Distributed steer-by-wire vehicle stability control method

Abstract

The invention provides a distributed steer-by-wire vehicle stability control method. The method comprises the steps that a distributed steer-by-wire vehicle dynamics model, a two-degree-of-freedom reference model and a four-wheel steering angle distribution model are established; in the design of the yaw stability controller, a hybrid sensitivity # imgabs0 # robust control method is adopted, the uncertainty of the system is fully considered, and the robustness of the system can be considered while the target tracking performance is ensured.

Description

Technical Field

[0001] The present invention relates to the field of automobile assisted driving, and in particular to a distributed steer-by-wire vehicle stability control method. Background Art

[0002] The distributed wire-controlled steering system has two sets of steering actuators on the front and rear axles (front and rear axle type) or four sets of steering actuators on four wheels (four-wheel distributed). Compared with the front-wheel wire-controlled steering, the distributed wire-controlled steering system is free from the mechanical connection constraints between the left and right wheels, and can provide a wider range of lateral control force. It shows more accurate, agile and stable steering performance during the steering process, and can complete special motion conditions such as low-speed steering, on-the-spot steering, oblique driving and translation. The four-wheel independent steering handling stability control is a highly nonlinear and complex process, and the four-wheel independent steering system is susceptible to uncertainty factors such as modeling uncertainty, external interference (road conditions and side wind, etc.), measurement noise and parameter changes. Therefore, it is urgent to introduce robust control in the four-wheel independent steering system to reduce the impact of uncertainty on the four-wheel independent steering handling stability control. Distributed wire-controlled steering vehicle stability control currently uses control methods such as sliding film control, PID control, model predictive control, and neural network control. Although sliding film control has the advantages of simple implementation and strong robustness, it has the defect of the vibration problem and is not suitable for application in distributed wire-controlled steering vehicle stability control. Although PID control has the characteristics of simple design and flexible structure, it is mostly used in single-input single-output systems. Model predictive control linearizes the vehicle model, which can reduce the amount of calculation in the control process and improve the real-time performance of the control, but it also reduces the control accuracy. Its computational burden will increase with the complexity of the system dynamics. Neural network control can approximate external disturbances and modeling errors, and has strong robustness and fault tolerance, but it has disadvantages such as slow learning speed and long calculation time, and it is difficult to prove the convergence and stability of the learning process in an analytical way. H∞ robust control has strong robustness and can reduce the impact of uncertainty on the four-wheel independent steering handling stability control. Summary of the invention

[0003] The purpose of the present invention is to propose a distributed steer-by-wire vehicle stability control method, which fully considers the uncertainty of the system and can ensure the target tracking performance while taking into account the robustness of the system.

[0004] To achieve the above object, the technical solution of the present invention is: a distributed steer-by-wire vehicle stability control method, comprising the following steps:

[0005] S1. Establish a distributed steer-by-wire vehicle dynamics model;

[0006] S2, establishing a two-degree-of-freedom vehicle reference model;

[0007] S3, establishing a four-wheel turning angle distribution model for a distributed line steer-by-wire vehicle;

[0008] S4. Design a distributed H∞ robust controller for yaw stability of steer-by-wire vehicles.

[0009] Preferably, the establishing of a distributed steer-by-wire vehicle dynamics model specifically includes:

[0010] Longitudinal dynamics model:

[0011]

[0012] Lateral dynamics model:

[0013]

[0014] Yaw dynamics model:

[0015]

[0016] Among them, for have:

[0017]

[0018] Where m is the vehicle mass; C D is the air resistance coefficient; A is the windward area; v x and v y are the components of the vehicle's center of mass velocity on the x-axis and y-axis respectively; a x is the longitudinal acceleration; a y is the lateral acceleration; ω r is the yaw rate of the vehicle; I z is the yaw moment of inertia of the vehicle rotating around the z-axis; a and b are the distances from the center of mass of the vehicle to the front and rear axles, respectively; T W is half of the wheelbase; ij = fl, fr, rl, rr represent the left front wheel, right front wheel, left rear wheel and right rear wheel of the vehicle respectively; F tyij 、F txij are tire lateral force and tire longitudinal force respectively; F xij 、F yij F txij 、F tyij The longitudinal force and lateral force of each wheel decomposed and synthesized in the vehicle coordinate system; δ ij is the wheel angle;

[0019] Vertical load on each wheel F zij for:

[0020]

[0021] Where g is the acceleration due to gravity; h is g is the height of the vehicle's center of mass from the ground;

[0022] Building the Magic Formula Tire Model:

[0023] Y(x)=Dsin{Carctan[Bx-E(Bx-arctan(Bx))]} (6)

[0024] Where Y(x) is the lateral force F of the tire tyij Or the longitudinal force F txij ; x is the tire slip angle α ij Or tire slip ratio λ ij ; B, C, D, and E are fitting parameters in the tire characteristic curve, which are stiffness factor, curve shape factor, curve peak factor, and curve curvature factor, respectively.

[0025] Preferably, the tire slip rate of each wheel is calculated as follows:

[0026]

[0027] In the formula, u ij is the wheel center speed of each wheel; w ij is the angular velocity of each wheel; r is the rolling radius of the wheel;

[0028] The wheel center speed of each wheel is expressed as:

[0029]

[0030] The calculation of the slip angle of the four wheels is as follows:

[0031]

[0032] Preferably, the establishment of a two-degree-of-freedom vehicle reference model is specifically as follows:

[0033]

[0034] In the formula, k f is the front wheel cornering stiffness of the reference model; k r is the rear wheel cornering stiffness of the reference model; δ f is the front wheel turning angle of the reference model; δ r is the rear wheel turning angle of the reference model; Δδ f The additional steering angle of the front wheels of the reference model; Δδ r is the additional steering angle of the rear wheels of the reference model; β is the sideslip angle of the vehicle's center of mass.

[0035] Preferably, the establishment of the distribution line steer-by-wire vehicle four-wheel turning angle distribution model is specifically as follows:

[0036] Based on the steering wheel angle sensor reading, when the steering wheel angle is set to a positive value, it means the vehicle is turning left; when the steering wheel angle is set to a negative value, it means the vehicle is turning right; when the steering wheel angle is set to a positive value, it means the wheel is rotating counterclockwise; when the steering wheel angle is set to a negative value, it means the wheel is rotating clockwise;

[0037] Introducing the vehicle front axle electric wheel steering judgment factor c f and the rear axle electric wheel steering judgment factor c r , the expression is set as:

[0038]

[0039] The four-wheel turning angle distribution model is:

[0040]

[0041] Where L is the wheelbase of the front and rear axles of the vehicle; B is the distance between the intersection of the kingpin axes of the left and right wheels and the ground.

[0042] Preferably, the establishment of the yaw stability H∞ robust controller comprises the following steps:

[0043] S4.1. Define the parameters in the H∞ robust controller;

[0044] S4.2. Combined with the two-degree-of-freedom vehicle reference model, establish the state space expression of the vehicle yaw stability H∞ robust controller;

[0045] S4.3. Establish the expression of the input-output transfer function in the H∞ robust controller;

[0046] S4.4. Solve the controller K(s) to make the system stable and meet the preset conditions.

[0047] Preferably, the parameters in the definition of the H∞ robust controller are specifically:

[0048] Select the additional turning angle Δδ of the front and rear wheels of the reference model f , Δδ r As the control quantity, that is, u=[Δδ f Δδ r ] T ; The vehicle's yaw rate ω r and the vehicle's center of mass side slip angle β is the system state, that is, x=z0=[β ω r ] T ; Set the reference center of mass sideslip angle β d , reference pendulum angular velocity ω rd , the driver inputs the equivalent front wheel steering angle δ f and rear wheel turning angle δ r and the side wind disturbance F ywAs the interference signal input of the system, that is, w = [β d ω rd δ f δ r F yw ] T The tracking error of the sideslip angle and yaw rate is the measured output signal and also the input signal of the controller, that is, y = e = [e1 e2] T =[β d -βω rd -ω r ] T ; z is the performance variable, also known as the controlled output, z = [z 11 z 12 z 21 z 22 z 31 z 32 ] T =[β d -βω rd -ω r β ω r Δδ f Δδ r ] T ; P(s) is the generalized controlled object, that is, the transfer function matrix from input w, u to output z, y; K(s) is the controller.

[0049] Preferably, the state space expression of establishing the vehicle yaw stability H∞ robust controller is specifically:

[0050]

[0051] Where: D 22 =

[00] .

[0052] Preferably, the expression for establishing the input-output transfer function in the H∞ robust controller is specifically:

[0053] Let the sensitivity function S be the closed-loop transfer function from w to y, the complementary sensitivity function T be the closed-loop transfer function from w to z0, and the input sensitivity function R be the closed-loop transfer function from w to u;

[0054] The control outputs Z1, Z2, and Z3 of the system are the weighted products of e, z0, and u, respectively, namely:

[0055]

[0056] In the formula, Z1=[Z 11 Z 12 ] Trepresents the target tracking performance and interference suppression performance of the system, Z 11 , Z 12 are the controlled outputs of the center of mass sideslip angle tracking error and the yaw angular velocity tracking error respectively; Z2=[Z 21 Z 22 ] T represents the robust stability and noise suppression performance of the system, Z 21 , Z 22 are the controlled outputs of the sideslip angle and yaw rate of the center of mass respectively; Z3=[Z 31 Z 32 ] T Indicates the size of the controller output, Z 31 , Z 32 are the controlled outputs of the additional steering angles of the front and rear wheels respectively; W1 = diag{W 11 ,W 12}、W2=diag{W 21 ,W 22} and W3=diag{W 31 ,W 32} represent the weighting functions of the three control performances Z1, Z2 and Z3 respectively;

[0057] Let the closed-loop transfer function from w to Z be T w→Z for:

[0058]

[0059] The input and output of the system are expressed as:

[0060]

[0061] Where Z = [Z1 Z2 Z3] T Indicates the total controlled output of the system; is δ f , δ r 、F yw to β and ω r The transfer function, G 11 , G 12 , G 13 They are δ f , δ r 、F yw Transfer function to the sideslip angle β, G 14 , G 15 , G 16 They are δ f , δ r 、F yw to the yaw angular velocity ω r The transfer function of is Δδ f, Δδ r to β and ω r The transfer function, G 01 , G 02 are Δδ f , Δδ r Transfer function to the sideslip angle β, G 03 , G 04 are Δδ f , Δδ r to the yaw angular velocity ω r The transfer function of .

[0062] Preferably, the controller K(s) is solved to make the system stable and satisfy the following preset conditions:

[0063]

[0064] In the formula, ξ is a very small positive number.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] The mixed sensitivity algorithm in H∞ robust control theory can design a weighted function based on the uncertain perturbation system, fully consider the uncertainty of the system, and give a design method for the robust control system based on the actual situation, which can ensure the target tracking performance while taking into account the robustness of the system. H∞ robust control has strong robustness and can reduce the influence of uncertainty factors such as modeling uncertainty, external interference (road conditions and side wind, etc.), measurement noise and parameter changes on the four-wheel independent steering handling stability control. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 Schematic diagram of the H∞ robust controller method for yaw stability of a distributed steer-by-wire vehicle according to the present invention.

[0068] Figure 2 This is a diagram of the distributed wire-controlled steering dynamics model of the present invention;

[0069] Figure 3 This is a reference model diagram of a two-degree-of-freedom vehicle according to the present invention. DETAILED DESCRIPTION

[0070] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0071] The present invention can be implemented in many different forms and should not be considered to be limited to the embodiments described herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete, and will fully express the scope of the present invention to those skilled in the art. In the accompanying drawings, components are enlarged for clarity.

[0072] like Figure 1-3 As shown in FIG. 1 , the establishment of the H∞ robust controller for the yaw stability of the distributed steer-by-wire vehicle, the dynamic model of the distributed steer-by-wire vehicle, the two-degree-of-freedom reference model and the four-wheel steering angle distribution model includes the following steps. In the figure, G(s) is the transfer function, v is the vehicle center of mass velocity, and F yf is the front wheel lateral force of the reference model, F yr is the rear wheel lateral force of the reference model, α f , α r are the front and rear wheel slip angles of the reference model respectively; other parameters will be defined below.

[0073] S1. Establish a distributed steer-by-wire vehicle dynamics model:

[0074] Longitudinal dynamics model:

[0075]

[0076] Lateral dynamics model:

[0077]

[0078] Yaw dynamics model:

[0079]

[0080] Among them, for have:

[0081]

[0082] Where m is the vehicle mass; C D is the air resistance coefficient; A is the windward area; v x and v y are the components of the vehicle's center of mass velocity on the x-axis and y-axis respectively; a x is the longitudinal acceleration; a y is the lateral acceleration; ω r is the yaw rate of the vehicle; I z is the yaw moment of inertia of the vehicle rotating around the z-axis; a and b are the distances from the center of mass of the vehicle to the front and rear axles, respectively; T W is half of the wheelbase; ij = fl, fr, rl, rr represent the left front wheel, right front wheel, left rear wheel and right rear wheel of the vehicle respectively; F tyij 、F txij are tire lateral force and tire longitudinal force respectively; F xij 、F yij F txij 、F tyij The longitudinal force and lateral force of each wheel decomposed and synthesized in the vehicle coordinate system; δ ij is the wheel angle.

[0083] Considering the vertical load transfer of each wheel of the vehicle caused by the longitudinal acceleration and lateral acceleration during the movement, the vertical load F of each wheel is calculated according to the moment balance relationship. zij for:

[0084]

[0085] Where g is the acceleration due to gravity; h is g is the height of the vehicle's center of mass from the ground.

[0086] Building the Magic Formula Tire Model:

[0087] Y(x)=Dsin{Carctan[Bx-E(Bx-arctan(Bx))]} (6)

[0088] Where Y(x) is the lateral force F of the tire tyij Or the longitudinal force F txij ; x is the tire slip angle α ij Or tire slip ratio λ ij ; B, C, D, and E are fitting parameters in the tire characteristic curve, which are stiffness factor, curve shape factor, curve peak factor, and curve curvature factor, respectively;

[0089] The tire slip rate of each wheel is calculated as:

[0090]

[0091] In the formula, u ij is the wheel center speed of each wheel; w ij is the angular velocity of each wheel; r is the rolling radius of the wheel;

[0092] The wheel center speed of each wheel can be expressed as:

[0093]

[0094] The slip angles of the four wheels are:

[0095]

[0096] S2. Establish a two-degree-of-freedom vehicle reference model:

[0097]

[0098] In the formula, k f is the front wheel cornering stiffness of the reference model; k r is the rear wheel cornering stiffness of the reference model; δ f is the front wheel turning angle of the reference model; δ r is the rear wheel turning angle of the reference model; Δδf The additional steering angle of the front wheels of the reference model; Δδ r is the additional steering angle of the rear wheels of the reference model; β is the side slip angle of the center of mass of the vehicle;

[0099] S3. Establishing a four-wheel turning angle distribution model for a distributed line steer-by-wire vehicle:

[0100] Introducing the vehicle front axle electric wheel steering judgment factor c f and the rear axle electric wheel steering judgment factor c r , its expression can be set as:

[0101]

[0102] Taking into account factors such as vehicle left and right steering and four-wheel steering same-direction and reverse steering mode selection, the four-wheel steering angle distribution model is:

[0103]

[0104]

[0105] Where L is the wheelbase of the front and rear axles of the vehicle; B is the distance between the intersection of the left and right kingpin axes of the wheels and the ground;

[0106] S4. Design a distributed steer-by-wire vehicle yaw stability H∞ robust controller, which specifically includes the following steps:

[0107] S4.1. Define the parameters in the H∞ robust controller: Select the additional steering angles Δδ of the front and rear wheels of the reference model f , Δδ r As the control quantity, that is, u=[Δδ f Δδ r ] T ; The vehicle's yaw rate ω r and the vehicle's center of mass side slip angle β is the system state, that is, x=z0=[βω r ] T ; Set the reference center of mass sideslip angle β d , reference pendulum angular velocity ω rd , the driver inputs the equivalent front wheel steering angle δ f and rear wheel turning angle δ r and the side wind disturbance F yw As the interference signal input of the system, that is, w = [β d ω rd δ f δ r F yw ] T The tracking error of the sideslip angle and yaw rate is the measured output signal and also the input signal of the controller, that is, y = e = [e1 e2]T =[β d -βω rd -ω r ] T ; z is the performance variable, also known as the controlled output, z = [z 11 z 12 z 21 z 22 z 31 z 32 ] T =[β d -βω rd -ω r β ω r Δδ f Δδ r ] T ; P(s) is the generalized controlled object, that is, the transfer function matrix from input w, u to output z, y; K(s) is the controller;

[0108] S4.2. Combined with the two-degree-of-freedom vehicle reference model, the state space expression of the vehicle yaw stability H∞ robust controller is established:

[0109]

[0110] Where: D 22 =

[00] ;

[0111] S4.3. Establish the expression of the input-output transfer function in the H∞ robust controller:

[0112] Let the sensitivity function S be the closed-loop transfer function from w to y, the complementary sensitivity function T be the closed-loop transfer function from w to z0, and the input sensitivity function R be the closed-loop transfer function from w to u;

[0113] The control outputs Z1, Z2, and Z3 of the system are the weighted products of e, z0, and u, respectively, namely:

[0114]

[0115] In the formula, Z1=[Z 11 Z 12 ] T represents the target tracking performance and interference suppression performance of the system, Z 11 , Z 12 are the controlled outputs of the center of mass sideslip angle tracking error and the yaw angular velocity tracking error respectively; Z2=[Z 21 Z 22 ] T represents the robust stability and noise suppression performance of the system, Z 21, Z 22 are the controlled outputs of the sideslip angle and yaw rate of the center of mass respectively; Z3=[Z 31 Z 32 ] T Indicates the size of the controller output, Z 31 , Z 32 are the controlled outputs of the additional steering angles of the front and rear wheels respectively; W1 = diag{W 11 ,W 12}、W2=diag{W 21 ,W 22} and W3=diag{W 31 ,W 32} represent the weighting functions of the three control performances Z1, Z2 and Z3 respectively;

[0116] Let the closed-loop transfer function from w to Z be T w→Z for:

[0117]

[0118] The input and output of the system are expressed as:

[0119]

[0120]

[0121] Where Z = [Z1 Z2 Z3] T Indicates the total controlled output of the system; is δ f , δ r 、F yw to β and ω r The transfer function, G 11 , G 12 , G 13 They are δ f , δ r 、F yw Transfer function to the sideslip angle β, G 14 , G 15 , G 16 They are δ f , δ r 、F yw to the yaw angular velocity ω r The transfer function of is Δδ f , Δδ r to β and ω r The transfer function, G 01 , G 02 are Δδ f , Δδ r Transfer function to the sideslip angle β, G03 , G 04 are Δδ f , Δδ r to the yaw angular velocity ω r The transfer function of

[0122] S4.4. Solve the controller K(s) to make the system stable and satisfy:

[0123]

[0124] In the formula, ξ is a very small positive number.

[0125] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0126] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A distributed steer-by-wire vehicle stability control method, characterized in that: The following steps are involved: S1. Establish a distributed steer-by-wire vehicle dynamics model; S2, establishing a two-degree-of-freedom vehicle reference model; S3, establishing a four-wheel turning angle distribution model for a distributed line steer-by-wire vehicle; S4. Design a distributed H∞ robust controller for yaw stability of steer-by-wire vehicles.

2. A distributed steer-by-wire vehicle stability control method according to claim 1, characterized in that: The establishment of a distributed steer-by-wire vehicle dynamics model specifically includes: Longitudinal dynamics model: Lateral dynamics model: Yaw dynamics model: Among them, for have: Where m is the vehicle mass; C D is the air resistance coefficient; A is the windward area; v x and v y are the components of the vehicle's center of mass velocity on the x-axis and y-axis respectively; a x is the longitudinal acceleration; a y is the lateral acceleration; ω r is the yaw rate of the vehicle; I z is the yaw moment of inertia of the vehicle rotating around the z-axis; a and b are the distances from the center of mass of the vehicle to the front and rear axles, respectively; T W is half of the wheelbase; ij = fl, fr, rl, rr represent the left front wheel, right front wheel, left rear wheel and right rear wheel of the vehicle respectively; F tyij 、F txij are tire lateral force and tire longitudinal force respectively; F xij 、F yij F txij 、F tyij The longitudinal force and lateral force of each wheel decomposed and synthesized in the vehicle coordinate system; δ ij is the wheel angle; Vertical load on each wheel F zij for: Where g is the acceleration due to gravity; h is g is the height of the vehicle's center of mass from the ground; Building the Magic Formula Tire Model: Y(x)=D sin{C arctan[Bx-E(Bx-arctan(Bx))]} (6) Where Y(x) is the lateral force F of the tire tyij Or the longitudinal force F txij ; x is the tire slip angle α ij Or tire slip ratio λ ij ; B, C, D, and E are fitting parameters in the tire characteristic curve, which are stiffness factor, curve shape factor, curve peak factor, and curve curvature factor, respectively.

3. A distributed steer-by-wire vehicle stability control method according to claim 2, characterized in that: The tire slip rate of each wheel is calculated as follows: In the formula, u ij is the wheel center speed of each wheel; w ij is the angular velocity of each wheel; r is the rolling radius of the wheel; The wheel center speed of each wheel is expressed as: The calculation of the slip angle of the four wheels is as follows:

4. A distributed steer-by-wire vehicle stability control method according to claim 1, characterized in that: The establishment of the two-degree-of-freedom vehicle reference model is specifically as follows: In the formula, k f is the front wheel cornering stiffness of the reference model; k r is the rear wheel cornering stiffness of the reference model; δ f is the front wheel turning angle of the reference model; δ r is the rear wheel turning angle of the reference model; Δδ f The additional steering angle of the front wheels of the reference model; Δδ r is the additional steering angle of the rear wheels of the reference model; β is the sideslip angle of the vehicle's center of mass.

5. The distributed steer-by-wire vehicle stability control method according to claim 1, characterized in that: The establishment of the four-wheel turning angle distribution model of the distribution line steer-by-wire vehicle is specifically as follows: Based on the steering wheel angle sensor reading, when the steering wheel angle is set to a positive value, it means the vehicle is turning left; when the steering wheel angle is set to a negative value, it means the vehicle is turning right; when the steering wheel angle is set to a positive value, it means the wheel is rotating counterclockwise; when the steering wheel angle is set to a negative value, it means the wheel is rotating clockwise; Introducing the vehicle front axle electric wheel steering judgment factor c f and the rear axle electric wheel steering judgment factor c r , the expression is set as: The four-wheel turning angle distribution model is: Where L is the wheelbase of the front and rear axles of the vehicle; B is the distance between the intersection of the kingpin axes of the left and right wheels and the ground.

6. The distributed steer-by-wire vehicle stability control method according to claim 1, characterized in that: The establishment of the yaw stability H∞ robust controller includes the following steps: S4.

1. Define the parameters in the H∞ robust controller; S4.

2. Combined with the two-degree-of-freedom vehicle reference model, establish the state space expression of the vehicle yaw stability H∞ robust controller; S4.

3. Establish the expression of the input-output transfer function in the H∞ robust controller; S4.

4. Solve the controller K(s) to make the system stable and meet the preset conditions.

7. The distributed steer-by-wire vehicle stability control method according to claim 6, characterized in that: The parameters in the H∞ robust controller are specifically defined as: Select the additional turning angle Δδ of the front and rear wheels of the reference model f , Δδ r As the control quantity, that is, u=[Δδ f Δδ r ] T ; The vehicle's yaw rate ω r and the vehicle's center of mass side slip angle β is the system state, that is, x=z0=[β ω r ] T ; The reference center of mass sideslip angle β d , reference pendulum angular velocity ω rd , the driver inputs the equivalent front wheel steering angle δ f and rear wheel turning angle δ r and the side wind disturbance F yw As the interference signal input of the system, that is, w = [β d ω rd δ f δ r F yw ] T The tracking error of the sideslip angle and yaw rate is the measured output signal and also the input signal of the controller, that is, y = e = [e1 e2] T =[β d -βω rd -ω r ] T ; z is the performance variable, also known as the controlled output, that is, z = [z 11 z 12 z 21 z 22 z 31 z 32 ] T =[β d -βω rd -ω r β ω r Δδ f Δδ r ] T ; P(s) is the generalized controlled object, that is, the transfer function matrix from input w, u to output z, y; K(s) is the controller.

8. The distributed steer-by-wire vehicle stability control method according to claim 6, characterized in that: The state space expression of establishing the vehicle yaw stability H∞ robust controller is specifically: Where: D 22 =[00].

9. The distributed steer-by-wire vehicle stability control method according to claim 6, characterized in that: The expression for establishing the input-output transfer function in the H∞ robust controller is specifically: Let the sensitivity function S be the closed-loop transfer function from w to y, the complementary sensitivity function T be the closed-loop transfer function from w to z0, and the input sensitivity function R be the closed-loop transfer function from w to u; The control outputs Z1, Z2, and Z3 of the system are the weighted products of e, z0, and u, respectively, namely: In the formula, Z1=[Z 11 Z 12 ] T represents the target tracking performance and interference suppression performance of the system, Z 11 , Z 12 are the controlled outputs of the center of mass sideslip angle tracking error and the yaw angular velocity tracking error respectively; Z2=[Z 21 Z 22 ] T represents the robust stability and noise suppression performance of the system, Z 21 , Z 22 are the controlled outputs of the sideslip angle and yaw rate of the center of mass respectively; Z3=[Z 31 Z 32 ] T Indicates the size of the controller output, Z 31 , Z 32 are the controlled outputs of the additional steering angles of the front and rear wheels respectively; W1 = diag{W 11 ,W 12 }、W2=diag{W 21 ,W 22 } and W3=diag{W 31 ,W 32 } represent the weighting functions of the three control performances Z1, Z2 and Z3 respectively; Let the closed-loop transfer function from w to Z be T w→Z for: The input and output of the system are expressed as: Where Z = [Z1 Z2 Z3] T Indicates the total controlled output of the system; is δ f ,δ r 、F yw to β and ω r The transfer function, G 11 , G 12 , G 13 They are δ f ,δ r 、F yw Transfer function to the sideslip angle β, G 14 , G 15 , G 16 They are δ f ,δ r 、F yw to the yaw angular velocity ω r The transfer function of is Δδ f , Δδ r to β and ω r The transfer function, G 01 , G 02 are Δδ f , Δδ r Transfer function to the sideslip angle β, G 03 , G 04 are Δδ f , Δδ r to the yaw angular velocity ω r The transfer function of .

10. The distributed steer-by-wire vehicle stability control method according to claim 6, characterized in that: Solve the controller K(s) to make the system stable and meet the following preset conditions: In the formula, ξ is a very small positive number.

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