A steering consistency angle distribution control method suitable for skateboard chassis

Abstract

The present invention discloses a steering consistency angle distribution control method suitable for a skateboard chassis, comprising: estimating the vehicle's yaw rate, slip angle, and the coordinates of the instantaneous steering center based on the vehicle coordinate system; establishing an ideal two-degree-of-freedom vehicle model based on the kinematic equations of the skateboard chassis; constructing an ideal value correction controller to optimize and compensate for the ideal value; calculating a target deviation from the ideal state based on the vehicle's yaw rate, slip angle, and the coordinates of the instantaneous steering center based on the vehicle coordinate system; establishing a four-wheel independent steering system model; calculating a virtual control force for lateral motion and a virtual control torque for yaw motion; and calculating the control angles of each tire based on the calculated geometric instantaneous center coordinates. The present method can effectively resolve the steering inconsistency problem caused by the existence of control redundancy and the increase in degrees of freedom, effectively improving vehicle steering stability.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile steering systems, and in particular relates to a steering consistency angle distribution control method applicable to a skateboard chassis. Background Art

[0002] As automotive technology continues to advance and evolve, users' demands for vehicle intelligence and comfort continue to rise, while manufacturers' demand for lower vehicle production costs also continues to increase. Existing emerging auto brands primarily produce their vehicles in a modularized subsystem approach, which prevents further optimization of the time and cost of individual vehicle production.

[0003] The skateboard chassis is mainly constructed with a "front axle + battery + thermal management + rear axle" structure, which includes the drive, brake, steering, battery and other devices required for a vehicle. Unlike other chassis, the skateboard chassis separates the upper and lower bodies through reserved electrical and body interfaces, so that the body and cockpit can be replaced as needed. In order to achieve upper and lower split vehicle manufacturing, the skateboard chassis adopts a fully integrated + full wire control solution, integrating power, braking, steering, thermal management, three-electric, etc. into the chassis. In order to meet the design requirements of different upper body functional needs, the vehicle skateboard chassis mostly adopts a fully wire-controlled independent steering structure design. Each wheel can be called a corner module, including wheel-side motors, steering motors and other actuators.

[0004] Since fully controlled-by-wire independent steering eliminates the traditional mechanical linkage between the left and right wheels and incorporates rear-wheel steering, there are issues with angle distribution during vehicle steering. The execution system of multiple steering motors requires high network synchronization, leading to inconsistent and unstable vehicle steering caused by asynchronous control times due to network latency. Existing control methods mostly use rear-wheel steering angles as compensation for the front-wheel steering process, which is insufficient to fully utilize the advantages of controlled-by-wire four-wheel independent steering systems. Therefore, establishing an effective control method and employing a robust control algorithm for angle distribution control in a controlled-by-wire four-wheel independent steering system suitable for a skateboard chassis is essential. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a steering consistency angle distribution control method suitable for a skateboard chassis. The four wheels of the skateboard chassis can rotate independently, greatly improving the freedom of vehicle driving; it can effectively solve the steering inconsistency problem caused by the existence of control redundancy and the increase in freedom, and effectively improve the steering stability of the vehicle.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a steering consistency angle distribution control method applicable to a skateboard chassis, comprising the following steps:

[0008] 1) Use the unscented Kalman filter algorithm to estimate the vehicle's yaw rate, sideslip angle, and the instantaneous coordinates of the steering center based on the vehicle coordinate system;

[0009] 2) Establish an ideal two-degree-of-freedom model of the vehicle based on the kinematic equations of the skateboard chassis; Based on the ideal two-degree-of-freedom model, consider the vehicle under steady-state steering conditions and calculate the desired ideal state of the vehicle, including the ideal yaw rate, ideal sideslip angle, and ideal instantaneous steering center based on the vehicle coordinate system; construct an ideal value correction controller to optimize the design and compensation of the ideal value; and calculate the target deviation value from the ideal state based on the vehicle yaw rate, sideslip angle, and the coordinates of the instantaneous steering center based on the vehicle coordinate system;

[0010] 3) establishing a four-wheel independent steering system model; according to the target deviation value in step 2), using the four-wheel independent steering system model, based on LQR control theory, calculating the virtual control force of lateral motion and the virtual control torque of yaw motion; using the functional relationship between the virtual control force of lateral motion, the virtual control torque of yaw motion and the geometric instantaneous center coordinates, designing a dual-domain controller that takes vehicle parameters into consideration, and outputting the geometric instantaneous center coordinates of the left domain and the right domain based on the vehicle coordinate system; and calculating the control angle of each tire based on the calculated geometric instantaneous center coordinates.

[0011] Furthermore, the step 1) uses an unscented Kalman filter algorithm to estimate the yaw rate, sideslip angle, and the instantaneous coordinates of the steering center based on the vehicle coordinate system, and the specific steps include:

[0012] 11) Calculate 2n+1 sigma points and their weights:

[0013]

[0014]

[0015] Where, X i is the sigma sampling point value, x is the mean value of the system probability distribution at the current moment, n is the number of state quantities, w i is the weight of the sigma point, The weights used to calculate the mean, The weight used to calculate the covariance, λ is a hyperparameter, P i is the covariance;

[0016] 12) Calculate the result of sigma point through nonlinear function:

[0017]

[0018]

[0019]

[0020] Where Y i is the propagation result of nonlinear function, is the weighted average, is the average value, P y for The covariance of P xy for and The mixed covariance of .

[0021] Furthermore, the kinematic equation of the vehicle skateboard chassis in step 2) is as follows:

[0022]

[0023] Where m is the mass of the vehicle skateboard chassis; v x and v y are the components of the center of mass velocity in the x and y directions respectively; ω is the yaw angular velocity; k f 、k r are the front and rear wheel cornering stiffness of the model, and k f ,k r >0;δ f and δ r are the turning angles of the front and rear wheels respectively; a and b are the distances from the front and rear axles to the center of mass respectively; β is the sideslip angle of the center of mass; I z is the moment of inertia of the vehicle skateboard chassis around the Z axis.

[0024] Furthermore, the step 2) of establishing an ideal vehicle two-degree-of-freedom model specifically includes:

[0025] According to the kinematic equation of the skateboard chassis, the equation is approximately deduced under small angle conditions, and the ideal vehicle two-degree-of-freedom model formula is established as follows:

[0026]

[0027] Furthermore, the vehicle in step 2) is in a steady-state steering condition, including the yaw angular velocity ω being a constant value and maintaining a steady state, and the lateral acceleration Yaw angular acceleration

[0028] Furthermore, the ideal yaw angular velocity ω in step 2) is * , ideal sideslip angle β * and the ideal turning center based on the vehicle coordinate system (X * O′ ,Y *O′ )The formula is as follows:

[0029]

[0030]

[0031]

[0032] Where L is the wheelbase between the front and rear axles, and K is the vehicle stability factor. R * is the ideal turning radius.

[0033] Furthermore, the ideal value correction controller in step 2) takes into account the vehicle lateral acceleration, body roll angle and tire load transfer, designs a weighted evaluation function J, and performs optimal analysis on the ideal value. The weight coefficient is related to the speed and steering curvature, and the expression is as follows:

[0034] J=j1a y +j2φ+j3(F zl -F zr ) 2

[0035] j i =f i (V,cur)

[0036] Where j1, j2, and j3 are the weight coefficients of lateral acceleration, roll angle, and tire load transfer, respectively; F zl is the vertical force of the left wheel; F zr is the vertical force of the right wheel; cur is the steering curvature; f i is the weight coefficient j i It is expressed as a function of speed and steering curvature, where i = 1, 2, 3; V is the longitudinal speed of the vehicle.

[0037] Furthermore, the target deviation value in step 2) includes the yaw rate deviation Δω, the sideslip angle deviation Δβ, and the steering instantaneous center coordinate deviation ΔO=(ΔX, ΔY) based on the vehicle coordinate system, and is expressed as follows:

[0038] Δω=ω * -ω+ω δ

[0039] Δβ=β * -β+β δ

[0040] ΔO=(ΔX,ΔY)=(X* O′ -X O′ ,Y* O′ -Y O′ )

[0041] Where, ω δ To correct the yaw rate, β δ To correct the sideslip angle, (X O′ ,Y O′ ) is the instantaneous coordinate of the steering center based on the vehicle coordinate system.

[0042] Furthermore, the four-wheel independent steering system model in step 3) includes a lateral motion system model, a yaw motion system model and a roll motion system model;

[0043] The lateral motion system model formula is as follows:

[0044]

[0045] Where φ is the roll angle, m s is the sprung mass, subscripts fl, fr, rl, and rr represent the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively. Xi is the tire longitudinal force corresponding to the subscript, F Yi is the tire lateral force corresponding to the subscript, δ i is the tire angle corresponding to the subscript, i = fl, fr, rl, rr;

[0046] The yaw motion system model formula is as follows:

[0047]

[0048] Where, I xz is the moment of inertia of the vehicle rotating around the roll axis, and c is half of the vehicle wheel spacing;

[0049] The roll motion system model formula is as follows:

[0050]

[0051]

[0052] Where, I x is the moment of inertia of the sprung mass about the longitudinal direction passing through the sprung mass center; h is the distance from the roll mass center to the roll axis; ∑M x is the required rolling moment; d Φf ,d Φr are the damping coefficients of the front and rear suspensions respectively; k Φf ,k Φr are the stiffness coefficients of the front and rear suspensions, respectively.

[0053] Furthermore, in step 3), the lateral motion virtual control force F is calculated yd and the yaw virtual control torque M dThe control variable U is solved by using LQR control theory. w , construct the new spatial state equation as follows:

[0054]

[0055] Among them, the state quantity Control quantity U w =[F yd M d ] T , A w ,B w is the corresponding coefficient matrix; let K w It can be obtained by solving the algebraic Riccati equation.

[0056] Furthermore, in step 3), the lateral motion virtual control force F yd and the yaw motion virtual control torque M d The relationship between the geometric instantaneous center coordinates can be divided into the relationship between the control force and torque and the tire side slip angle, and the relationship between the geometric instantaneous center coordinates and the tire side slip angle as shown in the following formula:

[0057] F xi =Dsin{Carctan[Bs-E(Bs-arctan(Bs))]}

[0058] F yi =Dsin{Carctan[Bα i -E(Bα i -arctan(Bα i ))]}

[0059]

[0060]

[0061] Where B, C, D, E are tire model coefficients, s is tire slip rate, α i is the tire slip angle.

[0062] Furthermore, the left and right domains of the vehicle in step 3) utilize a four-wheel independent steering system model, where the left front wheel and rear wheel controls are grouped into one control domain, and the right front wheel and rear wheel controls are grouped into one control domain.

[0063] Furthermore, in the dual-domain controller in step 3), the vehicle parameters include tire vertical force and tire adhesion utilization coefficient. For each tire's working condition, an optimization function based on the adhesion utilization coefficient and the instantaneous center distance is set to optimize the steering angle distribution and output the dual-domain geometric instantaneous center coordinates based on the vehicle coordinate system. The optimization function H is as follows:

[0064]

[0065] D i =L(O m -O n )

[0066] H=h1Var(γ i )+h2E(γ i )+h3Var(D i )

[0067] Where μ is the road adhesion coefficient; m = 0, 1, 2 represents the ideal turning center; n = 0, 1, 2 represents the dual-domain geometric turning center; h1, h2, h3 are the weights of each item; Var represents the variance function; E represents the mean function; γ i represents the adhesion utilization coefficient of the i-th tire; D i Represents the instantaneous center distance; i = fl, fr, rl, rr.

[0068] Furthermore, the relationship between the geometric instantaneous center coordinates of the left domain and the right domain based on the vehicle coordinate system and the turning angle in the control domain in step 3) is expressed as follows:

[0069]

[0070]

[0071] Where O1 and O2 represent the geometric instantaneous centers of the left and right domains, respectively; R1 is the turning radius of the left domain; R2 is the turning radius of the right domain; (X O1 ,Y O1 ) is the coordinate of the geometric instantaneous center of the left domain; (X O2 ,Y O2 ) is the coordinate of the geometric instantaneous center of the right domain, and the required rotation angle δ in the control domain is obtained through the above relationship fl ,δ fr ,δ rl ,δ rr , output to the executor for execution.

[0072] Beneficial effects of the present invention:

[0073] 1. This invention addresses the need for global considerations when tracking targets for a skateboard chassis. Three control targets are designed. In addition to the yaw rate and sideslip angle, the instantaneous steering center coordinates based on the vehicle coordinate system are added as control target parameters. This ensures the skateboard chassis' path tracking accuracy and stability, providing a foundation for the dual-domain controller of the turning angle allocation module.

[0074] 2. In view of the high computational complexity of the control process, the present invention uses the left and right steering geometric centers as intermediate control variables. The tire slip angle is indirectly controlled by the coordinate position difference between the steering center and the geometric center, thereby precisely controlling the tire force and improving the steering control accuracy of the skateboard chassis.

[0075] 3. The present invention takes into account the high degree of freedom of the four-wheel independent steering system, fully considers the working conditions of the four corner modules, and sets an optimization function based on the adhesion utilization coefficient and the instantaneous center distance, thereby giving full play to the high degree of freedom of the four-wheel independent steering system, realizing coordinated global optimal control, and improving the driving safety of the skateboard chassis. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 Schematic diagram of the method of the present invention;

[0077] Figure 2 This is a simplified schematic diagram of a dual-domain control model considering the left domain and the right domain in the present invention;

[0078] Figure 3 This is a model diagram of the four-wheel independent steering system of a skateboard chassis taking into account the instantaneous center of rotation of the present invention. DETAILED DESCRIPTION

[0079] In order to facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and drawings. The contents mentioned in the embodiments are not intended to limit the present invention.

[0080] Reference Figure 1-Figure 3 As shown, the present invention is a steering consistency angle distribution control method applicable to a skateboard chassis, and the steps are as follows:

[0081] 1) Use the unscented Kalman filter algorithm to estimate the vehicle's yaw rate, sideslip angle, and the instantaneous coordinates of the steering center based on the vehicle coordinate system;

[0082] Among them, the unscented Kalman filter algorithm is used to estimate the yaw rate, sideslip angle, and the instantaneous coordinates of the steering center based on the vehicle coordinate system. The specific steps include:

[0083] 11) Calculate 2n+1 sigma points and their weights:

[0084]

[0085]

[0086] Where, X i is the sigma sampling point value, x is the mean value of the system probability distribution at the current moment, n is the number of state quantities, w i is the weight of the sigma point, The weights used to calculate the mean, The weight used to calculate the covariance, λ is a hyperparameter, P i is the covariance;

[0087] 12) Calculate the result of sigma point through nonlinear function:

[0088]

[0089]

[0090]

[0091] Where Y i is the propagation result of nonlinear function, is the weighted average, is the average value, P y for The covariance of P xy for and The mixed covariance of .

[0092] 2) Establish an ideal two-degree-of-freedom model of the vehicle based on the kinematic equations of the skateboard chassis; Based on the ideal two-degree-of-freedom model, consider the vehicle under steady-state steering conditions and calculate the desired ideal state of the vehicle, including the ideal yaw rate, ideal sideslip angle, and ideal instantaneous steering center based on the vehicle coordinate system; construct an ideal value correction controller to optimize the design and compensation of the ideal value; and calculate the target deviation value from the ideal state based on the vehicle yaw rate, sideslip angle, and the coordinates of the instantaneous steering center based on the vehicle coordinate system;

[0093] The kinematic equation of the vehicle skateboard chassis is as follows:

[0094]

[0095] Where m is the mass of the vehicle skateboard chassis; v x and v y are the components of the center of mass velocity in the x and y directions respectively; ω is the yaw angular velocity; k f 、k r are the front and rear wheel cornering stiffness of the model, and k f ,k r >0;δ fand δ r are the turning angles of the front and rear wheels respectively; a and b are the distances from the front and rear axles to the center of mass respectively; β is the sideslip angle of the center of mass; I z is the moment of inertia of the vehicle skateboard chassis around the Z axis.

[0096] Among them, establishing an ideal vehicle two-degree-of-freedom model specifically includes:

[0097] According to the kinematic equation of the skateboard chassis, the equation is approximately deduced under small angle conditions, and the ideal vehicle two-degree-of-freedom model formula is established as follows:

[0098]

[0099] The vehicle is in a steady-state steering condition, including the yaw angular velocity ω being a constant and maintaining a steady state, and the lateral acceleration Yaw angular acceleration

[0100] Wherein, the ideal yaw angular velocity ω in step 2) is * , ideal sideslip angle β * and the ideal turning center based on the vehicle coordinate system (X * O′ ,Y * O′ )The formula is as follows:

[0101]

[0102]

[0103]

[0104] Where L is the wheelbase between the front and rear axles, and K is the vehicle stability factor. R * is the ideal turning radius.

[0105] The ideal value correction controller considers the vehicle lateral acceleration, body roll angle, and tire load transfer, designs a weighted evaluation function J, and performs optimal analysis on the ideal value. The weight coefficient is related to the speed and steering curvature, and the expression is as follows:

[0106] J=j1a y +j2φ+j3(F zl -F zr ) 2

[0107] j i =f i (V,cur)

[0108] Where j1, j2, and j3 are the weight coefficients of lateral acceleration, roll angle, and tire load transfer, respectively; F zl is the vertical force of the left wheel; F zr is the vertical force of the right wheel; cur is the steering curvature; f i is the weight coefficient j i It is expressed as a function of speed and steering curvature, where i = 1, 2, 3; V is the longitudinal speed of the vehicle.

[0109] In addition, the target deviation value in step 2) includes the yaw rate deviation Δω, the sideslip angle deviation Δβ, and the steering instantaneous center coordinate deviation ΔO=(ΔX, ΔY) based on the vehicle coordinate system, and is expressed as follows:

[0110] Δω=ω * -ω+ω δ

[0111] Δβ=β * -β+β δ

[0112] ΔO=(ΔX,ΔY)=(X * O′ -X O′ ,Y * O′ -Y O′ )

[0113] Where, ω δ To correct the yaw rate, β δ To correct the sideslip angle, (X O′ ,Y O′ ) is the instantaneous coordinate of the steering center based on the vehicle coordinate system.

[0114] 3) establishing a four-wheel independent steering system model; calculating a virtual lateral motion control force and a virtual yaw motion control torque based on the target deviation value in step 2) using the four-wheel independent steering system model and LQR control theory; utilizing the functional relationship between the virtual lateral motion control force and the virtual yaw motion control torque and the geometric instantaneous center coordinates to design a dual-domain controller that takes vehicle parameters into account, outputting the geometric instantaneous center coordinates of the left and right domains based on the vehicle coordinate system; and calculating the control angle of each tire based on the calculated geometric instantaneous center coordinates;

[0115] The four-wheel independent steering system model includes a lateral motion system model, a yaw motion system model and a roll motion system model;

[0116] The lateral motion system model formula is as follows:

[0117]

[0118] Where φ is the roll angle, m s is the sprung mass, subscripts fl, fr, rl, and rr represent the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively. Xi is the tire longitudinal force corresponding to the subscript, F Yi is the tire lateral force corresponding to the subscript, δ i is the tire angle corresponding to the subscript, i = fl, fr, rl, rr;

[0119] The yaw motion system model formula is as follows:

[0120]

[0121] Where, I xz is the moment of inertia of the vehicle rotating around the roll axis, and c is half of the vehicle wheel spacing;

[0122] The roll motion system model formula is as follows:

[0123]

[0124]

[0125] Where, I x is the moment of inertia of the sprung mass about the longitudinal direction passing through the sprung mass center; h is the distance from the roll mass center to the roll axis; ∑M x is the required rolling moment; d Φf ,d Φr are the damping coefficients of the front and rear suspensions respectively; k Φf ,k Φr are the stiffness coefficients of the front and rear suspensions, respectively.

[0126] Calculate the virtual control force F for lateral motion yd and the yaw virtual control torque M d The control variable U is solved by using LQR control theory. w , construct the new spatial state equation as follows:

[0127]

[0128] Among them, the state quantity Control quantity U w =[F yd M d ] T , A w ,B w is the corresponding coefficient matrix; let K w It can be obtained by solving the algebraic Riccati equation.

[0129] Virtual control force of lateral motion Fyd and the yaw motion virtual control torque M d The relationship between the geometric instantaneous center coordinates can be divided into the relationship between the control force and torque and the tire side slip angle, and the relationship between the geometric instantaneous center coordinates and the tire side slip angle as shown in the following formula:

[0130] F xi =Dsin{Carctan[Bs-E(Bs-arctan(Bs))]}

[0131] F yi =Dsin{Carctan[Bα i -E(Bα i -arctan(Bα i ))]}

[0132]

[0133]

[0134] Where B, C, D, E are tire model coefficients, s is tire slip rate, α i is the tire slip angle.

[0135] The left and right domains of the vehicle utilize the four-wheel independent steering system model, which groups the control of the left front and rear wheels into one control domain, and the control of the right front and rear wheels into one control domain.

[0136] In addition, the dual-domain controller in step 3) considers vehicle parameters, including tire vertical force and tire adhesion utilization coefficient. For each tire's working condition, an optimization function based on the adhesion utilization coefficient and instantaneous center distance is set to optimize the steering angle distribution and output the dual-domain geometric instantaneous center coordinates based on the vehicle coordinate system. The optimization function H is as follows:

[0137]

[0138] D i =L(O m -O n )

[0139] H=h1Var(γ i )+h2E(γ i )+h3Var(D i )

[0140] Where μ is the road adhesion coefficient; m = 0, 1, 2 represents the ideal turning center; n = 0, 1, 2 represents the dual-domain geometric turning center; h1, h2, h3 are the weights of each item; Var represents the variance function; E represents the mean function; γ irepresents the adhesion utilization coefficient of the i-th tire; D i Represents the instantaneous center distance; i = fl, fr, rl, rr.

[0141] The relationship between the geometric instantaneous center coordinates of the left and right domains based on the vehicle coordinate system and the turning angle in the control domain is expressed as follows:

[0142]

[0143]

[0144] Where O1 and O2 represent the geometric instantaneous centers of the left and right domains, respectively; R1 is the turning radius of the left domain; R2 is the turning radius of the right domain; is the coordinate of the geometric instantaneous center of the left domain; is the coordinate of the geometric instantaneous center of the right domain, and the required rotation angle δ in the control domain is obtained through the above relationship fl ,δ fr ,δ rl ,δ rr , output to the executor for execution.

[0145] The present invention has many specific application paths. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principles of the present invention. These improvements should also be considered as the scope of protection of the present invention.

Claims

1. A steering consistency angle distribution control method applicable to a skateboard chassis, characterized in that: Here are the steps: 1) Estimate the vehicle's yaw rate, sideslip angle, and instantaneous steering center coordinates based on the vehicle coordinate system; 2) Establish an ideal two-degree-of-freedom model of the vehicle based on the kinematic equations of the skateboard chassis; Based on the ideal two-degree-of-freedom model, consider the vehicle under steady-state steering conditions and calculate the desired ideal state of the vehicle, including the ideal yaw rate, ideal sideslip angle, and ideal instantaneous steering center based on the vehicle coordinate system; construct an ideal value correction controller to optimize the design and compensation of the ideal value; and calculate the target deviation value from the ideal state based on the vehicle yaw rate, sideslip angle, and the coordinates of the instantaneous steering center based on the vehicle coordinate system; 3) establishing a four-wheel independent steering system model; calculating a virtual lateral motion control force and a virtual yaw motion control torque using the four-wheel independent steering system model based on the target deviation value in step 2); designing a dual-domain controller that takes vehicle parameters into account using a functional relationship between the virtual lateral motion control force, the virtual yaw motion control torque, and the geometric instantaneous center coordinates, and outputting the geometric instantaneous center coordinates of the left and right domains based on the vehicle coordinate system; and calculating the control angle of each tire based on the calculated geometric instantaneous center coordinates; The ideal value correction controller in step 2) takes into account the vehicle lateral acceleration, body roll angle and tire load transfer, designs a weighted evaluation function J, and performs an optimal analysis on the ideal value. The weight coefficient is related to the speed and steering curvature, and the expression is as follows: J=j1a y +j2φ+j3(F zl -F zr ) 2 j i =f i (V,cur) Where j1, j2, and j3 are the weight coefficients of lateral acceleration, roll angle, and tire load transfer, respectively; F zl is the vertical force of the left wheel; F zr is the vertical force of the right wheel; cur is the steering curvature; f i is the weight coefficient j i The functional relationship between speed and steering curvature is expressed as follows: where i = 1, 2, 3; V is the longitudinal speed of the vehicle; φ is the roll angle; The dual-domain controller in step 3) considers vehicle parameters, including tire vertical force and tire adhesion utilization coefficient; according to the working condition of each tire, an optimization function based on the adhesion utilization coefficient and the instantaneous center distance is set to optimize the angle distribution and output the dual-domain geometric instantaneous center coordinates based on the vehicle coordinate system; the optimization function H is as follows: D k =L(O m -O n ) H=h1Var(γ i )+h2E(γ i )+h3Var(D i ) Where μ is the road adhesion coefficient; O m ,O n ∈{O′,O1,O2}, O′ represents the ideal turning center, O1 and O2 represent the geometric turning centers of the left and right domains respectively; h1, h2, h3 are the weights of each item; Var represents the variance function; E represents the mean function; γ i F represents the adhesion utilization coefficient of the i-th tire, i = fl, fr, rl, rr, where the subscripts fl, fr, rl, and rr represent the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; Xi is the tire longitudinal force corresponding to the subscript, F Yi is the tire lateral force corresponding to the subscript; D k represents the instantaneous center distance, k = 1, 2, 3; L is the wheelbase between the front and rear axles; The turning angle in the control domain is calculated based on the geometric instantaneous coordinates of the left and right domains of the vehicle coordinate system.

2. The steering consistency angle distribution control method applicable to a skateboard chassis according to claim 1, characterized in that: The step 1) uses an unscented Kalman filter algorithm to estimate the yaw rate, sideslip angle, and the instantaneous coordinates of the steering center based on the vehicle coordinate system, and the specific steps include: 11) Calculate 2n+1 sigma points and their weights: Where, X i is the sigma sampling point value, x is the mean value of the system probability distribution at the current moment, n is the number of state quantities, w i is the weight of the sigma point, The weights used to calculate the mean, The weight used to calculate the covariance, λ is a hyperparameter, P i is the covariance; 12) Calculate the result of sigma point through nonlinear function: Where Y i is the propagation result of nonlinear function, is the weighted average, is the average value, P y for The covariance of P xy for and The mixed covariance of .

3. The steering consistency angle distribution control method applicable to a skateboard chassis according to claim 1, characterized in that: The kinematic equation of the vehicle skateboard chassis in step 2) is as follows: Where m is the mass of the vehicle skateboard chassis; v x and v y are the components of the center of mass velocity in the x and y directions respectively; ω is the yaw angular velocity; k f 、k r are the front and rear wheel cornering stiffness of the model, and k f ,k r >0;δ f and δ r are the turning angles of the front and rear wheels respectively; a and b are the distances from the front and rear axles to the center of mass respectively; β is the sideslip angle of the center of mass; I z is the moment of inertia of the vehicle skateboard chassis around the Z axis.

4. The steering consistency angle distribution control method applicable to a skateboard chassis according to claim 3, characterized in that: The step 2) of establishing an ideal vehicle two-degree-of-freedom model specifically includes: According to the kinematic equation of the skateboard chassis, the equation is approximately deduced under small angle conditions, and the ideal vehicle two-degree-of-freedom model formula is established as follows:

5. The steering consistency angle distribution control method applicable to a skateboard chassis according to claim 4, characterized in that: The vehicle in step 2) is in a steady-state steering condition, including the yaw angular velocity ω being a constant value and maintaining a steady state, and the lateral acceleration Yaw angular acceleration 6. The steering consistency angle distribution control method applicable to a skateboard chassis according to claim 5, characterized in that: The ideal yaw angular velocity ω in step 2) * , ideal sideslip angle β * and the ideal turning center based on the vehicle coordinate system (X * O′ ,Y * O′ )The formula is as follows: Where L is the wheelbase between the front and rear axles, and K is the vehicle stability factor. R * is the ideal turning radius.

7. The steering consistency angle distribution control method applicable to a skateboard chassis according to claim 6, characterized in that: The target deviation value in step 2) includes the yaw rate deviation Δω, the sideslip angle deviation Δβ, and the steering instantaneous center coordinate deviation ΔO=(ΔX, ΔY) based on the vehicle coordinate system, and is expressed as follows: Give = oh * -oh+oh δ Δβ=β * -β+β δ ΔO=(ΔX,ΔY)=(X * O′ -X O′ ,Y * O′ -Y O′ ) Where, ω δ To correct the yaw rate, β δ To correct the sideslip angle, (X O′ ,Y O′ ) is the instantaneous coordinate of the steering center based on the vehicle coordinate system.

8. The steering consistency angle distribution control method applicable to a skateboard chassis according to claim 7, characterized in that: The four-wheel independent steering system model in step 3) includes a lateral motion system model, a yaw motion system model, and a roll motion system model; The lateral motion system model formula is as follows: Where φ is the roll angle, m s is the sprung mass, subscripts fl, fr, rl, and rr represent the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively. Xi is the tire longitudinal force corresponding to the subscript, F Yi is the tire lateral force corresponding to the subscript, δ i is the tire angle corresponding to the subscript, i = fl, fr, rl, rr; The yaw motion system model formula is as follows: Where, I xz is the moment of inertia of the vehicle rotating around the roll axis, and c is half of the vehicle wheel spacing; The roll motion system model formula is as follows: Where, I x is the moment of inertia of the sprung mass about the longitudinal direction passing through the sprung mass center; h is the distance from the roll center of mass to the roll axis; ∑M x is the required rolling moment; d Φf ,d Φr are the damping coefficients of the front and rear suspensions respectively; k Φf ,k Φr are the stiffness coefficients of the front and rear suspensions respectively; In step 3), the lateral motion virtual control force F is calculated. yd and the yaw virtual control torque M d The control variable U is solved by using LQR control theory. w , construct the new spatial state equation as follows: Among them, the state quantity Control quantity U w =[F yd M d ] T , A w ,B w is the corresponding coefficient matrix; let K w It can be obtained by solving the algebraic Riccati equation.

9. The steering consistency angle distribution control method applicable to a skateboard chassis according to claim 8, characterized in that: The dual-domain controller in step 3) considers vehicle parameters, including tire vertical force and tire adhesion utilization coefficient; according to the working condition of each tire, an optimization function based on the adhesion utilization coefficient and the instantaneous center distance is set to optimize the angle distribution and output the dual-domain geometric instantaneous center coordinates based on the vehicle coordinate system; the optimization function H is as follows: D k =L(O m -O n ) H=h1Var(γ i )+h2E(γ i )+h3Var(D i ) Where μ is the road adhesion coefficient; O m ,O n ∈{O′,O1,O2}, O′ represents the ideal turning center, O1 and O2 represent the geometric turning centers of the left and right domains respectively; h1, h2, h3 are the weights of each item; Var represents the variance function; E represents the mean function; γ i represents the adhesion utilization coefficient of the i-th tire; D k represents the instantaneous center distance, k = 1, 2, 3; The relationship between the geometric instantaneous center coordinates of the left domain and the right domain based on the vehicle coordinate system and the turning angle in the control domain in step 3) is expressed as follows: Where O1 and O2 represent the geometric turning centers of the left and right domains, respectively; R1 is the turning radius of the left domain; R2 is the turning radius of the right domain; is the coordinate of the geometric instantaneous center of the left domain; is the coordinate of the geometric instantaneous center of the right domain, and the required rotation angle δ in the control domain is obtained through the above relationship fl ,δ fr ,δ rl ,δ rr , output to the executor for execution.

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