Control system and control method

Abstract

Improve the vehicle's ability to follow the target route. [Solution] The control system S has a first acquisition unit 121 that acquires the distance deviation between the vehicle and a route point on the vehicle's target route, the azimuth angle deviation between a first azimuth angle of the route point and a second azimuth angle of the vehicle, and the steering angle of the vehicle, a generation unit 122 that generates a prediction model that predicts each of the distance deviation, the azimuth angle deviation, and the steering angle, a second acquisition unit 124 that acquires the degree of curvature of the road on which the vehicle is traveling, a calculation unit 125 that calculates the vehicle's sideslip angle based on the degree of curvature, an estimation unit 123 that estimates an estimated distance deviation, steering angle, and estimated azimuth angle deviation based on the prediction model, and a determination unit 126 that determines, as a target steering angle, a steering angle that minimizes an evaluation function whose parameters include the difference between the estimated azimuth angle deviation and the sideslip angle, the estimated distance deviation, and the steering angle.

Description

[Technical field]

[0001] The present invention relates to a control system and a control method for controlling the behavior of a vehicle. [Background technology]

[0002] There is known a control system for controlling the behavior of a vehicle. Patent Document 1 discloses a technology for determining a steering angle that minimizes a value of an evaluation function including a lateral deviation, an azimuth angle deviation, a steering angle, and a change amount of the steering angle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-140494 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when a vehicle turns, a sideslip angle occurs between the vehicle's traveling direction and the direction of the wheels. Therefore, when a vehicle is driven along a target route with a large curvature, the steering angle, which is the direction of the vehicle's wheels, must be set to an angle that generates a sideslip angle that moves the vehicle along the target route. However, a sideslip angle generated by a steering angle of the vehicle determined without taking the sideslip angle into consideration may differ from the sideslip angle that turns the vehicle along the target route. Therefore, a steering angle that does not take the sideslip angle into consideration causes the vehicle to turn so as to deviate from the target route, making it impossible for the vehicle to follow the target route.

[0005] The present invention has been made in consideration of these points, and has an object to improve the ability of a vehicle to follow a target route. [Means for solving the problem]

[0006] In a first aspect of the present invention, there is provided a control system having: a first acquisition unit that acquires a distance deviation between a route point of a target route of the vehicle and the vehicle, an azimuth angle deviation between a first azimuth angle of the route point and a second azimuth angle of the vehicle, and a steering angle of the vehicle; a generation unit that generates a prediction model that predicts each of the distance deviation, the azimuth angle deviation, and the steering angle; a second acquisition unit that acquires a degree of curvature of a road on which the vehicle is traveling; a calculation unit that calculates a sideslip angle of the vehicle based on the degree of curvature; an estimating unit that estimates an estimated distance deviation, a steering angle, and an estimated azimuth angle deviation based on the prediction model; and a determination unit that determines, as a target steering angle, the steering angle that minimizes an evaluation function whose parameters include a difference between the estimated azimuth angle deviation and the sideslip angle, the estimated distance deviation, and the steering angle. The calculation unit may calculate the sideslip angle based on a balance of forces in a vehicle width direction perpendicular to a traveling direction of the vehicle, the balance being determined according to the degree of turning, and a balance of forces in a rotational direction about a center of gravity of the vehicle.

[0007] The balance of forces in the vehicle width direction may be represented by a centrifugal force determined by the weight of the vehicle, the vehicle speed, and the degree of turning of the vehicle, and a centripetal force determined by the front wheel cornering stiffness of the vehicle, the sideslip angle of the front wheels of the vehicle, the rear wheel cornering stiffness of the vehicle, and the sideslip angle of the rear wheels of the vehicle, and the balance of forces in the rotational direction may be represented by a yaw moment of the front wheels determined by a first distance between the center of gravity of the vehicle and the front wheels, the front wheel cornering stiffness, and the sideslip angle of the front wheels, and a yaw moment of the rear wheels determined by a second distance between the center of gravity and the rear wheels, the rear wheel cornering stiffness, and the sideslip angle of the rear wheels.

[0008] The centrifugal force may be expressed as the product of the weight and the ratio of the square of the vehicle speed to a radius of curvature indicating the degree of turning, the centripetal force may be expressed as the sum of the product of the front wheel cornering stiffness and the side slip angle of the front wheels and the product of the rear wheel cornering stiffness and the side slip angle of the rear wheels, and the balance of forces in the rotational direction may be expressed as a first product of the first distance, the front wheel cornering stiffness, and the side slip angle of the front wheels, and a second product of the second distance, the rear wheel cornering stiffness, and the side slip angle of the rear wheels.

[0009] The calculation unit may calculate, as the slip angle, a slip angle of the rear wheels derived by eliminating the front wheel slip angle from an equation representing the balance of forces in the vehicle width direction represented by the centrifugal force and the centripetal force, and an equation representing the balance of forces in the rotational direction represented by the first product and the second product.

[0010] In a second aspect of the present invention, there is provided a control method including the steps of: acquiring a distance deviation between a route point of a target route of the vehicle and the vehicle, an azimuth angle deviation between a first azimuth angle of the route point and a second azimuth angle of the vehicle, and a steering angle of the vehicle, which are executed by a processor mounted on the vehicle; generating a prediction model for predicting each of the distance deviation, the azimuth angle deviation, and the steering angle; acquiring a degree of curvature of a road on which the vehicle is traveling; calculating a sideslip angle of the vehicle based on the degree of curvature; estimating an estimated distance deviation, a steering angle, and an estimated azimuth angle deviation based on the prediction model; and determining, as a target steering angle, the steering angle that minimizes an evaluation function whose parameters include a difference between the estimated azimuth angle deviation and the sideslip angle, the estimated distance deviation, and the steering angle. Effect of the Invention

[0011] According to the present invention, the effect of improving the ability of a vehicle to follow a target route is achieved. [Brief description of the drawings]

[0012] [Figure 1]FIG. 2 is a diagram for explaining the motion of a vehicle. [Diagram 2] FIG. 2 is a diagram for explaining a configuration of a control system. [Diagram 3] 4 is a flowchart showing an example of a process for controlling vehicle traveling. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Configuration of control system S] The configuration of the control system S will be described with reference to Figs. 1 and 2. Fig. 1 is a diagram for explaining the motion of vehicle A. Fig. 2 is a diagram for explaining the configuration of the control system S. The control system S is a system for causing vehicle A to travel along a target route B by controlling the steering angle δ of vehicle A. The control system S includes a vehicle control device 1 and is mounted on vehicle A. The target route B is a predetermined route and includes route points indicating multiple target travel positions for vehicle A and a target orientation for vehicle A at each route point.

[0014] In Fig. 1, an absolute coordinate system is used. In the absolute coordinate system of this embodiment, for example, the longitude direction is the X-axis and the latitude direction is the Y-axis, but the present invention is not limited to this. Hereinafter, the speed component in the vehicle width direction of the vehicle speed V of the vehicle A is the vehicle width direction speed Vy. The speed component in the traveling direction perpendicular to the vehicle width direction of the vehicle speed V is the longitudinal direction speed Vx.

[0015] The distance deviation z is the distance between the center of gravity C, which indicates the position of vehicle A, and route point D of the target route B of vehicle A. The azimuth angle deviation θ is the difference between a first azimuth angle ψ, which indicates the direction of route point D of target route B, and a second azimuth angle φ, which indicates the direction of vehicle A. The first azimuth angle ψ is the target direction of vehicle A. The first azimuth angle ψ is, for example, the direction of the tangent to route point D.

[0016] The vehicle control device 1 is, for example, an ECU (Electronic Control Unit). The vehicle control device 1 includes a storage unit 11 and a control unit 12. The storage unit 11 is a storage medium including a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk, etc. The storage unit 11 stores a program executed by the control unit 12.

[0017] The control unit 12 is a computation resource including a processor such as a CPU (Central Processing Unit). The control unit 12 executes a program stored in the storage unit 11 to realize functions as a first acquisition unit 121, a generation unit 122, an estimation unit 123, a second acquisition unit 124, a calculation unit 125, a determination unit 126, and a steering control unit 127.

[0018] The first acquisition unit 121 acquires a plurality of pieces of information related to the vehicle A. For example, the first acquisition unit 121 acquires a distance deviation z using coordinates indicating the position of the vehicle A identified by a positioning system that measures the position using a signal output from a satellite and coordinates indicating the position of a route point D of the target route. The first acquisition unit 121 acquires a first direction angle ψ and a second azimuth angle φ, and acquires the difference between the first direction angle ψ and the second azimuth angle φ as an azimuth angle deviation θ. The first acquisition unit 121 acquires a steering angle δ of the vehicle A. For example, the first acquisition unit 121 acquires the steering angle δ detected by the steering angle sensor 3 from the steering angle sensor 3 that detects the steering angle δ.

[0019] The generation unit 122 generates a prediction model that predicts the state of the vehicle A. For example, the generation unit 122 generates a prediction model that predicts each of the distance deviation z, the azimuth angle deviation θ, and the steering angle δ. Specifically, the generation unit 122 generates a state equation expressed by the following formula (1) as the prediction model, in which the distance deviation z, the azimuth angle deviation θ, and the steering angle δ are state variables. Note that the state equation of formula (1) is a discretized state equation.

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[0020] The second acquisition unit 124 acquires the degree of curvature of the road on which the vehicle A is traveling. The degree of curvature of the road is a curvature radius R or a curvature of the reciprocal of the curvature radius R. For example, the second acquisition unit 124 acquires the curvature radius R indicating the degree of curvature of the road. Specifically, the second acquisition unit 124 acquires the curvature radius R of the road by analyzing an image captured by an imaging device mounted on the vehicle A. In addition, the second acquisition unit 124 may acquire the curvature radius R of the road on which the vehicle A is traveling by referring to map information that associates the position of the road with the curvature radius R of the road. The map information is stored in the storage unit 11. In addition, the second acquisition unit 124 may acquire a curvature indicating the degree of curvature of the road instead of the curvature radius R.

[0021] The calculation unit 125 calculates the sideslip angle β of the vehicle A based on the radius of curvature R acquired by the second acquisition unit 124. For example, the calculation unit 125 calculates the sideslip angle β based on the balance of forces in the vehicle width direction perpendicular to the traveling direction of the vehicle A, which is determined according to the radius of curvature R, and the balance of forces in the rotational direction around the center of gravity of the vehicle A.

[0022] The balance of forces in the vehicle width direction is represented by the centrifugal force and centripetal force acting on vehicle A. The centrifugal force is determined by the weight m of the vehicle, the vehicle speed V of vehicle A, and the radius of curvature R of vehicle A. Specifically, the centrifugal force is represented by the product of the weight m and the ratio of the square of the vehicle speed V to the radius of curvature R. The centripetal force is represented by the front wheel cornering stiffness K f , the front wheel slip angle β f , Rear wheel cornering stiffness K r and the rear wheel slip angle β r Specifically, the centripetal force is determined by the front wheel cornering stiffness K f and the front wheel slip angle β f and the rear wheel cornering stiffness K r and the rear wheel slip angle β r The balance of forces in the vehicle width direction is expressed by the following equation (2).

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[0023] The balance of rotational forces around the center of gravity of vehicle A is expressed as the balance between the force that turns vehicle A clockwise and the force that turns vehicle A counterclockwise with respect to a vertical axis passing through the center of gravity of vehicle A. Specifically, the balance of rotational forces is expressed by the yaw moment of the front wheels and the yaw moment of the rear wheels.

[0024] The yaw moment of the front wheels is the first distance l between the center of gravity of vehicle A and the axle of the front wheels. f , Front wheel cornering stiffness K f and the front wheel slip angle β f Specifically, the yaw moment of the front wheels is determined by the first distance l f , Front wheel cornering stiffness K f and the front wheel slip angle β f The yaw moment of the rear wheels is expressed as the first product of the second distance l between the center of gravity and the rear wheel axle. r , Rear wheel cornering stiffness K r and the rear wheel slip angle β r Specifically, the yaw moment of the rear wheels is determined by the second distance l between the center of gravity and the rear wheels. r , Rear wheel cornering stiffness K r and the rear wheel slip angle β r The balance of the rotational forces is expressed by the following equation (3).

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[0025] The calculation unit 125 calculates the front wheel side slip angle β from the equation (2) expressing the balance of forces in the vehicle width direction and the equation (3) expressing the balance of forces in the rotational direction. f The rear wheel side slip angle β is derived by eliminating r The calculation unit 125 calculates the rear wheel slip angle β r The steady side slip angle θ ref The calculation unit 125 calculates the steady side slip angle θ using the following equation (4). ref Calculate the rear wheel slip angle β r The steady side slip angle θ refThe state equation in this case is simpler than the state equation in the case where the sideslip angle of the center of gravity is used.

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[0026] The determination unit 126 determines a target steering angle of the vehicle A. The determination unit 126 determines the steering angle that minimizes the evaluation function J as the target steering angle. The evaluation function J is a function of the estimated azimuth angle deviation and the steady-state side slip angle θ ref The parameters include the difference between the lateral deviation and the estimated distance deviation, and the steering angle. y and the weight of the azimuth deviation Q θ and the weight of the target steering angle R δ and the terminal weight of the lateral deviation Q δterm and the terminal weight of the azimuth deviation Q θterm Using and, it is expressed by the following equation (5).

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[0027] As shown in the above formula (5), the steering angle δ that minimizes the evaluation function J is determined by the azimuth angle deviation θ and the steady-state sideslip angle θ ref In other words, the determination unit 126 determines the direction of the vehicle A based on the steady-state side-slip angle θ ref This allows the steering angle δ to be determined so that the direction of vehicle A is at an angle that generates a lateral force according to the curvature radius R of the road on which vehicle A is traveling. As a result, vehicle A will travel along the target route B.

[0028] The steering control unit 127 operates the steering wheel 2 of the vehicle A to set the steering angle of the vehicle A to a target steering angle. For example, the steering control unit 127 controls an actuator that rotates the steering wheel 2 to rotate the steering wheel 2 so that the steering angle becomes the target steering angle.

[0029] After the steering control unit 127 sets the steering angle to the target steering angle, the first acquisition unit 121 again acquires the distance deviation z, the azimuth angle deviation θ, and the steering angle δ, and the second acquisition unit 124 again acquires the curvature radius R of the road on which vehicle A is traveling. The determination unit 126 determines the target steering angle based on the acquired information about vehicle A, and the steering control unit 127 rotates the steering wheel 2 of vehicle A so that the steering angle becomes the determined target steering angle.

[0030] In this way, the vehicle control device 1 mounted on vehicle A determines the target steering angle based on the acquired information about vehicle A, and rotates the steering wheel 2 of vehicle A so that the determined target steering angle is reached. While vehicle A is traveling, the vehicle control device 1 repeatedly executes processes from acquiring information about vehicle A to rotating the steering wheel 2, thereby making it possible to cause vehicle A to travel along the target route B.

[0031] The steering angle δ determined by the vehicle control device 1 is calculated by dividing the estimated azimuth angle deviation θ of the vehicle A and the steady-state side slip angle θ according to the curvature radius R of the road on which the vehicle A is traveling. ref The steering angle is the angle that minimizes the evaluation function J, which includes the difference between the estimated azimuth angle deviation θ and the steady side slip angle θ ref When the difference between the curvature radius R and the steady-state side slip angle θ ref That is, the steering angle δ of the vehicle A comes to coincide with an appropriate sideslip angle that enables the vehicle A to travel along the target route B with a large curvature. This enables the vehicle control device 1 to reduce the distance deviation z between the route point D of the target route B and the vehicle A, thereby improving the ability of the vehicle A to follow the target route B with a large curvature.

[0032] Incidentally, a straight road may be considered to have an infinite radius of curvature R. The second acquisition unit 124 acquires infinity as the radius of curvature R, but it is not limited to infinity and may be any sufficiently large value. A sufficiently large value is, for example, 10,000 times the radius of curvature R of the actual road, but is not limited to this. In this case, the calculation unit 125 calculates the steady side slip angle θ ref Calculate 0 as the steady side slip angle θ refThe steering angle δ that minimizes the evaluation function J when is 0 is a steering angle that reduces the difference between the second azimuth angle φ of vehicle A and the first azimuth angle ψ of route point D of target route B, and is a steering angle that aligns the direction of the wheels of vehicle A with the direction of travel.

[0033] In this way, the vehicle control device 1 can use the same evaluation function J whether the road on which the vehicle A is traveling is straight or curved. This makes it unnecessary for the vehicle control device 1 to change the processing depending on whether the road on which the vehicle A is traveling is straight or curved. Therefore, the vehicle control device 1 can drive the vehicle A using the same processing even if the target route B includes a mixture of straight and curved roads.

[0034] [Processing to control driving] 3 is a flowchart showing an example of a process for controlling the traveling of the vehicle A. The process for controlling the traveling of the vehicle A is executed while the vehicle A is traveling.

[0035] The first acquisition unit 121 acquires a distance deviation z, an azimuth angle deviation θ, and a steering angle δ (step S1). Specifically, the first acquisition unit 121 acquires the distance deviation z using coordinates indicating the position of the vehicle A identified by the positioning system and coordinates indicating the position of the route point D of the target route. The first acquisition unit 121 acquires a first azimuth angle ψ indicating the inclination of a tangent to the route point D and a second azimuth angle φ indicating the direction of the vehicle A, and acquires the difference between the first azimuth angle ψ and the second azimuth angle φ as the azimuth angle deviation θ. The first acquisition unit 121 acquires the steering angle δ detected by the steering angle sensor 3.

[0036] The generation unit 122 generates a prediction model for predicting each of the distance deviation z, the azimuth angle deviation θ, and the steering angle δ (step S2). Specifically, the generation unit 122 generates a state equation expressed by equation (1) as a prediction model. The estimation unit 123 estimates an estimated distance deviation, an estimated azimuth angle deviation, and a steering angle based on the prediction model expressed by equation (1) (step S3).

[0037] The second acquisition unit 124 acquires a radius of curvature R as the degree of curvature of the road on which the vehicle A is traveling (step S4). The calculation unit 125 calculates a vehicle slip angle β according to the acquired radius of curvature R (step S5). Specifically, the calculation unit 125 calculates the vehicle slip angle β based on the balance of forces in the vehicle width direction and the balance of forces in the rotational direction acting on the vehicle A. The processes of steps S4 and S5 may be executed before the processes of steps S1 to S3, or may be executed in parallel with the processes of steps S1 to S3.

[0038] The determination unit 126 determines, as the target steering angle, the steering angle that minimizes an evaluation function J that includes, as a parameter, the difference between the estimated azimuth angle deviation and the sideslip angle (step S6). Specifically, the determination unit 126 determines, as the target steering angle, the steering angle that minimizes an evaluation function J that includes, as a parameter, the difference between the estimated azimuth angle deviation and the sideslip angle, the estimated distance deviation, and the steering angle.

[0039] The first acquisition unit 121 determines whether or not vehicle A has stopped (step S7). If vehicle A has stopped (Yes in step S7), the first acquisition unit 121 ends the process of controlling the traveling of vehicle A. If vehicle A is traveling (No in step S7), the first acquisition unit 121 returns to step S1 and acquires the distance deviation z, the azimuth angle deviation θ, and the steering angle δ. Note that if vehicle A that is stopped starts traveling, the first acquisition unit 121 starts the process of controlling the traveling of vehicle A.

[0040] [Effects of Control System S] As described above, the control system S acquires the distance deviation between the route points of the vehicle's target route and vehicle A, the azimuth angle deviation between the first azimuth angle of the route points and the second azimuth angle of the vehicle, the steering angle, and the degree of curvature of the road on which vehicle A is traveling. Next, the control system S estimates an estimated distance deviation, steering angle, and estimated azimuth angle deviation based on a prediction model that predicts each of the distance deviation, azimuth angle deviation, and steering angle. Next, the control system S calculates the sideslip angle of vehicle A based on the degree of curvature. Then, the control system S determines the steering angle that minimizes an evaluation function whose parameters include the difference between the estimated azimuth angle deviation and the sideslip angle, the estimated distance deviation, and the steering angle, as the target steering angle.

[0041] The steering angle δ determined by the control system S is a steering angle that minimizes an evaluation function J that includes as a parameter the difference between the estimated azimuth deviation θ of the vehicle A and the side slip angle based on the curvature of the road on which the vehicle A is traveling. The steering angle that minimizes the evaluation function J is a steering angle that reduces the difference between the estimated azimuth deviation and the side slip angle. When the difference between the estimated azimuth deviation and the side slip angle becomes smaller, the steering angle of the vehicle A coincides with a side slip angle that generates a lateral force according to the curvature of the road. In other words, the steering angle of the vehicle A coincides with an appropriate side slip angle that enables the vehicle A to travel along the target route B with a large curvature. This allows the control system S to reduce the distance deviation between the route point D of the target route B and the vehicle A, thereby improving the tracking ability of the vehicle A to the target route B.

[0042] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by distributing or integrating functionally or physically in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment resulting from the combination combines the effect of the original embodiment. [Explanation of symbols]

[0043] 1 Vehicle control device 2 Steering wheel 3 Steering Angle Sensor 11 Storage section 12 Control section 121 First Acquisition Department 122 Generation part 123 Estimation Department 124 Second Acquisition Department 125 Calculation Section 126 Decision Section 127 Steering control unit A vehicle

Claims

1. a first acquisition unit that acquires a distance deviation between a route point of a target route of the vehicle and the vehicle, an azimuth angle deviation between a first azimuth angle of the route point and a second azimuth angle of the vehicle, and a steering angle of the vehicle; a generation unit that generates a prediction model that predicts each of the distance deviation, the azimuth angle deviation, and the steering angle; A second acquisition unit that acquires a degree of curvature of a road on which the vehicle is traveling; a calculation unit that calculates a steady side slip angle of the vehicle based on the degree of turning; an estimation unit that estimates an estimated distance deviation, the steering angle, and an estimated azimuth angle deviation based on the prediction model; a determination unit that determines, as a target steering angle, the steering angle that minimizes an evaluation function including parameters of the difference between the estimated azimuth angle deviation and the steady-state sideslip angle, the estimated distance deviation, and the steering angle; having the calculation unit calculates, as the steady-state sideslip angle, the sideslip angle of the rear wheels derived by eliminating the sideslip angle of the front wheels from an equation expressing a balance of forces in a vehicle width direction perpendicular to a traveling direction of the vehicle, which is represented by a centrifugal force represented by the product of a ratio of a square of a vehicle speed of the vehicle to a radius of curvature indicating the degree of turning and a weight of the vehicle, and a centripetal force represented by the sum of a product of a front wheel cornering stiffness and a sideslip angle of the front wheels of the vehicle and a product of a rear wheel cornering stiffness and a sideslip angle of the rear wheels of the vehicle, and an equation expressing a balance of forces in a rotational direction about the center of gravity of the vehicle, which is represented by a first distance between a center of gravity of the vehicle and the front wheels, a first product of the front wheel cornering stiffness and the sideslip angle of the front wheels, a second distance between the center of gravity and the rear wheels, and a second product of the rear wheel cornering stiffness and the sideslip angle of the rear wheels.

2. Executed by a processor installed in the vehicle, acquiring a distance deviation between a route point of a target route of the vehicle and the vehicle, an azimuth angle deviation between a first azimuth angle of the route point and a second azimuth angle of the vehicle, and a steering angle of the vehicle; generating a prediction model for predicting each of the distance deviation, the azimuth angle deviation, and the steering angle; acquiring a degree of curvature of a road on which the vehicle is traveling; a step of calculating, as a steady-state sideslip angle of the vehicle, a sideslip angle of the rear wheels derived by eliminating the sideslip angle of the front wheels from an equation expressing a balance of forces in a vehicle width direction perpendicular to a traveling direction of the vehicle, which is expressed by a centrifugal force expressed by the product of a ratio of a square of a vehicle speed of the vehicle to a radius of curvature indicating the degree of turning and a weight of the vehicle, and a centripetal force expressed by the sum of a product of a front wheel cornering stiffness and a sideslip angle of the front wheels of the vehicle and a product of a rear wheel cornering stiffness and a sideslip angle of the rear wheels of the vehicle, and an equation expressing a balance of forces in a rotational direction about the center of gravity of the vehicle, which is expressed by a first distance between the center of gravity of the vehicle and the front wheels, a first product of the front wheel cornering stiffness and the sideslip angle of the front wheels, a second distance between the center of gravity and the rear wheels, and a second product of the rear wheel cornering stiffness and the sideslip angle of the rear wheels; estimating an estimated distance deviation, the steering angle, and an estimated azimuth angle deviation based on the prediction model; determining, as a target steering angle, the steering angle that minimizes an evaluation function including parameters of the difference between the estimated azimuth angle deviation and the steady-state sideslip angle, the estimated distance deviation, and the steering angle; The control method includes:

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