A method for steering control of automobiles using a hub motor

Abstract

This invention discloses a wheel hub motor-based vehicle steering control method, comprising the following steps: setting the target rotational speed of the wheel hub motors during center turn; employing a common-parameter, different-proportion PI algorithm to calculate the target torque of each wheel based on the difference between the actual rotational speed and the target rotational speed of each wheel hub motor; calculating the sum of the target torques of the left and right wheel hub motors; and obtaining the larger value T of the sum of the target torques of the left and right wheel hub motors. max ; Calculate the sum of the target torques of the left and right motors and T max The algorithm calculates the difference between the left and right wheel hub motors and distributes them according to the percentage of rotational speed among the hub motors on the same side. It also calculates the first, second, and third target torques for each hub motor and sets the rotation directions and target torques for each motor. This algorithm enables the vehicle to steer around its geometric center by rotating the left and right wheel hub motors in both directions, significantly reducing the turning radius and improving the vehicle's passability.

Description

Technical Field

[0001] This invention belongs to the field of automotive steering technology, and more specifically, relates to a wheel hub motor automotive steering control method. Background Technology

[0002] Traditional automobiles rely on steering mechanisms for steering, resulting in large turning radii and poor maneuverability. Hub motor vehicles, with their independently controllable wheel states, have become a crucial component of electric vehicles. Because the rotation direction and torque of each wheel are independently controllable, hub motor vehicles can achieve vehicle rotation around a geometric center by having one hub motor rotate clockwise while the other rotates counter-clockwise, with the total torque on both sides simultaneously equal to zero. This solves the problem of large turning radii. Summary of the Invention

[0003] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a vehicle control method that reduces the turning radius of a vehicle and improves the vehicle's passability.

[0004] To achieve the above objectives, according to one aspect of the present invention, a hub motor-driven automobile steering control method is provided, comprising the following steps:

[0005] S100: Sets the target rotational speed of the hub motor during center turn. target ,w target >0;

[0006] w target = k*|θ|.

[0007] Where: θ—actual steering wheel rotation angle, θ=0 indicates the steering wheel is in the center position; θ<0 indicates turning the steering wheel to the left; θ>0 indicates turning the steering wheel to the right; k—target speed setting coefficient;

[0008] S200: Employs a common-parameter, different-proportion PI algorithm to calculate the target torque T for each wheel based on the difference between the actual speed and the target speed of each wheel hub motor. ij ;

[0009] S300: Calculate the sum of the target torques of the left and right hub motors;

[0010] S400: Obtain the larger of the target torque sum T of the left and right hub motors. max ;

[0011] T max =max(T) ladd T radd )

[0012] Wherein: T ladd—The sum of the target torques of the left-side hub motors; T radd —The sum of the target torques of the right-side hub motor.

[0013] S500: Calculate the sum of the target torques of the left and right motors and T max The difference;

[0014]

[0015] S600: The sum of the target torques of the hub motors on the same side and T max The difference is distributed between the hub motors on the same side according to the percentage of speed; the hub motor with a higher speed receives a smaller torque.

[0016] S700: Calculate the first, second, and third execution target torques of each hub motor by combining the target torque of each hub motor and the change in the target torque of each hub motor;

[0017] S800: Based on the steering wheel angle signal and the third execution target torque, the rotation direction of the left and right wheel hub motors and the execution drive target torque of each wheel hub motor are set.

[0018] Furthermore, in step S100, the target rotation speed of the hub motor during center steering is set according to the steering wheel angle:

[0019] The setting method is w target It is positively correlated with the absolute value of the steering wheel angle θ: w target = k*|θ|.

[0020] Where: θ—actual steering wheel rotation angle, θ=0 indicates the steering wheel is in the middle position; θ<0 indicates turning the steering wheel to the left; θ>0 indicates turning the steering wheel to the right; k—target speed setting state.

[0021] Furthermore, the calculation method for the target torque of each wheel in step S200 is as follows:

[0022]

[0023] Wherein: T 11 —Target torque of the left front wheel hub motor; T 12 —Target torque of the left rear wheel hub motor; T 21 —Target torque of the right front wheel hub motor; T 22 —Target torque of the right rear wheel hub motor; w 11 —Actual rotational speed of the left front wheel hub motor; w 12 —Actual rotational speed of the left rear wheel hub motor; w 21 —Actual rotational speed of the right front wheel hub motor; w 22—Actual speed of the right rear wheel hub motor; k —Common integral coefficient; k 11 —Adjustment ratio parameters for the left front wheel hub motor; k 12 —Adjustment ratio parameters for the left rear wheel hub motor; k 21 —Right front wheel hub motor adjustment ratio parameter; k 22 —Right rear wheel hub motor adjustment ratio parameter; t —Working time.

[0024] w 11 =0 indicates that the left front wheel hub motor is rotating, w 11 >0 indicates that the left front wheel hub motor is rotating in the forward direction. 11 <0 indicates that the left front wheel hub motor is in reverse, w 12 w 21 w 22 Similarly;

[0025] Furthermore, the k 11 k 12 k 21 k 22 The calculation method is as follows:

[0026]

[0027]

[0028]

[0029]

[0030] Where: k0 and k1 are proportional coefficients, with k0 > k1. Using k0 and k1, the adjustment time can be shortened when the actual speed of the hub motor differs significantly from the target speed, thus improving the system's response characteristics; Δw is the speed error threshold.

[0031] Furthermore, under steady-state conditions, the T 11 T 12 T 21 T 22 The following relationship exists:

[0032]

[0033] Wherein: F 11 —Wheel load borne by the left front hub motor; F 12 —Wheel load borne by the left rear hub motor; F 21 —Wheel load borne by the right front wheel hub motor; F 22 —Wheel load borne by the right rear wheel hub motor; μ x —Tire longitudinal adhesion coefficient;

[0034] μ on different road surfaces x Unlike other methods, the PI algorithm is used to automatically adjust the target torque of the hub motor to a torque relationship under stable operating conditions based on the speed difference.

[0035] Furthermore, the method for distributing torque between the hub motors in step S600 is as follows:

[0036]

[0037] Where: ΔT 11 —The change in target torque of the left front wheel hub motor; ΔT 12 —The change in target torque of the left rear wheel hub motor; ΔT 21 —The change in target torque of the right front wheel hub motor; ΔT 22 — Target torque change of the right rear wheel hub motor.

[0038] Furthermore, the calculation method for the first, second, and third execution target torques of each hub motor in step S700 is as follows:

[0039] Calculate the first execution target torque of each hub motor by combining the target torque of each hub motor and the change in the target torque of each hub motor:

[0040]

[0041] Among them: T1 11 —The first target torque for the left front wheel hub motor; T1 12 —The first target torque for the left rear wheel hub motor; T1 21 —The first target torque for the right front wheel hub motor; T1 22 —The first target torque for the right rear wheel hub motor;

[0042] To protect each motor, the torque of each motor is limited based on its output capacity, and the second target torque is calculated. The calculation formula is as follows:

[0043]

[0044] Among them: T2 11 —The second target torque for the left front wheel hub motor; T2 12 —The second target torque for the left rear wheel hub motor; T2 21 —The second target torque for the right front wheel hub motor; T2 22 —The second target torque for the right rear wheel hub motor; T 11max —Maximum permissible torque for the left front wheel hub motor; T 12max —Maximum permissible torque for the left rear wheel hub motor; T21max —Maximum permissible torque for the right front wheel hub motor; T 22max —Maximum permissible torque for the right rear wheel hub motor;

[0045] To ensure the vehicle's center of gravity remains stationary, the total torque on the left and right sides should be equal. Based on the second target torque, the minimum values ​​of the left and right torques are calculated, along with the proportion of the second target torque of the left and right front wheel hub motors to the total second target torque on the same side.

[0046]

[0047] Wherein: T min —Minimum total torque on the left and right sides; τ1 —Proportion of the second execution target torque of the left front wheel hub motor to the total second execution target torque on the left side; τ2 —Proportion of the second execution target torque of the right front wheel hub motor to the total second execution target torque on the right side;

[0048] Based on T min Calculate the third target torque for each hub motor using τ1 and τ2:

[0049]

[0050] Among them: T3 11 —The third target torque for the left front wheel hub motor; T3 12 —The third target torque for the left rear wheel hub motor; T3 21 —The third target torque for the right front wheel hub motor; T3 22 —The third target torque for the right rear wheel hub motor;

[0051] Based on the known formula, if We can obtain:

[0052]

[0053] Furthermore, the method for setting the rotation direction of the left and right hub motors and the target torque for each hub motor in step S800 based on the steering wheel angle signal and the third target torque is as follows:

[0054] If |θ|<θ1, then the left and right hub motors are set to non-working state, and the target torque of the left and right hub motors is 0.

[0055] If the steering wheel is turned to the right (θ>θ2), the rotation states of the left and right hub motors will be opposite, with the right hub motor set to reverse and the left hub motor set to forward.

[0056]

[0057] If the steering wheel is operated on the left, i.e., θ < -θ2, then the rotation states of the left and right hub motors are opposite, with the right hub motor set to forward rotation and the left hub motor set to reverse rotation.

[0058]

[0059] θ1—Intermediate position threshold; θ2—Anti-shake threshold, θ2>θ1; T d11 —The left front wheel hub motor executes the target driving torque; T d12 —The left rear wheel hub motor drives the target torque; T d21 —The right front wheel hub motor drives the target torque; T d22 —The left rear wheel hub motor drives the target torque.

[0060] According to another aspect of the present invention, an automobile is provided, including a steering control system, the steering control system having a steering mode that can be freely opened or closed, wherein when the steering mode is opened, the steering control device is used to perform the steering method as described in claims 1-8;

[0061] The steering control mode has a built-in target speed setting coefficient k, with multiple k value options for the driver to choose from.

[0062] Furthermore, the steering control mode also includes the following functions:

[0063] If the theoretical angular velocity w of the vehicle rotating around the geometry z The actual rotational angular velocity w of the vehicle act The absolute value of the difference |w z -w act If the value is less than or equal to the threshold m, the vehicle will turn normally. If the value is greater than m, it means that there is a foreign object protruding on the road surface that prevents the vehicle from turning laterally and cannot achieve center steering. In this case, the steering mode will be turned off and the vehicle will stop working.

[0064] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0065] 1. The algorithm of this invention enables the wheel hub motor vehicle to turn around the geometric center of the vehicle by rotating the left and right wheel hub motors in both directions, which greatly reduces the turning radius of the vehicle and improves the vehicle's passability;

[0066] 2. The algorithm of this invention limits the output torque of each hub to prevent the output torque from exceeding its capacity, effectively protecting the motor and improving its service life.

[0067] 3. The algorithm of this invention adjusts the target speed of each hub motor according to the rotation of the steering wheel. The higher the speed, the greater the output torque. The greater the torque, the faster the vehicle rotates around the geometric center. Thus, the rotation speed of the vehicle can be controlled according to the driver's intention. Attached Figure Description

[0068] Figure 1 This is a schematic flowchart of a wheel hub motor-driven automobile steering control method according to an embodiment of the present invention;

[0069] Figure 2 This is a schematic diagram of the forces acting on a vehicle according to an embodiment of the present invention, which describes a wheel hub motor-driven vehicle steering control method. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0071] Please refer to Figure 1 This invention provides a wheel hub motor-driven automotive steering control method, comprising the following steps:

[0072] S100: Sets the target rotational speed of the hub motor during center turn. target ,w target >0;w target The larger the value, the more severe the tire wear during center steering, therefore w target It shouldn't be set too high. Preferably, w target Take 50 rpm.

[0073] w target =k*|θ|

[0074] Where: θ—actual steering wheel rotation angle, θ=0 indicates the steering wheel is in the center position; θ<0 indicates turning the steering wheel to the left; θ>0 indicates turning the steering wheel to the right; k—target speed setting coefficient;

[0075] S200: Employs a common-parameter, different-proportion PI algorithm to calculate the target torque T for each wheel based on the difference between the actual speed and the target speed of each wheel hub motor. ij ;

[0076] The calculation method for the target torque of each wheel is as follows:

[0077]

[0078] Wherein: T 11—Target torque of the left front wheel hub motor; T 12 —Target torque of the left rear wheel hub motor; T 21 —Target torque of the right front wheel hub motor; T 22 —Target torque of the right rear wheel hub motor; w 11 —Actual rotational speed of the left front wheel hub motor; w 12 —Actual rotational speed of the left rear wheel hub motor; w 21 —Actual rotational speed of the right front wheel hub motor; w 22 —Actual speed of the right rear wheel hub motor; k —Common integral coefficient; k 11 —Adjustment ratio parameters for the left front wheel hub motor; k 12 —Adjustment ratio parameters for the left rear wheel hub motor; k 21 —Right front wheel hub motor adjustment ratio parameter; k 22 —Right rear wheel hub motor adjustment ratio parameter; t —Working time.

[0079] w 11 =0 indicates that the left front wheel hub motor is rotating, w 11 >0 indicates that the left front wheel hub motor is rotating in the forward direction. 11 <0 indicates that the left front wheel hub motor is in reverse, w 12 w 21 w 22 Similarly;

[0080] The k 11 k 12 k 21 k 22 The calculation method is as follows:

[0081]

[0082]

[0083]

[0084]

[0085] Where: k0 and k1 are proportional coefficients, with k0 > k1. Using k0 and k1, the adjustment time can be shortened when the actual speed of the hub motor differs significantly from the target speed, thus improving the system's response characteristics; Δw is the speed error threshold.

[0086] The T 11 T 12 T 21 T 22 The following relationship exists:

[0087]

[0088] Wherein: F 11 —Wheel load borne by the left front hub motor; F 12 —Wheel load borne by the left rear hub motor; F 21 —Wheel load borne by the right front wheel hub motor; F 22 —Wheel load borne by the right rear wheel hub motor; μ x —Tire longitudinal adhesion coefficient;

[0089] μ on different road surfaces x Unlike other methods, the PI algorithm is used to automatically adjust the target torque of the hub motor to a torque relationship under stable operating conditions based on the speed difference.

[0090] S300: Calculate the sum of the target torques of the left and right hub motors;

[0091]

[0092] Wherein: T ladd —The sum of the target torques of the left-side hub motors; T radd —The sum of the target torques of the right-side hub motor.

[0093] S400: Obtain the larger of the target torque sum T of the left and right hub motors. max ;

[0094] T max =max(T) ladd T radd )

[0095] Wherein: T ladd —The sum of the target torques of the left-side hub motors; T radd —The sum of the target torques of the right-side hub motor.

[0096] S500: Calculate the sum of the target torques of the left and right motors and T max The difference;

[0097]

[0098] Where: ΔT1—the sum of the target torques of the left wheel hub motor and T max The difference; ΔT2—the sum of the target torques of the right wheel hub motor and T max The difference.

[0099] If T ladd =T radd If T ladd >T radd If T ladd <Tradd If ΔT1 > 0, then ΔT2 = 0;

[0100] Therefore, ΔT1*ΔT2=0.

[0101] S600: The difference between the sum of the target torques of the hub motors on the same side and the torque distribution is allocated among the hub motors on the same side according to the percentage of their speeds. Hub motors with higher speeds receive a smaller torque, and vice versa. The allocation calculation method is as follows:

[0102]

[0103] Where: ΔT 11 —The change in target torque of the left front wheel hub motor; ΔT 12 —The change in target torque of the left rear wheel hub motor; ΔT 21 —The change in target torque of the right front wheel hub motor; ΔT 22 — Target torque change of the right rear wheel hub motor.

[0104] S700: Calculate the first, second, and third execution target torques of each hub motor by combining the target torque of each hub motor and the change in the target torque of each hub motor;

[0105] The first target torque is the theoretical target value, the second target torque is the value of each wheel after being limited by its maximum torque, and the third target torque is the redistribution target value where the total torque on the left and right sides is equal and cannot exceed the capacity of each motor.

[0106] Calculate the first execution target torque of each hub motor by combining the target torque of each hub motor and the change in the target torque of each hub motor:

[0107]

[0108] Among them: T1 11 —The first target torque for the left front wheel hub motor; T1 12 —The first target torque for the left rear wheel hub motor; T1 21 —The first target torque for the right front wheel hub motor; T1 22 —The first target torque for the right rear wheel hub motor;

[0109] To protect each motor, the torque of each motor is limited based on its output capacity, and the second target torque is calculated. The calculation formula is as follows:

[0110]

[0111] Among them: T2 11 —The second target torque for the left front wheel hub motor; T2 12—The second target torque for the left rear wheel hub motor; T2 21 —The second target torque for the right front wheel hub motor; T2 22 —The second target torque for the right rear wheel hub motor; T 11max —Maximum permissible torque for the left front wheel hub motor; T 12max —Maximum permissible torque for the left rear wheel hub motor; T 21max —Maximum permissible torque for the right front wheel hub motor; T 22max —Maximum permissible torque for the right rear wheel hub motor;

[0112] T 11max T 12max T 21max T 22max It is determined by the operating status of each motor. Simultaneously, the following relationships apply:

[0113]

[0114] We can obtain:

[0115]

[0116] To ensure the vehicle's center of gravity remains stationary, the total torque on the left and right sides should be equal. Based on the second target torque, the minimum values ​​of the left and right torques are calculated, along with the proportion of the second target torque of the left and right front wheel hub motors to the total second target torque on the same side.

[0117]

[0118] Wherein: T min —Minimum total torque on the left and right sides; τ1 —Proportion of the second execution target torque of the left front wheel hub motor to the total second execution target torque on the left side; τ2 —Proportion of the second execution target torque of the right front wheel hub motor to the total second execution target torque on the right side;

[0119] And because

[0120]

[0121] We can obtain:

[0122]

[0123] We can obtain:

[0124]

[0125] We can obtain:

[0126]

[0127] We can obtain:

[0128]

[0129] We can obtain:

[0130]

[0131] We can obtain:

[0132]

[0133] We can obtain:

[0134] T min =T2 11 +T2 12 =T2 21 +T2 22

[0135] That is, when the maximum allowable torque of the hub motor is greater than its first execution target torque, the sum of the first execution target torques on the left is equal to the sum of the first execution target torques on the right.

[0136] Based on T min Calculate the third target torque for each hub motor using τ1 and τ2:

[0137]

[0138] Among them: T3 11 —The third target torque for the left front wheel hub motor; T3 12 —The third target torque for the left rear wheel hub motor; T3 21 —The third target torque for the right front wheel hub motor; T3 22 —The third target torque for the right rear wheel hub motor;

[0139] We can obtain:

[0140]

[0141] We can obtain:

[0142]

[0143] We can obtain:

[0144]

[0145] We can obtain:

[0146]

[0147] That is, the third target torque of each hub motor is always less than or equal to its maximum allowable torque.

[0148] like There is another T min =T2 11 +T2 12 =T2 21 +T2 22

[0149] We can obtain:

[0150]

[0151] We can obtain:

[0152]

[0153] We can obtain:

[0154]

[0155] We can obtain:

[0156]

[0157] That is, when the first execution target torque of each hub motor is less than its maximum allowable torque, the third execution target torque of each hub motor is always equal to the first execution target torque of each hub motor, and there is no limitation on the output torque, so as to maximize the torque required for the wheel to rotate around the geometric center.

[0158] S800: Based on the steering wheel angle signal and the third execution target torque, the rotation direction of the left and right wheel hub motors and the execution drive target torque of each wheel hub motor are set.

[0159] If |θ|<θ1, then the left and right hub motors are set to non-working state, and the target torque of the left and right hub motors is 0.

[0160] If the steering wheel is turned to the right (θ>θ2), the rotation states of the left and right hub motors will be opposite, with the right hub motor set to reverse and the left hub motor set to forward.

[0161]

[0162] If the steering wheel is operated on the left, i.e., θ < -θ2, then the rotation states of the left and right hub motors are opposite, with the right hub motor set to forward rotation and the left hub motor set to reverse rotation.

[0163]

[0164] θ1—Intermediate position threshold; θ2—Anti-shake threshold, θ2>θ1; T d11 —The left front wheel hub motor executes the target driving torque; T d12 —The left rear wheel hub motor drives the target torque; T d21 —The right front wheel hub motor drives the target torque; T d22 —The left rear wheel hub motor drives the target torque.

[0165] The rotation effect of this algorithm is theoretically demonstrated below:

[0166] Given that the sum of the total torque on the left and the total torque on the right is equal to 0, it can be concluded that to ensure the vehicle's center of mass does not move when rotating around its geometric center, this prevents the vehicle from veering off course, which could lead to increased turning weight or uncontrollable cornering behavior. That is: (T d11 +T d12 )+(T d21 +T d22 The proof is as follows: ) = 0

[0167] (T d11 +T d12 )+(T d21 +T d22 )=(T3 11 +T3 12 )+(-T3 21 -T3 22 )

[0168] or (T) d11 +T d12 )+(T d21 +T d22 )=(-T3 11 -T3 12 )+(T3 21 +T3 22 )

[0169] We can obtain: (T) d11 +T d12 )+(T d21 +T d22 ) = T min -T min =0

[0170] We can obtain: (T) d11 +T d12 )+(T d21 +T d22 )=(-T3 11 -T3 12 )+(T3 21 +T3 22 ) = 0

[0171] Calculate the rotational speed of the vehicle about its geometric center:

[0172] The rotational torque generated by the driving force provided by the ground is:

[0173]

[0174] The drag torque generated by the ground in the lateral direction of the tire is:

[0175]

[0176] The resistance torque generated by the rolling resistance of the wheel is:

[0177]

[0178] Where: M x —The ground provides the driving force, generating a torque that rotates around the vehicle's geometric center; d—the vehicle's track width; d0—the straight-line distance from the vehicle's geometric center to the hub motor; θ0—the angle between the line segment from the vehicle's geometric center to the hub motor and the length direction of the vehicle body; M y —The drag torque generated by the lateral frictional resistance of the vehicle, which rotates geometrically around the vehicle; μ y — The coefficient of adhesion in the lateral direction of the tire; M fx — Rotational resistance torque around the geometric center of the vehicle generated by the rolling friction resistance of the grinding wheel; f — Tire rolling friction coefficient; r — Tire radius.

[0179] It can be known that d0 and θ0 are:

[0180]

[0181] Where: l — wheelbase between the front and rear axles of the vehicle.

[0182] The rotational angular acceleration can be calculated from the total torque at the vehicle's geometric center:

[0183] J*α=M x -M fx -M y

[0184] Right now:

[0185] Where: J—moment of inertia of the vehicle about its geometric center; α—angular acceleration of the vehicle about its geometric center.

[0186] The angular velocity of the vehicle around its geometric center can be determined as follows:

[0187]

[0188] Where: w z —The theoretical angular velocity of the vehicle rotating around the geometry.z =0 indicates that the car is not rotating around the center.

[0189] If the theoretical angular velocity w of the vehicle rotating around the geometry z The actual rotational angular velocity w of the vehicle act The absolute value of the difference |w z -w act If the value is less than or equal to the threshold m, the vehicle will turn normally. If the value is greater than m, it means that there is a foreign object protruding on the road surface that prevents the vehicle from turning laterally and thus cannot achieve center steering.

[0190] This application also provides an automobile, including a steering control system, the steering control system having a steering mode that can be freely turned on or off, and when the steering mode is turned on, the steering control device is used to execute the steering method.

[0191] The steering control mode has a built-in target speed setting coefficient k, with multiple k value options for the driver to choose from.

[0192] The steering control mode also includes the following functions:

[0193] If the theoretical angular velocity w of the vehicle rotating around the geometry z The actual rotational angular velocity w of the vehicle act The absolute value of the difference |w z -w act If the value is less than or equal to the threshold m, the vehicle will turn normally. If the value is greater than m, it means that there is a foreign object protruding on the road surface that prevents the vehicle from turning laterally and cannot achieve center steering. In this case, the steering mode will be turned off and the vehicle will stop working.

[0194] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling automotive steering using a hub motor, characterized in that, Includes the following steps: S100: Sets the target rotational speed of the hub motor during center turn. target ,w target >0; w target =k*|θ|; Where: θ—actual steering wheel rotation angle, θ=0 indicates the steering wheel is in the center position; θ<0 indicates turning the steering wheel to the left; θ>0 indicates turning the steering wheel to the right; k—target speed setting coefficient; S200: Employs a common-parameter, different-proportion PI algorithm to calculate the target torque T of each wheel based on the difference between the actual speed of each wheel hub motor and the target speed. ij ; S300: Calculate the sum of the target torques of the left hub motor and the sum of the target torques of the right hub motor; S400: Obtain the larger of the target torque sum T of the left and right hub motors. max ; T max =max(T ladd ,T radd ); Wherein: T ladd —The sum of the target torques of the left wheel hub motors; T radd —The sum of the target torques of the right-side hub motor; S500: Calculate the sum of the target torques of the left and right motors and T max The difference; ； ΔT1——The total target torque T of the left wheel hub motor ladd With T max The difference; ΔT2—the sum of the target torques of the right wheel hub motor and T max The difference; S600: The sum of the target torques of the hub motors on the same side and T max The torque difference is distributed between the hub motors on the same side according to the percentage of their rotational speeds; the hub motor with the higher rotational speed receives a smaller torque. The method for distributing torque between the hub motors in step S600 is as follows: ； Where: ΔT 11 —The change in target torque of the left front wheel hub motor; ΔT 12 —The change in target torque of the left rear wheel hub motor; ΔT 21 —The change in target torque of the right front wheel hub motor; ΔT 22 —The change in target torque of the right rear wheel hub motor; w 11 —Actual rotational speed of the left front wheel hub motor; w 12 —Actual rotational speed of the left rear wheel hub motor; w 21 —Actual rotational speed of the right front wheel hub motor; w 22 —Actual speed of the right rear wheel hub motor; S700: Calculate the first, second, and third execution target torques of each hub motor by combining the target torque of each hub motor and the change in the target torque of each hub motor; The calculation methods for the first, second, and third execution target torques of each hub motor in step S700 are as follows: Calculate the first execution target torque of each hub motor by combining the target torque of each hub motor and the change in the target torque of each hub motor: ； Among them: T1 11 —The first target torque for the left front wheel hub motor; T1 12 —The first target torque for the left rear wheel hub motor; T1 21 —The first target torque for the right front wheel hub motor; T1 22 —First execution of the right rear wheel hub motor Target torque; To protect each motor, the torque of each motor is limited based on its output capacity, and the second target torque is calculated; the calculation formula is: ； Among them: T2 11 —The second target torque for the left front wheel hub motor; T2 12 —The second target torque for the left rear wheel hub motor; T2 21 —The second target torque for the right front wheel hub motor; T2 22 —Second execution of the right rear wheel hub motor Target torque; T 11max —Maximum permissible torque for the left front wheel hub motor; T 12max —Maximum permissible torque for the left rear wheel hub motor; T 21max —Maximum permissible torque for the right front wheel hub motor; T 22max —Maximum permissible torque for the right rear wheel hub motor; To ensure the vehicle's center of gravity remains stationary, the total torque on the left and right sides should be equal. Based on the second target torque, the minimum values ​​of the left and right torques are calculated, along with the proportion of the second target torque of the left and right front wheel hub motors to the total second target torque on the same side. ； Wherein: T min —Minimum total torque on the left and right sides; τ1 —Proportion of the second execution target torque of the left front wheel hub motor to the total second execution target torque on the left side; τ2 —Proportion of the second execution target torque of the right front wheel hub motor to the total second execution target torque on the right side; Based on T min Calculate the third target torque for each hub motor using τ1 and τ2: ； Among them: T3 11 —The third target torque for the left front wheel hub motor; T3 12 —The third target torque for the left rear wheel hub motor; T3 21 —The third target torque for the right front wheel hub motor; T3 22 —The third actuator of the right rear wheel hub motor Target torque; Based on the known formula, if We can obtain: ； S800: Based on the steering wheel angle signal and the third target torque, set the rotation direction of the left and right hub motors and the target torque for each hub motor.

2. The in-wheel motor-driven automobile steering control method according to claim 1, characterized in that, In step S100, the target speed of the hub motor during center steering is set according to the steering wheel angle: The setting method is w target It is positively correlated with the absolute value of the steering wheel angle θ: w target =k*|θ|; Where: θ—actual steering wheel rotation angle, θ=0 indicates the steering wheel is in the middle position; θ<0 indicates turning the steering wheel to the left; θ>0 indicates turning the steering wheel to the right; k—target speed setting state.

3. The in-wheel motor-driven automobile steering control method according to claim 2, characterized in that, The calculation method for the target torque of each wheel in step S200 is as follows: ; Wherein: T 11 —Target torque of the left front wheel hub motor; T 12 —Target torque of the left rear wheel hub motor; T 21 —Target torque of the right front wheel hub motor; T 22 —Target torque of the right rear wheel hub motor; w 11 —Actual rotational speed of the left front wheel hub motor; w 12 —Actual rotational speed of the left rear wheel hub motor; w 21 —Actual rotational speed of the right front wheel hub motor; w 22 —Actual speed of the right rear wheel hub motor; k —Common integral coefficient; k 11 —Adjustment ratio parameters for the left front wheel hub motor; k 12 —Adjustment ratio parameters for the left rear wheel hub motor; k 21 —Right front wheel hub motor adjustment ratio parameter; k 22 —Right rear wheel hub motor adjustment ratio parameter; t —Working time; w 11 =0 indicates that the left front wheel hub motor is rotating, w 11 >0 indicates that the left front wheel hub motor is rotating in the forward direction. 11 <0 indicates that the left front wheel hub motor is in reverse, w 12 w 21 w 22 Similarly.

4. The in-wheel motor vehicle steering control method according to claim 3, characterized in that, The k 11 k 12 k 21 k 22 The calculation method is as follows: ； Where: k0, k1—proportional coefficient values, and k0>k1; by using k0, k1, the adjustment time can be shortened when the actual speed of the hub motor differs greatly from the target speed; the response characteristics of the system are improved; Δw—speed error threshold.

5. The in-wheel motor vehicle steering control method according to claim 4, characterized in that, Under steady-state conditions, the T 11 T 12 T 21 T 22 The following relationship exists: ; Wherein: F 11 —Wheel load borne by the left front hub motor; F 12 —Wheel load borne by the left rear hub motor; F 21 —Wheel load borne by the right front wheel hub motor; F 22 —Wheel load borne by the right rear wheel hub motor; μ x —Tire longitudinal adhesion coefficient; μ on different road surfaces x Unlike other methods, the PI algorithm is used to automatically adjust the target torque of the hub motor to a torque relationship under stable operating conditions based on the speed difference.

6. The in-wheel motor vehicle steering control method according to claim 1, characterized in that, The method for setting the rotation direction of the left and right hub motors and the target driving torque of each hub motor in step S800 based on the steering wheel angle signal and the third target torque is as follows: If |θ|<θ1, then the left and right hub motors are set to non-working state, and the target torque of the left and right hub motors is 0. If the steering wheel is turned to the right (θ>θ2), the rotation states of the left and right hub motors will be opposite, with the right hub motor set to reverse and the left hub motor set to forward. ； If the steering wheel is operated on the left (θ < -θ2), then the rotation states of the left and right hub motors are opposite, and the right hub motor is set... The left wheel hub motor is set to reverse rotation while the left wheel hub motor is set to forward rotation. ； θ1—Intermediate position threshold; θ2—Anti-shake threshold, θ2>θ1; Td 11 —The left front wheel hub motor executes the target drive torque; Td 12 —The left rear wheel hub motor drives the target torque; Td 21 —The right front wheel hub motor drives the target torque; Td 22 —The left rear wheel hub motor drives the target torque.

7. A car, characterized in that, The system includes a steering control system, which has a steering mode that can be freely turned on or off. When the steering mode is turned on, the steering control device is used to execute the steering control method as described in any one of claims 1-5. The steering mode has a built-in target speed setting coefficient k, with multiple k value options for the driver to choose from.

8. A car according to claim 7, characterized in that: The steering mode also includes the following functions: If the theoretical angular velocity w of the vehicle rotating around the geometry z The actual rotational angular velocity w of the vehicle act The absolute value of the difference |w z -w act If the value is less than or equal to the threshold m, the vehicle will turn normally. If the value is greater than m, it means that there is a foreign object protruding on the road surface that prevents the vehicle from turning laterally and cannot achieve center steering. In this case, the steering mode will be turned off and the vehicle will stop working.

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