Vehicle steering control method, vehicle steering system and vehicle

Abstract

The invention discloses a vehicle steering control method, a vehicle steering system and a vehicle, the vehicle comprises a distributed driving system, and the vehicle steering control method comprises the steps that according to a steering wheel target steering angle and a steering wheel actual steering angle, a steering wheel steering angle error is determined; determining a target differential torque of a steering wheel according to the steering wheel angle error; and according to the target differential torque of the steering wheel, a driving motor corresponding to the steering wheel in the distributed driving system is controlled, so that the target differential torque of the steering wheel is distributed to the steering wheel. According to the method and the system, the problem of inaccurate steering possibly caused by a fault of a vehicle steering system can be solved, additional hardware does not need to be added, the manufacturing cost is low, the vehicle structure and the control design are simple, and the occupied space is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of assisted driving, and in particular to a vehicle steering control method, a vehicle steering system and a vehicle. Background Art

[0002] The reliability and accuracy of the vehicle steering system are crucial to driving safety and maneuverability. For vehicles with distributed drive systems, when the vehicle steering system fails, accurate steering operation cannot be achieved, posing a serious safety hazard. In the related art, even if the accuracy of the steering operation can be improved, the structure is complex and the cost is high. Therefore, a steering control method is urgently needed to solve this problem. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the first object of the present invention is to provide a vehicle steering control method, which can solve the problem of inaccurate steering that may be caused by a vehicle steering system failure, and does not require additional hardware, has low manufacturing cost, simple vehicle structure and control design, and saves space.

[0004] A second objective of the present invention is to provide a vehicle steering system.

[0005] A third object of the present invention is to provide a vehicle.

[0006] In order to achieve the above-mentioned purpose, a vehicle steering control method according to an embodiment of the first aspect of the present invention comprises a vehicle including a distributed drive system, and the vehicle steering control method comprises: determining a steering wheel angle error according to a steering wheel target angle and an actual steering wheel angle; determining a steering wheel target differential torque according to the steering wheel angle error; and controlling a drive motor corresponding to a steering wheel in the distributed drive system according to the steering wheel target differential torque, so as to distribute the steering wheel target differential torque to the steering wheel.

[0007] According to the vehicle steering control method of the embodiment of the present invention, based on the distributed drive system of the vehicle, the distributed drive system has the characteristic that each drive motor of the corresponding wheel can work independently, and the target differential torque of the steering wheel is controlled, so as to realize the tracking and closed-loop control of the steering wheel angle, thereby solving the problem of inaccurate steering that may be caused by a malfunction of the vehicle steering system. In addition, the steering control function is realized without adding additional hardware, the manufacturing cost is low, the vehicle structure and control design are simplified, the occupied space is saved, and it is conducive to the actual vehicle layout.

[0008] In order to achieve the above-mentioned objectives, the vehicle steering system of the second embodiment of the present invention includes: a distributed drive system for driving each wheel of the vehicle; a sensor system for collecting steering sensor information; and a controller, which is communicatively connected with the distributed drive system and the sensor system, and is used to execute the vehicle steering control method described in the above embodiment.

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

[0010] In order to achieve the above-mentioned object, a third aspect of the present invention further provides a vehicle, comprising the vehicle steering system described in the above embodiment.

[0011] The vehicle according to the embodiment of the present invention, by adopting the vehicle steering control method described in the above embodiment, realizes the steering control function based on the distributed drive system of the vehicle without adding additional hardware, and multiple drive motors control different steering wheels. This distributed configuration enables each steering wheel to be independently controlled, thereby realizing redundancy of steering control, and can solve the problem of inaccurate steering that may be caused by a failure of the vehicle steering system. The manufacturing cost is low, the vehicle structure and control design are simple, space is saved, and it is conducive to actual vehicle layout.

[0012] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0018] Reference numerals:

[0019] Vehicle 100;

[0020] Vehicle steering system 1;

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

[0022] First controller 331; second controller 332. DETAILED DESCRIPTION

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

[0024] In view of the problems of complex structure, high cost and large space occupied by vehicle steering systems in related technologies, an embodiment of the present invention proposes a vehicle steering control method. The vehicle steering control method of the embodiment of the present invention can be based on the distributed drive system of the vehicle without adding additional hardware, that is, based on the four-wheel independently controlled drive system of the vehicle to achieve vehicle steering control.

[0025] In order to facilitate the description of the technical solution, the vehicle steering system according to an embodiment of the present invention is first described below.

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

[0027] Among them, a distributed drive system can refer to a vehicle powertrain system in which multiple drive motors are distributed on different wheels of the vehicle to provide independent control and power output for driving each wheel of the vehicle. This system is usually used in electric vehicles or hybrid vehicles to achieve more flexible power distribution and enhance performance. The main 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 a vehicle with a steering wheel at the front, such a vehicle is usually equipped with at least two drive motors, the left front and the right front. The two drive motors can be independently controlled to provide driving force for the front wheels, thereby pushing the vehicle forward or backward. When steering is required, the left front and the right front drive motors can operate at different speeds to achieve the steering operation.

[0029] For vehicles with steering rear wheels, such vehicles are usually equipped with at least two drive motors, the left rear and the right rear. These two drive motors can be controlled independently to provide driving force for the rear wheels, thereby pushing the vehicle forward or backward. When steering is required, the left rear and the right rear drive motors can work at different speeds to achieve steering operations.

[0030] In addition, for four-wheel drive vehicles, this vehicle can be equipped with a drive motor on each wheel to achieve optimal traction and dynamic performance. During differential steering, the four motors can change the speed of the wheels through different controls to help the vehicle achieve more flexible steering operations.

[0031] The sensor system is used to collect the sensor information required during the vehicle steering process, including but not limited to longitudinal acceleration, yaw rate, vehicle speed, steering wheel angle, angular velocity information, etc. The sensor system may include a variety of sensors, such as an IMU (Inertial Measurement Unit) sensor 22, a steering wheel angle sensor 21, a vehicle speed sensor, etc. These sensors can monitor the state and motion parameters of the vehicle 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 the controller is connected to the distributed drive system and the sensor system for communication. The controller uses the information collected by the sensor system to process and analyze data, and executes the corresponding control strategy according to the vehicle steering control method described in the following embodiment. According to the operating state and steering requirements of the vehicle, the controller will apply different torques to each drive motor of the distributed drive system to achieve steering control. At the same time, the controller can also adjust the steering control process in real time according to the data collected by the sensor to ensure the stability and safety of the vehicle.

[0033] According to the vehicle steering system 1 of the embodiment of the present invention, the distributed drive system adopts multiple drive motors to drive each wheel of the vehicle respectively, the sensor system is responsible for monitoring the steering wheel angle, wheel angle, vehicle speed and other parameters of the vehicle, the controller receives real-time data from the sensor system and executes the vehicle steering control method below to realize the distribution of the target differential torque of the steering wheel and the steering control, thereby realizing the steering control function without adding additional hardware, and multiple drive motors control different steering wheels. This distributed configuration allows each steering wheel to be independently controlled, realizes the redundancy of steering control, reduces manufacturing costs, simplifies the structure and control design of the vehicle, and saves 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 drive torque, reverse drive torque, and regenerative braking torque. This means that each drive motor can control the movement of the corresponding wheel, including forward drive, backward drive, and regenerative braking. Through this design, the vehicle steering system 1 can control the torque output of each wheel separately as needed, thereby achieving more precise and flexible vehicle steering and motion control. Such a system design helps to improve the handling performance and stability of the vehicle, and can also enhance the energy efficiency and energy recovery capabilities of the vehicle.

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

[0036] The right front drive motor 14 is responsible for driving the movement of the right front wheel. The right front drive motor transmits the output torque to the right front wheel through the reduction gear device to achieve control of 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 the output torque to the right rear wheel through the reduction gear device to achieve control of the right rear wheel of the vehicle.

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

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

[0039] The steering drive and control device 31 is in communication connection with the automatic driving controller and is used to execute the steering control instructions in the automatic driving mode. In the 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 instructions, thereby realizing the control of the vehicle's turning, steering or automatic driving path.

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

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

[0042] Among them, one of the first controller 331 and the second controller 332 is a master controller and the other is a slave controller, and the two controllers are redundant with each other, that is, they have the same function. Under normal circumstances, the master controller is responsible for executing the steering control instruction and controlling the steering drive and control device 31 to realize the steering control of the vehicle. At the same time, the slave controller serves as a backup, receives information from the master controller and maintains a communication connection with the vehicle.

[0043] In the vehicle steering system 1, a redundancy mechanism is implemented between the master control and the slave control. If the master control has an abnormality, such as a fault or failure, and cannot continue to execute the steering control instruction, the slave control will detect the abnormality of the master control and automatically take over the authority of the master control. Once the slave control obtains the master control authority, it will immediately start to issue steering control instructions and control the steering drive and control device 31 to ensure that the vehicle continues to perform steering control according to the predetermined path, thereby ensuring the safety and stability of the vehicle. The design of this dual-control device can improve the reliability and redundancy of the system to cope with possible failures or abnormal situations, thereby ensuring the safe operation of the vehicle in the automatic driving mode.

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

[0045] Among them, Ackerman steering is a traditional steering system suitable for traditional wheeled vehicles. This system achieves vehicle turning by making the steering wheels have different steering angles. When the vehicle turns, the inner steering wheel will turn a larger angle to ensure that the vehicle's trajectory can be closer to the expected arc, while reducing the lateral slip between the inner and outer tires and improving the stability of the vehicle.

[0046] The steer-by-wire system is an electronic steering system for electric or hybrid vehicles. The system uses electronics and electric motors to achieve vehicle steering instead of traditional mechanical steering connections. By controlling the steering of the vehicle through electronic signals, more precise and flexible steering control can be achieved. In the autonomous driving mode, the steer-by-wire system can execute steering control instructions through a communication connection with the first controller 331 and the second controller 332. After the autonomous driving controller issues a steering instruction, the steer-by-wire system can adjust the steering angle and torque of the vehicle according to the instruction to achieve steering control of the vehicle.

[0047] In short, the vehicle steering system 1 of the embodiment of the present invention can combine the Ackerman steering system and the wire steering system to select the appropriate steering mode according to different situations. In the traditional driving mode, the Ackerman steering system may be used to achieve the steering control of the vehicle. In the automatic driving mode, especially in the advanced automatic driving mode, the wire steering system may be used to achieve more precise and flexible steering control.

[0048] In some embodiments, the Ackerman steering system includes a steering wheel 41 , a steering column 42 , a universal joint 43 , a worm rack 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] Among them, the steering wheel 41 can be a manual input device used by the driver to control the steering of the vehicle. The driver applies a torque by turning the steering wheel 41 to indicate the direction in which the vehicle is turning. The steering column 42 can be a structure connecting the steering wheel 41 and the steering gear, and transmits the rotational torque applied on 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 the steering torque at different angles to ensure the flexibility of the vehicle when turning. The worm rack steering gear 44 can convert the rotational torque from the steering wheel 41 into linear motion, and drive the steering tie rod 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 rack steering gear 44, and are used to transmit the steering torque to the left front wheel and the right front wheel of the vehicle to achieve the steering of the vehicle. The steering drive and control device 31 is connected to the worm 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, which are used to automatically control the steering torque output of the steering system.

[0050] In some embodiments, the steering wheel 41, the steering column 42, the universal joint 43, and the worm rack steering gear 44 are connected in sequence to transmit the torque and the angle of rotation applied to the steering wheel 41 to the worm part of the worm rack steering gear 44. The rack of the worm rack steering gear 44 is driven and the movement of the left front steering tie rod 45 and the right front steering tie rod 46 is controlled to transmit the steering force to the left front wheel and the right front wheel of the vehicle, thereby realizing the steering control of the vehicle. In addition, in some specific cases, such as in certain automatic driving modes or emergency situations, the steering command can be reversed and transmitted to the steering wheel 41. This ensures that when the system is abnormal or the vehicle needs to be manually controlled, the driver can control the steering of the vehicle through the steering wheel 41, thereby ensuring the driver's control and safety over the vehicle.

[0051] At the same time, the steering drive and control device 31 is connected to the worm rack steering gear 44, and the steering drive and control device 31 can accurately control the movement of the rack of the worm rack steering gear 44 to adjust the steering angle and torque of the vehicle, thereby making the steering more accurate and stable. The steering drive and control device 31 and the torque on the steering wheel 41 can be superimposed on the rack of the worm rack steering gear 44. The steering wheel angle sensor 21 is fixedly connected to the steering column 42, and is used to measure the 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] Among them, the left front brake assembly 51, the left rear brake assembly 52, the right rear brake assembly 53, and the right front brake assembly 54 are located on each wheel of the vehicle to realize the braking function of the vehicle. They are composed of a brake disc (or brake drum) and a brake caliper. The brake disc is located on the wheel hub where the wheel rotates, and the brake caliper is located on both sides of the brake disc. When the brake assembly is controlled, the brake caliper clamps the brake disc, thereby generating a braking torque, slowing down the rotation of the wheel, and realizing the braking effect of the vehicle.

[0054] The left rear brake fluid transmission pipe 55, the right rear brake fluid transmission pipe 56, the right front brake fluid transmission pipe 57 and the left front brake fluid transmission pipe 59 can respectively connect the left rear brake assembly 52, the right rear brake assembly 53, the right front brake assembly 54 and the 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 that controls the entire brake system. It may include a brake fluid storage device and a brake fluid control unit. The brake fluid storage device is used to store brake fluid, and the brake fluid control unit controls the braking torque of the brake assembly according to the braking command of the vehicle. When the driver steps on the brake pedal or the automatic driving system needs to brake, the brake fluid supply and control device 58 can transfer the brake fluid to the corresponding brake assembly through the brake fluid transmission pipe to generate the required braking torque, thereby achieving vehicle braking.

[0056] In short, the function of the steer-by-wire system is to achieve the steering of the vehicle by controlling the braking torque of the brake assembly. In the automatic driving mode, the controller will calculate the required braking torque according to the steering command of the vehicle, and control the braking torque of the brake assembly through the brake fluid supply and control device 58 to achieve the steering of the vehicle. By controlling the distribution of the braking torque, the steer-by-wire system can enable the vehicle to achieve precise steering control, thereby ensuring the stability and safety of the vehicle in the automatic driving mode.

[0057] In some embodiments, the vehicle steering system 1 also includes a wheel system. The 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 constitute the chassis system of the vehicle, and they provide the necessary support and stability for the vehicle through contact with the ground. At the same time, they can provide corresponding braking torque and driving torque according to the driver's driving instructions or the control of the automatic driving system, thereby controlling the speed and steering of the vehicle and achieving safe and stable driving.

[0058] In some embodiments, under normal circumstances, the steering control instruction is executed by the steering drive and control device 31. However, when the steering drive and control device 31 fails and cannot work normally, the vehicle controller 32 will execute the steering control instruction. In the execution of the steering control instruction by the vehicle controller 32, the steering angle acceleration can be generated around the kingpin line by the torque of the left front wheel assembly 61 and the right front wheel assembly 64. First, the left front wheel assembly 61 and the right front wheel assembly 64 transmit torque 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 rack steering gear 44. The difference of the synthesized result will drive the rack of the worm rack steering gear 44 to move, thereby causing the left front wheel assembly 61 and the right front wheel assembly 64 to generate a turning angle, thereby achieving steering control.

[0059] At the same time, the rack movement of the worm rack steering gear 44 can also drive the steering column 42 and the steering wheel 41 to rotate through 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 means of the power transmission of the left front wheel assembly 61 and the right front wheel assembly 64, and ensure that safe steering control can still be performed in the automatic driving mode.

[0061] In general, the vehicle steering control method of the embodiment of the present invention is based on a four-wheel independent drive vehicle steering system. In the embodiment, when the electronic control part of the Ackerman steering system fails, the redundant steering function can be realized by integrating the distributed drive system and the wire control brake system without adding additional hardware structure, with low cost, small space occupation, and actual vehicle layout.

[0062] Reference below Figure 2 and Figure 3 A vehicle steering control method according to an embodiment of the present invention is described.

[0063] In the embodiment, the vehicle steering control method of the embodiment of the present invention is applicable to the automatic driving mode. When the steering drive and control device cannot work normally, the vehicle controller can perform backup steering control to realize the vehicle steering control required for automatic driving. Of course, in some embodiments, it can also be applied to the driver working mode.

[0064] Figure 2 is a flow chart of a vehicle steering control method according to an embodiment of the present invention. Figure 2As shown, the vehicle steering control method comprises at least steps S1-S3, which are specifically as follows: wherein the vehicle comprises a distributed drive system, and the distributed drive system has the characteristic of independent drive control corresponding to each wheel.

[0065] S1, determining a steering wheel angle error according to a steering wheel target angle and an actual steering wheel angle.

[0066] In some embodiments, the target steering wheel angle may 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 may be the actual steering wheel angle measured by the vehicle's sensor system, indicating the vehicle's current steering angle. These two angle values ​​are important input parameters for subsequent steering control.

[0067] The steering wheel angle error can be 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 that the vehicle needs to make a greater degree of steering adjustment, while a smaller error means that the vehicle's steering control is more accurate. 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 the calculation of subsequent steps to achieve accurate correction of steering control.

[0068] S2, determining the target differential torque of the steering wheel according to the steering wheel angle error.

[0069] The target differential torque of the steering wheel may be a desired differential torque for steering control, which determines the torque that the driving motor of the steering wheel in the distributed drive system should output to achieve the steering control of the vehicle. In an embodiment, the calculation of the target differential torque of the steering wheel may be obtained using a vehicle dynamics model and a control algorithm.

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

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

[0072] Specifically, in a distributed drive system, each wheel can be controlled by a drive motor. Based on the characteristics of each drive motor being independently controlled in a distributed drive system, the wheel can generate a corresponding steering torque by controlling the output torque of each drive motor, thereby realizing the steering action of the vehicle. Therefore, in step S4, it is necessary to distribute the target differential torque to the drive motors of each steering wheel according to the calculation result of the target differential torque. In this way, each steering wheel will be driven accordingly according to the requirements of the target differential torque, thereby realizing the steering control of the vehicle. In addition, due to the use of a distributed drive system, each drive motor independently controls a steering wheel. Even if a steering motor fails, other steering motors can still continue to work, ensuring the redundancy and stability of the 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. In order to achieve the steering effect of the target differential torque, it can be distributed in the following manner:

[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, through such distribution, the left front wheel and the right rear wheel will produce opposite steering torques, thereby realizing the steering action of the vehicle, while the right front wheel and the left rear wheel will also produce opposite steering torques to ensure the balance and stability of the vehicle.

[0079] According to the vehicle steering control method of the embodiment of the present invention, the steering wheel angle error is calculated by obtaining the steering wheel target angle and the actual steering wheel angle, and the steering wheel target differential torque is obtained according to the steering wheel angle error and the reference vehicle speed, and the system controls the drive motor corresponding to the steering wheel in the distributed drive system. By controlling the output torque of each drive motor, the steering wheel target differential torque is distributed to each steering wheel, and the tracking and closed-loop control of the steering wheel angle can be achieved through the control of the steering wheel differential torque. In addition, the method is based on the existing distributed drive system, and the steering control function is realized without adding additional hardware, and multiple drive motors control different steering wheels. This distributed configuration enables each steering wheel to be independently controlled, thereby realizing redundant steering function, low manufacturing cost, simplified vehicle structure and control design, saved occupied space, and facilitated actual vehicle layout.

[0080] In some embodiments, the vehicle steering control method also includes: determining a yaw control compensation torque. Distributing the yaw control compensation torque to the non-steering wheels. Wherein, yaw may refer to the rotational movement generated by the vehicle when turning, usually the rotational movement between the front and rear of the vehicle. The yaw control compensation torque may be an additional torque used to offset or adjust the yaw motion of the vehicle. This yaw control compensation torque may be determined based on the yaw motion of the vehicle and other factors. The yaw control compensation torque is not applied directly to the steering wheel, but is distributed to the non-steering wheel. This means that this additional torque is used to influence the non-steering wheels of the vehicle, which may be the front wheels or the rear wheels, to control the yaw motion. By applying a torque to the non-steering wheels, the yaw characteristics of the vehicle can be changed to better control its behavior when turning.

[0081] The purpose of this approach is to enhance the vehicle's yaw stability and handling. In situations such as high speeds or tight turns, the vehicle may experience yaw issues, which can lead to a loss of control. By introducing a yaw control compensation torque and applying it to the non-steering wheels, the vehicle can be helped to better handle these situations, ensuring the vehicle remains stable and moves the way the driver intended.

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

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

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

[0085] Further, the required yaw control compensation torque is calculated based on the yaw rate deviation and the rotational inertia of the vehicle. The rotational inertia is the inertial characteristic of the vehicle around the center of mass. Considering the rotational inertia of the vehicle can more accurately calculate the compensation torque required for yaw control. In an embodiment, the yaw control compensation torque is an auxiliary torque applied to the vehicle to achieve stable lateral movement of the vehicle. During the steering process, if the vehicle is yaw unstable or oversteering, the yaw control compensation torque can help adjust the lateral movement of the vehicle so that the vehicle better follows the expected steering path.

[0086] In some embodiments, in addition to using the inertia of the entire vehicle about the center of mass to calculate the compensation torque, a two-dimensional lookup table can also be constructed based on the reference vehicle speed and yaw rate deviation. This lookup table can be calibrated in advance to determine the size of the yaw control compensation torque required under different vehicle speed and angular velocity deviation conditions. Obtaining the compensation torque through a lookup table can simplify the calculation and also help optimize for different vehicle types and driving conditions.

[0087] Further, after the yaw control compensation torque is obtained, 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 according to the vehicle's motion state and the driver's needs. When the yaw control system is activated, the vehicle steering system will distribute the yaw control compensation torque according to the activation state. This means that in different driving conditions, the size of the yaw control compensation torque can be adjusted as needed to meet different control requirements. In steering control, usually only the non-steering wheels are affected by 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 introducing the calculation of yaw rate deviation and yaw control compensation torque, and making reasonable torque distribution according to the activation state of the yaw control system, the vehicle steering system can more accurately control the lateral movement of the vehicle, thereby improving the vehicle's handling performance and stability. Such a vehicle steering control method can achieve more flexible and safe steering control in different driving situations.

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

[0090] The purpose of this approach can be to enhance the yaw stability and handling of the vehicle, whether or not 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 speed of the vehicle, and determining a steering wheel target differential torque according to the steering wheel angle error and the reference speed of the vehicle.

[0092] The reference vehicle speed may be the current target speed or expected speed of the vehicle, which is usually set by the driver through the accelerator pedal. This speed can be used to help calculate the target differential torque of the steering wheel.

[0093] In some embodiments, the target differential torque of the steering wheel is determined according to the steering wheel angle error and the reference speed of the vehicle, including: querying a mapping relationship according to the steering wheel angle error and the reference speed to obtain the target differential torque of the steering wheel, wherein the mapping relationship is a corresponding relationship between the steering wheel angle error, the reference speed and the steering wheel differential torque. 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 wheel. This function can be obtained through experiments and calibration to ensure that it can accurately reflect the dynamic characteristics and control requirements of the vehicle.

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

[0095] In some embodiments, the steering wheel target differential torque can also be obtained according to the steering wheel angle error, the reference vehicle speed and the steering component parameters of the vehicle. The steering component parameters of the vehicle may include physical properties related to the vehicle steering system, such as the equivalent inertia of the steering column, the parameters of the kingpin line, etc.

[0096] In some embodiments, the drive motor corresponding to the steering wheel in the distributed drive system is controlled according to the steering wheel target differential torque to distribute the steering wheel target differential torque to the steering wheel, including: controlling two drive motors corresponding to two steering wheels in the distributed drive system according to the steering wheel target differential torque to evenly distribute the steering wheel target differential torque to the two steering wheels. Through such distribution, the left steering wheel and the right steering wheel will generate opposite steering torques, thereby realizing the steering action of the vehicle, and since the steering wheel target differential torques of the two steering wheels are evenly distributed, it is ensured that the vehicle maintains balance and stability during the steering process.

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

[0098] Specifically, when the steering wheel target differential torque is distributed between the two coaxial wheels, the steering wheel target differential torque is first evenly distributed between the two coaxial wheels, which ensures that the two wheels obtain equal target differential torques, thereby achieving a balanced steering effect.

[0099] Furthermore, it is checked whether the torque of the first wheel of the two coaxial wheels after vector superposition exceeds the first execution limit of the wheel. The first execution limit may 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, the torque of the first wheel is kept unchanged, and the drive motors corresponding to the two wheels continue to be controlled according to the evenly distributed torque.

[0100] If the torque after the vector superposition of the first wheel exceeds the first execution limit, the torque needs to be redistributed. The torque of the first execution limit is allocated to the first wheel to ensure that its torque does not exceed the limit. And the difference between the torque after the vector superposition of the first wheel and the torque of the first execution limit is allocated to the second wheel of the two coaxial wheels. In this way, the second wheel obtains additional torque to achieve a stronger steering effect.

[0101] Further, it is checked whether the total torque of the second wheel after distribution 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 of the second wheel, 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, the vehicle steering control method can effectively handle the distribution of the differential torque between the two coaxial wheels and ensure that the torque of each wheel is controlled within a safe range. Such a vehicle steering control method can improve the stability and controllability of the vehicle and ensure 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 to achieve steering and drive control.

[0104] In order to realize the steering control, it is necessary to obtain the reference speed of the vehicle so as to calculate and execute the steering control strategy. In an embodiment, the reference speed can be obtained based on the speed information of the left front drive motor, the left rear drive motor, the right rear drive motor and the right front drive motor and the inertia information of the vehicle.

[0105] The speed information may refer to the change in the speed of the drive motor, which can be obtained through sensors or encoders to monitor the operating status of the drive motor. At the same time, it is also necessary to obtain the inertial information of the vehicle, such as the acceleration, angular velocity, and speed change rate of the vehicle. The inertial information can be obtained through sensors such as the inertial measurement unit equipped on the vehicle.

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

[0107] In some embodiments, for obtaining the reference vehicle speed, other fusion algorithms and sensors may be considered to further improve the accuracy of vehicle speed estimation. 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) may also be tried. In addition, the vehicle may also be equipped with wheel speed sensors, GPS and other equipment, and this information may also be used to estimate the reference vehicle speed.

[0108] In some embodiments, the vehicle steering control method further includes: calculating the slip rate of each wheel according to a reference vehicle speed, obtaining a slip limiting compensation torque according to the reference vehicle speed and the slip rate, or obtaining the slip limiting compensation torque according to the slip rate and the rotational inertia of each wheel, and performing torque limiting on each wheel according to the slip limiting compensation torque.

[0109] Specifically, the rotation speed of each wheel and the reference vehicle speed are obtained through the sensor system, and the slip rate of each wheel is calculated based on these data. The slip rate can be the ratio of the vehicle sliding or rotating during driving. These parameters can reflect the movement state of the vehicle when turning or braking, and are important indicators for evaluating the vehicle's handling and stability.

[0110] Further, the slip limiting compensation torque can be calculated according to the reference vehicle speed and the slip rate of the wheel, or according to the slip rate and the rotational inertia of each wheel. The slip limiting compensation torque can be an auxiliary torque applied to the wheel to limit the slip or slip of the vehicle tire. Under certain driving conditions, excessive slip rate of the wheel may cause the vehicle to lose control or have poor handling. The role of the slip limiting compensation torque is to offset the instability caused by the slip of the vehicle during the steering control process, thereby improving the accuracy and stability of the steering control.

[0111] In addition, a two-dimensional lookup table can be established based on the reference vehicle speed and slip rate, and the reference vehicle speed and slip rate are used as input parameters to obtain the corresponding slip limit compensation torque value. Such a two-dimensional lookup table can be established through experiments and calibration to obtain accurate slip limit compensation torque values.

[0112] Further, the slip limiting compensation torque is allocated based on whether the vehicle's drive anti-skid system is activated. The drive anti-skid system can be activated or deactivated based on the vehicle's motion state and the driver's needs. When the drive anti-skid system is activated, the vehicle steering system will allocate the slip limiting compensation torque based on the activation state. Specifically, the slip limiting compensation torque may be increased or decreased to adapt to the current driving situation. For example, when the road surface is slippery or when driving on a curve, activating the drive anti-skid system may require increasing the slip limiting compensation torque to improve the stability of the vehicle.

[0113] By considering the reference speed and slip rate of the vehicle, calculating the slip limit compensation torque based on these parameters, and making reasonable torque distribution according to the activation state of the drive anti-skid system, the vehicle steering system can respond to the vehicle's steering needs more accurately, thereby improving the performance and safety of steering control. Such a vehicle steering control method can enable the vehicle to maintain stable and flexible steering performance in various driving situations.

[0114] In some embodiments, torque is limited to each wheel according to the slip limit compensation torque, including: when the vehicle's drive anti-skid system (ASR / TCS, Acceleration Slip Regulation) is not activated, torque is limited to each wheel according to the slip limit compensation torque. This means that even though the vehicle's drive anti-skid system is in the off state, torque can still be limited to each wheel according to the slip limit compensation torque. For example, in the event of emergency braking, rapid steering, or sudden road changes, the vehicle may slip or spin, which may lead to loss of control. If the drive anti-skid system is not activated or the drive anti-skid system fails, the torque of the wheel can be limited according to the slip limit compensation torque to help stabilize the vehicle and prevent uncontrolled slipping. This method can be considered a safety mechanism that helps to deal with potentially dangerous situations and improve the overall performance of the vehicle.

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

[0116] Specifically, when the driver or the automatic driving system triggers a braking request during vehicle driving, the vehicle steering system can receive the request and prepare to brake the vehicle. The system will distribute the braking demand torque to the front and rear axles of the vehicle in proportion according to the preset ideal braking force distribution curve. Such braking force distribution can optimize the braking performance according to the dynamic characteristics and suspension layout of the vehicle, ensuring the stability and balance of the vehicle during braking. On the basis of distributing the braking torque between the front and rear axles, the braking torque is further evenly distributed between the wheels on each axle to ensure that each wheel is subjected to the corresponding braking force during braking.

[0117] In some embodiments, the braking torque may include motor regenerative braking torque and brake system braking torque. Motor regenerative braking may refer to converting vehicle kinetic energy into electrical energy and storing it during braking, which helps improve energy efficiency and reduce brake wear. Braking system braking torque may refer to the braking torque applied to the wheels through traditional braking components such as brake discs and brake pads to slow down or stop the vehicle.

[0118] Specifically, according to the vehicle's battery SOC (State of Charge) and the capacity of the motor, 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 working in reverse with the motor, thereby extending the battery's service life and improving energy utilization efficiency. If the regenerative braking torque meets the braking requirement torque, it will be directly applied during the braking process. However, if the regenerative braking torque is not sufficient to meet the braking requirement torque, the vehicle steering system can compensate for the shortfall through the braking system braking torque (such as hydraulic braking torque) to ensure the realization of braking performance.

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

[0120] In some embodiments, the drive motor corresponding to the steering wheel in the distributed drive system is controlled according to the target differential torque of the steering wheel to distribute the target differential torque of the steering wheel to the steering wheel, including: on the basis of the total braking torque of the steering shaft remaining unchanged, the target differential torque of the steering wheel is evenly distributed and then vector-superimposed to the two steering wheels. The total braking torque of the steering shaft may 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 obtain the same steering torque during braking, so that the vehicle can stably complete the steering action.

[0121] It should be noted that when performing vector superposition, the total braking torque of the steering axis should be kept unchanged. This means that even when steering control is performed, the braking torque distribution of the non-steering wheels should remain in the original stable state. The purpose of this is to avoid interference with the braking of the non-steering wheels and ensure the stability and balance of the vehicle when turning.

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

[0123] In some embodiments, if the vehicle's yaw control system and the drive anti-skid system are not activated, it means that the vehicle does not need to perform slip control, but only yaw control. In this case, the torque assigned to the steering wheel remains unchanged, that is, the steering wheel continues to execute the previously assigned steering wheel target differential torque. Then, yaw control is achieved by superimposing the yaw control compensation torque vector on the non-steering wheel. Through such vector superposition, the non-steering wheel will be subjected to additional torque, thereby assisting the steering wheel in performing the vehicle's yaw control together.

[0124] In some embodiments, if the yaw control system of the vehicle is not activated and the drive anti-skid system is activated, it means that the vehicle does not need to perform yaw control, but only needs to perform slip control. In this case, the slip limit compensation torque and the steering wheel target differential torque will be vector superimposed. The slip limit compensation torque is the compensation torque previously calculated based on the reference vehicle speed and slip rate, and its function is to control the slip rate of the wheel, avoid tire slippage of the vehicle, 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 the two torques are vector superimposed, they are sent to each drive motor and reduction transmission device, as well as the vehicle's brake fluid supply and control device for execution. The drive motor will make corresponding drive torque adjustments based on this synthesized torque value, and the brake fluid supply and control device will adjust the braking torque distribution based on the synthesized torque value.

[0125] In some embodiments, if the yaw control system and the drive anti-skid system of the vehicle are not activated, it means that the vehicle does not need to perform yaw control or slip control. In this case, the slip limit compensation torque, the yaw control compensation torque and the steering wheel target differential torque are vector-superimposed. The slip limit compensation torque is to control the slip rate of the wheel, the yaw control compensation torque is to achieve the lateral stability of the vehicle, and the steering wheel target differential torque can be used for steering control.

[0126] By vector superposition of these three torques, a composite torque value is obtained. The composite torque value is sent to 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 brake fluid supply and control device. The drive motor will adjust the corresponding drive torque according to this composite torque value, and the brake fluid supply and control device will adjust the braking torque distribution according to 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 evenly distributing the target differential torque of the steering wheels and superimposing them on the two steering wheels.

[0128] Specifically, when the vehicle is in a non-braking condition, it means that the vehicle does not need to brake at present. In this case, 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 of the vehicle is kept unchanged. This is because the braking request is not triggered, the vehicle does not need to slow down or stop, and the driving torque of the front and rear axles remains unchanged, which helps to maintain the vehicle's motion state.

[0129] Furthermore, during the steering control process, the driving torque of the front and rear axles remains unchanged, which means that the steering control will not affect the acceleration or deceleration of the vehicle. Only the driving motor of the steering wheel is controlled by the steering wheel target differential torque, and under the premise of keeping the driving torque of the front and rear axles unchanged, the steering wheel target differential torque is evenly distributed and superimposed on the two steering wheels. This ensures that the two steering wheels obtain the same steering wheel target differential torque during the steering process. Then, this steering wheel target differential torque value will be converted into the actual drive motor output torque and superimposed on the steering wheel drive motor to achieve steering control.

[0130] In some embodiments, when the vehicle is in a non-braking condition, if the yaw control system and the drive anti-skid system of the vehicle are both activated, the vehicle steering system needs to simultaneously perform yaw stability control and slip control of the vehicle. The yaw control system is used to adjust the lateral movement of the vehicle to maintain a stable yaw angular velocity. The drive anti-skid system is used to monitor the slip of each wheel to ensure that the wheel does not slip excessively or slip during braking or acceleration. In this case, the steering wheel target differential torque assigned to each wheel is directly transmitted to the left front drive motor, the left rear drive motor, the right rear drive motor and the right front drive motor to perform corresponding steering control and slip control.

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

[0132] Specifically, since the drive anti-skid system is not activated, the vehicle does not need to adjust the braking torque of each wheel to control the slip, so the distributed torque of the steering wheel remains unchanged. However, the yaw control function of the vehicle is activated. In order to achieve yaw stability control, the yaw control compensation torque will be superimposed on the non-steering wheel. The purpose of this is to control the yaw movement of the vehicle by adjusting the driving torque of the non-steering wheel, thereby enhancing the lateral stability of the vehicle.

[0133] In some embodiments, if the vehicle's yaw control system is not activated but the drive anti-skid 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, the left rear drive motor, the right rear drive motor and the right front drive motor for execution.

[0134] Specifically, when the yaw control system is not activated and the drive anti-skid system is activated, the slip limit compensation torque and the steering wheel target differential torque are vector-superimposed, and the two torques are vector-superimposed and transmitted to the left front drive motor, the left rear drive motor, the right rear drive motor and the right front drive motor.

[0135] In some embodiments, if the yaw control system and the driving anti-skid system of the vehicle are not activated, the slip limit compensation torque, the yaw control compensation torque and the steering wheel target differential torque are vector-superimposed. After vector-superimposing these three torques, a synthetic torque value is obtained, and the synthetic torque value is transmitted to the left front drive motor, the left rear drive motor, the right rear drive motor and the right front drive motor. By executing these drive motors, the control of the wheels is realized, thereby realizing steering control.

[0136] In general, on the one hand, through the control of the steering wheel target differential torque, the vehicle steering system can achieve tracking and closed-loop control of the steering wheel angle. This means that the system can calculate the steering wheel angle error based on the driver's steering wheel input (steering wheel target angle) and the vehicle's actual steering wheel angle (actual steering wheel angle). Then, based on this error and the reference vehicle speed, the steering wheel target differential torque, that is, the torque required by the steering wheel, is calculated to achieve vehicle steering control. Through this closed-loop control, the vehicle steering system can continuously adjust the steering wheel torque to make the actual steering wheel angle as close to the expected target angle as possible, 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 the yaw stability control of the vehicle. When the vehicle yaws, the yaw control compensation torque can be calculated and distributed to the non-steering wheels according to the activation state of the system. By evenly distributing the yaw control compensation torque to the non-steering wheels, the vehicle steering system can suppress the vehicle's yaw motion and maintain the stability of the vehicle, so that it remains stable when turning or driving at high speeds.

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

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

[0140] In some embodiments, when the vehicle is in a braking condition, the vehicle steering control method also includes reducing the absolute value of the negative torque of the wheel by reducing the absolute value of the hydraulic braking torque. If the negative torque reduction requirement 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 wheel can be reduced, thereby reducing the negative torque of the wheel. Such an adjustment strategy is suitable for the case where the slip control function is activated, where the slip limit compensation torque may cause the negative torque of the wheel to increase, and by reducing the hydraulic braking torque, the torque distribution of the wheel can be balanced. Then, in order to maintain the overall braking effect, the vehicle steering system can reduce the absolute value of the regenerative braking torque accordingly. In this way, while the hydraulic braking torque is reduced, the reduction in the regenerative braking torque can make up for part of the braking demand and ensure that the negative torque reduction demand of the wheel is met. If the above two methods are still not sufficient to meet the target negative torque requirements, the vehicle steering control method can be further adjusted in a driving manner to achieve a reduction in negative torque.

[0142] In addition, the vehicle steering control method also includes increasing the absolute value of the negative torque of the wheel by increasing the absolute value of the regenerative braking torque, and the regenerative braking torque can be a braking torque generated when the drive motor of the electric vehicle converts kinetic energy into electrical energy through an inverter during braking. By increasing the absolute value of the regenerative braking torque, the braking torque of the wheel can be increased, thereby increasing the negative torque of the wheel. If the increase in the regenerative braking torque is limited by the motor capacity or the battery power, it can be adjusted by increasing the absolute value of the hydraulic brake to achieve the target negative torque requirement.

[0143] Through the above two methods, the vehicle steering control method can flexibly adjust the torque of each wheel when braking intervention to achieve braking energy recovery and control. Through a reasonable torque superposition method, this method can maximize the use of braking energy, and at the same time make adjustments according to the negative torque of the wheel to ensure the stability and efficiency of the braking process. Such a vehicle steering control method can optimize the performance and driving experience of the vehicle during braking and improve the energy efficiency of the vehicle.

[0144] Figure 3 is a working flow chart of a vehicle steering control method according to an embodiment of the present invention, such as Figure 3 As shown, the working process of the vehicle steering control method according to the embodiment of the present invention at least includes steps S10-S34, which are specifically as follows.

[0145] S10, receiving a steering wheel target angle request from the automatic driving controller.

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

[0147] S12, calculating the steering wheel target differential torque according to the steering wheel angle error and the reference vehicle speed.

[0148] S13, determine whether a braking request is received, if so, proceed to step S14, if not, proceed to step S23.

[0149] S14, distributing regenerative braking and hydraulic braking.

[0150] S15, keeping the non-steering wheel braking torque distribution unchanged; and based on the unchanged total braking torque of the steering shaft, evenly distributing the target differential torque and then superimposing it on the two steering wheels.

[0151] S16, determine whether the yaw control system is activated, if so, proceed to step S17, if not, proceed to step S20.

[0152] S17, determine whether the drive anti-skid system is activated, if so, proceed to step S18, if not, proceed to step S19.

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

[0154] S19, vector superposition of the steering wheel target differential torque and the slip limit compensation torque.

[0155] S20, determine whether the drive anti-skid system is activated, if so, proceed to step S21, if not, proceed to step S

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

[0157] S22, superimposing the steering wheel target differential torque, the yaw control compensation torque and the slip limit compensation torque vector.

[0158] S23, keeping the driving torque of the front and rear axles unchanged, the target differential torque is evenly distributed and then superimposed on the two steering wheels.

[0159] S24, determine whether the yaw control system is activated, if so, proceed to step S25, if not, proceed to step S28.

[0160] S25, determining whether the slip control function is activated, if so, proceeding to step S26, if not, proceeding to step S27.

[0161] S26, transmitting the execution torque of each target motor to each motor controller.

[0162] S27, vector superposition of the steering wheel target differential torque and the slip limit compensation torque.

[0163] S28, determine whether the slip control function is activated, if so, proceed to step S29, if not, proceed to step S30.

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

[0165] S30: vectorally superimpose the steering wheel target differential torque, the yaw control compensation torque and the slip limit compensation torque.

[0166] S31, estimate the reference vehicle speed using a Kalman filter algorithm based on the wheel speed sensor information and the IMU information.

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

[0168] S33, calculating the yaw rate deviation, and calculating the required yaw control compensation torque according to the yaw rate deviation, and then evenly distributing the torque to the two wheels of the non-steering axle.

[0169] S34, calculating the slip or slip rate of each wheel based on the reference vehicle speed, and obtaining a slip limiting compensation torque.

[0170] Reference below Figure 4 A vehicle according to an embodiment of the present invention is described.

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

[0172] The vehicle 100 according to the embodiment of the present invention, by adopting the vehicle steering control method described in the above embodiment, realizes the steering control function based on the existing distributed drive system without adding additional hardware, and multiple drive motors control different steering wheels. This distributed configuration enables each steering wheel to be independently controlled, thereby realizing redundancy of steering control, and can solve the problem of inaccurate steering that may be caused by a vehicle steering system failure. The manufacturing cost is low, the vehicle structure and control design are simple, space is saved, and it is conducive to actual vehicle layout.

[0173] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0174] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention 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, and the vehicle steering control method includes: Determine the steering wheel angle error according to the steering wheel target angle and the actual steering wheel angle; Determining a steering wheel target differential torque according to the steering wheel angle error; The drive motor corresponding to the steering wheel in the distributed drive system is controlled according to the steering wheel target differential torque to distribute the steering wheel target differential torque to the steering wheel.

2. The vehicle steering control method according to claim 1, characterized in that: The vehicle steering control method further includes: Determine the yaw control compensation torque; The yaw control compensation torque is distributed to the non-steering wheels.

3. The vehicle steering control method according to claim 2, characterized in that: The determining of the yaw control compensation torque comprises: Obtaining an ideal yaw rate according to the target steering wheel angle and a reference vehicle speed of the vehicle; Obtaining a yaw rate deviation according to the ideal yaw rate and the actual yaw rate; A yaw control compensation torque is obtained according to the yaw angular velocity deviation.

4. The vehicle steering control method according to claim 2, characterized in that: Distributing the yaw control compensation torque to the non-steering wheels includes: When a yaw control system of the vehicle is not activated, the yaw control compensation torque is distributed to the non-steering wheels.

5. The vehicle steering control method according to claim 1, characterized in that: The vehicle steering control method further includes: Obtaining a reference speed of the vehicle; The steering wheel target differential torque is determined according to the steering wheel angle error and a reference vehicle speed of the vehicle.

6. The vehicle steering control method according to claim 5, characterized in that: Determining the steering wheel target differential torque according to the steering wheel angle error and the reference vehicle speed of the vehicle includes: querying a mapping relationship between the steering wheel angle error and the reference vehicle speed to obtain the steering wheel target differential torque, wherein the mapping relationship is a corresponding relationship between the steering wheel angle error, the reference vehicle speed and the steering wheel target differential torque; Alternatively, the steering wheel target differential torque is obtained by calculation based on the steering wheel angle error, the reference vehicle speed and steering component parameters of the vehicle.

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

8. The vehicle steering control method according to claim 7, characterized in that: The method of controlling two drive motors corresponding to two steering wheels in the distributed drive system according to the steering wheel target differential torque 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, the torque of the first wheel is maintained unchanged; If the vector-superimposed torque of the first wheel exceeds the first execution limit, the first execution limit is allocated to the first wheel, and the torque difference between the vector-superimposed torque of the first wheel and the first execution limit is allocated to the second wheel of the two coaxial wheels; If the torque difference is distributed to the second wheel and the total torque distributed to the second wheel does not exceed the second execution limit of the second wheel, the drive motors corresponding to the two coaxial wheels are controlled according to the distributed torque; If the torque difference is distributed to the second wheel and 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.

9. The vehicle steering control method according to claim 8, 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 according to the rotation speed information of the left front drive motor, the left rear drive motor, the right rear drive motor and the right front drive motor and the inertia information of the vehicle.

10. The vehicle steering control method according to claim 1, characterized in that: The vehicle steering control method further includes: Calculating the slip rate of each wheel according to the reference vehicle speed; Obtaining a slip limiting compensation torque according to the reference vehicle speed and the slip ratio, or obtaining the slip limiting compensation torque according to the slip ratio and the rotational inertia of each wheel; Torque limitation is performed on each wheel according to the slip limiting compensation torque.

11. The vehicle steering control method according to claim 10, characterized in that: The method of limiting the torque of each wheel according to the slip limiting compensation torque includes: When the driving anti-skid system of the vehicle is not activated, torque limitation is performed on each wheel according to the slip limiting compensation torque.

12. The vehicle steering control method according to any one of claims 1 to 11, characterized in that: The vehicle steering control method further includes: When the vehicle is in a braking condition, distributing the braking demand torque to the front and rear axles of the vehicle; The braking torque allocated to the front and rear axles is evenly distributed to the corresponding wheels, wherein the braking torque includes the motor regenerative braking torque and the braking system braking torque.

13. The vehicle steering control method according to claim 12, characterized in that: The controlling the driving motor corresponding to the steering wheel in the distributed drive system according to the steering wheel target differential torque to distribute the steering wheel target differential torque to the steering wheel includes: On the basis of keeping the total braking torque of the steering shaft unchanged, the target differential torque of the steering wheels is evenly distributed and then vector-superimposed on the two steering wheels.

14. The vehicle steering control method according to claim 13, 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 negative torque reduction requirement of the wheel cannot be met, the shortfall is achieved by reducing the absolute value of the motor regenerative braking torque. Alternatively, the absolute value of the negative torque of the wheel is increased by increasing the absolute value of the motor regenerative braking torque, and if the motor capacity or battery power limit is received, the absolute value of the hydraulic brake is increased.

15. A vehicle steering system, characterized in that: include: Distributed drive system, used to drive the individual wheels of the vehicle; A sensor system for collecting steering sensor information; A controller, wherein the controller is communicatively connected with the distributed drive system and the sensor system, and is used to execute the vehicle steering control method according to any one of claims 1-14.

16. The vehicle steering system according to claim 15, 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.

17. The vehicle steering system according to claim 15, characterized in that: The controller comprises: An automatic driving controller, used to issue steering control instructions in the automatic driving mode; A steering drive and control device, in communication with the automatic driving controller, for executing the steering control instruction; A vehicle controller is communicatively connected with the automatic driving controller and is used for executing the steering control instruction when the steering drive and control device is abnormal.

18. The vehicle steering system according to claim 17, characterized in that: The automatic driving controller includes a first controller and a second controller, wherein one of the first controller and the second controller is a master controller and the other is a slave controller, and when the master controller is abnormal, the slave controller obtains the master controller authority.

19. The vehicle steering system according to any one of claims 15 to 18, characterized in that: The vehicle steering system also includes an Ackerman steering system and a steer-by-wire system.

20. The vehicle steering system according to claim 19, characterized in that: The Ackerman steering system comprises: Steering wheel, steering column, universal joint, worm rack steering gear, left front steering tie rod, right front steering tie rod and the steering drive and control device; The steering wheel, the steering column, the universal joint, and the worm rack steering gear are connected in sequence to transmit the torque and the angle of rotation applied on the steering wheel to the worm rack steering gear, drive the rack of the worm rack steering gear 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.

21. The vehicle steering system according to claim 19, characterized in that: The steer-by-wire system comprises: 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; Wherein, 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 with 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.

22. A vehicle, characterized in that: A vehicle steering system comprising any one of claims 15-21.

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