Vehicle four-wheel independent steering control method and device

Abstract

A vehicle four-wheel independent steering control method, comprising: on the basis of an ideal steering angle and an actual steering angle of each wheel in a steering mode, a first output rotational speed of a vehicle virtual main shaft, and a second output rotational speed of each wheel steering actuator, determining a driving torque for each steering actuator; and controlling each steering actuator to output the corresponding driving torque, so as to drive each wheel to rotate. Further disclosed are a vehicle four-wheel independent steering control device, a vehicle, and a computer-readable storage medium. The control method can enable each wheel to synchronously reach a corresponding ideal steering angle, can realize friction speed and synchronous control of steering angles for vehicle four-wheel independent steering, reduce the degree of tire wear during vehicle steering, and improve vehicle steering stability.

Description

Vehicle four-wheel independent steering control method and device Cross-reference to Related Applications

[0001] This application claims priority to Chinese Patent Application No. 202410825425X, filed on June 25, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of automotive technology, and in particular to a vehicle four-wheel independent steering control method and device. BACKGROUND

[0003] Each wheel of a four-wheel independent steering vehicle is equipped with a steering motor, enabling independent steering of each wheel. For a four-wheel independent steering vehicle, as there is no physical constraint of a traditional steering mechanism, all wheels need to be coordinated to steer during cornering, and collectively complete the action of cornering. In this process, according to the Ackerman steering principle, the turning angles of each wheel are not the same, and if the turning angles of each wheel are not synchronized during steering, tire drag will occur, causing severe tire wear and making the vehicle unable to travel along the predetermined trajectory, affecting the steering stability of the vehicle. Therefore, in order to reduce tire wear and improve steering stability, the problem of non-uniform speed synchronization control of the turning angles of four-wheel independent steering needs to be considered. SUMMARY

[0004] The present application provides a vehicle four-wheel independent steering control method and device, which solves the technical problem of how to achieve non-uniform speed synchronization control of the turning angles of four-wheel independent steering.

[0005] In one aspect, the present application provides the following technical solutions:

[0006] A vehicle four-wheel independent steering control method, comprising:

[0007] Determining a steering mode of the vehicle when the vehicle is steering;

[0008] Determining ideal turning angles of each wheel in the steering mode;

[0009] Obtaining actual turning angles of each wheel, a first output speed of a virtual main shaft of the vehicle, and a second output speed of a steering execution mechanism of each wheel;

[0010] Determining driving torques of each steering execution mechanism according to the ideal turning angles, the actual turning angles, the first output speed, and the second output speed;

[0011] Controlling each steering execution mechanism to output a corresponding driving torque to drive each wheel to rotate.

[0012] Optionally, determining the ideal steering angles of the wheels in the steering mode comprises:

[0013] If the steering mode is a crab steering mode, determining the ideal steering angles of the left front wheel and the right front wheel as both 90°, and the ideal steering angles of the left rear wheel and the right rear wheel as both -90°.

[0014] Optionally, determining the ideal steering angles of the wheels in the steering mode comprises:

[0015] If the steering mode is a wedge steering mode, determining the ideal steering angles of the left front wheel, the right front wheel, the left rear wheel and the right rear wheel as the same.

[0016] Optionally, determining the ideal steering angles of the wheels in the steering mode comprises:

[0017] If the steering mode is a crab steering mode, determining the ideal steering angles of the left front wheel and the right front wheel as both 90°, and the ideal steering angles of the left rear wheel and the right rear wheel as both -90°.

[0018] Optionally, determining the ideal steering angles of the wheels in the steering mode comprises:

[0019] If the steering mode is a wedge steering mode, determining the ideal steering angles of the left front wheel, the right front wheel, the left rear wheel and the right rear wheel as the same.

[0020] Optionally, determining the ideal steering angles of the wheels in the steering mode comprises:

[0021] If the steering mode is a front wheel steering mode, obtaining a vehicle speed, a front axle steering angle and a yaw rate of the vehicle;

[0022] calculating the ideal steering angles of the left front wheel and the right front wheel according to the vehicle speed, the front axle steering angle and the yaw rate.

[0023] Optionally, calculating the ideal steering angles of the left front wheel and the right front wheel according to the vehicle speed, the front axle steering angle and the yaw rate comprises:

[0024] calculating the ideal steering angle of the left front wheel according to the formula calculating the ideal steering angle of the right front wheel according to the formula , , , , , a vehicle speed in a vehicle longitudinal direction, B is a left-right wheel base of the vehicle, and L is a front-rear wheel base of the vehicle. a distance from a vehicle center of mass to a front axle, a yaw rate, a vehicle speed in a vehicle longitudinal direction, B is a left-right wheel base of the vehicle, and L is a front-rear wheel base of the vehicle.

[0025] Optionally, determining the ideal steering angles of the wheels in the steering mode comprises:

[0026] if the steering mode is a four-wheel steering mode, obtaining a vehicle speed, a front axle steering angle, and a yaw rate of the vehicle;

[0027] calculating the ideal steering angles of the wheels according to the vehicle speed, the front axle steering angle, and the yaw rate.

[0028] Optionally, calculating the ideal steering angles of the wheels according to the vehicle speed, the front axle steering angle, and the yaw rate comprises:

[0029] calculating the ideal steering angle of the left front wheel according to the formula calculating the ideal steering angle of the right front wheel according to the formula , is the ideal steering angle of the left front wheel, is the ideal steering angle of the right front wheel, is the front axle steering angle;

[0030] calculating the ideal steering angle of the left rear wheel according to the formula calculating the ideal steering angle of the right rear wheel according to the formula , is the ideal steering angle of the left rear wheel, is the ideal steering angle of the right rear wheel, is a rear axle steering angle of the vehicle, is a constant greater than zero, and m is a total vehicle mass, is the vehicle speed, is a distance from a vehicle center of mass to a front axle, is a front wheel cornering stiffness, and b is a distance from a vehicle center of mass to a rear axle, is a rear wheel cornering stiffness, is the yaw rate;

[0031] is determined by the equation .

[0032] is determined by the equation .

[0033] ​ a divided speed of the vehicle speed in a lateral direction of the vehicle, a divided speed of the vehicle speed in a longitudinal direction of the vehicle, B is a wheelbase of the vehicle in a lateral direction, and L is a wheelbase of the vehicle in a longitudinal direction.

[0034] Optionally, determining the driving torque of each of the steering actuators according to the ideal steering angle, the actual steering angle, the first output speed and the second output speed comprises:

[0035] calculating a target speed of each of the steering actuators according to the ideal steering angle, the actual steering angle and the first output speed;

[0036] calculating the driving torque of each of the steering actuators according to the second output speed and the target speed.

[0037] Optionally, calculating a target speed of each of the steering actuators according to the ideal steering angle, the actual steering angle and the first output speed comprises:

[0038] calculating the target speed according to the formula , , i = 1, 2, 3, 4, i = 1 represents the left front wheel, i = 2 represents the right front wheel, i = 3 represents the left rear wheel, and i = 4 represents the right rear wheel;

[0039] the actual steering angle of the i-th wheel, , , , , the ideal steering angle of the left front wheel, the ideal steering angle of the right front wheel, the ideal steering angle of the left rear wheel, the ideal steering angle of the right rear wheel, a steering angle deviation corresponding to the i-th wheel, a maximum value among the steering angle deviations corresponding to each wheel, a proportional adjustment coefficient corresponding to the i-th wheel, the first output speed, a target speed of the steering actuator of the i-th wheel.

[0040] Optionally, after calculating a target speed of each of the steering actuators according to the ideal steering angle, the actual steering angle and the first output speed, and before calculating the driving torque of each of the steering actuators according to the second output speed and the target speed, the method further comprises:

[0041] acquire the moment of inertia of each of the steering actuators, the moments of inertia of two adjacent steering actuators of each of the steering actuators and the output rotation speed;

[0042] calculate the rotation speed compensation of each of the steering actuators according to the second output rotation speed, the moment of inertia of the steering actuators, the moments of inertia of two adjacent steering actuators and the output rotation speed;

[0043] compensate the target rotation speed according to the rotation speed compensation.

[0044] Optionally, the calculating of the rotation speed compensation of each of the steering actuators according to the second output rotation speed, the moment of inertia of the steering actuators, the moments of inertia of two adjacent steering actuators and the output rotation speed comprises:

[0045] calculating the rotation speed compensation of each of the steering actuators according to the formula , , i=1, 2, 3, 4, i=1 represents the left front wheel, i=2 represents the right front wheel, i=3 represents the left rear wheel and i=4 represents the right rear wheel;

[0046] is the moment of inertia of the steering actuator of the i-th wheel, , is the moment of inertia of the two adjacent steering actuators respectively, , is the feedback gain compensation coefficient of the two adjacent steering actuators respectively, is the second output rotation speed of the steering actuator of the i-th wheel, , is the output rotation speed of the two adjacent steering actuators respectively, is the rotation speed compensation of the steering actuator of the i-th wheel.

[0047] Optionally, the calculating of the driving torque of each of the steering actuators according to the second output rotation speed and the target rotation speed comprises:

[0048] calculating the driving torque according to the formula i=1, 2, 3, 4, i=1 represents the left front wheel, i=2 represents the right front wheel, i=3 represents the left rear wheel and i=4 represents the right rear wheel;

[0049] is the second output rotation speed of the steering actuator of the i-th wheel, is the target rotation speed of the steering actuator of the i-th wheel, a damping coefficient of a transmission link between the steering actuator of the i th wheel and the virtual kingpin, a stiffness coefficient of a transmission link between the steering actuator of the i th wheel and the virtual kingpin, the driving torque of the steering actuator of the i th wheel.

[0050] In another aspect, the present application also provides the following technical solutions:

[0051] A vehicle four-wheel independent steering control device comprises:

[0052] A determination module is configured to determine a steering mode of a vehicle when the vehicle is steering.

[0053] An ideal steering angle of each wheel in the steering mode is determined.

[0054] An acquisition module is configured to acquire an actual steering angle of each wheel, a first output speed of a virtual kingpin of the vehicle, and a second output speed of a steering actuator of each wheel.

[0055] The determination module is further configured to determine a driving torque of each steering actuator according to the ideal steering angle, the actual steering angle, the first output speed, and the second output speed.

[0056] A control module is configured to control each steering actuator to output a corresponding driving torque to drive each wheel to rotate.

[0057] In another aspect, the present application also provides the following technical solutions:

[0058] A vehicle comprises a controller and a plurality of steering actuators, and the controller controls the plurality of steering actuators to act by using any of the above vehicle four-wheel independent steering control methods.

[0059] In another aspect, the present application also provides the following technical solutions:

[0060] A computer readable storage medium has a computer program stored thereon, and the computer program is executed by a processor to implement the steps of any of the vehicle four-wheel independent steering control methods.

[0061] One or more technical solutions provided by the present application have at least the following technical effects or advantages:

[0062] The application determines the driving torque of each steering actuator according to the ideal turning angle, the actual turning angle, the first output rotating speed of the virtual main shaft of the vehicle and the second output rotating speed of each steering actuator, controls each steering actuator to output the corresponding driving torque to drive each wheel to rotate, which is equivalent to determining the proportional adjustment coefficient of the actual output rotating speed of each steering actuator according to the deviation between the ideal turning angle and the actual turning angle of the wheel, determining the target rotating speed of each steering actuator according to the proportional adjustment coefficient, and adjusting the actual output rotating speed of each steering actuator according to the target rotating speed, so as to adjust the output torque of each steering actuator, so that each wheel can synchronously reach the corresponding ideal turning angle, the turning angle allometric synchronous control of the four-wheel independent steering of the vehicle can be realized, the tire wear degree during the steering of the vehicle is reduced, and the steering stability of the vehicle is improved. BRIEF DESCRIPTION OF DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the technical scheme of the application, the drawings needed to be used in the description of the technical scheme will be briefly introduced as follows. Obviously, the drawings in the following description are some technical solutions of the application, and other drawings can also be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0064] Fig. 1 is a flow chart of the four-wheel independent steering control method of the vehicle in the technical scheme of the application;

[0065] Fig. 2 is a relationship diagram of the left and right wheel turning angles of the vehicle in the technical scheme of the application;

[0066] Fig. 3 is a control structure diagram of the four-wheel independent steering control method of the vehicle in the technical scheme of the application;

[0067] Fig. 4 is a schematic diagram of the four-wheel independent steering control device of the vehicle in the technical scheme of the application. EMBODIMENT

[0068] The technical scheme of the application provides a four-wheel independent steering control method and device of a vehicle, and solves the technical problem of how to realize the turning angle allometric synchronous control of the four-wheel independent steering of the vehicle.

[0069] In order to better understand the technical scheme of the application, the technical scheme of the application will be described in detail below in combination with the drawings of the specification and specific embodiments.

[0070] As shown in Fig. 1, the four-wheel independent steering control method of the vehicle in the technical scheme of the application comprises:

[0071] Step S1, determining the steering mode of the vehicle during steering;

[0072] Step S2, determining the ideal turning angle of each wheel in the steering mode;

[0073] Step S3, acquiring the actual rotation angle of each wheel, the first output rotation speed of the virtual main shaft of the vehicle, and the second output rotation speed of each wheel steering actuator;

[0074] Step S4, determining the driving torque of each steering actuator according to the ideal rotation angle, the actual rotation angle, the first output rotation speed, and the second output rotation speed;

[0075] Step S5, controlling each steering actuator to output the corresponding driving torque to drive each wheel to rotate.

[0076] In step S1, the steering mode of the vehicle can include a spot steering mode, a wedge steering mode, a crab steering mode, an axle steering mode, a front wheel steering mode, and a four-wheel steering mode, and the ideal rotation angle of each wheel is different in different steering modes.

[0077] For the spot steering mode, the wedge steering mode, the crab steering mode, and the axle steering mode, step S2 can include:

[0078] If the steering mode is the spot steering mode, the ideal rotation angle of the left front wheel and the right rear wheel is determined to be-arctan(B / L), and the ideal rotation angle of the right front wheel and the left rear wheel is determined to be arctan(B / L), where B is the left-right wheelbase of the vehicle, and L is the front-rear wheelbase of the vehicle.

[0079] If the steering mode is the wedge steering mode, the ideal rotation angles of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel are determined to be the same.

[0080] If the steering mode is the crab steering mode, the ideal rotation angle of the left front wheel and the right front wheel is determined to be 90°, and the ideal rotation angle of the left rear wheel and the right rear wheel is determined to be-90°.

[0081] If the steering mode is the axle steering mode, the ideal rotation angle of the left front wheel and the right rear wheel is determined to be 0°, the ideal rotation angle of the right front wheel is determined to be 90°, and the ideal rotation angle of the left rear wheel is determined to be-90°.

[0082] It should be noted that in the technical solution of the present application, the wheel rotation angle is defined as a positive value when the vehicle turns right.

[0083] For the front wheel steering mode, based on the vehicle left-right wheel rotation angle relationship diagram shown in FIG. 2, the relationship between the tire side slip angle of the left front wheel , the tire side slip angle of the right front wheel, the ideal rotation angle of the left front wheel , and the ideal rotation angle of the right front wheel can be obtained as follows:

[0084] ,

[0085] ​[Corrected according to Rule 91 on 14.10.2024] For the front-wheel steering mode, based on the vehicle left and right wheel angle relationship diagram shown in FIG. 2, the relationship between the tire side slip angle a fl of the left front wheel, the tire side slip angle a fr of the right front wheel, the ideal steering angle δ fl of the left front wheel, and the ideal steering angle δ fr of the right front wheel can be obtained:

[0086] The vehicle steering motion can be decomposed into movement around the instantaneous steering center and fixed-axis rotation around the vehicle's center of mass, and the angular velocity of the fixed-axis rotation is the vehicle's yaw angular velocity. The yaw angular velocity of the vehicle during steering satisfies the relationship:

[0087] ; R is the instantaneous turning radius of the vehicle;

[0088] The instantaneous turning radius R of the vehicle is represented by the front and rear wheelbase and the front axle steering angle, i.e.:

[0089] ; L is the front and rear wheelbase of the vehicle;

[0090] wherein is the front axle steering angle, is the front axle side slip angle, , satisfies the relationship:

[0091] ;

[0092] is the ideal steering angle of the left front wheel , the ideal steering angle of the right front wheel , i.e.:

[0093] ;

[0094] The center of mass side slip angle of the vehicle during driving is related to the front axle steering angle , satisfies the relationship:

[0095] ;

[0096] and the center of mass side slip angle of the vehicle during driving is also related to the structural parameters of the vehicle and the front axle steering angle , i.e.:

[0097] ; b is the distance from the center of mass of the vehicle to the rear axle;

[0098] Based on the above analysis, the constraint relationship between the ideal turning angle of the left front wheel and the ideal turning angle of the right front wheel when the vehicle is driving around a curve at any vehicle speed

[0099]

[0100] Let , , then:

[0101]

[0102] It can be seen that , which indicates that for any given vehicle speed and front axle turning angle , there is a certain determined value, that is, the ideal turning angle of the left front wheel and the ideal turning angle of the right front wheel are uniquely determined. That is, for the front wheel steering mode, step S2 can include: if the steering mode is the front wheel steering mode, obtaining the vehicle speed, the front axle turning angle, and the yaw rate of the vehicle; calculating the ideal turning angles of the left front wheel and the right front wheel according to the vehicle speed, the front axle turning angle, and the yaw rate. Wherein, calculating the ideal turning angles of the left front wheel and the right front wheel according to the vehicle speed, the front axle turning angle, and the yaw rate, includes: calculating the ideal turning angle of the left front wheel according to the formula , calculating the ideal turning angle of the right front wheel according to the formula , is the ideal turning angle of the left front wheel, is the ideal turning angle of the right front wheel, is determined by the equation .

[0103] For the four-wheel steering mode, the front and rear wheel turning angles satisfy the relationship:

[0104]

[0105] Wherein, , are proportional coefficients, is a constant greater than zero, m is the mass of the vehicle, is the front wheel cornering stiffness, is the rear wheel cornering stiffness, follows the vehicle speed ;

[0106] ​​​​​​According to the relationship between the front and rear wheel turning angles and the relationship between the left and right wheel turning angles when steering, the relationship between the left and right rear wheel turning angles can be obtained:

[0107] is the ideal turning angle of the left rear wheel, is the ideal turning angle of the right rear wheel, is the rear axle turning angle of the vehicle, is determined by the following formula:

[0108]

[0109] It can be seen that is a certain determined value related to and , indicating that for any given vehicle speed and front axle turning angle , the ideal turning angle of the left rear wheel and the ideal turning angle of the right rear wheel are uniquely determined. That is, for the four-wheel steering mode, step S2 can include: if the steering mode is the four-wheel steering mode, obtaining the vehicle speed, the front axle turning angle, and the yaw angular velocity of the vehicle; calculating the ideal turning angles of each wheel according to the vehicle speed, the front axle turning angle, and the yaw angular velocity. Wherein, calculating the ideal turning angles of each wheel according to the vehicle speed, the front axle turning angle, and the yaw angular velocity, includes: calculating the ideal turning angle of the left front wheel according to the formula , calculating the ideal turning angle of the right front wheel according to the formula , calculating the ideal turning angle of the left rear wheel according to the formula , and calculating the ideal turning angle of the right rear wheel according to the formula , , is the yaw angular velocity; Δ is determined by the equation ; is determined by the equation .

[0110] Step S4 specifically includes: calculating the target speed of each steering actuator according to the ideal turning angle, the actual turning angle, and the first output speed; calculating the driving torque of each steering actuator according to the second output speed and the target speed.

[0111] Wherein, calculating the target speed of each steering actuator according to the ideal turning angle, the actual turning angle, and the first output speed, can include: calculating the target speed according to the formula , , , i = 1, 2, 3, 4, i = 1 represents the left front wheel, i = 2 represents the right front wheel, i = 3 represents the left rear wheel, and i = 4 represents the right rear wheel.​​​ actual rotation angle of the i-th wheel, rotation angle deviation corresponding to the i-th wheel, maximum value among the rotation angle deviations corresponding to the wheels, proportional adjustment coefficient corresponding to the i-th wheel, first output rotation speed, target rotation speed of the steering actuator of the i-th wheel.

[0112] wherein the driving torque of each steering actuator is calculated according to the second output rotation speed and the target rotation speed, which can comprise calculating the driving torque according to the formula second output rotation speed of the steering actuator of the i-th wheel, damping coefficient of the transmission link between the steering actuator of the i-th wheel and the virtual main shaft, stiffness coefficient of the transmission link between the steering actuator of the i-th wheel and the virtual main shaft, driving torque of the steering actuator of the i-th wheel.

[0113] wherein the synchronous movement of the wheels needs to satisfy .

[0114] After obtaining the driving torque of each steering actuator, each wheel can be driven to rotate by step S5, so that each wheel synchronously reaches the corresponding ideal rotation angle, and the rotation angle asynchronous synchronous control of the four-wheel independent steering of the vehicle is realized.

[0115] As can be seen from the above, the four-wheel independent steering control method of the vehicle according to the technical scheme of the present application determines the driving torque of each steering actuator according to the ideal rotation angle, the actual rotation angle of each wheel, the first output rotation speed of the virtual main shaft of the vehicle, and the second output rotation speed of each steering actuator of the wheel under the steering mode, controls each steering actuator to output the corresponding driving torque, so as to drive each wheel to rotate, which is equivalent to determining the proportional adjustment coefficient of the actual output rotation speed of each steering actuator according to the deviation between the ideal rotation angle and the actual rotation angle of the wheel, determining the target rotation speed of each steering actuator according to the proportional adjustment coefficient, and adjusting the actual output rotation speed of each steering actuator according to the target rotation speed feedback, so as to adjust the output torque of each steering actuator, so that each wheel can synchronously reach the corresponding ideal rotation angle, and the rotation angle asynchronous synchronous control of the four-wheel independent steering of the vehicle can be realized, which reduces the tire wear degree during vehicle steering and improves the steering stability of the vehicle.

[0116] ​​​​​The technical scheme of the application finds that when a certain steering actuator (motor) is disturbed, the actual speed thereof will change, causing synchronization error with other steering actuators, and affecting the asynchronous speed synchronization control. In order to reduce the synchronization error caused by the disturbance of the steering actuator (motor), in step S4, after the target speed of each steering actuator is calculated according to the ideal angle, the actual angle and the first output speed, and before the driving torque of each steering actuator is calculated according to the second output speed and the target speed, step S4 can further include: obtaining the moment of inertia of each steering actuator, the moments of inertia of the adjacent two steering actuators of each steering actuator and the output speed; calculating the speed compensation amount of each steering actuator according to the second output speed, the moment of inertia of the steering actuator, the moments of inertia of the adjacent two steering actuators and the output speed; and compensating the target speed according to the speed compensation amount.

[0117] In the formula, the speed compensation amount of each steering actuator is calculated according to the second output speed, the moment of inertia of the steering actuator, the moments of inertia of the adjacent two steering actuators and the output speed, which includes: calculating the speed compensation amount of each steering actuator according to the formula is the moment of inertia of the steering actuator of the i-th wheel, are the moments of inertia of the adjacent two steering actuators, are the feedback gain compensation coefficients of the adjacent two steering actuators, are the output speeds of the adjacent two steering actuators, is the speed compensation amount of the steering actuator of the i-th wheel. The compensation of the target speed according to the speed compensation amount can be directly adding the target speed before compensation to the speed compensation amount. is the average value of the actual output speeds of the four wheels, which is used as the reference speed of the steering actuator, represents the output speed error of the steering actuator. It can be seen that if a certain steering actuator is disturbed and the output speed decreases, will increase, at which time the speed tracking controller will increase the driving torque to adjust the output speed of the disturbed steering actuator to ​​​​​​The synchronization error between each steering actuator can be reduced by reducing the disturbance steering actuator speed change and transmitting the disturbance steering actuator speed change to other steering actuators through the average speed of the four wheels, and synchronously compensating the steering actuator through the output speed difference between the steering actuator and the adjacent two steering actuators.

[0118] The control structure diagram of the vehicle four-wheel independent steering asynchronous synchronization control can be finally obtained as shown in FIG. 3. represents disturbance.

[0119] As shown in FIG. 4, the technical scheme of the present application further provides a vehicle four-wheel independent steering control device, comprising:

[0120] A determination module is configured to determine a steering mode of the vehicle when the vehicle is steering.

[0121] The determination module is further configured to determine ideal steering angles of each wheel in the steering mode.

[0122] An acquisition module is configured to acquire actual steering angles of each wheel, a first output speed of a virtual main shaft of the vehicle, and second output speeds of steering actuators of each wheel.

[0123] The determination module is further configured to determine driving torques of each steering actuator according to the ideal steering angles, the actual steering angles, the first output speed, and the second output speeds.

[0124] A control module is configured to control each steering actuator to output a corresponding driving torque to drive each wheel to rotate.

[0125] Further, the determination module is further configured to determine that the ideal steering angles of the left front wheel and the right rear wheel are both-arctan(B / L), and the ideal steering angles of the right front wheel and the left rear wheel are both arctan(B / L) if the steering mode is a spot steering mode, where B is a left-right wheelbase of the vehicle, and L is a front-rear wheelbase of the vehicle.

[0126] Further, the determination module is further configured to determine that the ideal steering angles of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel are the same if the steering mode is a wedge steering mode.

[0127] Further, the determination module is further configured to determine that the ideal steering angles of the left front wheel and the right front wheel are both 90°, and the ideal steering angles of the left rear wheel and the right rear wheel are both-90° if the steering mode is a crab steering mode.

[0128] Further, the determination module is further configured to determine that the ideal steering angles of the left front wheel and the right rear wheel are both 0°, the ideal steering angle of the right front wheel is 90°, and the ideal steering angle of the left rear wheel is-90° if the steering mode is an axle steering mode.

[0129] Further, the determining module can be further configured to: if the steering mode is the front wheel steering mode, acquire a vehicle speed, a front axle steering angle and a yaw rate of the vehicle; and calculate ideal steering angles of the left front wheel and the right front wheel according to the vehicle speed, the front axle steering angle and the yaw rate.

[0130] Further, the determining module can be further configured to: if the steering mode is the front wheel steering mode, acquire a vehicle speed, a front axle steering angle and a yaw rate of the vehicle; and calculate ideal steering angles of the left front wheel and the right front wheel according to the vehicle speed, the front axle steering angle and the yaw rate.

[0131] the ideal steering angle of the left front wheel is calculated according to the formula the ideal steering angle of the right front wheel is calculated according to the formula the ideal steering angle of the left front wheel is calculated according to the formula the ideal steering angle of the right front wheel is calculated according to the formula the ideal steering angle of the left front wheel is calculated according to the formula the ideal steering angle of the right front wheel is calculated according to the formula is determined according to the formula is a component of the vehicle speed in the lateral direction of the vehicle, is a distance from the center of mass of the vehicle to the front axle, is the yaw rate, is a component of the vehicle speed in the longitudinal direction of the vehicle, B is the wheelbase of the vehicle, and L is the front-rear wheelbase of the vehicle.

[0132] Further, the determining module can be further configured to: if the steering mode is the front wheel steering mode, acquire a vehicle speed, a front axle steering angle and a yaw rate of the vehicle; and calculate ideal steering angles of the left front wheel and the right front wheel according to the vehicle speed, the front axle steering angle and the yaw rate.

[0133] Further, the determining module can be further configured to: if the steering mode is the front wheel steering mode, acquire a vehicle speed, a front axle steering angle and a yaw rate of the vehicle; and calculate ideal steering angles of the left front wheel and the right front wheel according to the vehicle speed, the front axle steering angle and the yaw rate.

[0134] the ideal steering angle of the left front wheel is calculated according to the formula the ideal steering angle of the right front wheel is calculated according to the formula the ideal steering angle of the left front wheel is calculated according to the formula the ideal steering angle of the right front wheel is calculated according to the formula the ideal steering angle of the left front wheel is calculated according to the formula the ideal steering angle of the right front wheel is calculated according to the formula the ideal steering angle of the left rear wheel is calculated according to the formula the ideal steering angle of the right rear wheel is calculated according to the formula , the ideal steering angle of the left rear wheel is calculated according to the formula the ideal steering angle of the right rear wheel is calculated according to the formula is a constant greater than zero, and m is the mass of the vehicle, is the vehicle speed, is a distance from the center of mass of the vehicle to the front axle, is the front wheel cornering stiffness, and b is a distance from the center of mass of the vehicle to the rear axle. is a rear wheel side slip stiffness, is a yaw rate;

[0135] is determined by equation

[0136] is determined by equation

[0137] is a vehicle speed in a vehicle lateral direction, is a vehicle speed in a vehicle longitudinal direction, B is a left-right wheel base of the vehicle, and L is a front-rear wheel base of the vehicle.

[0138] Further, the determining module can be further configured to: calculate a target rotation speed of each steering actuator according to the ideal rotation angle, the actual rotation angle, and the first output rotation speed; and calculate a driving torque of each steering actuator according to the second output rotation speed and the target rotation speed.

[0139] Further, the determining module can be further configured to: calculate a target rotation speed of each steering actuator according to the ideal rotation angle, the actual rotation angle, and the first output rotation speed; and calculate a driving torque of each steering actuator according to the second output rotation speed and the target rotation speed.

[0140] According to formula , i = 1, 2, 3, 4, i = 1 represents a left front wheel, i = 2 represents a right front wheel, i = 3 represents a left rear wheel, and i = 4 represents a right rear wheel;

[0141] is an actual rotation angle of the i th wheel, , is an ideal rotation angle of the left front wheel, is an ideal rotation angle of the right front wheel, is an ideal rotation angle of the left rear wheel, is an ideal rotation angle of the right rear wheel, is a rotation angle deviation corresponding to the i th wheel, is a maximum value in rotation angle deviations corresponding to each wheel, is a proportional adjustment coefficient corresponding to the i th wheel, is the first output rotation speed, is a target rotation speed of a steering actuator of the i th wheel.

[0142] ​​​​​​​Further, the acquisition module can be further configured to acquire the moment of inertia of each steering actuator, the moment of inertia of each adjacent two steering actuators of the steering actuator, and the output rotation speed;

[0143] The determination module can be further configured to calculate the rotation speed compensation of each steering actuator according to the second output rotation speed, the moment of inertia of the steering actuator, the moment of inertia of each adjacent two steering actuators, and the output rotation speed; and compensate the target rotation speed according to the rotation speed compensation.

[0144] Further, the determination module can calculate the rotation speed compensation of each steering actuator according to the second output rotation speed, the moment of inertia of the steering actuator, the moment of inertia of each adjacent two steering actuators, and the output rotation speed, which can include:

[0145] According to the formula , , calculate the rotation speed compensation of each steering actuator, i = 1, 2, 3, 4, i = 1 represents the left front wheel, i = 2 represents the right front wheel, i = 3 represents the left rear wheel, and i = 4 represents the right rear wheel;

[0146] is the moment of inertia of the steering actuator of the i-th wheel, , is the moment of inertia of each adjacent two steering actuators, , is the feedback gain compensation coefficient of each adjacent two steering actuators, is the second output rotation speed of the steering actuator of the i-th wheel, , is the output rotation speed of each adjacent two steering actuators, is the rotation speed compensation of the steering actuator of the i-th wheel.

[0147] Further, the determination module can calculate the driving torque of each steering actuator according to the second output rotation speed and the target rotation speed, which includes:

[0148] According to the formula calculate the driving torque, i = 1, 2, 3, 4, i = 1 represents the left front wheel, i = 2 represents the right front wheel, i = 3 represents the left rear wheel, and i = 4 represents the right rear wheel;

[0149] is the second output rotation speed of the steering actuator of the i-th wheel, is the target rotation speed of the steering actuator of the i-th wheel, is the transmission link damping coefficient between the steering actuator of the i-th wheel and the virtual main shaft, a transmission link stiffness coefficient between the steering actuator of the ith wheel and the virtual kingpin, a driving torque of the steering actuator of the ith wheel.

[0150] Based on the same inventive concept as the vehicle four-wheel independent steering control method above, the technical solution of the present application also provides a vehicle comprising a controller and a plurality of steering actuators, the controller controls the plurality of steering actuators to act through any one of the vehicle four-wheel independent steering control methods above. The vehicle of the technical solution of the present application can make each wheel reach the corresponding ideal steering angle synchronously, can realize the angular asynchronous control of the vehicle four-wheel independent steering, and can reduce the tire wear degree and improve the steering stability of the vehicle.

[0151] Based on the same inventive concept as the vehicle four-wheel independent steering control method above, the technical solution of the present application also provides a computer readable storage medium, which stores a computer program, the computer program is executed by a processor to implement the steps of any one of the vehicle four-wheel independent steering control methods above.

[0152] Those skilled in the art should understand that the technical solution of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can adopt a completely hardware technical solution, a completely software technical solution, or a technical solution combining software and hardware aspects. Moreover, the present application can adopt a computer program product in the form of being implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program codes.

[0153] The present application is described with reference to flowcharts and / or block diagrams of the method, device (system), and computer program product according to the technical solution of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices produce a device for implementing the functions specified in one or more flows in the flowcharts and / or one or more blocks in the block diagrams.

[0154] These computer program instructions can also be stored in a computer readable storage medium to guide the computer or other programmable data processing devices to work in a specific manner, so that the instructions stored in the computer readable storage medium produce a manufactured product comprising instruction devices, which implement the functions specified in one or more flows in the flowcharts and / or one or more blocks in the block diagrams.

[0155] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart and / or block diagram block or blocks.

[0156] Although the preferred embodiments of the application have been described, those skilled in the art will be able to make modifications and alterations to these preferred embodiments without departing from the spirit and scope of the application. Accordingly, it is intended that the appended claims be construed as including all such alterations and modifications as fall within the scope of the application.

[0157] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A method for controlling independent steering of four wheels of a vehicle, comprising: Determine the vehicle's steering mode when turning; Determine the ideal steering angle for each wheel in the steering mode; The actual rotation angle of each wheel, the first output speed of the vehicle's virtual spindle, and the second output speed of each wheel's steering actuator are obtained. The driving torque of each steering actuator is determined based on the ideal turning angle, the actual turning angle, the first output speed, and the second output speed. The steering actuator is controlled to output the corresponding driving torque to drive each wheel to rotate.

2. The vehicle four-wheel independent steering control method as described in claim 1, wherein, Determining the ideal steering angle for each wheel in the steering mode includes: If the steering mode is the stationary steering mode, then the ideal steering angles of the left front wheel and the right rear wheel are both -arctan(B / L), and the ideal steering angles of the right front wheel and the left rear wheel are both arctan(B / L), where B is the left and right wheelbase of the vehicle, and L is the front and rear wheelbase of the vehicle.

3. The vehicle four-wheel independent steering control method as described in claim 1, wherein, Determining the ideal steering angle for each wheel in the steering mode includes: If the steering mode is a wedge steering mode, then the ideal steering angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel are determined to be the same.

4. The vehicle four-wheel independent steering control method as described in claim 1, wherein, Determining the ideal steering angle for each wheel in the steering mode includes: If the steering mode is crab steering mode, then the ideal steering angles for the left front wheel and the right front wheel are both determined to be 90°, and the ideal steering angles for the left rear wheel and the right rear wheel are both determined to be -90°.

5. The vehicle four-wheel independent steering control method as described in claim 1, wherein, Determining the ideal steering angle for each wheel in the steering mode includes: If the steering mode is the axis steering mode, then the ideal steering angles of the left front wheel and the right rear wheel are both 0°, the ideal steering angle of the right front wheel is 90°, and the ideal steering angle of the left rear wheel is -90°.

6. The vehicle four-wheel independent steering control method as described in claim 1, wherein, Determining the ideal steering angle for each wheel in the steering mode includes: If the steering mode is front-wheel steering mode, then the vehicle speed, front axle steering angle, and yaw rate are obtained; The ideal steering angles of the left and right front wheels are calculated based on the vehicle speed, the front axle steering angle, and the yaw rate.

7. The vehicle four-wheel independent steering control method as described in claim 6, wherein, Calculating the ideal steering angles of the left and right front wheels based on the vehicle speed, the front axle steering angle, and the yaw rate includes: According to the formula Calculate the ideal steering angle of the left front wheel according to the formula. Calculate the ideal steering angle of the right front wheel. The ideal steering angle for the left front wheel is... The ideal steering angle for the right front wheel is... The front axle rotation angle, From the equation Sure, Let be the component of the vehicle speed in the lateral direction. This is the distance from the vehicle's center of gravity to the front axle. The yaw rate is... Let B be the longitudinal component of the vehicle speed, B be the left and right wheelbases of the vehicle, and L be the front and rear wheelbases of the vehicle.

8. The vehicle four-wheel independent steering control method as described in claim 1, wherein, Determining the ideal steering angle for each wheel in the steering mode includes: If the steering mode is four-wheel steering mode, then the vehicle speed, front axle steering angle and yaw rate are obtained; The ideal steering angle of each wheel is calculated based on the vehicle speed, the front axle steering angle, and the yaw rate.

9. The vehicle four-wheel independent steering control method as described in claim 8, wherein, The ideal steering angle of each wheel is calculated based on the vehicle speed, the front axle steering angle, and the yaw rate, including: According to the formula Calculate the ideal steering angle of the left front wheel according to the formula. Calculate the ideal steering angle of the right front wheel. The ideal steering angle for the left front wheel is... The ideal steering angle for the right front wheel is... The front axle rotation angle; According to the formula Calculate the ideal steering angle of the left rear wheel according to the formula. Calculate the ideal steering angle of the right rear wheel. ， The ideal steering angle for the left rear wheel, The ideal steering angle for the right rear wheel is... This refers to the rear axle steering angle of the vehicle. Let m be a constant greater than zero, and let m be the total vehicle mass. For the vehicle speed, This is the distance from the vehicle's center of gravity to the front axle. Let be the front wheel lateral stiffness, and b be the distance from the vehicle's center of gravity to the rear axle. For rear wheel lateral stiffness, The yaw rate is the stated angular velocity. From the equation Sure; From the equation Sure; Let be the component of the vehicle speed in the lateral direction. Let B be the longitudinal component of the vehicle speed, B be the left and right wheelbases of the vehicle, and L be the front and rear wheelbases of the vehicle.

10. The vehicle four-wheel independent steering control method as described in claim 1, wherein, Determining the driving torque of each steering actuator based on the ideal steering angle, the actual steering angle, the first output speed, and the second output speed includes: Calculate the target speed of each steering actuator based on the ideal turning angle, the actual turning angle, and the first output speed. The driving torque of each steering actuator is calculated based on the second output speed and the target speed.

11. The vehicle four-wheel independent steering control method as described in claim 10, wherein, Calculating the target speed of each steering actuator based on the ideal steering angle, the actual steering angle, and the first output speed includes: According to the formula 、 、 Calculate the target rotational speed, i=1, 2, 3, 4, where i=1 represents the left front wheel, i=2 represents the right front wheel, i=3 represents the left rear wheel, and i=4 represents the right rear wheel; Let be the actual turning angle of the i-th wheel. 、 、 、 ， The ideal steering angle for the left front wheel is... The ideal steering angle for the right front wheel is... The ideal steering angle for the left rear wheel, The ideal steering angle for the right rear wheel is... The steering angle deviation corresponding to the i-th wheel. This represents the maximum value among the steering angle deviations corresponding to each wheel. This represents the proportional adjustment coefficient corresponding to the i-th wheel. The first output speed. Let be the target rotational speed of the steering actuator of the i-th wheel.

12. The vehicle four-wheel independent steering control method as described in claim 10 or 11, wherein, After calculating the target speed of each steering actuator based on the ideal steering angle, the actual steering angle, and the first output speed, and before calculating the driving torque of each steering actuator based on the second output speed and the target speed, the method further includes: The moment of inertia of each steering actuator, the moment of inertia of two adjacent steering actuators, and the output speed are obtained. The speed compensation amount of each steering actuator is calculated based on the second output speed, the moment of inertia of the steering actuator, the moment of inertia of the two adjacent steering actuators, and the output speed. The target rotational speed is compensated according to the rotational speed compensation amount.

13. The vehicle four-wheel independent steering control method as described in claim 12, wherein, The speed compensation amount for each steering actuator is calculated based on the second output speed, the moment of inertia of the steering actuator, the moments of inertia of the two adjacent steering actuators, and the output speed, including: According to the formula 、 、 Calculate the speed compensation amount for each of the steering actuators, i=1, 2, 3, 4, where i=1 represents the left front wheel, i=2 represents the right front wheel, i=3 represents the left rear wheel, and i=4 represents the right rear wheel; Let be the moment of inertia of the steering actuator of the i-th wheel. 、 These are the moments of inertia of the two adjacent steering actuators, respectively. 、 These are the feedback gain compensation coefficients for the two adjacent steering actuators, respectively. The second output rotational speed of the steering actuator of the i-th wheel. 、 These are the output speeds of the two adjacent steering actuators, respectively. The rotational speed compensation amount is the amount of the steering actuator of the i-th wheel.

14. The vehicle four-wheel independent steering control method as described in claim 10, wherein, Calculating the driving torque of each steering actuator based on the second output speed and the target speed includes: According to the formula Calculate the driving torque, i=1, 2, 3, 4, where i=1 represents the left front wheel, i=2 represents the right front wheel, i=3 represents the left rear wheel, and i=4 represents the right rear wheel; The second output rotational speed of the steering actuator of the i-th wheel. Let the target rotational speed be the steering actuator of the i-th wheel. Let be the damping coefficient of the transmission link between the steering actuator of the i-th wheel and the virtual spindle. Let be the stiffness coefficient of the transmission link between the steering actuator of the i-th wheel and the virtual spindle. The driving torque is the steering actuator of the i-th wheel.

15. A vehicle four-wheel independent steering control device, wherein, include: The determination module is used to determine the vehicle's steering mode when the vehicle is turning; Determine the ideal steering angle for each wheel in the steering mode; The acquisition module is used to acquire the actual rotation angle of each wheel, the first output speed of the vehicle's virtual spindle, and the second output speed of each wheel's steering actuator. The determining module is further configured to determine the driving torque of each of the steering actuators based on the ideal turning angle, the actual turning angle, the first output speed and the second output speed; The control module is used to control each of the steering actuators to output the corresponding driving torque so as to drive each wheel to rotate.

16. A vehicle comprising a controller and a plurality of steering actuators, the controller controlling the actuation of the plurality of steering actuators by means of the method of any one of claims 1-14.

17. A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method according to any one of claims 1-14.

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