CN119037545B

CN119037545B - Vehicle steering control method, device and storage medium

Info

Publication number: CN119037545B
Application number: CN202411523013.7A
Authority: CN
Inventors: 凌和平; 姜龙; 丘国维; 李桂忠; 石明川
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2024-10-29
Filing date: 2024-10-29
Publication date: 2025-02-11
Anticipated expiration: 2044-10-29
Also published as: CN119037545A

Abstract

The invention discloses a vehicle steering control method, a vehicle steering control device and a storage medium, which relate to the technical field of vehicle steering and can reduce the turning radius of a vehicle. The method comprises the steps of responding to a vehicle steering instruction, controlling a first motor corresponding to a first rear wheel of a vehicle to output first torque and controlling a second motor corresponding to a second rear wheel to output second torque, wherein the first rear wheel is a rear wheel positioned on a steering side in two rear wheels of the vehicle, and the second rear wheel is a rear wheel positioned on a non-steering side in the vehicle.

Description

Vehicle steering control method, device and storage medium

Technical Field

The present invention relates to the field of vehicle steering technologies, and in particular, to a vehicle steering control method, device and storage medium.

Background

In the related art, steering performance is one of the basic characteristics of a vehicle, and a key index for evaluating steering performance is the turning radius of the vehicle. At present, in the steering process of a vehicle, two front wheels and rear wheels of the vehicle rotate towards the turning direction, and the problem of overlarge turning radius of the vehicle is easily caused.

Disclosure of Invention

The embodiment of the application provides a vehicle steering control method, a vehicle steering control device and a storage medium, which can reduce the turning radius of a vehicle. It should be understood that the vehicle steering control method provided by the embodiment of the application can be applied to a distributed three-motor vehicle, and can also be applied to a four-wheel independent drive or rear-wheel independent drive vehicle so as to realize the in-situ steering function.

In order to achieve the above purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a vehicle steering control method comprising controlling a first motor corresponding to a first rear wheel of a vehicle to output a first torque and a second motor corresponding to a second rear wheel to output a second torque in response to a vehicle steering command.

The first torque is in reverse direction, the second torque is in forward direction, the first rear wheel is the rear wheel positioned on the steering side in the vehicle, and the second rear wheel is the rear wheel positioned on the non-steering side in the vehicle.

In some embodiments, controlling a first motor corresponding to a first rear wheel of a vehicle to output a first torque and a second motor corresponding to a second rear wheel of the vehicle to output a second torque in response to a vehicle steering command includes controlling the first motor corresponding to the first rear wheel to output the first torque to effect rotation of the first rear wheel and controlling the second motor corresponding to the second rear wheel to output the second torque to effect forward rotation of the second rear wheel in response to the vehicle steering command;

Wherein the rotation of the first rear wheel includes forward rotation or reverse rotation.

In some embodiments, the first torque is determined by obtaining a first actual slip rate and a first target slip rate of the first rear wheel, determining a first slip rate difference and a first difference change rate based on the first actual slip rate and the first target slip rate, the first slip rate difference being a difference between the first target slip rate and the first actual slip rate, the first difference change rate being a change rate of the first slip rate difference over a unit time, and determining the first torque based on the first slip rate difference and the first difference change rate.

In some embodiments, the first actual slip rate is determined based on obtaining a rear axle center point speed of the vehicle, determining a target wheel speed of the first rear wheel based on the rear axle center point speed and a yaw rate of the vehicle, and determining the actual slip rate of the first rear wheel based on the target wheel speed of the first rear wheel and the actual wheel speed of the first rear wheel.

In some embodiments, the first target slip rate is determined based on a steering mode of the vehicle and a pre-calibrated slip rate map for indicating a target slip rate for each of a plurality of candidate steering modes of the vehicle, the steering mode being one of the plurality of candidate steering modes.

In some embodiments, determining the first torque based on the first slip ratio difference and the first difference rate of change includes determining a first integral gain coefficient and a first proportional gain coefficient based on the first slip ratio difference and the first difference rate of change, and performing PI operation on the first slip ratio difference based on the first integral gain coefficient and the first proportional gain coefficient to obtain the first torque.

In some embodiments, the second torque is determined by obtaining a second target slip rate and a second actual slip rate of the second rear wheel, determining a second slip rate difference and a second difference change rate based on the second target slip rate and the second actual slip rate, the second slip rate difference being a difference between the second target slip rate and the second actual slip rate, the second difference change rate being a change rate of the second slip rate difference over a unit time, and determining the second torque based on the second slip rate difference and the second difference change rate.

In some embodiments, the second actual slip ratio is determined by obtaining a rear axle center point speed of the vehicle, determining a target wheel speed of the second rear wheel based on the rear axle center point speed and a yaw rate of the vehicle, and determining the second actual slip ratio based on the target wheel speed of the second rear wheel and the actual wheel speed of the second rear wheel.

In some embodiments, the second target slip rate is determined based on a steering mode of the vehicle and a pre-calibrated slip rate map for indicating a target slip rate for each of a plurality of candidate steering modes of the vehicle, the steering mode being one of the plurality of candidate steering modes.

In some embodiments, determining the second torque based on the second slip ratio difference and the second difference rate of change includes determining a second integral gain coefficient and a second proportional gain coefficient based on the second slip ratio difference and the second difference rate of change, and PI operating the second slip ratio difference based on the second integral gain coefficient and the second proportional gain coefficient to obtain the second torque.

In some embodiments, the plurality of candidate steering modes includes a rotational turn-around mode and a non-rotational turn-around mode, the non-rotational turn-around mode including a normal mode and a racetrack mode, the normal mode corresponding to a target slip rate that is less than a target slip rate of the racetrack mode.

In some embodiments, the method further includes controlling a first front wheel brake of the vehicle and a second front wheel forward rotation in response to a vehicle steering command, where the first front wheel is a front wheel on a steering side of two front wheels of the vehicle and the second front wheel is another front wheel of the two front wheels of the vehicle other than the first front wheel, when the vehicle is in the spin-around mode.

In some embodiments, controlling the first front wheel brake and the second front wheel forward rotation of the vehicle in response to the vehicle steering command with the vehicle in the spin-tie mode includes controlling a braking system of the first front wheel to apply a braking force to the first front wheel to effect the first front wheel brake and controlling a motor of the second front wheel to output a third torque to effect the forward rotation of the second front wheel in response to the vehicle steering command.

In view of this, in the spin-turn mode, the first front wheel brake, the second front wheel forward rotation, the first rear wheel reverse rotation, and the second rear wheel forward rotation are fused, so that the vehicle can achieve in-situ turn with a very small turning radius, and the vehicle can generate a yaw moment while making the user experience a "tail flick" effect.

In some embodiments, the method further comprises controlling, with the vehicle in a non-rotating turn-around mode, forward rotation of both the first front wheel and the second front wheel of the vehicle in response to a vehicle steering command.

In some embodiments, controlling the first front wheel and the second front wheel of the vehicle to both rotate in a forward direction in response to a vehicle steering command when the vehicle is in a non-rotational turn-around mode includes controlling the motor of the first front wheel and the motor of the second front wheel to output a third torque in response to the vehicle steering command to achieve both forward rotation of the first front wheel and the second front wheel.

In some embodiments, the method further includes determining a third torque based on a first mapping relationship corresponding to an accelerator pedal depth of the vehicle, a motor speed, and a steering mode of the vehicle. The first mapping relation is a mapping relation among the depth of an accelerator pedal, the rotating speed of a motor and the third torque, and different steering modes correspond to different first mapping relations.

In some embodiments, the method further includes displaying a steering mode setting interface including a plurality of candidate steering modes of the vehicle, and determining a steering mode of the vehicle from the plurality of candidate steering modes in response to a setting operation by a user on the steering mode setting interface.

In some embodiments, the method further includes exiting a vehicle-activated steering mode in response to a running operation of the vehicle and adjusting a current torque of the vehicle at a torque adjustment rate, the torque adjustment rate being determined based on the current torque and the desired torque.

In some embodiments, the operation includes at least one of a vehicle speed greater than a preset threshold, a brake pedal depth greater than a depth threshold, a steering wheel speed greater than a speed threshold, a turn-off mode operation, a rear wheel slip greater than a slip threshold, a rear wheel slip change greater than a change threshold, a gear change, and an electronic hand brake activation.

In a second aspect, the embodiment of the application provides a vehicle steering control device, which comprises a processing unit and a processing unit, wherein the processing unit is used for responding to a vehicle steering instruction and controlling a first motor corresponding to a first rear wheel of a vehicle to output a first torque and a second motor corresponding to a second rear wheel to output a second torque.

In a third aspect, the present application provides a vehicle comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor executing the program to implement the vehicle steering control method described above.

In a fourth aspect, the present application provides a computer-readable storage medium having instructions stored therein that, when executed on a terminal, cause the terminal to perform the vehicle steering control method described above.

In a fifth aspect, the present application provides a computer program product comprising instructions which, when executed by a computer, cause the computer to perform the vehicle steering control method described above.

In a sixth aspect, the present application provides a chip comprising a processor and a communications interface, the communications interface and the processor being coupled, the processor being for running a computer program or instructions to implement the vehicle steering control method described above.

Specifically, the chip provided in the embodiment of the application further includes a memory, which is used for storing a computer program or instructions.

Based on the above technical solution, according to the vehicle steering control method provided by the embodiment of the present application, the steering control system controls the first torque, which is output by the first motor and is output by the second motor, to be in the opposite direction, and the second torque, which is output by the second motor and is output by the second motor, to be in the forward direction, corresponding to the first rear wheel of the vehicle, in response to the vehicle steering command, so that the rotational speed of the second rear wheel is higher than the rotational speed of the first rear wheel when the vehicle steers, and therefore, a wheel speed difference is generated between the two rear wheels, and the wheel speed difference can enable the vehicle to steer more flexibly, thereby reducing the turning radius.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic view of an ackerman corner of a vehicle according to an embodiment of the present application;

FIG. 2 is a schematic diagram of a vehicle according to an embodiment of the present application;

FIG. 3 is a schematic diagram of a steering control system according to an embodiment of the present application;

FIG. 4 is a flow chart of a vehicle steering control method according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a non-rotational turn-around mode according to an embodiment of the present application;

FIG. 6 is a schematic diagram of a rotation turn-around mode according to an embodiment of the present application;

FIG. 7 is a schematic diagram of longitudinal force and lateral force coefficients at different slip rates according to an embodiment of the present application;

fig. 8 is a schematic diagram of a fuzzy PI control algorithm according to an embodiment of the present application;

FIG. 9 is a flow chart of another vehicle steering control method provided by an embodiment of the present application;

FIG. 10 is a schematic illustration of a steering mode activation provided by an embodiment of the present application;

FIG. 11 is a schematic diagram of a steering mode exit according to an embodiment of the present application;

Fig. 12 is a schematic view of a vehicle steering control device according to an embodiment of the present application.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or relative positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Unless otherwise specified, the above description of the azimuth may be flexibly set in the course of practical application in the case where the relative positional relationship shown in the drawings is satisfied.

The terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.

In the description of the present invention, it should be noted that, unless explicitly stated and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected. Can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In embodiments of the present invention, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, article or apparatus that comprises the element.

In embodiments of the invention, words such as "exemplary" or "such as" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "e.g." in an embodiment of the present invention is not to be taken as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.

In the description of the present specification, a particular feature, structure, material, or characteristic may be combined in any suitable manner in one or more embodiments or examples.

In the related art, the steering performance of a vehicle is one of its basic characteristics, and a key index for evaluating the steering performance is the turning radius of the vehicle. The minimum turning radius refers to the radius of a track circle drawn by the center of the outer steering wheel on the supporting surface when the steering wheel turns to the extreme limit and the vehicle turns at the lowest steady speed.

For conventional vehicles, the minimum turning radius is mainly determined by the wheelbase of the wheels and the maximum front wheel turning angle, and the minimum turning radius is also determined by the design and shaping of the general vehicle. The minimum turning radius also reflects to a large extent the ability of the vehicle to traverse narrow curved areas or to bypass obstacles that cannot pass directly.

As shown in fig. 1, in the steering process of the existing vehicle, both front wheels and rear wheels of the vehicle rotate in the turning direction, so that the minimum turning radius of the vehicle is easily affected, and the problem of overlarge turning radius R is caused.

Where V _L1 is the speed of the front wheel on the turning side, V _R1 is the speed of the front wheel on the non-turning side, V _L2 is the speed of the rear wheel on the turning side, and V _R2 is the speed of the rear wheel on the non-turning side.

The following describes embodiments of the present application in detail with reference to the drawings.

As shown in fig. 2, a vehicle 100 according to an embodiment of the present application may include a chassis 110, a body 120, and wheels 130. It is understood that the vehicle 100 may be a fuel-powered vehicle, an electric vehicle, a hybrid electric vehicle, a gas vehicle, a methanol vehicle, a solar vehicle, etc.

For example, the vehicle 100 may be a passenger car such as a car, a sport utility vehicle (sport utility vehicle, SUV), a utility vehicle (MPV), or a passenger car, a truck, a semi-trailer, or the like. The present application is not particularly limited thereto.

It is to be understood that the above components are merely examples of a portion of the components of the vehicle 100 and are not limiting of the specific structure of the vehicle 100.

Optionally, the vehicle 100 may further include a steering control system 140 for controlling the vehicle. The steering control system 140 may implement steering control of the vehicle 100.

Fig. 3 is a schematic diagram of a steering control system according to an embodiment of the present application. The steering control system may include a steering system 210, a brake control system 220, a vehicle controller 230, a front wheel motor 240, and a rear wheel motor. The steering system 210, the brake control system 220, the front wheel motor 240 and the rear wheel motor are connected with the whole vehicle controller 230 through a controller area network (controller area network, CAN).

In some embodiments, the vehicle controller 230 sends a vehicle steering command to the steering system 210, and controls the corresponding first motor of the vehicle to output a first torque and the corresponding second motor of the second rear wheel to output a second torque through the steering system 210.

For example, the vehicle controller 230 may receive a steering intention signal of a driver and transmit a vehicle steering command to the steering system 210, control the rear wheel motor to output a first torque to implement the rotation of the first rear wheel and control the rear wheel motor to output a second torque to implement the reverse rotation of the second rear wheel through the steering system 210.

Optionally, the rear wheel motors include a first motor 250 corresponding to the first rear wheel and a second motor 260 corresponding to the second rear wheel.

As yet another example, the overall vehicle controller 230 may receive a steering intention signal of the driver, and when an entry condition of a steering function is satisfied, control the first motor 250 corresponding to the first rear wheel to output a first torque to implement the rotation of the first rear wheel through the steering system 210, and control the second motor 260 corresponding to the second rear wheel to output a second torque to implement the forward rotation of the second rear wheel.

Similarly, the front wheel motor 240 may output torque to effect front wheel rotation.

In some embodiments, the overall vehicle controller 230 may control the brake control system 220 to apply braking forces to any one or more wheels of the vehicle in response to vehicle steering commands.

Optionally, the steering control system 140 further includes a front axle differential 270, the front axle differential 270 being disposed on the front axle of the vehicle and mechanically coupled to the front wheel motor 240.

The front axle differential 270 is used for adjusting the rotation speed difference of the inner and outer driving wheels when the vehicle turns, so as to ensure that the rotation speed of the outer driving wheel is higher than that of the inner driving wheel, thereby improving the turning performance of the vehicle.

Optionally, the steering control system 140 further includes a wheel speed sensor 280, wherein the wheel speed sensor 280 is connected with the vehicle controller 230 through a CAN network. The wheel speed sensor 280 is used for measuring the rotational speed of wheels of the vehicle during running, i.e., wheel speed information, and transmitting the wheel speed information of four wheels of the vehicle to the overall vehicle controller 230.

Wherein the wheels of the vehicle are in one-to-one correspondence with the wheel speed sensors 280.

Optionally, the steering control system 140 further includes a yaw rate sensor 290, the yaw rate sensor 290 being coupled to the overall vehicle controller 230 via a CAN network. The yaw rate sensor 290 is used to monitor the motion track of the vehicle about its vertical axis (i.e., the vertical axis) to determine whether the vehicle is slipping or out of control, and to send the yaw information of the vehicle to the vehicle controller 230.

It should be noted that, the control system described in the embodiment of the present application is for more clearly describing the technical solution of the embodiment of the present application, and does not constitute a limitation on the technical solution provided in the embodiment of the present application, and those skilled in the art can know that, with the evolution of the electronic device and the appearance of other electronic devices, the technical solution provided in the embodiment of the present application is applicable to similar technical problems. The methods in the following embodiments may be implemented in a control system having the above-described hardware configuration.

The methods in the following embodiments may be implemented in a control system having the above-described hardware configuration.

The following describes in detail a vehicle steering control method according to an embodiment of the present application with reference to the accompanying drawings.

The vehicle steering control method provided by the embodiment of the application can be applied to steering control of a vehicle. As shown in fig. 4, the vehicle steering control method may include steps 301 to 302. Step 301 may also be referred to as a "acquire vehicle steering command" flow, and step 302 may be referred to as a "steer control for vehicle" flow. Steps 301 to 302 are described in detail below.

Step 301, a vehicle steering instruction is acquired.

In some embodiments, the vehicle steering command includes at least a first rear wheel steering command and a second rear wheel steering command. The first rear wheels are rear wheels positioned on the steering side in the vehicle, and the second rear wheels are rear wheels positioned on the non-steering side in the vehicle. The first rear wheel may be referred to as an inboard rear wheel and the second rear wheel may be referred to as an outboard rear wheel, without limitation.

In some embodiments, the vehicle steering commands may further include first and second front wheel forward rotation commands, or first and second front wheel braking commands. Wherein the first front wheel is a front wheel located on a steering side of two front wheels of the vehicle, and the second front wheel is another front wheel other than the first front wheel of the two front wheels of the vehicle.

Step 302, responding to a vehicle steering command, and controlling a first motor corresponding to a first rear wheel of the vehicle to output a first torque and a second motor corresponding to a second rear wheel to output a second torque.

The torque direction of the first torque is reverse, and the torque direction of the second torque is forward.

As one possible implementation manner, in response to a vehicle steering instruction, a first motor corresponding to a first rear wheel is controlled to output a first torque to achieve rotation of the first rear wheel, and a second motor corresponding to a second rear wheel is controlled to output a second torque to achieve forward rotation of the second rear wheel. Wherein the rotation of the first rear wheel includes forward rotation or reverse rotation.

It should be appreciated that in addition to the steering force and steering direction of the front wheels, the rear wheel steering system is capable of steering the rear wheels as well, helping to reduce the rotational speed of the inner rear wheels by controlling the first torque in which the motor output torque direction of the inner rear wheels is reversed, while controlling the second torque in which the motor output torque direction of the outer rear wheels is forward helps to increase the rotational speed of the outer wheels, imparting a yaw moment to the vehicle in the same direction as the steering direction, enabling the wheels to make turns with a smaller turning radius.

Further, since the reverse rotation of the inner rear wheels reduces the rotation speed of the inner wheels, the vehicle is more likely to tilt inward, and the forward rotation of the outer rear wheels increases the rotation speed and friction of the outer wheels, a yaw moment in the same direction as the steering direction is applied to the vehicle. The two are combined, so that the vehicle can more compactly run around the central point when turning, and the turning radius of the vehicle is reduced.

The vehicle provided by the embodiment of the application has a plurality of different candidate steering modes, such as a rotary turning mode and a non-rotary turning mode. The non-rotating turning mode comprises at least one of a normal mode and a racing track mode. The normal mode can be used as a normal starting mode of the vehicle, and the normal mode can reduce tire wear and increase the smoothness of running of the vehicle. The racing track mode can enable the vehicle to rapidly pass through the U-shaped sharp bend, and the vehicle over-bending time is reduced by adjusting the torque output of the motor.

In some embodiments, in response to a vehicle steering command, both the first front wheel and the second front wheel of the vehicle are controlled to rotate in a forward direction while in the non-rotational turn mode.

As an example, in a case where the vehicle is in the normal mode or the racetrack mode, as shown in fig. 5, the steering control system controls the motors of the first front wheel and the second front wheel to output a third torque in response to the first front wheel and the second front wheel forward rotation command to achieve forward rotation of both the first front wheel and the second front wheel, and controls the first motor corresponding to the first rear wheel to output the first torque to achieve forward rotation of the first rear wheel and controls the second motor corresponding to the second rear wheel to output the second torque to achieve forward rotation of the second rear wheel in response to the first rear wheel forward rotation command and the second rear wheel forward rotation command. The rotation of the first rear wheel may be either forward rotation or reverse rotation, which is not limited in the embodiment of the present application.

It can be appreciated that the steering control system controls the first motor of the first rear wheel of the vehicle to output torque in the reverse direction in response to the vehicle steering command to achieve the first rear wheel rotation and controls the second motor of the second rear wheel to output torque in the forward direction to achieve the second rear wheel forward rotation, so that the rotational speed of the second rear wheel is higher than the rotational speed of the first rear wheel when the vehicle is steered, thereby causing a wheel speed difference between the two rear wheels, which can enable the vehicle to steer more flexibly, thereby reducing the turning radius.

It will be appreciated that the torques output by the normal mode and racetrack mode motors are not the same and thus different objectives can be achieved. In addition, the target slip ratio corresponding to the normal mode is smaller than that of the track mode.

In some embodiments, the first front wheel brake and the second front wheel of the vehicle are controlled to rotate in a forward direction in response to a vehicle steering command with the vehicle in a spin-turn mode.

Illustratively, as shown in fig. 6, the braking system of the first front wheel is controlled to apply a braking force to the first front wheel to brake the first front wheel in response to a first front wheel braking command, and to output a third torque to rotate the second front wheel in forward direction in response to a second front wheel forward direction rotation command, and to output a first torque to effect rotation of the first rear wheel in response to a first rear wheel rotation command and a second rear wheel forward direction rotation command, and to output a second torque to effect forward direction rotation of the second rear wheel in response to a first rear wheel rotation command and a second rear wheel forward direction rotation command.

In the turning mode, if the rotation of the first rear wheel is reverse rotation, the turning radius of the vehicle can be further reduced.

The braking force applied to the first front wheels is proportional to the depth of an accelerator pedal of the vehicle, and the torque of the front wheel motor can be provided to the second front wheels as much as possible by applying the braking force to the first front wheels, so that the yaw gain of the vehicle during steering is increased. In addition, after the braking force of the first front wheel reaches the braking force threshold value, the first front wheel can be controlled to roll at a certain slip rate, so that the situation that the wheels are worn is avoided.

It will be appreciated that applying a braking force to the front wheels on the steering side causes the deceleration of the vehicle when cornering to create a force towards the inside of the curve which may assist the vehicle to travel more closely along the turn around curve. That is, when braking force is applied to the front wheel on the steering side, the vehicle may be more prone to make a turn around the front wheel (the static steering center point) due to a large steering angle and a reduced speed of the front wheel, thereby reducing the turning radius. And the first rear wheel is matched with the first rear wheel to rotate reversely, and the second rear wheel is matched with the first rear wheel to rotate positively, so that the turning radius of the vehicle is further reduced.

The above has outlined in detail how the vehicle steering control is performed, and the following describes in detail how the first torque of the first rear wheel, the second torque of the second rear wheel, and the third torque of the second front wheel are calculated.

In one possible implementation, the first torque of the first rear wheel may be determined by obtaining a first actual slip rate and a first target slip rate of the first rear wheel, and determining a first slip rate difference and a first difference change rate based on the first actual slip rate and the first target slip rate, and further determining the first torque based on the first slip rate difference and the first difference change rate.

The first slip rate difference value is a difference value between the first target slip rate and the first actual slip rate, and the first difference value change rate is a change rate of the first slip rate difference value in unit time. Slip ratio refers to the proportion of the slip component of the wheel in the longitudinal movement of the wheel.

It should be noted that the first target slip rate may be determined based on a steering mode of the vehicle and a pre-calibrated slip rate map for indicating target slip rates corresponding to each of a plurality of candidate steering modes of the vehicle. That is, the first target slip ratio of the corresponding first rear wheel may be obtained according to the steering mode of the vehicle. For example, when the vehicle is in the normal mode, the first target slip ratio of the first rear wheel may be obtained according to a slip ratio map corresponding to the normal mode. Similarly, when the vehicle is in the track mode or the rotation turning mode, the corresponding slip rate mapping table of the corresponding mode can be obtained, and then the target slip rate is obtained.

It should be understood that the user may select a steering mode according to the driving habit according to the requirement, and further, the steering control system may obtain the corresponding slip ratio mapping table according to the steering mode selected by the user, so as to obtain the first target slip ratio of the first rear wheel. The degree of the different steering modes for reducing the turning radius of the vehicle can be a normal mode < a track mode < a spin-turn mode, namely, the spin-turn mode has the greatest degree for reducing the turning radius, then a track mode and finally a normal mode.

In some embodiments, as shown in fig. 7, in order to effectively reduce the turning radius of the vehicle, the rear wheels of the vehicle do slip or spin to some extent while turning. However, when the driving force of the tire reaches its limit value, the longitudinal adhesion of the tire may be significantly reduced, which may lead to a decrease in vehicle stability. Therefore, during the control, the output torque of the rear wheels must be precisely controlled to prevent the rear wheels from being excessively rotated (i.e., spinning).

It is to be understood that the calculation formulas of the wheel slip rate S and the slip rate S _t may be the following formulas 1 and 2 when the vehicle is in a straight running state or is being steered at a small steering angle.

Equation 1;

equation 2;

Where v is the vehicle speed, w _r is the angular velocity of the wheel, and r is the rolling radius of the wheel.

In conventional vehicle speed estimation, the average of the wheel speeds of the non-driven front wheels or the non-driven rear wheels is generally used to approximate the vehicle speed. However, this method may generate a deviation when the vehicle turns at a large steering angle. Because the wheel speed of the inboard wheel will be lower than the outboard wheel and the wheel speed of the front wheel is generally higher than the rear wheel. If the slip ratio S and slip ratio are calculated by the above formula 1 and formula 2Inaccurate results may result, thereby impairing the performance of the steering control system. Thus, embodiments of the present application provide a method for a first actual slip ratio, as specifically described below.

In some embodiments, the first actual slip rate may be determined by obtaining a rear axle center point speed of the vehicle and determining a target wheel speed of the first rear wheel based on the rear axle center point speed and a yaw rate of the vehicle, and further determining the first actual slip rate based on the target wheel speed of the first rear wheel and the actual wheel speed of the first rear wheel.

In the case where both front wheels are rotated in the forward direction, the rear axle center speed is determined based on the front axle center speed. In the case of the first front wheel brake and the second front wheel rotating in the forward direction, the rear axle center point speed is determined based on the actual wheel speed of the second front wheel.

As an example, and as shown in connection with FIG. 1, while the vehicle is turning, it may be derived from a monorail bicycle modelSimplifying this equation gives equation 3 for the turning radius R of the vehicle.

Equation 3;

Wherein, Δ1 is the left front wheel rotation angle, δ2 is the left and right front wheel rotation angle, L is the vehicle wheelbase, B is the distance of the centroid from the rear axle, and B is the vehicle wheelbase.

Based on the dynamics of the vehicle, the yaw rates of the points on the vehicle are equal, and the following equation 4 can be obtained.

Equation 4;

Wherein V ₁ is the front axle center speed, V ₂ is the rear axle center speed, and V _R1 is the theoretical wheel speed of the right front wheel.

The rear axle center speed V ₂ can be obtained by the above formula 4, and further the theoretical wheel speed of the left rear wheel and the theoretical wheel speed of the right rear wheel can be calculated according to the following formulas 5 and 6.

Equation 5;

equation 6;

wherein V _L2 is the theoretical wheel speed of the left rear wheel, V _R2 is the theoretical wheel speed of the right rear wheel, and w is the yaw rate of the vehicle.

After the theoretical wheel speed of the rear wheel is calculated and determined, the slip rate or slip rate of the rear wheel can be determined according to the theoretical wheel speed and the real wheel speed of the rear wheel, specifically as in the following formulas 7 and 8.

Equation 7;

equation 8;

Wherein, In order for the slip ratio to be the same,For slip ratio, V _v is the theoretical wheel speed of the wheel and V _w is the true wheel speed of the wheel.

As yet another example, as shown in connection with FIG. 5, the vehicle is in a non-rotating turn-around mode. At this time, the first rear wheel is rotated by the first torque whose motor output torque direction is reverse, the second rear wheel is rotated by the second torque whose motor output torque direction is forward, and the two front wheels are rotated forward toward the steering side. Since the two front wheels have no slip ratio, the wheel speeds of the two front wheels can be approximately expressed as the front axle center speed V ₁, and the front axle center speed V ₁ is obtained by the following formula 9.

Equation 9;

Wherein, For the actual wheel speed of the first front wheel,Is the actual wheel speed of the second front wheel,Is the corner of the outboard front wheel.

Further, the following equation 10 is substituted into the above equation 9 to obtain the rear axle center speedThat is, the rear axle center point speed is calculated from the front axle center point speed V ₁ :

Equation 10;

speed of center point of rear axle And the yaw rate w of the vehicle are substituted into the following equations 11 and 12 to obtain the slip ratio S _L2 of the first rear wheel and the slip ratio T _R2 of the second rear wheel, respectively.

Equation 11;

equation 12;

Wherein, The target wheel speed (theoretical wheel speed) of the first rear wheel can be understood as the one in the formula 7 or the formula 8;The actual wheel speed of the first rear wheel can be understood as the above equation 7 or equation 8。

In some embodiments, the steering control system may determine a first integral gain coefficient and a first proportional gain coefficient based on the first slip ratio difference and the first difference rate of change, and perform PI operation on the first slip ratio difference based on the first integral gain coefficient and the first proportional gain coefficient to obtain the first torque.

Illustratively, as shown in FIG. 8, a first slip rate difference value and a first difference change rate are determined according to a first target slip rate and a first actual slip rate, the first slip rate difference value and the first difference change rate are input into a PI fuzzy rule table to obtain an adaptively changed proportional gain coefficient K _p and an integral gain coefficient K _i, and the proportional gain coefficient K _p and the integral gain coefficient K _i are input into a proportional-integral [ ]PI) control system determines a first torque of the first rear wheel.

The PI fuzzy rule table comprises a K _p fuzzy rule table and a K _i fuzzy rule table. The details are shown in tables 1 and 2 below.

TABLE 1K _p fuzzy rule Table

TABLE 2K _i fuzzy rule Table

In tables 1 and 2, NL is negative large, NM is negative medium, NS is negative small, ZE is zero, PS is positive small, PM is medium, and PL is positive large.

For example, a two-dimensional table look-up may be performed according to the first difference change rate EC and the first slip rate difference E to determine the proportional gain coefficient K _p and the integral gain coefficient K _i of the first rear wheel.

Taking the first difference change rate EC as 0%, the first slip rate difference E is 0.2 as an example. Firstly, looking up a K _p fuzzy rule table, wherein the first difference change rate EC is 0%, the fuzzy amount of the first difference change rate EC can be determined to be ZE, the first slip rate difference E is 0.2, the fuzzy amount of the first slip rate difference E can be determined to be PS, the ZE is combined with the PS, the proportional gain coefficient K _p is NS, the integral gain coefficient K _i is ZE, and then the proportional gain coefficient K _p (NS) and the integral gain coefficient K _i (ZE) are input into a PI control system to obtain the first torque of the first rear wheel.

Optionally, when the steering control system is in an initial stage, the first slip rate difference E is larger, and a larger proportional gain coefficient K _p and a smaller integral gain coefficient K _i are obtained by the two-dimensional table look-up method, so as to improve the response speed of the system.

When the steering control system is in a pre-stabilization stage, the first slip rate difference E is in a certain range, the slip rate of steering control is near a target value, and the proportional gain coefficient K _p and the integral gain coefficient K _i can be kept at proper sizes.

When the steering control system is in a stable stage, the first slip rate difference E is very small, and in order to improve the robustness of the system and improve the response speed of the system, the proportional gain coefficient K _p and the integral gain coefficient K _i can be appropriately increased.

In one possible implementation, the second torque of the second rear wheel may be determined by obtaining a second target slip ratio and a second actual slip ratio corresponding to the second rear wheel, determining a second slip ratio difference and a second difference change rate based on the second target slip ratio and the second actual slip ratio, and determining the second torque based on the second slip ratio difference and the second difference change rate.

The second slip rate difference value is a difference value between the second target slip rate and the second actual slip rate, and the second difference value change rate is a change rate of the second slip rate difference value in unit time. Slip ratio refers to the degree to which a wheel slips during driving.

The second target slip rate is determined based on the steering mode of the vehicle and a pre-calibrated slip rate map table, wherein the slip rate map table is used for indicating target slip rates corresponding to a plurality of candidate steering modes of the vehicle. That is, the second target slip ratio of the corresponding second rear wheel may be obtained according to the steering mode of the vehicle. For example, when the vehicle is in the normal mode, the second target slip ratio of the second rear wheel may be obtained according to a slip ratio map corresponding to the normal mode. Similarly, when the vehicle is in the track mode or the rotation turning mode, the corresponding slip rate mapping table of the corresponding mode can be obtained, and then the target slip rate is obtained.

In some embodiments, the second actual slip ratio is determined by obtaining a rear axle center point speed of the vehicle and determining a target wheel speed of the second rear wheel based on the rear axle center point speed and a yaw rate of the vehicle, and further determining the second actual slip ratio based on the target wheel speed of the second rear wheel and the actual wheel speed of the second rear wheel.

Illustratively, as shown in connection with FIG. 6, the vehicle is in a spin-turn mode. At this time, the first rear wheel is rotated by the first torque whose motor output torque direction is reverse, the second rear wheel is rotated by the second torque whose motor output torque direction is forward, and braking force is applied to the first front wheel and third torque is applied to the second front wheel. Since the first front wheel (front wheel on the steering side) is in a braking state, the rear axle center speed V ₂ can be calculated from the actual wheel speed of the second front wheel, as specifically shown in the following equation 13.

Equation 13;

Further, the rear axle center speed V ₂ obtained above may be substituted into the above-described formulas 11 and 12 to obtain the slip ratio S _L2 of the first rear wheel and the slip ratio T _R2 of the second rear wheel.

Optionally, the actual wheel speeds of the wheels are obtained through wheel speed sensors installed on the wheels, but because the wheel speeds of the wheels may be low when the vehicle activates the non-turning mode or the turning mode, the wheel speeds collected by the wheel speed sensors have the problems of low precision, low updating speed and the like, and further the wheel speeds obtained by the motor rotation speed and the wheel speeds collected by the wheel speed sensors can be weighted and then the wheel slip rate or the slip rate is calculated. Wherein the rotation speed of the motor is usedCalculated wheel speedIn the manner shown in equation 14 below.

Equation 14;

wherein r is the rolling radius of the wheel, and rate is the transmission speed ratio of the motor.

In some embodiments, the steering control system determines a second integral gain coefficient and a second proportional gain coefficient based on the second slip ratio difference and the second difference rate of change, and performs PI operation on the second slip ratio difference based on the second integral gain coefficient and the second proportional gain coefficient to obtain a second torque.

Illustratively, a second slip ratio difference value and a second difference change rate are determined according to a second target slip ratio and a second actual slip ratio, the second slip ratio difference value and the second difference change rate are input into a PI fuzzy rule table, so as to obtain an adaptively changed proportional gain coefficient K _p and an integral gain coefficient K _i, and further the proportional gain coefficient K _p and the integral gain coefficient Ki are input into a PI control system, so that a second torque of a second rear wheel is determined.

For example, the steering control system may perform a two-dimensional look-up table based on the second differential change rate EC and the second slip rate differential E to determine the proportional gain coefficient K _p and the integral gain coefficient K _i for the second rear wheel. It is to be understood that the proportional gain coefficient K _p and the integral gain coefficient K _i of the second rear wheel are determined in the same manner as the proportional gain coefficient K _p and the integral gain coefficient K _i of the first rear wheel, and are not described herein.

Preferably, in the embodiment of the present application, an adaptive fuzzy PI control algorithm is adopted to control the slip rate (or slip rate) of the wheel to be near the desired slip rate, and the present application is not limited to the PI control algorithm, and other control algorithms may be adopted.

It should be noted that the slip ratio or slip ratio mentioned in the embodiment of the present application may also be replaced by a wheel speed, which is not limited to this embodiment.

In one possible implementation, the third torque of the second front wheel may be determined based on an accelerator pedal depth of the vehicle, a motor speed, and a steering mode of the vehicle.

In some embodiments, the steering control system may determine the third torque based on a first mapping relationship corresponding to an accelerator pedal depth of the vehicle, a motor speed, and a steering mode of the vehicle.

The first mapping relation is a mapping relation among the depth of an accelerator pedal, the rotating speed of a motor and the third torque, and different steering modes correspond to different first mapping relations.

For example, according to the current steering mode of the vehicle, a corresponding weighted acceleration graph (first mapping relation) is determined, and further, according to the depth of the accelerator pedal and the rotation speed of the motor, a corresponding third torque is obtained in the weighted acceleration graph.

Alternatively, the driver may control the torque output of the motor by the accelerator pedal depth, thereby controlling the vehicle speed of the vehicle.

The above description is made in detail of how the first torque of the first rear wheel, the second torque of the second rear wheel, and the third torque of the second front wheel are calculated.

It should be understood that the vehicle steering control method provided by the embodiment of the application can be applied to a distributed three-motor vehicle, and can also be applied to a four-wheel independent drive or rear-wheel independent drive vehicle so as to realize the in-situ steering function.

Based on the technical scheme, the steering control system controls the motor output torque direction of the first rear wheel of the vehicle to be reverse first torque and the motor output torque direction of the second rear wheel to be forward second torque in response to the vehicle steering instruction, so that the rotating speed of the second rear wheel is higher than that of the first rear wheel when the vehicle steers, and a wheel speed difference is generated between the two rear wheels, and the vehicle can steer more flexibly, so that the turning radius is reduced.

As shown in fig. 9, the overall flow of the vehicle steering control method provided by the embodiment of the present application is summarized, and specifically includes the following steps 901 to 905.

Step 901, displaying a steering mode setting interface.

The steering mode setting interface comprises a plurality of candidate steering modes of the vehicle, wherein the plurality of candidate steering modes comprise a normal mode, a track mode and a rotation turning mode.

The normal mode can be used as a normal starting function, the mode can reduce the tire abrasion and increase the smoothness of vehicle running, the first rear wheel slip rate and the second rear wheel slip rate are controlled within 10% in the mode, the tire abrasion is within an acceptable range, and the turning radius can be reduced by about 12%.

The racing track mode can be used for enabling the vehicle to quickly pass through the U-shaped sharp bend, and further reducing the vehicle over-bending time. It should be understood that when the race track mode entry condition is satisfied, the state of the vehicle at this time may be determined according to signals such as the current vehicle speed, the steering wheel angle, the yaw rate, etc., so as to adjust the torque output of the front and rear motors in real time, and reduce the vehicle over-bending time.

The rotary turning mode can be used for turning the vehicle when the road is narrow, when the entering condition of the rotary turning mode is met, the steering wheel is fully filled clockwise (or anticlockwise), meanwhile, after the depth of the electric door is larger than a set threshold value, the quick turning function is activated, and the quick turning is realized by applying braking force to the first front wheel (the front wheel at the side of the steering direction) and controlling the motor output torque direction of the first rear wheel to be reverse first torque, and controlling the motor output torque direction of the second rear wheel to be forward second torque.

For example, a central display screen of the vehicle may display a plurality of candidate steering modes of the vehicle for selection by a user. The driver may touch a physical key or a virtual key to select different candidate steering modes.

Step 902, responsive to a user setting operation on a steering mode setting interface, determines a steering mode of the vehicle from a plurality of candidate steering modes.

For example, the user may view a plurality of candidate steering modes displayed on the center control large screen, select a desired steering mode according to his own demand, and the vehicle may determine the steering mode of the vehicle in response to a setting operation by the user.

Step 903, based on the running state of the vehicle, it is determined whether to activate the steering mode of the vehicle.

The running state of the vehicle comprises at least one of a running state, a curve state and an out-of-curve state.

The operating state of the vehicle may be determined based on vehicle motion parameters including at least one of accelerator pedal depth, brake pedal depth, steering wheel angle, yaw rate, centroid slip angle acceleration, lateral acceleration, longitudinal acceleration.

In some embodiments, as shown in fig. 10, the steering control system may input the accelerator pedal depth, the brake pedal depth, the steering wheel angle, the yaw rate, the centroid slip angle acceleration, the lateral acceleration, the longitudinal acceleration to the state recognition unit, and determine the current running state of the vehicle.

Further, when the running state of the vehicle is changed from the running state to the curve-in state in the curve state, the steering mode of the vehicle is activated.

In an exemplary embodiment, when the vehicle steering mode selected by the user is the normal mode and the vehicle is idling, it is determined whether the steering wheel angle is greater than the first steering angle threshold, and if so, it is determined that the running state of the vehicle is changed from the running state to the in-curved state, and then the normal mode is activated.

In yet another example, when the user selects the vehicle steering mode to be the track mode, it is determined whether the vehicle speed is greater than a speed threshold and whether the steering wheel angle is greater than a steering angle threshold, and if both are greater than the steering angle threshold, it is determined that the running state of the vehicle is changed from the running state to the in-curve state, and then the track mode is activated.

Optionally, determining whether to activate the racetrack mode may further determine whether the accelerator pedal depth is greater than a threshold value, and whether the self-slip angle is greater than an angle threshold value (an angle between a direction of movement of the vehicle and the steering wheel), where the racetrack mode is activated with a vehicle speed greater than a speed threshold value, a steering wheel angle greater than a steering angle threshold value, an accelerator pedal depth greater than a threshold value, and a self-slip angle greater than an angle threshold value.

In yet another example, in the case where the user-selected vehicle steering mode is the spin-turn mode, it is determined whether the steering wheel angle is greater than a second angle threshold, i.e., whether the steering wheel is full, and in the case of greater than, the racetrack mode is activated.

Step 904, responding to a vehicle steering instruction, and controlling a first motor corresponding to a first rear wheel of the vehicle to output a first torque and a second motor corresponding to a second rear wheel to output a second torque.

Reference may be made in particular to the embodiment shown in step 302 above. And will not be described in detail herein.

Step 905, in response to a running operation of the vehicle, exiting a steering mode of the vehicle and adjusting a current torque of the vehicle at a torque adjustment rate.

In some embodiments, as shown in fig. 11, the steering control system inputs the current vehicle speed, rear wheel slip ratio, slip change ratio, brake pedal depth, steering wheel speed, gear change state, electronic hand brake state into the state recognition unit, and determines the current running state of the vehicle.

Further, when the running state of the vehicle is changed from the curve state to the curve-out state, the steering mode in which the vehicle has been activated is returned, and the current torque of the vehicle is adjusted at the torque adjustment rate.

The running operation comprises at least one of a vehicle speed greater than a preset threshold, a brake pedal depth greater than a depth threshold, a steering wheel speed greater than a speed threshold, a gear change, an electronic hand brake activation, a user turning off steering mode operation, a rear wheel slip ratio greater than a slip threshold, and a rear wheel slip change ratio greater than a change threshold. The rear wheel slip ratio may include a slip ratio of the first rear wheel and a slip ratio of the second rear wheel, and the corresponding rear wheel slip change ratio may include a slip change ratio of the first rear wheel and a slip change ratio of the second rear wheel.

Illustratively, when the vehicle satisfies any two or more of the above running operations, it is explained that the vehicle is shifted from the curve state to the curve-out state, the vehicle exits the activated steering mode, and the current torque of the vehicle is adjusted to the driver's required torque at the torque adjustment rate. For example, the steering control system exits the activated steering mode due to a large change in road adhesion, resulting in an actual slip rate of the first rear wheel or an actual slip rate of the second rear wheel being greater than a corresponding threshold, or a change rate thereof being greater than a change threshold.

It should be noted that the torque adjustment rate is determined by performing a table look-up calculation based on the difference between the current torque and the required torque. It should be appreciated that when the steering mode exits or the slip rate/slip rate of the wheels is uncontrollable, the current torque of the vehicle is adjusted through the torque adjustment rate, so that the output torque of the vehicle is smooth, the vehicle frustration caused by torque change is reduced, and the driving feeling of the driver is improved.

As yet another example, in the event that the user turns off the steering mode, the user may exit the steering mode by displaying a large screen, physical keys, voice assistant, or the like.

Optionally, prompt identifiers such as 'mode exited' can be displayed on the vehicle machine and the instrument of the vehicle, so that a user can know the current situation of the vehicle conveniently.

Based on the technical scheme, the steering control method provided by the embodiment of the application can enable a user to select different steering modes according to the use scene, and judge whether to activate the steering mode selected by the user according to the current running state of the vehicle, so that the accurate steering control of the vehicle can be conveniently carried out subsequently.

The foregoing description of the solution provided by the embodiments of the present application has been mainly presented in terms of a method. In order to achieve the above functions, the steering control system includes a hardware structure and/or a software module that perform the respective functions. Those of skill in the art will readily appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as hardware or combinations of hardware and computer software. Whether a function is implemented as hardware or computer software driven hardware depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

The embodiment of the application can divide the functional modules of the steering control system according to the method, for example, the steering control system can comprise each functional module corresponding to each functional division, or two or more functions can be integrated in one processing module. The integrated modules may be implemented in hardware or in software functional modules. It should be noted that, in the embodiment of the present application, the division of the modules is schematic, which is merely a logic function division, and other division manners may be implemented in actual implementation.

As shown in fig. 12, a schematic diagram of a vehicle steering control device is provided, the device comprises a processing unit 1201 and an acquisition unit 1202, the acquisition unit 1202 is used for acquiring a vehicle steering command, and the processing unit 1201 is used for controlling a first motor corresponding to a first rear wheel of a vehicle to output a first torque and a second motor corresponding to a second rear wheel to output a second torque in response to the vehicle steering command.

In one possible implementation, the processing unit 1201 is specifically configured to control a first motor corresponding to a first rear wheel to output a first torque to effect rotation of the first rear wheel and control a second motor corresponding to a second rear wheel to output a second torque to effect forward rotation of the second rear wheel in response to a vehicle steering command. Wherein the rotation of the first rear wheel includes forward rotation or reverse rotation.

In one possible implementation, the first torque is determined by obtaining a first actual slip rate and a first target slip rate of the first rear wheel, determining a first slip rate difference and a first difference change rate based on the first actual slip rate and the first target slip rate, the first slip rate difference being a difference between the first target slip rate and the first actual slip rate, the first difference change rate being a change rate of the first slip rate difference over a unit time, and determining the first torque based on the first slip rate difference and the first difference change rate.

In one possible implementation, the first actual slip rate is determined from acquiring a rear axle center point speed of the vehicle, determining a target wheel speed of the first rear wheel based on the rear axle center point speed and a yaw rate of the vehicle, and determining the actual slip rate of the first rear wheel based on the target wheel speed of the first rear wheel and the actual wheel speed of the first rear wheel.

In one possible implementation, the first target slip rate is determined based on a steering mode of the vehicle and a pre-calibrated slip rate map for indicating a target slip rate for each of a plurality of candidate steering modes of the vehicle, the steering mode being one of the plurality of candidate steering modes.

In one possible implementation, the processing unit 1201 is specifically configured to determine a first integral gain coefficient and a first proportional gain coefficient based on the first slip ratio difference and the first difference change rate, and perform PI operation on the first slip ratio difference based on the first integral gain coefficient and the first proportional gain coefficient to obtain a first torque.

In one possible implementation, the second torque is determined by obtaining a second target slip rate and a second actual slip rate of the second rear wheel, determining a second slip rate difference and a second difference change rate based on the second target slip rate and the second actual slip rate, the second slip rate difference being a difference between the second target slip rate and the second actual slip rate, the second difference change rate being a change rate of the second slip rate difference per unit time, and determining the second torque based on the second slip rate difference and the second difference change rate.

In one possible implementation, the second actual slip rate is determined by obtaining a rear axle center point speed of the vehicle, determining a target wheel speed of the second rear wheel based on the rear axle center point speed and a yaw rate of the vehicle, and determining the second actual slip rate based on the target wheel speed of the second rear wheel and the actual wheel speed of the second rear wheel.

In one possible implementation, the second target slip rate is determined based on a steering mode of the vehicle and a pre-calibrated slip rate map for indicating a target slip rate for each of a plurality of candidate steering modes of the vehicle, the steering mode being one of the plurality of candidate steering modes.

In one possible implementation, the processing unit 1201 is specifically configured to determine a second integral gain coefficient and a second proportional gain coefficient based on the second slip ratio difference and the second difference change rate, and perform PI operation on the second slip ratio difference based on the second integral gain coefficient and the second proportional gain coefficient to obtain a second torque.

In one possible implementation, the plurality of candidate steering modes includes a rotational turn-around mode and a non-rotational turn-around mode, the non-rotational turn-around mode including a normal mode and a racetrack mode, the normal mode corresponding to a target slip ratio that is less than a target slip ratio of the racetrack mode.

In one possible implementation, the processing unit 1201 is further configured to control a first front wheel of the vehicle to brake and a second front wheel to rotate in a forward direction in response to a vehicle steering command when the vehicle is in a spin-turn mode, wherein the first front wheel is a front wheel on a steering side of two front wheels of the vehicle and the second front wheel is another front wheel of the two front wheels of the vehicle other than the first front wheel.

In one possible implementation, the processing unit 1201 is further configured to control the braking system of the first front wheel to apply a braking force to the first front wheel to effect braking of the first front wheel and control the motor of the second front wheel to output a third torque to effect forward rotation of the second front wheel in response to a vehicle steering command.

In one possible implementation, the processing unit 1201 is further configured to control both the first front wheel and the second front wheel of the vehicle to rotate in a forward direction in response to a vehicle steering command when the vehicle is in a non-rotating turn-around mode.

In one possible implementation, the processing unit 1201 is specifically configured to control the motors of the first front wheel and the second front wheel to output a third torque in response to a vehicle steering command to achieve forward rotation of both the first front wheel and the second front wheel.

In one possible implementation, the processing unit 1201 is specifically configured to determine the third torque based on a first mapping relationship corresponding to an accelerator pedal depth of the vehicle, a motor speed, and a steering mode of the vehicle. The first mapping relation is a mapping relation among the depth of an accelerator pedal, the rotating speed of a motor and the third torque, and different steering modes correspond to different first mapping relations.

In one possible implementation, the processing unit 1201 is further configured to display a steering mode setting interface including a plurality of candidate steering modes of the vehicle, and determine a steering mode of the vehicle from the plurality of candidate steering modes in response to a setting operation by a user on the steering mode setting interface.

In one possible implementation, the processing unit 1201 is further configured to exit the vehicle-activated steering mode in response to a running operation of the vehicle and adjust a current torque of the vehicle at a torque adjustment rate, the torque adjustment rate being determined based on the current torque and the desired torque.

In one possible implementation, the operation includes at least one of a vehicle speed greater than a preset threshold, a brake pedal depth greater than a depth threshold, a steering wheel speed greater than a speed threshold, a closed steering mode operation, a rear wheel slip rate greater than a slip threshold, a rear wheel slip rate greater than a change threshold, a gear change, and an electronic hand brake activation.

The foregoing is merely illustrative embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think about variations or substitutions within the technical scope of the present invention, and the invention should be covered. Therefore, the protection scope of the invention is subject to the protection scope of the claims.

Claims

1. A vehicle steering control method, characterized by comprising:

The method comprises the steps of responding to a vehicle steering instruction, controlling a first motor corresponding to a first rear wheel of a vehicle to output first torque and a second motor corresponding to a second rear wheel to output second torque, wherein the torque direction of the first torque is reverse, the torque direction of the second torque is forward, the first rear wheel is a rear wheel positioned on a steering side in the vehicle, and the second rear wheel is a rear wheel positioned on a non-steering side in the vehicle;

the first torque is determined by:

Acquiring a first actual slip rate and a first target slip rate of the first rear wheel;

Determining a first slip rate difference value and a first difference change rate based on the first actual slip rate and a first target slip rate, wherein the first slip rate difference value is a difference value between the first target slip rate and the first actual slip rate, and the first difference change rate is a change rate of the first slip rate difference value in unit time;

the first torque is determined based on the first slip ratio difference and the first difference rate of change.

2. The method of claim 1, wherein controlling the corresponding first motor of the vehicle to output the first torque and the corresponding second motor of the second rear wheel to output the second torque in response to the vehicle steering command comprises:

In response to the vehicle steering instruction, controlling a first motor corresponding to the first rear wheel to output a first torque to realize the rotation of the first rear wheel, and controlling a second motor corresponding to the second rear wheel to output a second torque to realize the forward rotation of the second rear wheel;

3. The method of claim 1, wherein the first actual slip rate is determined according to:

acquiring the speed of a rear axle center point of the vehicle;

Determining a target wheel speed of the first rear wheel based on the rear axle center point speed and the yaw rate of the vehicle;

An actual slip ratio of the first rear wheel is determined based on a target wheel speed of the first rear wheel and an actual wheel speed of the first rear wheel.

4. The method of claim 1, wherein the first target slip rate is determined based on a steering mode of the vehicle and a pre-calibrated slip rate map for indicating a target slip rate for each of a plurality of candidate steering modes of the vehicle, the steering mode being one of the plurality of candidate steering modes.

5. The method of any one of claims 1-4, wherein the determining the first torque based on the first slip ratio difference and the first difference rate of change comprises:

Determining a first integral gain coefficient and a first proportional gain coefficient based on the first slip ratio difference and the first difference rate of change;

And performing PI operation on the first slip rate difference value based on the first integral gain coefficient and the first proportional gain coefficient to obtain the first torque.

6. The method of claim 2, wherein the second torque is determined by:

acquiring a second target slip rate and a second actual slip rate of the second rear wheel;

Determining a second slip rate difference value and a second difference change rate based on the second target slip rate and a second actual slip rate, wherein the second slip rate difference value is a difference value between the second target slip rate and the second actual slip rate, and the second difference change rate is a change rate of the second slip rate difference value in unit time;

The second torque is determined based on the second slip ratio difference and the second difference rate of change.

7. The method of claim 6, wherein the second actual slip rate is determined by:

acquiring the speed of a rear axle center point of the vehicle;

Determining a target wheel speed of the second rear wheel based on the rear axle center point speed and the yaw rate of the vehicle;

The second actual slip ratio is determined based on a target wheel speed of the second rear wheel and an actual wheel speed of the second rear wheel.

8. The method of claim 6, wherein the second target slip ratio is determined based on a steering mode of the vehicle and a pre-calibrated slip ratio map for indicating a target slip ratio for each of a plurality of candidate steering modes of the vehicle, the steering mode being one of the plurality of candidate steering modes.

9. The method of any of claims 6-8, wherein the determining the second torque based on the second slip ratio difference and the second difference rate of change comprises:

determining a second integral gain coefficient and a second proportional gain coefficient based on the second slip ratio difference and the second difference rate of change;

and performing PI operation on the second slip ratio difference value based on the second integral gain coefficient and the second proportional gain coefficient to obtain the second torque.

10. The method of claim 4 or 8, wherein the plurality of candidate steering modes includes a rotational turn-around mode and a non-rotational turn-around mode, the non-rotational turn-around mode including a normal mode and a racetrack mode, the normal mode corresponding to a target slip rate that is less than a target slip rate of the racetrack mode.

11. The method according to claim 1, wherein the method further comprises:

And under the condition that the vehicle is in a rotation turning mode, controlling a first front wheel of the vehicle to brake and a second front wheel to rotate positively in response to a vehicle steering instruction, wherein the first front wheel is the front wheel positioned on the steering side of the two front wheels of the vehicle, and the second front wheel is the other front wheel except the first front wheel.

12. The method of claim 11, wherein controlling the first front wheel brake and the second front wheel forward rotation of the vehicle in response to a vehicle steering command with the vehicle in a spin-around mode comprises:

In response to the vehicle steering command, controlling a braking system of the first front wheel to apply a braking force to the first front wheel to achieve the first front wheel braking, and controlling a motor of the second front wheel to output a third torque to achieve the forward rotation of the second front wheel.

13. The method of claim 11, wherein the method further comprises:

In response to a vehicle steering command, the first front wheel and the second front wheel of the vehicle are controlled to both rotate in a forward direction when the vehicle is in a non-rotating turn-around mode.

14. The method of claim 13, wherein the controlling the first front wheel and the second front wheel of the vehicle to both rotate in a forward direction in response to a vehicle steering command with the vehicle in a non-rotating turn-around mode comprises:

And controlling the motors of the first front wheels and the motors of the second front wheels to output third torque in response to the vehicle steering command so as to realize forward rotation of both the first front wheels and the second front wheels.

15. The method according to claim 12 or 14, characterized in that the method further comprises:

determining the third torque based on a first mapping relationship corresponding to an accelerator pedal depth, a motor speed, and a steering mode of the vehicle;

The first mapping relation is a mapping relation among the depth of the accelerator pedal, the rotating speed of the motor and the third torque, and different steering modes correspond to different first mapping relations.

16. The method according to claim 1, wherein the method further comprises:

Displaying a steering mode setting interface, the steering mode setting interface comprising a plurality of candidate steering modes of the vehicle;

A steering mode of the vehicle is determined from the plurality of candidate steering modes in response to a setting operation by a user on a steering mode setting interface.

17. The method of claim 16, wherein the method further comprises:

And in response to a running operation of the vehicle, exiting the vehicle-activated steering mode and adjusting a current torque of the vehicle at a torque adjustment rate, the torque adjustment rate being determined based on the current torque and a desired torque.

18. The method of claim 17, wherein the running operation comprises at least one of:

the vehicle speed is greater than a preset threshold;

the brake pedal depth is greater than a depth threshold;

steering wheel speed is greater than a speed threshold;

Turning off the steering mode operation;

the rear wheel slip ratio is greater than the slip threshold;

the rear wheel slip change rate is greater than a change threshold;

a gear change;

And activating the electronic hand brake.

19. A vehicle steering control apparatus is characterized by comprising a processing unit;

The processing unit is used for responding to a vehicle steering instruction, controlling a first motor corresponding to a first rear wheel of the vehicle to output first torque and a second motor corresponding to a second rear wheel to output second torque, wherein the torque direction of the first torque is reverse, the torque direction of the second torque is forward, the first rear wheel is a rear wheel positioned at a steering side of two rear wheels of the vehicle, and the second rear wheel is the other rear wheel except the first rear wheel of the two rear wheels of the vehicle;

the first torque is determined by:

20. A vehicle comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor executing the program to implement the method of any one of claims 1 to 18.

21. A computer readable storage medium having instructions stored therein, characterized in that, when executed by a computer, the computer performs the method of any of the preceding claims 1 to 18.

22. A computer program product comprising instructions which, when executed on a computer, perform the method of any one of claims 1 to 18.