Control method for transient switching process of vehicle under extreme working conditions and application of control method

Abstract

The invention belongs to the technical field of vehicle control, and relates to a control method for a transient switching process of a vehicle under extreme working conditions and application of the control method. When the vehicle is in the transient switching process, the motion state of the vehicle is expressed as a coordinate point in a phase plane, namely a drift point, and a steady-state equation of the drift point is constructed according to a vehicle kinetic equation; solving a controllable domain in a steady state through a steady-state control variable, namely, a value boundary of a drift point, and searching a moving track for moving from a current drift point to a target drift point within the shortest time in a phase plane by utilizing a track searching method based on a graph theory, the actual moving track is adjusted and controlled through the optimal track adjusting control strategy to be close to the moving track, and the vehicle in the limiting working condition can be controlled to be in a normal state or a drifting state; the method solves the problems of difficult nonlinear solution and low switching speed, and can be applied to drift control.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle motion state control, and in particular relates to a control method for a transient switching process of a vehicle under extreme working conditions and its application. Background Art

[0002] Vehicles are prone to loss of control under extreme conditions, such as on icy or snowy roads. Loss of control can be extremely dangerous if improperly controlled. Drifting on icy or snowy roads is a special stable condition under normal driving conditions, where the vehicle does not lose control. Therefore, if the vehicle is at risk of losing control or has already lost control (hereinafter referred to as "instability"), electronic control software can bring the vehicle back to normal or drifting conditions, thereby ensuring stability. However, vehicle control during instability often exhibits strong nonlinearity (the force on the tires is not proportional to their deformation), making control very difficult. Therefore, current research typically focuses on maintaining the vehicle in such stable conditions when it approaches normal or drifting conditions. However, relatively little research has been conducted on how to control the vehicle from instability to a stable state, a process characterized by strong nonlinearity. For example, the patent with publication number CN120056996A proposes a closed-loop control structure based on the error relationship between the yaw rate of the vehicle's drift equilibrium state and the actual state. The theoretical basis of this type of control method is unclear, and the feedback parameters are adjusted according to the actual control effect. It is an empirical control method. Therefore, in the actual transient switching process, the convergence of the yaw rate is very slow. The patent with publication number CN120171532A requires the driver to control the vehicle to near the drift equilibrium state first, and then the proposed control strategy intervenes to ensure that the vehicle's state remains near the equilibrium state. The patent with publication number CN120096574A proposes an optimal control solution method based on cost functions and constraints. In theory, this control method can handle transient switching processes, but due to the nonlinearity of the vehicle, the optimization solution of the cost function will be extremely computationally intensive, resulting in the need for high-performance computers to implement control in practical applications. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a control method for a transient switching process of a vehicle under extreme operating conditions and its application.

[0004] To achieve the purpose of the present invention, the present invention is implemented by adopting the following technical solutions.

[0005] A control method for a transient switching process of a vehicle under extreme operating conditions comprises the following steps: S1. When the vehicle is in a transient switching process, the vehicle's motion state is represented as a coordinate point in the phase plane, i.e., a drift point. The steady-state equation of the drift point is constructed based on the vehicle dynamics equation. The controllable domain of the drift point in the steady state, i.e., the value boundary of the drift point, is solved using the steady-state control variable. S2. Based on the value boundaries, a trajectory search method based on graph theory is used to find a moving trajectory in the phase plane that can complete the movement from the current drift point to the target drift point in the shortest time, and the actual moving trajectory is adjusted and controlled through the optimal trajectory adjustment control strategy to make it close to the moving trajectory, which can control the vehicle in extreme working conditions to a normal state or a drift state.

[0006] Furthermore, the vehicle dynamics equation is: , In the formula 、 is the lateral force of the front and rear wheels, is the front wheel turning angle, is the vehicle mass, 、 are the longitudinal and lateral velocities, is the yaw angular velocity, 、 is the distance from the center of mass to the front and rear axles, is the vehicle's moment of inertia in the plane, is the lateral speed Differentiation with respect to time, is the yaw angular velocity Differentiation with respect to time.

[0007] Furthermore, the steady-state equation is: .

[0008] Where: 、 is the lateral force of the front and rear wheels in equilibrium state, is the yaw angular velocity in equilibrium state.

[0009] Furthermore, the expression of the value boundary is: ; Where: Represent the four vertices of the quadrilateral in the phase plane, i.e., the limits of the rates of change of beta and r, where i takes the values ​​T, B, L, and R to represent the top, bottom, left, and right vertices, respectively; , represents the projection of the front wheel lateral force in the lateral direction of the vehicle body, and express The maximum and minimum values ​​of is the lateral force on the rear wheel, and express The maximum and minimum values ​​of .

[0010] Furthermore, the method for determining the shortest time includes the following steps: S51, the phase plane is arranged with the same width and height Divided into chessboard grids, each grid is divided ... To represent the grid; S52, the center point coordinates of each grid The control variables of the front and rear wheels corresponding to the vehicle motion state represented by and The maximum and minimum values ​​of the value boundary are brought into the expression, and the control domain of each grid can be obtained. ; S53, the center point coordinates of each grid The movement direction is limited to eight directions, namely up, down, left, right, upper left, lower left, upper right, and lower right, and is represented by a vector representation, which means that each movement can only move to one of the eight adjacent grids; wherein: the expression of the vector representation is: ; Where: is a set of moving directions, and the vector in the brackets represents the moving direction. Indicates moving to the right. Indicates moving to the left. Indicates downward movement. Indicates upward movement. Move to the lower right. Move to the lower left. Move to the upper right. Indicates movement to the upper left; Indicates that the width and height of the chessboard grid are the same, The vector represented by , which means the distance to the right is , The vector represented by , which means the distance to the left is ; The vector represented by , indicating that the downward movement distance is ; The vector represented by , indicating that the upward movement distance is ; The vector represented by , which means the distance to move to the lower right is ; The vector represented by , which means the distance to the lower left is ; The vector represented by , indicating that the distance to move to the upper right is ; The vector represented by , which means the distance to move to the upper left is ; S54, give the center point of the current grid The 8 paths are assigned movement costs, and the movement time is selected as the movement cost, and the movement time is defined as: ; Where: is the target moving direction, For the control domain The vector with the smallest angle and the longest length indicates that the change along this vector The grid represented by this direction will be reached fastest; if and Angle , which means that any value in the control domain cannot reach the grid, then the time to reach the grid is recorded as infinite (inf), otherwise The time required for movement is the shortest, so the moving time is: .

[0011] Furthermore, the trajectory search method includes the following steps: S61, the current motion state and target motion state They are respectively assigned to the nearest grid, recorded as and ; S62, will and The connection line is recorded as the initial path , initial path The number of moving grids is recorded as n, and the current number of moving grids i is recorded as 1; S63. According to the expression of vector representation and the expression of moving time, use Path search algorithm calculation arrive The path P with the lowest evaluation function among them; where: the evaluation function is: , Where: is the Euclidean distance, which represents the geometric distance between the current motion state and the target motion state. The moving time cost is , The weight of the moving time can be adjusted by changing the value The weighting of distance and time during search; S64. When i≤n, it means that the end point has not been reached yet, and the following steps are repeated until i≤n is not satisfied or Changes occurred: S641, Judgment All inflection points P in the given path are inserted into Between the starting point and the end point of the collection, The i-th point Assign to the current target point , calculate the current position The distance from the inflection point is ; S642, Judgment Is it satisfied? If so, jump to the next inflection point until it is not satisfied. ; S643, according to the current target point calculate and Control objectives and , calculated as , , where: For the expected convergence time, if you want faster convergence, reduce this value, but it may cause oscillation; S644, according to the control domain The actual situation, limitations and No more than the control domain ,get and For ultimate control.

[0012] The present invention also discloses an application based on the above method in vehicle drift control, comprising the following steps: S1. When the vehicle is in a transient switching process, the vehicle's motion state is represented as a coordinate point in the phase plane, i.e., a drift point. The steady-state equation of the drift point is constructed based on the vehicle dynamics equation. The controllable domain of the drift point in the steady state, i.e., the value boundary of the drift point, is solved using the steady-state control variable. S2. Based on the value boundary, a trajectory search method based on graph theory is used to find a movement trajectory in the phase plane that completes the movement from the current drift point to the target drift point in the shortest time, and the actual movement trajectory is adjusted and controlled by the optimal trajectory adjustment control strategy to make it approach the movement trajectory; S3. Substituting a drift point in the actual moving trajectory that is close to the moving trajectory into the steady-state equation to obtain control targets for the front and rear wheel control variables at the drift point, and converting the front and rear wheel control variables into the front wheel steering angle and rear wheel speed, respectively, using the magic formula of the tire; S4. Input the front wheel steering angle into a PID controller designed based on the sideslip angle error, and the output value of the PID controller is the front wheel steering angle compensation value to obtain the actual front wheel steering angle control value; input the rear wheel speed into a PID controller designed based on the yaw rate error, and the output value of the PID controller is the rear wheel speed compensation value to obtain the actual rear wheel speed control value, and use the actual front wheel steering angle control value and the actual rear wheel speed control value to control the vehicle in the extreme working condition to a normal state or a drift state.

[0013] Beneficial effects This method addresses the safety control requirements of vehicles under extreme operating conditions and addresses the transient switching process that a vehicle must undergo when switching between different steady states (normal operation, left drift, right drift), or from transient to steady state. It solves the problems of difficult nonlinear solutions and slow switching speeds in existing technologies. The application of this method in vehicle drift control involves switching the vehicle from drifting to the left to drifting to the right (or from right to left) to achieve drifting in a figure-8 manner. It can also perform many complex drifting actions. At the same time, when the vehicle is in an unstable state, it can be controlled to normal operation or drifting state through transient switching control to improve vehicle safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the control domain; the angles between the top, upper left, left, lower left and bottom directions and the control domain are all greater than pi / 4 , then the arrival time is inf , while the arrival times of the upper right, right, and lower right can be calculated as 0.061s, 0.053s, and 0.053s; Figure 2 The moving trajectory diagram from the initial point to the target point using different strategies; Figure 3 A comparison chart of convergence time under different working conditions; Figure 4 The actual drift curve under the adhesion condition of 0.75, where: (a) is the actual drift curve of the sideslip angle; (b) is the actual drift curve of the yaw angular velocity; (c) is the actual drift curve of the actual motion trajectory. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0016] As an embodiment of the present invention, Figure 1 As shown, a control method for a transient switching process of a vehicle under extreme working conditions includes the following steps: 1. Calculation Method of Steady-State and Controllable Region of Vehicle Drift The yaw rate can usually be used to describe the vehicle's motion state. , side slip angle and longitudinal speed (vehicle speed) To express, as long as these three quantities are determined, the motion of a vehicle in the plane is also determined. However, since the longitudinal speed of the vehicle usually does not change under transient switching conditions, the coordinates in the plane can be used. The vehicle's steady state is calculated using the following method.

[0017] Step 1: Construct the vehicle's dynamic equations. The known vehicle motion equations are as follows: (1) Where: 、 is the lateral force of the front and rear wheels, is the front wheel turning angle, is the vehicle mass, 、 are the longitudinal and lateral velocities, is the yaw angular velocity, 、 is the distance from the center of mass to the front and rear axles, is the vehicle's moment of inertia in the plane, is the lateral speed Differentiation with respect to time, is the yaw angular velocity Differentiation with respect to time; According to the definition of sideslip angle , the above formula can be rewritten as: (2) (3) Step 2: Construct the steady-state equation. For the steady-state drift point, the vehicle's motion state remains unchanged, that is, and , by substituting into equations (2) and (3), we can obtain the steady-state equation: (4) In the formula: superscript Indicates that the variable is a steady-state control variable.

[0018] Step 3: Solve for the steady state The controllable domain, that is When the vehicle is in the current state hour, and The range of change of is eliminated by formulas (2) and (3) Calculate formula (5): (5) Where: for abbreviation of .

[0019] Bundle The maximum value , minimum value and The maximum value and minimum value Substituting them into formula (5), we can get The value boundary of : (6) Where: T, B, L, R represent The upper, lower, left, and right vertices of the value boundary.

[0020] 2. Arrival time calculation method based on control domain.

[0021] In the phase plane, the current state of the vehicle is recorded as , the target state of the vehicle is recorded as ,from arrive The switching process is the transient switching process, which can complete the switching process in the shortest time (the switching trajectory at each moment in the switching process The trajectory drawn on the phase plane is the optimal trajectory. In order to find the optimal switching trajectory, we propose a trajectory search method based on graph theory.

[0022] Step 1: In order to reduce the amount of calculation, the phase plane is arranged with the same width and height Divide into a chessboard grid, each grid is divided into a grid with the coordinates of its center point to represent the grid.

[0023] Step 2: Calculate the control domain of each grid , which is calculated by taking the center point This status corresponds to and Substituting the maximum and minimum values ​​of into formula (6), we can get the control domain.

[0024] Step 3: In order to reduce the amount of computation required for path search, The movement direction is limited to eight directions: up, down, left, right, upper left, lower left, upper right, and lower right. They are expressed as vectors in Equation (7), which means that each movement can only move to one of the eight adjacent grids. Obviously, other grid division methods can also be selected here to refine the path, but this will increase the computational complexity.

[0025] (7) Where: is a set of moving directions, and the vector in the brackets represents the moving direction. Indicates moving to the right. Indicates moving to the left. Indicates downward movement. Indicates upward movement. Move to the lower right. Move to the lower left. Move to the upper right. Indicates movement to the upper left; Indicates that the width and height of the chessboard grid are the same, The vector represented by , which means the distance to the right is , The vector represented by , which means the distance to the left is ; The vector represented by , indicating that the downward movement distance is ; The vector represented by , indicating that the upward movement distance is ; The vector represented by , which means the distance to move to the lower right is ; The vector represented by , which means the distance to the lower left is ; The vector represented by , indicating that the distance to move to the upper right is ; The vector represented by , which means the distance to move to the upper left is ; Step 4: Give the center point of the current grid The eight paths are assigned movement costs. Here we choose movement time as the movement cost, which is defined as: (8) Where: is the target moving direction, as defined in formula (7), For the control domain The vector with the smallest angle and the longest length (indicates that the change along this vector will reach the grid represented by that direction fastest).

[0026] In formula (8), if and Angle , which means that any value in the control domain cannot reach the grid, then the time to reach the grid is recorded as infinite (inf), otherwise according to The time required for movement is the shortest, so the moving time is .

[0027] The results of steps 1-4 above are as follows: Figure 1 As shown, at this time and -1.4 respectively rad / s and -0.7 rad , the vehicle speed is 5m / s, the adhesion is 0.3, Figure 1 The red area in the middle is the control domain, where the angles between the top, upper left, left, lower left and bottom directions and the control domain are all greater than pi / 4 , then the arrival time is inf , and the arrival times of the upper right, right, and lower right can be calculated as 0.061s, 0.053s, and 0.053s.

[0028] 3. Optimal Trajectory Search Method for Transient Switching Process Based on Graph Theory Step 1: Current state and target state Assigned to its nearest grid, denoted as: and .

[0029] Step 2: and The connection line is recorded as the initial path , the number of moving grids of the initial path is recorded as n, and the current moving grid number i is recorded as 1.

[0030] Step 3: Calculate the optimal path: According to formula (7) and formula (8), use Path search algorithm calculation arrive The path P with the lowest evaluation function. The evaluation function is , where: is the Euclidean distance, which represents the geometric distance between the current point and the target point. The moving time cost is , The weight of the moving time can be adjusted by changing the value The weighting of distance and time when searching.

[0031] S4, adjust the control strategy according to the optimal path. The optimal path obtained by the search can be used for drift control, which contains different strategies. In actual control, it is necessary to adjust the control strategy according to the current state so that the actual trajectory in the phase plane is closest to The searched path is as follows: When i≤n, it means that the destination has not been reached yet, and the following steps are repeated until i≤n is not satisfied or Change has occurred.

[0032] S41. Judgment Given all the inflection points P in the path (inflection points indicate the points where the path changes direction), insert them into Between the starting point and the end point of the collection, The i-th point Assign to the current target point , calculate the current position The distance from the inflection point is ; S42, Judgment Is it satisfied? If it is satisfied, jump to the next inflection point (indicating that the distance moved to this inflection point is greater than the distance of the previous inflection point, then this inflection point is meaningless), until it is not satisfied. ; S43, according to the current target point Then we can calculate and Control objectives and , calculated as , , where: For the expected convergence time, if you want faster convergence, reduce this value, but it may cause oscillation.

[0033] S44, according to the control domain The actual situation, limitations and Does not exceed the control domain, and gets and For ultimate control.

[0034] As an embodiment of the present invention, a control method for a transient switching process of a vehicle under extreme operating conditions is applied to drift control, that is, a vehicle drift control method, including the following steps: Step 1: and Substitute into formula (4), and we get and control objectives; Step 2: According to the magic formula of the tire, Converted to front wheel angle ,Will Converted to rear wheel speed ; Step 3: Based on the sideslip angle error Design a PID controller. The output value of the PID controller is the front wheel angle compensation value. , then the actual control value of the front wheel angle is ; Based on the yaw rate error Design a PID controller, the output value of the controller is the rear wheel speed compensation , the actual control value of the rear wheel speed is .

[0035] The control effect of a control method for transient switching process of vehicle extreme working conditions in practical application: Figure 2 Figure 2 shows the trajectory of the vehicle from the initial point to the target point using different strategies. The red color represents the graph search method proposed in this paper, the green color represents the yaw rate first and then the slip angle, the pink color represents the slip angle first and then the yaw rate, and the blue color represents the simultaneous control of the yaw rate and slip angle.

[0036] Figure 3 The figure shows a comparison of the convergence time under different working conditions, where working condition 1 is adhesion 0.75 and speed 10 m / s, working condition 2 is adhesion 0.3 and speed 10 m / s, working condition 3 is adhesion 0.75 and speed 5 m / s, and working condition 4 is adhesion 0.4 and speed 5 m / s. The proposed method has the fastest convergence in all four working conditions.

[0037] Figure 4 The actual drift curve under the condition of adhesion of 0.75 is shown in the figure. Figure 4 As can be seen in Figures (a), (b), and (c) of the figure, the vehicle drifts in the opposite direction at 25 seconds, and the vehicle trajectory forms an "8" shape. Under the working conditions, this is a process of switching from one drift transient point to another. During this process, the sideslip angle and yaw angular velocity both converge quickly to the target values.

[0038] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and essence of the present invention should be within the scope of the present invention.

Claims

1. A control method for a transient switching process of a vehicle under extreme operating conditions, characterized by: The steps include: S1. When the vehicle is in a transient switching process, the vehicle's motion state is represented as a coordinate point in the phase plane, i.e., a drift point. The steady-state equation of the drift point is constructed based on the vehicle dynamics equation. The controllable domain of the drift point in the steady state, i.e., the value boundary of the drift point, is solved using the steady-state control variable. S2. Based on the value boundaries, a trajectory search method based on graph theory is used to find a moving trajectory in the phase plane that can complete the movement from the current drift point to the target drift point in the shortest time, and the actual moving trajectory is adjusted and controlled through the optimal trajectory adjustment control strategy to make it close to the moving trajectory, which can control the vehicle in extreme working conditions to a normal state or a drift state.

2. The control method for a vehicle extreme operating condition transient switching process according to claim 1, characterized in that: The vehicle dynamics equation is: ， Where: 、 is the lateral force of the front and rear wheels, is the front wheel turning angle, is the vehicle mass, 、 are the longitudinal and lateral velocities, is the yaw angular velocity, 、 is the distance from the center of mass to the front and rear axles, is the vehicle's moment of inertia in the plane, is the lateral speed Differentiation with respect to time, is the yaw angular velocity Differentiation with respect to time.

3. The control method for a vehicle extreme operating condition transient switching process according to claim 1, characterized in that: The steady-state equation is: ； Where: 、 is the lateral force of the front and rear wheels in equilibrium state, is the yaw angular velocity in equilibrium state.

4. The control method for a vehicle extreme operating condition transient switching process according to claim 1, characterized in that: The expression of the value boundary is: ； Where: Represent the four vertices of the quadrilateral in the phase plane, i.e., the limits of the rates of change of beta and r, where i takes the values ​​T, B, L, and R to represent the top, bottom, left, and right vertices, respectively; It represents the projection of the front wheel lateral force on the lateral direction of the vehicle body. and express The maximum and minimum values ​​of is the lateral force on the rear wheel, and express The maximum and minimum values ​​of .

5. The control method for a transient switching process of a vehicle under extreme operating conditions according to claim 1, characterized in that: The method for determining the shortest time comprises the following steps: S51, the phase plane is arranged in the same width and height Divided into chessboard grids, each grid is divided ... To represent the grid; S52, the center point coordinates of each grid The control variables of the front and rear wheels corresponding to the vehicle motion state represented by and The maximum and minimum values ​​of the value boundary are brought into the expression, and the control domain of each grid can be obtained. ; S53, the center point coordinates of each grid The movement direction is limited to eight directions, namely up, down, left, right, upper left, lower left, upper right, and lower right, and is represented by a vector representation, which means that each movement can only move to one of the eight adjacent grids; wherein: the expression of the vector representation is: ； Where: is a set of moving directions, and the vector in the brackets represents the moving direction. Indicates moving to the right. Indicates moving to the left. Indicates downward movement. Indicates upward movement. Move to the lower right. Move to the lower left. Move to the upper right. Indicates movement to the upper left; Indicates that the width and height of the chessboard grid are the same, The vector represented by , which means the distance to the right is , The vector represented by , which means the distance to the left is ; The vector represented by , indicating that the downward movement distance is ; The vector represented by , indicating that the upward movement distance is ; The vector represented by , which means the distance to move to the lower right is ; The vector represented by , which means the distance to the lower left is ; The vector represented by , indicating that the distance to move to the upper right is ; The vector represented by , which means the distance to move to the upper left is ; S54, give the center point of the current grid The 8 paths are assigned movement costs, and the movement time is selected as the movement cost, and the movement time is defined as: ； Where: is the target moving direction, For the control domain The vector with the smallest angle and the longest length indicates that the change along this vector The grid represented by this direction will be reached fastest; if and Angle , which means that any value in the control domain cannot reach the grid, then the time to reach the grid is recorded as infinite inf, otherwise The time required for movement is the shortest, so the moving time is: .

6. The control method for a vehicle extreme operating condition transient switching process according to claim 1, characterized in that: The trajectory search method comprises the following steps: S61, the current motion state and target motion state They are assigned to the grid closest to each other, recorded as and ; S62, will and The connection line is recorded as the initial path , initial path The number of moving grids is recorded as n, and the current number of moving grids i is recorded as 1; S63. According to the expression of vector representation and the expression of moving time, use Path search algorithm calculation arrive The path P with the lowest evaluation function among them; where: the evaluation function is: ， Where: is the Euclidean distance, which represents the geometric distance between the current motion state and the target motion state. The moving time cost is , The weight of the moving time can be adjusted by changing the value The weighting of distance and time during search; S64. When i≤n, it means that the end point has not been reached yet, and the following steps are repeated until i≤n is not satisfied or Changes occurred: S641, Judgment All inflection points P in the given path are inserted into Between the starting point and the end point of the collection, The i-th point Assign to the current target point , calculate the current position The distance from the inflection point is ; S642, Judgment Is it satisfied? If so, jump to the next inflection point until it is not satisfied. ; S643, according to the current target point calculate and Control objectives and , calculated as , , where: is the expected convergence time. If the convergence speeds up, Adjust the value to smaller; S644, according to the control domain The actual situation, limitations and No more than the control domain ,get and For ultimate control.

7. Application of the method according to any one of claims 1 to 6 in vehicle drift control, characterized in that: The steps include: S1. When the vehicle is in a transient switching process, the vehicle's motion state is represented as a coordinate point in the phase plane, i.e., a drift point. The steady-state equation of the drift point is constructed based on the vehicle dynamics equation. The controllable domain of the drift point in the steady state, i.e., the value boundary of the drift point, is solved using the steady-state control variable. S2. Based on the value boundary, a trajectory search method based on graph theory is used to find a movement trajectory in the phase plane that completes the movement from the current drift point to the target drift point in the shortest time, and the actual movement trajectory is adjusted and controlled by the optimal trajectory adjustment control strategy to make it approach the movement trajectory; S3. Substituting a drift point in the actual moving trajectory that is close to the moving trajectory into the steady-state equation to obtain control targets for the front and rear wheel control variables at the drift point, and converting the front and rear wheel control variables into the front wheel steering angle and rear wheel speed, respectively, using the magic formula of the tire; S4. Input the front wheel steering angle into a PID controller designed based on the sideslip angle error, and the output value is the front wheel steering angle compensation amount to obtain the actual front wheel steering angle control value; input the rear wheel speed into a PID controller designed based on the yaw rate error, and the output value is the rear wheel speed compensation amount to obtain the actual rear wheel speed control value, and use the actual front wheel steering angle control value and the actual rear wheel speed control value to control the vehicle in extreme working conditions to a normal state or a drift state.

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