) and the vehicle's actual steering wheel angle (actual steering wheel angle). Then, based on this error and the reference vehicle speed, the target differential torque of the steering wheels, i.e., the torque required by the steering wheels, is calculated to achieve vehicle steering control. Through this closed-loop control, the vehicle steering system can continuously adjust the torque of the steering wheels to make the actual steering wheel angle as close as possible to the expected target angle, thereby achieving precise vehicle steering control.

[0137] On the other hand, the method of evenly distributing the yaw control compensation torque to the non-steering wheels is used to achieve vehicle yaw stability control. When the vehicle yaws, the yaw control compensation torque can be calculated and distributed to the non-steering wheels according to the system's activation state. By evenly distributing the yaw control compensation torque to the non-steering wheels, the vehicle steering system can suppress vehicle yaw, maintain vehicle stability, and keep it smooth during cornering or high-speed driving.

[0138] Furthermore, this even distribution method helps reduce the impact on closed-loop control of steering wheel angle, making the vehicle's driving feel closer to that of a centralized steering system. Centralized steering systems are used in traditional non-distributed drive vehicles, where all steering torque is concentrated in a single, conventional steering system. By evenly distributing yaw control compensation torque to non-steering wheels, the steering system of a distributed drive vehicle can more closely resemble the performance of a centralized steering system when handling yaw stability, thereby enhancing the driver's control and stability.

[0139] Therefore, by controlling the differential torque of the steering wheels to achieve closed-loop control of the steering wheel angle, and by evenly distributing the yaw control compensation torque to the non-steering wheels to achieve vehicle yaw stability control, the vehicle steering system can provide precise steering control and stability, improving the driving experience and driving safety.

[0140] In some embodiments, when the vehicle is in braking condition, the vehicle steering control method further includes reducing the absolute value of the negative torque of the wheel by reducing the absolute value of the hydraulic braking torque. If the requirement to reduce the negative torque of the wheel cannot be met, the shortfall is achieved by reducing the absolute value of regenerative braking.

[0141] Specifically, by reducing the absolute value of the hydraulic braking torque, the braking torque of the wheels can be reduced, thereby reducing the negative torque of the wheels. This adjustment strategy is applicable when the slip control function is activated, where the slip limiting compensation torque may lead to an increase in the negative torque of the wheels, and reducing the hydraulic braking torque can balance the torque distribution of the wheels. Then, to maintain the overall braking effect, the vehicle steering system can correspondingly reduce the absolute value of the regenerative braking torque. In this way, while the hydraulic braking torque decreases, the reduction in regenerative braking torque can compensate for part of the braking demand, ensuring that the requirement to reduce the negative torque of the wheels is met. If the above two methods are still insufficient to achieve the target negative torque requirement, the vehicle steering control method can be further adjusted by using a drive mechanism to achieve a further reduction in negative torque.

[0142] Furthermore, vehicle steering control methods also include increasing the absolute value of the negative torque at the wheels by increasing the absolute value of the regenerative braking torque. The regenerative braking torque can be the braking torque generated when the electric vehicle's drive motor converts kinetic energy into electrical energy via an inverter during braking. By increasing the absolute value of the regenerative braking torque, the braking torque at the wheels can be increased, thereby increasing the negative torque at the wheels. If the increase in regenerative braking torque is limited by motor capacity or battery power, it can be adjusted by increasing the absolute value of hydraulic braking to achieve the target negative torque requirement.

[0143] Through these two methods, vehicle steering control can flexibly adjust the torque of each wheel during braking intervention to achieve brake energy recovery and control. By using a reasonable torque superposition method, this approach can maximize the utilization of braking energy while adjusting according to the negative torque of the wheels to ensure the stability and efficiency of the braking process. This vehicle steering control method can optimize vehicle performance and driving experience during braking, and improve the vehicle's energy efficiency.

[0144] Figure 3 This is a flowchart of a vehicle steering control method according to an embodiment of the present invention, as follows: Figure 3 As shown, the workflow of the vehicle steering control method of this embodiment includes at least steps S10-S34, as detailed below.

[0145] S10 receives a steering wheel target angle request from the autopilot controller.

[0146] S11, calculate the steering angle error based on the received target steering wheel angle and the actual steering wheel angle detected by the steering wheel angle sensor.

[0147] S12 calculates the target differential torque of the steering wheels based on the steering wheel angle error and the reference vehicle speed.

[0148] S13, determine whether a braking request has been received. If yes, proceed to step S14; otherwise, proceed to step S23.

[0149] S14, performs the distribution of regenerative braking and hydraulic braking.

[0150] S15, keep the non-steering wheel braking torque distribution unchanged; and based on the total braking torque of the steering shaft remaining unchanged, distribute the target differential torque evenly and then superimpose it onto the two steering wheels.

[0151] S16. Determine whether the yaw control system is activated. If yes, proceed to step S17; otherwise, proceed to step S20.

[0152] S17. Determine whether the anti-slip system is activated. If yes, proceed to step S18; otherwise, proceed to step S19.

[0153] S18 transmits the hydraulic braking torque of each target to the brake controller, and transmits the motor execution torque of each target to the motor controller.

[0154] S19, which vectorically superimposes the target differential torque of the steering wheel and the slip limiting compensation torque.

[0155] S20, determine whether the anti-slip system is activated. If yes, proceed to step S21; otherwise, proceed to step S22.

[0156] S21, the target differential torque of the steering wheel and the yaw control compensation torque are vector-superimposed.

[0157] S22, which vectorically superimposes the target differential torque of the steering wheel, the yaw control compensation torque, and the slip limitation compensation torque.

[0158] S23, keeping the driving torque of the front and rear axles constant, distributes the target differential torque evenly and then superimposes it onto the two steering wheels.

[0159] S24. Determine whether the yaw control system is activated. If yes, proceed to step S25; otherwise, proceed to step S28.

[0160] S25. Determine whether the sliding control function is activated. If yes, proceed to step S26; otherwise, proceed to step S27.

[0161] S26 transmits the torque of each target motor to each motor controller.

[0162] S27, the target differential torque of the steering wheel and the slip limiting compensation torque are vector-superimposed.

[0163] S28. Determine whether the sliding control function is activated. If yes, proceed to step S29; otherwise, proceed to step S30.

[0164] S29, the target differential torque of the steering wheel and the yaw control compensation torque are vector-superimposed.

[0165] S30 vectorically superimposes the target differential torque of the steering wheel, the yaw control compensation torque, and the slip limitation compensation torque.

[0166] S31 uses a Kalman filter algorithm to estimate the reference vehicle speed based on wheel speed sensor information combined with IMU information.

[0167] S32 calculates the ideal yaw rate based on the target steering wheel angle, reference vehicle speed, and a two-degree-of-freedom model.

[0168] S33, calculate the yaw rate deviation, and calculate the required yaw control compensation torque based on the yaw rate deviation, and then distribute it evenly to the two wheels of the non-steering axle.

[0169] S34 calculates the slip or slip ratio of each wheel based on the reference vehicle speed and obtains the slip limiting compensation torque.

[0170] The following is for reference. Figure 4 A vehicle described in an embodiment of the present invention.

[0171] Figure 4 This is a block diagram of a vehicle according to an embodiment of the present invention, such as... Figure 4As shown, the vehicle 100 of this embodiment includes the vehicle steering system 1 described in the above embodiment.

[0172] According to the vehicle 100 of the present invention, by adopting the vehicle steering control method described in the above embodiment, the steering control function is realized based on the existing distributed drive system without adding additional hardware. Moreover, multiple drive motors control different steering wheels. This distributed configuration allows each steering wheel to be controlled independently, thereby realizing the redundancy of steering control. It can solve the problem of inaccurate steering that may occur in the vehicle steering system under fault conditions. It has low manufacturing cost, simple vehicle structure and control design, saves space, and is conducive to actual vehicle layout.

[0173] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0174] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A vehicle steering control method, characterized in that, The vehicle includes a distributed drive system, a yaw control system, and a traction control system. The vehicle steering control method is used in autonomous driving mode, and the vehicle steering control method includes: Based on the target steering wheel angle and the actual steering wheel angle, determine the steering wheel angle error, determine the target differential torque of the steering wheel based on the steering wheel angle error, determine the yaw control compensation torque, and obtain the slip limit compensation torque; The drive motors of the corresponding steering wheels in the distributed drive system are controlled according to the target differential torque of the steering wheels to distribute the target differential torque to the steering wheels. Additionally, the yaw control compensation torque is distributed according to the activation state of the yaw control system, wherein when the vehicle's yaw control system is not activated, the yaw control compensation torque is distributed to the non-steering wheels. Furthermore, the slip limiting compensation torque is distributed according to the activation state of the anti-slip drive system, wherein when the vehicle's anti-slip drive system is not activated, torque is limited on each wheel according to the slip limiting compensation torque. When both the vehicle's yaw control system and drive anti-slip system are activated, the target differential torque of the steering wheels allocated to each wheel is directly transmitted to each drive motor. When the yaw control system is activated but the anti-slip system is not activated, the target differential torque of the steering wheel and the slip limiting compensation torque are vector-superimposed. When the yaw control system is not activated but the anti-slip system is activated, the target differential torque of the steering wheel and the yaw control compensation torque are vector-superimposed. When neither the yaw control system nor the drive anti-slip system is activated, the slip limiting compensation torque, the yaw control compensation torque, and the steering wheel target differential torque are vector-superimposed.

2. The vehicle steering control method according to claim 1, characterized in that, The determination of the yaw control compensation torque includes: The ideal yaw rate is obtained based on the target steering wheel angle and the vehicle's reference speed; The deviation of the yaw rate is obtained based on the ideal yaw rate and the actual yaw rate. The yaw control compensation torque is obtained based on the yaw angular velocity deviation.

3. The vehicle steering control method according to claim 1, characterized in that, The vehicle steering control method further includes: Obtain the reference speed of the vehicle; The target differential torque of the steering wheel is determined based on the steering wheel angle error and the vehicle's reference speed.

4. The vehicle steering control method according to claim 3, characterized in that, Determining the target differential torque of the steering wheels based on the steering wheel angle error and the vehicle's reference speed includes: The target differential torque of the steering wheel is obtained by querying the mapping relationship between the steering wheel angle error and the reference vehicle speed, wherein the mapping relationship is the correspondence between the steering wheel angle error, the reference vehicle speed and the target differential torque of the steering wheel; Alternatively, the target differential torque of the steering wheel can be calculated based on the steering wheel angle error, the reference vehicle speed, and the steering component parameters of the vehicle.

5. The vehicle steering control method according to claim 1, characterized in that, Controlling the drive motor of the corresponding steering wheel in the distributed drive system according to the target differential torque of the steering wheels, so as to distribute the target differential torque of the steering wheels to the steering wheels, includes: The two drive motors corresponding to the two steering wheels in the distributed drive system are controlled according to the target differential torque of the steering wheels, so as to distribute the target differential torque of the steering wheels evenly to the two steering wheels.

6. The vehicle steering control method according to claim 5, characterized in that, The step of controlling two drive motors corresponding to two steering wheels in the distributed drive system based on the target differential torque of the steering wheels includes: If the torque of the first wheel of the two coaxial wheels after vector superposition does not exceed the first execution limit of the first wheel, then the torque of the first wheel remains unchanged. If the torque of the first wheel after vector superposition exceeds the first execution limit, then the first execution limit is allocated to the first wheel, and the torque difference between the first wheel after vector superposition and the first execution limit is allocated to the second wheel of the two coaxial wheels. If the torque difference is allocated to the second wheel and the total torque allocated to the second wheel does not exceed the second execution limit of the second wheel, then the drive motors corresponding to the two coaxial wheels are controlled according to the allocated torque. If the torque difference is allocated to the second wheel and the total torque allocated to the second wheel exceeds the second execution limit, then the drive motor corresponding to the second wheel is controlled according to the second execution limit.

7. The vehicle steering control method according to claim 3, characterized in that, The distributed drive system includes a left front drive motor, a left rear drive motor, a right rear drive motor, and a right front drive motor; The reference vehicle speed is obtained based on the rotational speed information of the left front drive motor, the left rear drive motor, the right rear drive motor, and the right front drive motor, as well as the vehicle's inertia information.

8. The vehicle steering control method according to claim 3, characterized in that, The obtained slip limiting compensation torque includes: Calculate the slip ratio of each wheel based on the reference vehicle speed; The slip limiting compensation torque is obtained based on the reference vehicle speed and the slip ratio, or based on the slip ratio and the moment of inertia of each wheel.

9. The vehicle steering control method according to any one of claims 1-8, characterized in that, The vehicle steering control method further includes: When the vehicle is in braking condition, the braking torque is distributed to the front and rear axles of the vehicle; The braking torque distributed between the front and rear axles is evenly distributed to the corresponding wheels, wherein the braking torque includes the regenerative braking torque of the motor and the braking torque of the braking system.

10. The vehicle steering control method according to claim 9, characterized in that, The step of controlling the drive motor of the corresponding steering wheel in the distributed drive system according to the target differential torque of the steering wheel, so as to distribute the target differential torque of the steering wheel to the steering wheel, includes: With the total braking torque of the steering shaft remaining constant, the target differential torque of the steering wheels is evenly distributed and then vector-superimposed onto the two steering wheels.

11. The vehicle steering control method according to claim 10, characterized in that, The vehicle steering control method further includes: The absolute value of the negative torque of the wheel is reduced by reducing the absolute value of the hydraulic braking torque. If the requirement to reduce the negative torque of the wheel cannot be met, the shortfall is achieved by reducing the absolute value of the regenerative braking torque of the motor. Alternatively, the absolute value of the negative torque of the wheel can be increased by increasing the absolute value of the regenerative braking torque of the motor. If the motor capacity or battery power is limited, the absolute value of the hydraulic braking can be increased.

12. A vehicle steering system, characterized in that, include: A distributed drive system is used to drive the individual wheels of a vehicle; The sensor system is used to collect steering sensing information; A controller, which is communicatively connected to the distributed drive system and the sensor system, is used to execute the vehicle steering control method according to any one of claims 1-11.

13. The vehicle steering system according to claim 12, characterized in that, The distributed drive system includes a left front drive motor, a left rear drive motor, a right rear drive motor, and a right front drive motor.

14. The vehicle steering system according to claim 12, characterized in that, The controller includes: The autonomous driving controller is used to issue steering control commands in autonomous driving mode; A steering drive and control device, communicatively connected to the automatic driving controller, is used to execute the steering control commands; The vehicle controller is communicatively connected to the autonomous driving controller and is used to execute the steering control command when the steering drive and control device malfunctions.

15. The vehicle steering system according to claim 14, characterized in that, The autonomous driving controller includes a first controller and a second controller, one of which is the master controller and the other is the slave controller. When the master controller malfunctions, the slave controller acquires the master controller authority.

16. The vehicle steering system according to any one of claims 12-15, characterized in that, The vehicle steering system also includes the Ackermann steering system and the steer-by-wire system.

17. The vehicle steering system according to claim 16, characterized in that, The Ackermann steering system includes: Steering wheel, steering column, universal joint, rack and pinion steering gear, left front steering tie rod, right front steering tie rod, and the steering drive and control device; The steering wheel, steering column, universal joint, and rack and pinion steering gear are connected in sequence to transmit the torque and angle applied on the steering wheel to the rack and pinion steering gear, drive the rack of the rack and control the movement of the left front steering tie rod and the right front steering tie rod. The steering drive and control device is connected to the worm rack steering gear, and the steering drive and control device is used to control the movement of the rack of the worm rack steering gear.

18. The vehicle steering system according to claim 16, characterized in that, The steer-by-wire system includes: Left front brake assembly, left rear brake assembly, right rear brake assembly, right front brake assembly, left rear brake fluid transmission pipe, right rear brake fluid transmission pipe, right front brake fluid transmission pipe, brake fluid supply and control device and left front brake fluid transmission pipe; The left rear brake fluid transmission pipe, the right rear brake fluid transmission pipe, the right front brake fluid transmission pipe, and the left front brake fluid transmission pipe can respectively connect the left rear brake assembly, the right rear brake assembly, the right front brake assembly, and the left front brake assembly to the brake fluid supply and control device to realize the transmission of brake fluid. The brake fluid supply and control device is used to control the braking torque of the left rear brake assembly, the right rear brake assembly, the right front brake assembly, and the left front brake assembly.

19. A vehicle, characterized in that, Includes the vehicle steering system as described in any one of claims 12-18.

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