Active rear wheel steering control method, device and vehicle

Abstract

The application aims to provide an active rear wheel steering control method, device and vehicle considering the influence of communication delay and rear wheel steering system time delay, so as to reduce the influence of communication delay and rear wheel steering system time delay, weaken the influence of front wheel steering interference and tire nonlinear characteristics on the control effect, and improve the controllability and stability of the vehicle with the rear wheel steering system. The method comprises the following steps: establishing a system state error model based on the actual vehicle mass side slip angle, actual yaw rate, actual vehicle speed, actual rear wheel steering angle and actual front wheel steering angle; establishing an augmented system model considering rear wheel steering delay based on the actual rear wheel steering angle and target rear wheel steering angle, and combining the established system state error model; and calculating the target rear wheel steering angle considering the rear wheel steering delay, front wheel steering interference and tire nonlinear characteristics based on the system state error model and the augmented system model considering the rear wheel steering delay, and performing active rear wheel steering control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of active rear wheel steering control of vehicles, and more particularly to an active rear wheel steering control method, device and vehicle considering the influence of communication delay and steering system time lag. BACKGROUND

[0002] Active rear wheel steering (ARS) technology, as a chassis control system to improve vehicle handling and stability, has a very broad development prospect in the future. When the car is driving at low speed, ARS technology can make the vehicle more flexible in handling, which is very helpful when driving in the city, parking or avoiding obstacles. When the car is driving at high speed, ARS technology can improve the understeering ability of the vehicle and make the vehicle more stable and safe. In addition, ARS technology can also be combined with active safety control, automatic driving and other technologies to improve the driving experience and safety.

[0003] CN201710762932.3 provides a method for variable side slip angle control of a vehicle with a rear wheel steering system. This scheme is based on a simple K proportional feedforward control method, and proposes two driving modes: the first human driving mode is based on the subjective angle of the driver, and in order to reduce the driving steering difference of the rear wheel steering vehicle compared with the normal front wheel steering vehicle, the transmission angle ratio K is divided by a coefficient a (a>1); the second automatic driving mode is to minimize the center of mass side slip angle, and is completely based on the K proportional feedforward control method. This control method requires accurate model parameters, and when the vehicle is in the nonlinear region, this simple open-loop control method is difficult to suppress the overshoot of the yaw rate, and the center of mass side slip angle cannot be optimized, and the control effect needs to be improved. On the other hand, the method proposed by this prior art can accurately control the feedback of the active rear wheel steering system, but this control technology still needs to solve the problem of different execution of rear wheel steering angle and front wheel steering angle caused by communication delay and steering system time lag, thereby causing high-speed shaking instability. SUMMARY

[0004] Based on the above background of the prior art, aspects of the present application aim to provide an active rear wheel steering control method, device and vehicle considering the influence of communication delay and rear wheel steering system time lag, to reduce the influence of communication delay and rear wheel steering system time lag, and also to weaken the influence of front wheel steering interference and tire nonlinear characteristics on the control effect, and to improve the handling and stability of vehicles with rear wheel steering systems.

[0005] The technical scheme of the present application is:

[0006] The present application provides an active rear wheel steering control method, comprising:

[0007] Based on the actual vehicle center of mass side slip angle, actual yaw rate, actual vehicle speed, actual rear wheel angle and actual front wheel angle, a system state error model is established;

[0008] Based on the actual rear wheel angle and target rear wheel angle of the vehicle, and in combination with the established system state error model, an augmented system model considering rear wheel steering delay is established;

[0009] Based on the system state error model and the augmented system model considering rear wheel steering delay, the target rear wheel angle considering rear wheel steering delay, front wheel steering interference and tire nonlinear characteristics is calculated, and active rear wheel steering control is performed.

[0010] Preferably, the step of establishing the system state error model comprises:

[0011] A linear two-degree-of-freedom rear wheel steering model is established, taking the transpose of the matrix composed of the actual center of mass side slip angle and the actual yaw rate as the first state quantity, taking the actual rear wheel angle as the control quantity, and taking the actual front wheel angle as the interference quantity;

[0012] The ideal rear wheel steering model is improved to obtain an improved ideal rear wheel steering model, taking the actual center of mass side slip angle as zero as the target, and taking the transpose of the matrix composed of the target center of mass side slip angle and the target yaw rate as the target state quantity, and taking the actual front wheel angle as the interference quantity;

[0013] The difference between the first state quantity and the target state quantity is obtained to obtain the system state error model.

[0014] Preferably, the established system state error model is:

[0015]

[0016] Wherein, e is the vehicle state error quantity, is the first derivative of the vehicle state error quantity, δ r is the actual rear wheel angle, δ f is the actual front wheel angle, is the first derivative of δ f The expression of matrix A is:

[0017]

[0018] The expression of matrix B is:

[0019]

[0020] The expression of matrix C is:

[0021]

[0022] Matrix A d The expression of matrix A is:

[0023]

[0024] The expression of the proportional coefficient ε of the actual rear wheel steering angle and the actual front wheel steering angle is:

[0025]

[0026] v x is the actual vehicle speed, K s is the stability factor;

[0027] a is the distance from the vehicle mass center to the front axle, b is the distance from the vehicle mass center to the rear axle, m is the total mass of the vehicle, L is the distance between the front and rear axles of the vehicle, k1 is the tire cornering stiffness of the front axle of the vehicle, k2 is the tire cornering stiffness of the rear axle of the vehicle, I z is the moment of inertia of the vehicle.

[0028] Preferably, the step of establishing the augmented system model considering the rear wheel steering delay comprises:

[0029] establishing a first-order inertial system representing the rear wheel steering delay based on the actual rear wheel steering angle and the target rear wheel steering angle;

[0030] discretizing the established first-order inertial system to obtain a discrete form of the first-order inertial system;

[0031] discretizing the established system state error model to obtain a discrete form of the system state error model, ignoring the disturbance quantity with the actual front wheel steering angle;

[0032] taking the transpose of a matrix composed of the current vehicle state error quantity, the actual rear wheel steering angle at the current time, and the target rear wheel steering angle at the previous time as the second state quantity, and combining the discrete form of the system state error model and the discrete form of the first-order inertial system to obtain the augmented system model considering the rear wheel steering delay.

[0033] Preferably, the established augmented system model considering the rear wheel steering delay is:

[0034]

[0035] wherein, matrix A The expression of matrix A is:

[0036]

[0037] matrix B The expression of matrix B is:

[0038]

[0039] τ is the rear wheel steering delay time; T is the communication period; δ r (k+1) is the predicted actual rear wheel steering angle at time k+1, δ rd (k) is the target rear wheel steering angle at time k, Δδ rd (k) is the rear wheel steering angle increment at time k; δ rd (k-1) is the target rear wheel steering angle at time k-1 output by the controller, δ r (k) is the actual rear wheel steering angle at time k, e r (k) is the actual yaw rate error at time k, e β (k) is the actual center of mass side slip angle error at time k, e r (k+1) is the actual yaw rate error at time k+1, e β (k+1) is the actual center of mass side slip angle error at time k+1; wherein, δ

[0040]

[0041] a is the distance from the center of mass of the vehicle to the front axle, b is the distance from the center of mass of the vehicle to the rear axle, m is the total mass of the vehicle, L is the front and rear wheelbase of the vehicle, k1 is the front axle tire cornering stiffness of the vehicle, k2 is the rear axle tire cornering stiffness of the vehicle, I z is the moment of inertia of the vehicle, v x is the actual vehicle speed at the current time.

[0042] Preferably, the step of calculating the target rear wheel steering angle considering the rear wheel steering error, the front wheel steering disturbance and the tire nonlinear characteristics based on the system state error model and the augmented system model considering the rear wheel steering delay comprises:

[0043] Based on the standard linear quadratic optimal control theory, the performance index of the rear wheel steering system is established in combination with the actual center of mass side slip angle, the actual yaw rate, the actual rear wheel steering angle and the target rear wheel steering angle.

[0044] The standard optimal control law is obtained in combination with the performance index of the rear wheel steering system and the augmented system model considering the rear wheel steering delay.

[0045] The disturbance compensation is performed on the disturbance quantity in the established system state error model by introducing a series compensation term, and a feedforward compensation quantity is obtained.

[0046] The target rear wheel steering angle considering the rear wheel steering delay, the front wheel steering disturbance and the tire nonlinear characteristics is calculated based on the standard optimal control law, the feedforward compensation quantity and the target rear wheel steering angle at the previous time.

[0047] Preferably, the expression of the established performance index J of the rear wheel steering system is:

[0048]

[0049] wherein q β , q r , respectively represent the importance of the actual center of mass side slip angle β, the actual yaw rate r, the actual rear wheel angle δ r and the target rear wheel angle δ rd . R represents the importance of the rear wheel angle increment Δδ rd ;

[0050]

[0051] R = r Δδrd ;

[0052] The standard optimal control law u1 is expressed as:

[0053] u1 = (1 - λ)u 11 + λu 12 ;

[0054]

[0055] λ is a state indicating the tendency of the tire characteristics to be nonlinear;

[0056]

[0057] α is the front wheel side slip angle, R1 is a weight matrix of the linear region of the tire, R2 is a weight matrix of the nonlinear region of the tire, P1 is a solution of the Riccati equation calculated in the linear region of the tire, P2 is a solution of the Riccati equation calculated in the nonlinear region of the tire, is the transpose of the matrix , and the expression of the matrix is:

[0058] τ is a rear wheel steering delay time based on a first order inertia system representing the rear wheel steering delay, and T is a communication period.

[0059] Preferably, the expression of the feedforward compensation amount u2 is:

[0060]

[0061] wherein,

[0062] The expression of the matrix A is:

[0063]

[0064] In the expression, the expression of the matrix B is:

[0065]

[0066] The expression of matrix C is:

[0067]

[0068] The expression of matrix A d is:

[0069]

[0070] δ f is the actual front wheel steering angle, a is the distance from the vehicle mass center to the front axle, b is the distance from the vehicle mass center to the rear axle, m is the total mass of the vehicle, L is the distance between the front and rear axles of the vehicle, k1 is the tire cornering stiffness of the front axle of the vehicle, k2 is the tire cornering stiffness of the rear axle of the vehicle, I z is the moment of inertia of the vehicle.

[0071] The application also provides an active rear wheel steering control device, comprising:

[0072] A system state error model establishing module is configured to establish a system state error model based on the actual mass center cornering angle, the actual yaw rate, the actual vehicle speed, the actual rear wheel steering angle and the actual front wheel steering angle of the vehicle.

[0073] An augmented system model establishing module is configured to establish an augmented system model considering the rear wheel steering delay based on the actual rear wheel steering angle and the target rear wheel steering angle of the vehicle, in combination with the established system state error model.

[0074] A steering control module is configured to calculate the target rear wheel steering angle considering the rear wheel steering delay, the front wheel steering interference and the tire nonlinear characteristics based on the system state error model and the augmented system model considering the rear wheel steering delay, and perform active rear wheel steering control.

[0075] Preferably, the system state error model establishing module comprises:

[0076] A linear two-degree-of-freedom rear wheel steering model establishing unit is configured to establish a linear two-degree-of-freedom rear wheel steering model by taking the transpose of a matrix composed of the actual mass center cornering angle and the actual yaw rate as the first state quantity, taking the actual rear wheel steering angle as the control quantity, and taking the actual front wheel steering angle as the interference quantity.

[0077] An ideal rear wheel steering model establishing unit is configured to improve an ideal rear wheel steering model by taking the actual mass center cornering angle as zero as the target, and obtain an improved ideal rear wheel steering model; in the improved ideal rear wheel steering model, the transpose of a matrix composed of the target mass center cornering angle and the target yaw rate is taken as the target state quantity, and the actual front wheel steering angle is taken as the interference quantity.

[0078] The system state error model establishing unit is configured to subtract the first state quantity from the target state quantity to obtain a system state error model.

[0079] Preferably, the system state error model is established as follows:

[0080]

[0081] wherein e is a vehicle state error quantity, is a first derivative of the vehicle state error quantity, δ r is an actual rear wheel steering angle, δ f is an actual front wheel steering angle, is a first derivative of δ f ; the expression of the matrix A is as follows:

[0082]

[0083] The expression of the matrix B is as follows:

[0084]

[0085] The expression of the matrix C is as follows:

[0086]

[0087] The expression of the matrix A d is as follows:

[0088]

[0089] The expression of a proportional coefficient ε of the actual rear wheel steering angle and the actual front wheel steering angle is as follows:

[0090]

[0091] v x is an actual vehicle speed, K s is a stability factor;

[0092] a is a distance from a vehicle center of mass to a front axle, b is a distance from the vehicle center of mass to a rear axle, m is a total mass of the vehicle, L is a front-rear wheelbase of the vehicle, k1 is a front axle tire cornering stiffness of the vehicle, k2 is a rear axle tire cornering stiffness of the vehicle, I z is a moment of inertia of the vehicle.

[0093] Preferably, the augmented system model establishing module comprises:

[0094] a first-order inertia system establishing unit configured to establish a first-order inertia system representing a rear wheel steering delay based on the actual rear wheel steering angle and the target rear wheel steering angle;

[0095] The first discretization processing unit is configured to discretize the first-order inertia system to obtain a discretized first-order inertia system.

[0096] The second discretization processing unit is configured to ignore the disturbance quantity with the actual front wheel steering angle, and discretize the system state error model to obtain a discretized system state error model.

[0097] The augmented system model establishing unit is configured to take the transpose of a matrix composed of the vehicle state error quantity at the current time, the actual rear wheel steering angle at the current time and the target rear wheel steering angle at the previous time as the second state quantity, and combine the discretized system state error model and the discretized first-order inertia system to obtain an augmented system model considering the rear wheel steering delay.

[0098] Preferably, the established augmented system model considering the rear wheel steering delay is as follows:

[0099]

[0100] wherein the matrix is expressed as:

[0101]

[0102] The matrix is expressed as:

[0103]

[0104] τ is the rear wheel steering delay time; T is the communication period; δ r (k+1) is the predicted actual rear wheel steering angle at the k+1 time, δ rd (k) is the target rear wheel steering angle at the k time, Δδ rd (k) is the rear wheel steering angle increment at the k time; δ rd (k-1) is the target rear wheel steering angle at the k-1 time output by the controller, δ r (k) is the actual rear wheel steering angle at the k time, e r (k) is the actual yaw rate error at the k time, e β (k) is the actual mass center side slip angle error at the k time, e r (k+1) is the actual yaw rate error at the k+1 time, e β (k+1) is the actual mass center side slip angle error at the k+1 time; wherein the following conditions are met:

[0105]

[0106] a is the distance from the vehicle center of mass to the front axle, b is the distance from the vehicle center of mass to the rear axle, m is the total mass of the vehicle, L is the wheelbase of the vehicle, k1 is the tire cornering stiffness of the front axle of the vehicle, k2 is the tire cornering stiffness of the rear axle of the vehicle, I z is the moment of inertia of the vehicle, v x is the actual vehicle speed at the current time.

[0107] Preferably, the steering control module comprises:

[0108] a performance index establishment unit, configured to establish a performance index of the rear wheel steering system based on a standard linear quadratic optimal control theory, in combination with an actual center of mass side slip angle, an actual yaw rate, an actual rear wheel steering angle and a target rear wheel steering angle of the vehicle;

[0109] a standard optimal control law determination unit, configured to obtain a standard optimal control law in combination with the performance index of the rear wheel steering system and in consideration of an augmented system model of rear wheel steering delay;

[0110] a feedforward compensation amount determination unit, configured to introduce a series compensation term to compensate for disturbance in the established system state error model, to obtain a feedforward compensation amount;

[0111] a target rear wheel steering angle determination unit, configured to calculate a target rear wheel steering angle considering rear wheel steering delay, front wheel steering disturbance and tire nonlinear characteristics based on the standard optimal control law, the feedforward compensation amount and a target rear wheel steering angle at the previous time.

[0112] Preferably, the expression of the established performance index J of the rear wheel steering system is:

[0113]

[0114] wherein q β , q r , respectively represent the importance of the actual center of mass side slip angle β, the actual yaw rate r, the actual rear wheel steering angle δ r and the target rear wheel steering angle δ rd ; and R represents the importance of the rear wheel steering angle increment Δδ rd .

[0115]

[0116]

[0117] The expression of the standard optimal control law u1 is:

[0118] u1=(1-λ)u 11 +λu 12

[0119]

[0120] λ is a state indicating a tire characteristic tends to be nonlinear;

[0121]

[0122] α is a front wheel side slip angle, R1 is a weight matrix of a tire linear region; R2 is a weight matrix of a tire nonlinear region, P1 is a solution of a Riccati equation calculated in a tire linear region, P2 is a solution of a Riccati equation calculated in a tire nonlinear region, is a transpose of a matrix The expression of the matrix is as follows:

[0123] τ is a rear wheel steering delay time obtained based on a first order inertia system representing a rear wheel steering delay; and T is a communication period.

[0124] Preferably, the expression of the feedforward compensation amount u2 is as follows:

[0125]

[0126] wherein,

[0127] The expression of the matrix A is as follows:

[0128]

[0129] In the formula, the expression of the matrix B is as follows:

[0130]

[0131] The expression of the matrix C is as follows:

[0132]

[0133] The expression of the matrix A d is as follows:

[0134]

[0135] δ f is an actual front wheel steering angle, a is a distance from a vehicle mass center to a front axle, b is a distance from the vehicle mass center to a rear axle, m is a total mass of the vehicle, L is a front and rear axle distance of the vehicle, k1 is a front axle tire cornering stiffness of the vehicle, k2 is a rear axle tire cornering stiffness of the vehicle, I z is a moment of inertia of the vehicle.

[0136] The application also provides a vehicle comprising the active rear wheel steering control device described above.

[0137] The application further provides a control device, comprising a processor, a memory, and a program or instructions stored on the memory and executable on the processor, which, when executed by the processor, implement the steps of the active rear wheel steering control method.

[0138] The application further provides a readable storage medium, which stores a program or instructions, which, when executed by a processor, implement the steps of the active rear wheel steering control method.

[0139] The application has the following advantages:

[0140] The application provides a linear quadratic optimal control method with rear wheel steering delay compensation, which, on the basis of considering optimal control in the whole speed range, rear wheel steering delay characteristics, front wheel steering interference, and nonlinear characteristics of tires, respectively performs ideal rear wheel reference model processing, system augmentation processing, series compensation processing, and variable weight matrix processing. The control method has wide application range and strong robustness, and can achieve good tracking effect in the whole speed range. The control method solves the problem of rear wheel steering delay, and enables the vehicle to achieve optimal control effect even in the case that the rear wheel steering actuator has poor following effect, and can improve the low-speed maneuverability and high-speed stability of the vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0141] Figure 1 FIG. 1 is a control logic architecture diagram in an embodiment of the application;

[0142] Figure 2 FIG. 2 is a control method flowchart in an embodiment of the application;

[0143] Figure 3 FIG. 3 is a detailed control method flowchart in an embodiment of the application;

[0144] Figure 4 FIG. 4 is a linear two-degree-of-freedom rear wheel steering vehicle model in an embodiment of the application;

[0145] Figure 5 FIG. 5 is a delay test data diagram of the active rear wheel steering system in an embodiment of the application. DETAILED DESCRIPTION

[0146] Embodiments of the application will be described below with reference to the accompanying drawings and preferred embodiments, and other advantages and effects of the application can be easily understood by those skilled in the art from the disclosure herein. The application can also be implemented or applied by different specific embodiments, and various modifications or changes can be made to the details in the specification based on different views and applications without departing from the spirit of the application. It should be understood that the preferred embodiments are only for illustrating the application, and are not intended to limit the protection scope of the application.

[0147] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concepts of the present application in a schematic manner, and only the components related to the present application are shown in the diagrams, rather than being drawn according to the number, shape and size of the components in actual implementation. The shapes, number and proportions of the components in actual implementation can be arbitrarily changed, and the layout pattern of the components can be more complex.

[0148] For the purpose of better illustrating the objects and advantages of the present application, the present application is further described below without limiting the present application by referring to the accompanying drawings.

[0149] Referring to Figure 1 , the control logic architecture diagram of the method of the present application.

[0150] The sensor signal processing module converts the steering wheel angle signal into the actual front wheel angle δ f , and compares it with the actual vehicle speed v x to send to the ideal rear wheel steering model to calculate the target mass side slip angle β d and the target yaw rate r d . At the same time, the actual mass side slip angle β and the actual yaw rate r are obtained to calculate the vehicle state error e. Considering the rear wheel steering system delay, the tire nonlinear characteristics, and the front wheel disturbance variable interference, a linear quadratic optimal control strategy is designed to obtain the target rear wheel angle u considering the rear wheel steering delay, the front wheel steering interference and the tire nonlinear characteristics, which is converted into the rear axle rack displacement and input to the gear rack steering actuator of the vehicle rear axle. The detailed steps are as follows Figure 2 , a steering time delay compensation based active rear wheel steering control method is provided, comprising the following steps:

[0151] Step S1, based on the actual mass side slip angle, the actual yaw rate, the actual vehicle speed, the actual rear wheel angle and the actual front wheel angle of the vehicle, a system state error model is established.

[0152] Step S2, based on the actual rear wheel angle and the target rear wheel angle of the vehicle, and combined with the established system state error model, an augmented system model considering the rear wheel steering delay is established.

[0153] Step S3, based on the system state error model and the augmented system model considering the rear wheel steering delay, the target rear wheel angle considering the rear wheel steering delay is calculated, and active rear wheel steering control is performed.

[0154] As Figure 3 , wherein, for step S1, the establishment of the system state error model comprises the following steps:

[0155] Step S11, based on the derivation mechanism of the linear two-degree-of-freedom front wheel steering model, the rear wheel steering angle is added to establish a linear two-degree-of-freedom rear wheel steering model, such as Figure 4 Let the first state variable x = [β r] T , the control variable u = δ r , the disturbance variable w = δ f , and the state space equation of the linear two-degree-of-freedom rear wheel steering model is expressed as follows:

[0156]

[0157] In the formula, a and b are the distances from the vehicle mass center to the front and rear axles, m is the total mass of the vehicle, v x is the longitudinal vehicle speed, L is the vehicle wheelbase, k1 and k2 are the tire cornering stiffness of the front and rear axles of the vehicle, I z is the moment of inertia of the vehicle, δ f is the actual front wheel steering angle, and δ r is the actual rear wheel steering angle.

[0158] Step S12, based on the ideal rear wheel steering model, the ideal rear wheel steering model is improved with the actual mass center cornering angle β as the target, and the target mass center cornering angle β d and the target yaw rate r d are calculated according to the actual vehicle speed v x and the actual front wheel steering angle δ f . Let the target state variable x d = [β d r d ] T , w = δ f , and the improved ideal rear wheel steering model is designed as follows:

[0159] x d = A d w (2)

[0160]

[0161] In the formula, K s is a stability factor,

[0162] ε is the actual rear wheel steering angle and the actual front wheel steering angle, which is calculated based on the linear two-degree-of-freedom vehicle model formula (1) with the mass center cornering angle steady-state value as the target, and the expression is as follows:

[0163]

[0164] Step S13, the actual mass center cornering angle β and the actual yaw rate r are obtained, and the actual values are subtracted from the target values (i.e., the first state variable x is subtracted from the target state variable xd (By subtracting the values), we obtain the system state error model. The difference between the actual value and the target value is e = x. d =[e β e r ] T =[β-β d rr d ] T By combining equations (1) and (2), we can obtain:

[0165]

[0166] The system state error model is summarized as follows:

[0167]

[0168] Let e ​​be the first derivative of the vehicle state error.

[0169] Ignoring the interference term involving the front wheel steering angle, equation (5) is discretized using the forward Euler method to obtain a discrete form of the system state error model:

[0170]

[0171] δ r (k+1) is the predicted actual rear wheel steering angle at time k+1, δ rd (k) represents the target rear wheel steering angle at time k, Δδ rd (k) represents the rear wheel steering angle increment at time k; δ rd (k-1) The target rear wheel rotation angle at time k-1 output by the controller, δ r (k) is the actual rear wheel steering angle at time k, e r (k) represents the actual yaw rate error at time k, e β (k) represents the actual centroid sideslip angle error at time k, e r (k+1) represents the actual yaw rate error at time k+1, e β (k+1) represents the actual centroid sideslip angle error at time k+1.

[0172] Specifically, for step S2, considering the rear-wheel steering system delay, an augmented matrix is ​​established to obtain the final augmented system model, including the following steps:

[0173] Step S21, the target rear wheel steering angle δ calculated by the controller is... rd Compared with the actual rear wheel steering angle δ r In comparison, the rear wheel steering delay time τ is obtained, see [reference needed]. Figure 5 The delay of the rear-wheel steering system is approximated using a first-order inertial system, expressed as follows:

[0174]

[0175] where τ is a time constant, which needs to be adjusted to a suitable value to calibrate the actual rear wheel steering system, and is set to 0.2 s in the embodiment; δ r is the actual rear wheel steering angle, δ rd is the target rear wheel steering angle calculated by the controller.

[0176] In step S22, the actual rear wheel steering angle δ r (k+1) at the next time k+1 is predicted, and a discretization process is performed to obtain an augmented system model. The first-order inertial system in a discrete form is obtained by discretizing equation (7) using the forward Euler method:

[0177]

[0178] where T is a communication period, which is set to 0.005 s in the embodiment. k and k+1 represent the kth and (k+1)th sampling time, respectively. δ r (k+1) is the predicted actual rear wheel steering angle at time k+1, δ r (k) is the predicted actual rear wheel steering angle at time k.

[0179] Since the target rear wheel steering angle increment Δδ rd has the following relationship with the target rear wheel steering angle δ rd

[0180] δ rd (k) = δ rd (k-1) + Δδ rd (k) (9)

[0181] δ rd (k) is the target rear wheel steering angle at time k, δ rd (k-1) is the target rear wheel steering angle at time k-1, and Δδ rd (k) is the target rear wheel steering angle increment at time k.

[0182] Therefore, equation (8) is converted to:

[0183]

[0184] Let the second state variable x Combining equation (6) and equation (10) (i.e., combining the discrete form of the system state error model and the discrete form of the first-order inertial system), and ignoring the disturbance term, the augmented system model considering the rear wheel steering delay is obtained as:

[0185]

[0186] For step S3, the following steps are included: ​

[0187] Step S31, based on the standard linear quadratic optimal control theory, the actual centroid side slip angle, the actual yaw rate, the actual rear wheel steering angle and the target rear wheel steering angle are combined to establish the performance index of the rear wheel steering system. The performance index J expression is:

[0188]

[0189] Wherein, Q, R are weighted diagonal matrix, q β , q r , Respectively represent the importance of the actual centroid side slip angle β, the actual yaw rate r, the actual rear wheel steering angle δ r And the target rear wheel steering angle δ rd (The specific values of these parameters are pre-assigned). R represents the importance of the rear wheel steering angle increment Δδ rd (Precise assignment is obtained).

[0190] Combined with formula (11) and formula (12), the full state feedback quantity is calculated according to the standard optimal control law. For the standard linear system, there is a standard optimal control law u1, the expression is:

[0191] U1=-R -1 B T Px (13)

[0192] Wherein, the matrix P is the solution of the standard Riccati equation.

[0193] Step S32, the disturbance is compensated by introducing a series compensation term. According to formula (5), it can be seen that the state error model of the system exists about the front wheel steering angle δ f And the first derivative of the front wheel steering angle Variable disturbance term, which is a complex nonlinear system with cross interference term. The specific compensation is as follows:

[0194] According to the modeling of the disturbance term of the series compensation, the feedforward compensation quantity is calculated. For nonlinear system, such as Let u=-Kx+K1v+K2w, substitute to get: When BK1+C1=0, BK2+C2=0, the steady-state error of the system is zero. The feedforward compensation term can be obtained: K1=-B -1 C1, K2=-B -1 C2. If B is a vector and cannot be inverted, B -1 Can be optimally replaced by matrix

[0195] Combined with formula (5), the feedforward compensation quantity u2 is:

[0196]

[0197] Stepped input of steering wheel angle will cause the first derivative of front wheel angle Discontinuity, resulting in the rear wheel angle is not smooth enough to affect the stability of the vehicle. The present invention ignores the first derivative of the front wheel angle This interference term, formula (14) will become:

[0198]

[0199] Step S33, the tire characteristics are simply divided into linear and nonlinear regions, and different weight matrices are designed for different regions to meet different requirements of different regions on handling and stability.

[0200] Introducing λ to weight the linear and nonlinear regions of the tire, λ represents the state of the tire characteristics tending to nonlinearity.

[0201]

[0202] Wherein, α is the front wheel side slip angle.

[0203] Then the expression of u1 in formula (13) can be improved as:

[0204]

[0205] R1 is the weight matrix of the linear region of the tire; R2 is the weight matrix of the nonlinear region of the tire, P1 is the solution of the Riccati equation calculated in the linear region of the tire, and P2 is the solution of the Riccati equation calculated in the nonlinear region of the tire, is the transpose of the matrix .

[0206] Since the control input is in the form of rear wheel angle increment, the control amount u3 at the moment is added:

[0207] u3=δ rd (k-1) (18)

[0208] Finally, the target rear wheel angle u considering the rear wheel steering delay, front wheel steering interference and tire nonlinear characteristics is calculated as follows:

[0209] u=u1+u2+u3 (19)

[0210] Wherein, u1 is the standard optimal control law, u2 is the feedforward compensation, and u3 is the control amount at the last moment.

[0211] The present application also provides an active rear wheel steering control device, comprising:

[0212] The system state error model establishing module is configured to establish a system state error model based on the actual vehicle center side slip angle, the actual yaw rate, the actual vehicle speed, the actual rear wheel steering angle and the actual front wheel steering angle.

[0213] The augmented system model establishing module is configured to establish an augmented system model considering the rear wheel steering delay based on the actual rear wheel steering angle and the target rear wheel steering angle, and in combination with the established system state error model.

[0214] The steering control module is configured to calculate the target rear wheel steering angle considering the rear wheel steering delay, the front wheel steering disturbance and the tire nonlinear characteristics based on the system state error model and the augmented system model considering the rear wheel steering delay, and to perform active rear wheel steering control.

[0215] Preferably, the system state error model establishing module comprises:

[0216] The linear two-degree-of-freedom rear wheel steering model establishing unit is configured to establish a linear two-degree-of-freedom rear wheel steering model with the transpose of a matrix composed of the actual vehicle center side slip angle and the actual yaw rate as the first state quantity, the actual rear wheel steering angle as the control quantity and the actual front wheel steering angle as the disturbance quantity.

[0217] The ideal rear wheel steering model establishing unit is configured to improve the ideal rear wheel steering model to obtain an improved ideal rear wheel steering model with the actual vehicle center side slip angle as zero as the target, and with the transpose of a matrix composed of the target vehicle center side slip angle and the target yaw rate as the target state quantity and the actual front wheel steering angle as the disturbance quantity.

[0218] The system state error model establishing unit is configured to subtract the first state quantity from the target state quantity to obtain the system state error model.

[0219] Preferably, the established system state error model is:

[0220]

[0221] wherein e is a vehicle state error quantity, is a first order derivative of the vehicle state error quantity, δ r is the actual rear wheel steering angle, δ f is the actual front wheel steering angle, is a first order derivative of δ f ; and the expression of the matrix A is:

[0222]

[0223] wherein the expression of the matrix B is:

[0224]

[0225] The expression of matrix C is:

[0226]

[0227] The expression of matrix A is: d

[0228]

[0229] The expression of the proportional coefficient ε of the actual rear wheel steering angle and the actual front wheel steering angle is:

[0230]

[0231] v x is the actual vehicle speed, K s is a stability factor;

[0232] a is the distance from the vehicle center of mass to the front axle, b is the distance from the vehicle center of mass to the rear axle, m is the total mass of the vehicle, L is the distance between the front and rear axles of the vehicle, k1 is the tire cornering stiffness of the front axle of the vehicle, k2 is the tire cornering stiffness of the rear axle of the vehicle, I z is the moment of inertia of the vehicle.

[0233] Preferably, the augmented system model establishing module comprises:

[0234] a first-order inertia system establishing unit, configured to establish a first-order inertia system representing rear wheel steering delay based on the actual rear wheel steering angle and the target rear wheel steering angle;

[0235] a first discretization processing unit, configured to discretize the established first-order inertia system to obtain a discretized first-order inertia system;

[0236] a second discretization processing unit, configured to ignore the disturbance quantity with the actual front wheel steering angle and discretize the established system state error model to obtain a discretized system state error model;

[0237] an augmented system model establishing unit, configured to take the transpose of a matrix composed of the vehicle state error quantity at the current time, the actual rear wheel steering angle at the current time and the target rear wheel steering angle at the previous time as a second state quantity, and combine the discretized system state error model and the discretized first-order inertia system to obtain an augmented system model considering rear wheel steering delay, front wheel steering disturbance and tire nonlinear characteristics.

[0238] Preferably, the established augmented system model considering rear wheel steering delay is:

[0239]

[0240] wherein the expression of matrix is:​

[0241]

[0242] matrix The expression is:

[0243]

[0244] τ is the rear wheel steering delay time; T is the communication period; δ r (k+1) is the predicted actual rear wheel steering angle at time k+1, δ rd (k) is the target rear wheel steering angle at time k, Δδ rd (k) is the rear wheel steering angle increment at time k; δ rd (k-1) is the target rear wheel steering angle at time k-1 output by the controller, δ r (k) is the actual rear wheel steering angle at time k, e r (k) is the actual yaw rate error at time k, e β (k) is the actual center of mass side slip angle error at time k, e r (k+1) is the actual yaw rate error at time k+1, e β (k+1) is the actual center of mass side slip angle error at time k+1; wherein:

[0245]

[0246] a is the distance from the vehicle center of mass to the front axle, b is the distance from the vehicle center of mass to the rear axle, m is the total mass of the vehicle, L is the front and rear wheelbase of the vehicle, k1 is the front axle tire cornering stiffness of the vehicle, k2 is the rear axle tire cornering stiffness of the vehicle, I z is the moment of inertia of the vehicle, v x is the actual vehicle speed at the current time.

[0247] Preferably, the steering control module comprises:

[0248] a performance index establishment unit, configured to establish a performance index of the rear wheel steering system based on a standard linear quadratic optimal control theory, in combination with the actual center of mass side slip angle, the actual yaw rate, the actual rear wheel steering angle, and the target rear wheel steering angle;

[0249] a standard optimal control law determination unit, configured to obtain a standard optimal control law in combination with the performance index of the rear wheel steering system and considering an augmented system model of the rear wheel steering delay;

[0250] a feedforward compensation amount determination unit, configured to introduce a series compensation term to interfere with the disturbance compensation in the established system state error model, and obtain a feedforward compensation amount;

[0251] The target rear wheel steering angle determination unit is configured to calculate a target rear wheel steering angle that takes into account rear wheel steering delay, front wheel steering interference, and tire nonlinear characteristics, based on a standard optimal control law, a feedforward compensation amount, and a target rear wheel steering angle at a previous time.

[0252] Preferably, the expression of the performance index J of the established rear wheel steering system is:

[0253]

[0254] wherein Q and R are weighted diagonal matrices, q β , q r , respectively represent the importance of the actual center of mass side slip angle β, the actual yaw rate r, and the actual rear wheel steering angle δ r and the target rear wheel steering angle δ rd . R represents the importance of the rear wheel steering angle increment Δδ rd ;

[0255]

[0256]

[0257] The expression of the standard optimal control law u1 is:

[0258] u1 = (1 - λ)u 11 + λu 12

[0259]

[0260] λ represents a state in which the tire characteristics tend to be nonlinear;

[0261]

[0262] α is the front wheel side slip angle, R1 is a weight matrix of the tire linear region, R2 is a weight matrix of the tire nonlinear region, P1 is a solution of the Riccati equation calculated in the tire linear region, P2 is a solution of the Riccati equation calculated in the tire nonlinear region, is the transpose of the matrix The expression of the matrix is:

[0263] τ is a rear wheel steering delay time obtained based on a first-order inertia system representing rear wheel steering delay; and T is a communication period.

[0264] Preferably, the expression of the feedforward compensation amount u2 is:

[0265]

[0266] wherein

[0267] The expression of matrix A is:

[0268]

[0269] The expression of matrix B is:

[0270]

[0271] The expression of matrix C is:

[0272]

[0273] The expression of matrix A d is:

[0274]

[0275] δ f is the actual front wheel steering angle, a is the distance from the vehicle mass center to the front axle, b is the distance from the vehicle mass center to the rear axle, m is the total mass of the vehicle, L is the distance between the front and rear axles of the vehicle, k1 is the tire cornering stiffness of the front axle of the vehicle, k2 is the tire cornering stiffness of the rear axle of the vehicle, I z is the moment of inertia of the vehicle.

[0276] The application also provides a vehicle comprising the active rear wheel steering control device described above.

[0277] The application also provides a control device comprising a processor, a memory, and a program or instructions stored in the memory and executable on the processor, and the program or instructions, when executed by the processor, implement the steps of the active rear wheel steering control method described above.

[0278] The application also provides a readable storage medium, and the readable storage medium stores a program or instructions, and the program or instructions, when executed by a processor, implement the steps of the active rear wheel steering control method described above.

[0279] The above embodiments are preferred embodiments of the application, but the embodiments of the application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the application shall be equivalent replacement modes, and all shall be included in the protection scope of the application.

Claims

1. An active rear-wheel steering control method, characterized in that, include: A system state error model is established based on the vehicle's actual center of gravity sideslip angle, actual yaw rate, actual vehicle speed, actual rear wheel steering angle, and actual front wheel steering angle. Based on the vehicle's actual rear wheel steering angle and target rear wheel steering angle, and combined with the established system state error model, an augmented system model considering rear wheel steering delay is established. Based on the system state error model and the augmented system model considering rear wheel steering delay, the target rear wheel steering angle considering rear wheel steering delay, front wheel steering disturbance and tire nonlinear characteristics is calculated, and active rear wheel steering control is performed. The steps to establish an augmented system model that takes into account rear-wheel steering lag include: Based on the actual rear wheel steering angle and the target rear wheel steering angle, a first-order inertial system representing the rear wheel steering delay is established; Discretize the established first-order inertial system to obtain a discrete form of the first-order inertial system; Ignoring the interference with the actual front wheel steering angle, the established system state error model is discretized to obtain a discrete form of the system state error model; The transpose of the matrix consisting of the current vehicle state error, the current actual rear wheel steering angle, and the previous target rear wheel steering angle is used as the second state variable. Combined with the discrete system state error model and the discrete first-order inertial system, an augmented system model considering rear wheel steering delay is obtained. Based on the system state error model and the augmented system model considering rear wheel steering delay, the steps for calculating the target rear wheel steering angle, taking into account rear wheel steering delay, front wheel steering disturbance, and tire nonlinear characteristics, include: Based on the standard linear quadratic optimal control theory, and combined with the vehicle's actual center of gravity sideslip angle, actual yaw rate, actual rear wheel steering angle and target rear wheel steering angle, the performance index of the rear wheel steering system is established. By combining the performance indicators of the rear-wheel steering system with the augmented system model that considers the rear-wheel steering delay, the standard optimal control law is obtained; A series compensation term is introduced to compensate for the disturbance in the established system state error model, resulting in a feedforward compensation term. Based on the standard optimal control law, feedforward compensation, and the target rear wheel steering angle at the previous moment, the target rear wheel steering angle considering rear wheel steering delay, front wheel steering interference, and tire nonlinear characteristics is calculated.

2. The active rear-wheel steering control method according to claim 1, characterized in that, The steps to establish a system state error model include: A linear two-degree-of-freedom rear wheel steering model is established by taking the transpose of the matrix consisting of the actual center of gravity sideslip angle and the actual yaw rate as the first state variable, the actual rear wheel steering angle as the control variable, and the actual front wheel steering angle as the disturbance variable. With the goal of zero actual centroid sideslip angle, the ideal rear wheel steering model is improved to obtain the improved ideal rear wheel steering model. In the improved ideal rear wheel steering model, the transpose of the matrix formed by the target centroid sideslip angle and the target yaw rate is used as the target state variable, and the actual front wheel steering angle is used as the disturbance variable. The system state error model is obtained by subtracting the first state variable from the target state variable.

3. The active rear-wheel steering control method according to claim 2, characterized in that, The established system state error model is as follows: in, This represents the vehicle state error. This is the first derivative of the vehicle state error. This is the actual rear wheel steering angle. This is the actual front wheel steering angle. for First derivative; matrix The expression is: In the formula, the matrix The expression is: matrix The expression is: matrix The expression is: The ratio of the actual rear wheel steering angle to the actual front wheel steering angle The expression is: This is the actual vehicle speed. As a stability factor; ; This is the distance from the vehicle's center of gravity to the front axle. This is the distance from the vehicle's center of gravity to the rear axle. For the total mass of the vehicle. This refers to the front and rear wheelbase of the vehicle. This refers to the lateral stiffness of the vehicle's front axle tires. This refers to the lateral stiffness of the vehicle's rear axle tires. Let represent the vehicle's moment of inertia.

4. The active rear-wheel steering control method according to claim 1, characterized in that, The augmented system model considering rear-wheel steering lag is as follows: Among them, matrix The expression is: matrix The expression is: This is the rear wheel steering delay time; For communication cycles; The actual rear wheel steering angle at time k+1 is the predicted value. Let k be the target rear wheel steering angle. The rear wheel steering angle increment at time k; The target rear wheel steering angle at time k-1 output by the controller. The actual rear wheel steering angle at time k. The actual yaw rate error at time k. The actual centroid sideslip angle error at time k. The actual yaw rate error at time k+1 Let be the actual centroid sideslip angle error at time k+1; where satisfies: This is the distance from the vehicle's center of gravity to the front axle. This is the distance from the vehicle's center of gravity to the rear axle. For the total mass of the vehicle. This refers to the front and rear wheelbase of the vehicle. This refers to the lateral stiffness of the vehicle's front axle tires. This refers to the lateral stiffness of the vehicle's rear axle tires. For the vehicle's moment of inertia, This represents the actual vehicle speed at the current moment.

5. The active rear-wheel steering control method according to claim 1, characterized in that, The expression for the performance index J of the rear-wheel steering system is: in, , , , These represent the actual sideslip angle θ, the actual yaw rate φ, and the actual rear wheel steering angle, respectively. and target rear wheel angle The degree of importance attached to it; 𝑅 indicates the increment of the rear wheel steering angle. The degree of importance attached to it; Standard optimal control law The expression is: , 𝜆 represents the state where tire characteristics tend to be non-linear; The front wheel slip angle, This is the weight matrix for the linear region of the tire; This is the weight matrix for the tire's nonlinear region. The solution to the Riccati equation calculated for the linear region of the tire. The solution to the Riccati equation for the tire nonlinear region calculation. For matrix transpose of matrix The expression is: , The rear wheel steering delay time is obtained based on a first-order inertial system representing the rear wheel steering delay. This refers to the communication cycle.

6. The active rear-wheel steering control method according to claim 1, characterized in that, Feedforward compensation The expression is: in, ; matrix The expression is: In the formula, the matrix The expression is: matrix The expression is: matrix The expression is: This is the actual front wheel steering angle. This is the distance from the vehicle's center of gravity to the front axle. This is the distance from the vehicle's center of gravity to the rear axle. For the total mass of the vehicle. This refers to the front and rear wheelbase of the vehicle. This refers to the lateral stiffness of the vehicle's front axle tires. This refers to the lateral stiffness of the vehicle's rear axle tires. Let represent the vehicle's moment of inertia.

7. An active rear-wheel steering control device, characterized in that, include: The system state error model establishment module is used to establish a system state error model based on the vehicle's actual center of gravity sideslip angle, actual yaw rate, actual vehicle speed, actual rear wheel steering angle, and actual front wheel steering angle. The augmented system model building module is used to build an augmented system model that considers rear wheel steering delay based on the vehicle's actual rear wheel steering angle and target rear wheel steering angle, combined with the established system state error model. The steering control module is used to calculate the target rear wheel steering angle based on the system state error model and the augmented system model that considers rear wheel steering delay, front wheel steering interference and tire nonlinear characteristics, and to perform active rear wheel steering control. The augmented system model building module includes: A first-order inertial system establishment unit is used to establish a first-order inertial system representing the rear wheel steering delay based on the actual rear wheel steering angle and the target rear wheel steering angle. The first discretization processing unit is used to discretize the established first-order inertial system to obtain a discrete form of the first-order inertial system. The second discretization unit is used to ignore the interference with the actual front wheel angle and discretize the established system state error model to obtain a discrete system state error model. The augmented system model building unit is used to take the transpose of the matrix consisting of the vehicle state error at the current moment, the actual rear wheel steering angle at the current moment, and the target rear wheel steering angle at the previous moment as the second state variable, and combine it with the discrete form of the system state error model and the discrete form of the first-order inertial system to obtain an augmented system model that considers the rear wheel steering delay. The steering control module includes: The performance index establishment unit is used to establish the performance index of the rear wheel steering system based on the standard linear quadratic optimal control theory, combined with the vehicle's actual center of gravity sideslip angle, actual yaw rate, actual rear wheel steering angle and target rear wheel steering angle. The standard optimal control law determination unit is used to combine the performance indicators of the rear wheel steering system with the augmented system model that considers the rear wheel steering delay to obtain the standard optimal control law; The feedforward compensation quantity determination unit is used to introduce a series compensation term to compensate for the interference in the established system state error model and obtain the feedforward compensation quantity. The target rear wheel steering angle determination unit is used to calculate the target rear wheel steering angle based on the standard optimal control law, feedforward compensation, and the target rear wheel steering angle at the previous moment, taking into account the rear wheel steering delay, front wheel steering interference, and tire nonlinear characteristics.

8. The active rear wheel steering control device according to claim 7, characterized in that, The system state error model establishment module includes: The linear two-degree-of-freedom rear wheel steering model establishment unit is used to establish a linear two-degree-of-freedom rear wheel steering model by taking the transpose of the matrix composed of the actual center of gravity sideslip angle and the actual yaw rate as the first state variable, the actual rear wheel steering angle as the control variable, and the actual front wheel steering angle as the disturbance variable. The ideal rear wheel steering model establishment unit is used to improve the ideal rear wheel steering model with the actual center of gravity sideslip angle being zero as the target, and obtain the improved ideal rear wheel steering model. In the improved ideal rear wheel steering model, the transpose of the matrix composed of the target center of gravity sideslip angle and the target yaw rate is used as the target state variable, and the actual front wheel steering angle is used as the disturbance variable. The system state error model establishment unit is used to calculate the difference between the first state variable and the target state variable to obtain the system state error model.

9. The active rear wheel steering control device according to claim 8, characterized in that, The established system state error model is as follows: in, This is the vehicle state error. The first derivative of the vehicle state error. This is the actual rear wheel steering angle. This is the actual front wheel steering angle. for First derivative; matrix The expression is: In the formula, the matrix The expression is: matrix The expression is: matrix The expression is: The ratio of the actual rear wheel steering angle to the actual front wheel steering angle The expression is: This is the actual vehicle speed. As a stability factor; ; This is the distance from the vehicle's center of gravity to the front axle. This is the distance from the vehicle's center of gravity to the rear axle. For the total mass of the vehicle. This refers to the front and rear wheelbase of the vehicle. This refers to the lateral stiffness of the vehicle's front axle tires. This refers to the lateral stiffness of the vehicle's rear axle tires. Let represent the vehicle's moment of inertia.

10. The active rear wheel steering control device according to claim 7, characterized in that, The augmented system model considering rear-wheel steering lag is as follows: Among them, matrix The expression is: matrix The expression is: This is the rear wheel steering delay time; For communication cycles; The actual rear wheel steering angle at time k+1 is the predicted value. Let k be the target rear wheel steering angle. The rear wheel steering angle increment at time k; The target rear wheel steering angle at time k-1 output by the controller. The actual rear wheel steering angle at time k. The actual yaw rate error at time k. The actual centroid sideslip angle error at time k. The actual yaw rate error at time k+1 Let be the actual centroid sideslip angle error at time k+1; where satisfies: This is the distance from the vehicle's center of gravity to the front axle. This is the distance from the vehicle's center of gravity to the rear axle. For the total mass of the vehicle. This refers to the front and rear wheelbase of the vehicle. This refers to the lateral stiffness of the vehicle's front axle tires. This refers to the lateral stiffness of the vehicle's rear axle tires. For the vehicle's moment of inertia, This represents the actual vehicle speed at the current moment.

11. The active rear wheel steering control device according to claim 7, characterized in that, The expression for the performance index J of the rear-wheel steering system is: in, , , , These represent the actual sideslip angle θ, the actual yaw rate φ, and the actual rear wheel steering angle, respectively. and target rear wheel angle The degree of importance attached to it; 𝑅 indicates the increment of the rear wheel steering angle. The degree of importance attached to it; Standard optimal control law The expression is: , 𝜆 represents the state where tire characteristics tend to be non-linear; The front wheel slip angle, This is the weight matrix for the linear region of the tire; This is the weight matrix for the tire's nonlinear region. The solution to the Riccati equation calculated for the linear region of the tire. The solution to the Riccati equation for the tire nonlinear region calculation. For matrix transpose of matrix The expression is: , The rear wheel steering delay time is obtained based on a first-order inertial system representing the rear wheel steering delay. This refers to the communication cycle.

12. The active rear wheel steering control device according to claim 7, characterized in that, Feedforward compensation The expression is: ； in, ; matrix The expression is: In the formula, the matrix The expression is: matrix The expression is: matrix The expression is: This is the actual front wheel steering angle. This is the distance from the vehicle's center of gravity to the front axle. This is the distance from the vehicle's center of gravity to the rear axle. For the total mass of the vehicle. This refers to the front and rear wheelbase of the vehicle. This refers to the lateral stiffness of the vehicle's front axle tires. This refers to the lateral stiffness of the vehicle's rear axle tires. Let represent the vehicle's moment of inertia.

13. A vehicle, characterized in that, Includes the active rear wheel steering control device as described in any one of claims 7-12.

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