Intelligent steer-by-wire vehicle robust stability control method

Abstract

The invention provides an intelligent steer-by-wire vehicle robust stability control method which comprises the following steps: firstly, establishing a two-degree-of-freedom vehicle dynamics model, and solving a yaw velocity and a side slip angle of a vehicle under a steady-state working condition; then, a control target of vehicle stability control is further modified, and a reference model of robust controller design is established based on the two-degree-of-freedom vehicle dynamics model; and finally, designing and solving a steer-by-wire vehicle robust stability controller based on # imgabs0 # mixed sensitivity control for performing steer-by-wire vehicle robust stability control. According to the method, the robust stability and trajectory tracking performance of the intelligent steer-by-wire vehicle can be effectively improved.

Description

Technical Field

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

[0002] The stability of a vehicle is directly related to the comfort of the passengers and the safety of the entire vehicle. However, common stability control technologies rarely consider both the actual control output of the system and the robustness of the system to uncertain interference when controlling the stability of the vehicle. This often means that a larger control output is required to achieve the desired control effect when pursuing system stability, and the system has a weak ability to resist internal and external interference.

[0003] For vehicles with front-wheel steering by wire, on the one hand, the front wheel steering angle cannot be increased infinitely. On the other hand, considering the nonlinear characteristics of the tire, the cornering force will tend to saturate or even decrease with the increase of the cornering angle. In addition, the nonlinearity of the vehicle system and the complexity of the driving conditions require not only the robust stability of the vehicle to be considered in the design process of the vehicle stability controller, but also the control output of the control system and the dynamic response performance of the system, that is, to achieve the robust stability of the vehicle with as small a control output as possible. Summary of the invention

[0004] The purpose of the present invention is to propose a robust stability control method for an intelligent steer-by-wire vehicle, which can effectively improve the robust stability and trajectory tracking performance of the intelligent steer-by-wire vehicle.

[0005] To achieve the above object, the technical solution of the present invention is: a method for controlling robust stability of an intelligent steer-by-wire vehicle, the steps of which are as follows:

[0006] S1. Establish a two-degree-of-freedom vehicle dynamics model under the conditions of small angle assumption and linear tire model;

[0007] S2. According to the established two-degree-of-freedom vehicle dynamics model, the yaw rate and the sideslip angle of the vehicle under steady-state conditions are solved;

[0008] S3, considering that the vehicle is restricted by the road adhesion conditions during actual driving, setting the control target for vehicle stability control;

[0009] S4. Establish a reference model for robust controller design based on a two-degree-of-freedom vehicle dynamics model;

[0010] S5. Design and solve the problem based on H2 / H ∞ A hybrid sensitivity controlled steer-by-wire vehicle robust stability controller is provided for performing robust stability control of a steer-by-wire vehicle.

[0011] Preferably, the two-degree-of-freedom vehicle dynamics model under the small angle assumption and linear tire model conditions in S1 is as follows:

[0012]

[0013] In the formula, v x is the longitudinal velocity of the vehicle; γ is the yaw rate of the vehicle; β is the sideslip angle of the center of mass of the vehicle; m is the mass of the vehicle; I z is the moment of inertia of the vehicle around the Z axis; 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; k f is the front wheel cornering stiffness; k r is the rear wheel cornering stiffness; f is the front wheel steering angle resulting from driver input.

[0014] Preferably, the yaw rate and the sideslip angle of the vehicle under steady-state conditions are solved in S2 as follows:

[0015]

[0016] In the formula, is the stability factor; L=a+b is the wheelbase of the vehicle.

[0017] Preferably, the control target of the vehicle stability control in S3 is as follows:

[0018]

[0019] Where μ is the road adhesion coefficient; g is the gravitational acceleration; γ d is the reference yaw rate; β d is the reference center of mass sideslip angle.

[0020] Preferably, the reference model for the robust controller design in S4 is as follows:

[0021]

[0022] In the formula, F yw is the lateral wind force; l yw is the distance from the side wind action point to the center of mass; Δδ f Additional front wheel steering angle for controller input.

[0023] Preferably, the design steps of the robust stability controller of the steer-by-wire vehicle in S5 are as follows:

[0024] S5.1. Select additional front wheel turning angle Δδ f As the control input, that is, u=[Δδ f ]; the vehicle's yaw rate γ and center of mass sideslip angle β are used as state variables, that is, x = [βγ]T ; In addition, the reference center of mass side slip angle β d , reference yaw rate γ d , the driver inputs the equivalent front wheel steering angle δ f and the side wind disturbance F yw As the interference input signal, that is, w = [β d γ d δ f F yw ] T The tracking error of the sideslip angle and yaw rate is used as the measurement output, i.e., y = [e1 e2] T =[ΔβΔγ] T =[β d -βγ d -γ] T ; Select z ∞ =[z ∞1 z ∞2 z ∞3 z ∞4 ] T =[βγΔβΔγ] T As the controlled system H ∞ Performance; Select z2 = [Δδ f ]H2 performance as the controlled system;

[0025] S5.2. Establishment based on H2 / H ∞ The state space of vehicle robust stability control with mixed sensitivity control is:

[0026]

[0027] In the formula, D 12 =[0] 4x1 ; C2 = [0] 1x2 ;D 21 =[0] 1x4 ;D 22 =[1] 1x1 ;

[0028]

[0029] S5.3. Derive the generalized control object and closed-loop system of the steer-by-wire vehicle robust stability control based on the established state space:

[0030]

[0031]

[0032]

[0033] Where P(s) is the generalized control object; K(s) is the robust stability controller; Z1 = [Z ∞3 Z ∞4 ] T and Z3=[Z ∞ 1Z ∞2 ] T is the output of the controlled system, where Z1 represents the target tracking performance and interference suppression performance of the controlled system, Z3 represents the robust stability and noise suppression performance of the controlled system; Z2 represents the size of the controller output; W1=diag{W 11 ,W 12}、W2=diag{W 21 ,W 22} and W3 represent the weighting functions of the three performances Z1, Z3 and Z2 respectively; is the transfer function from disturbance input to controlled output, G 11 , G 12 They are δ f 、F yw Transfer function to the sideslip angle β, G 13 , G 14 They are δ f 、F yw Transfer function to yaw rate γ; G0 = [G 01 G 02 ] T is the transfer function from the controller output to the controlled output, G 01 , G 02 Respectively represent Δδ f Transfer function to the sideslip angle β and yaw rate γ of the center of mass;

[0034] S5.4. Solve the robust stability controller K(s) to make the closed-loop system stable and satisfy the following constraints:

[0035]

[0036] In the formula, and They are w=[β d γ d δ f F yw ] T Transfer function to Z1, Z2 and Z3; η is a constant.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] Designed H2 / H ∞The hybrid sensitivity controller takes into account the robustness and controller output performance of the intelligent steer-by-wire vehicle, improving the stability and dynamic response of the vehicle system under uncertain disturbances. In addition, the robust stability controller takes into account the vehicle's yaw rate and center of mass sideslip angle tracking performance at the same time, thereby not only improving the vehicle's robust stability performance, but also enhancing the vehicle's trajectory tracking performance, so it has broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of robust stability control of an intelligent steer-by-wire vehicle according to the present invention. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0041] The present invention may be implemented in many different forms and should not be considered limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0042] The present invention discloses a robust stability control method for an intelligent steer-by-wire vehicle. The steps of the robust stability control method for an intelligent steer-by-wire vehicle are as follows:

[0043] S1. Establish a two-degree-of-freedom vehicle dynamics model under the conditions of small angle assumption and linear tire model;

[0044]

[0045] In the formula, v x is the longitudinal velocity of the vehicle; γ is the yaw rate of the vehicle; β is the sideslip angle of the center of mass of the vehicle; m is the mass of the vehicle; I z is the moment of inertia of the vehicle around the Z axis; 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; k f is the front wheel cornering stiffness; k r is the rear wheel cornering stiffness; f is the front wheel steering angle resulting from driver input.

[0046] S2. According to the established two-degree-of-freedom vehicle dynamics model, solve the vehicle's yaw rate and center-of-mass sideslip angle under steady-state conditions:

[0047]

[0048] In the formula, is the stability factor; L=a+b is the wheelbase of the vehicle.

[0049] S3. Considering that the vehicle is restricted by road adhesion conditions and other factors during actual driving, the control target of vehicle stability control is further modified as follows:

[0050]

[0051] Where μ is the road adhesion coefficient; g is the gravitational acceleration; γ d is the reference yaw rate; β d is the reference center of mass sideslip angle.

[0052] S4. A reference model for robust controller design is established based on a two-degree-of-freedom vehicle dynamics model, namely:

[0053]

[0054] In the formula, F yw is the lateral wind force; l yw is the distance from the side wind action point to the center of mass; Δδ f Additional front wheel steering angle for controller input.

[0055] S5. Design and solve the problem based on H2 / H ∞ Robust stability controller for steer-by-wire vehicles with hybrid sensitivity control.

[0056] like Figure 1 As shown, the design steps of the steer-by-wire vehicle robust stability controller are as follows:

[0057] S5.1. Select additional front wheel turning angle Δδ f As the control input, that is, u=[Δδ f ]; the vehicle's yaw rate γ and center of mass sideslip angle β are used as state variables, that is, x = [βγ] T ; In addition, the reference center of mass side slip angle β d , reference yaw rate γ d , the driver inputs the equivalent front wheel steering angle δ f and the side wind disturbance F yw As the interference input signal, that is, w = [β d γ d δ f F yw ] T The tracking error of the sideslip angle and yaw rate is used as the measurement output, i.e., y = [e1 e2] T =[ΔβΔγ] T =[β d -βγ d -γ] T ; Select z ∞ =[z ∞1 z ∞2 z∞3 z ∞4 ] T =[βγΔβΔγ] T As the controlled system H ∞ Performance; Select z2 = [Δδ f ] as the H2 performance of the controlled system.

[0058] S5.2. Establishment based on H2 / H ∞ The state space of vehicle robust stability control with mixed sensitivity control is:

[0059]

[0060] In the formula, D 12 =[0] 4x1 ; C2 = [0] 1x2 ;D 21 =[0] 1x4 ;D 22 =[1] 1x1 ;

[0061]

[0062] S5.3. Derive the generalized control object and closed-loop system of the steer-by-wire vehicle robust stability control based on the established state space:

[0063]

[0064]

[0065]

[0066] Where P(s) is the generalized control object; K(s) is the robust stability controller; Z1 = [Z ∞3 Z ∞4 ] T and Z3=[Z ∞ 1Z ∞2 ] T is the output of the controlled system, where Z1 represents the target tracking performance and interference suppression performance of the controlled system, Z3 represents the robust stability and noise suppression performance of the controlled system; Z2 represents the size of the controller output; W1=diag{W 11 ,W 12}、W2=diag{W 21 ,W 22} and W3 represent the weighting functions of the three performances Z1, Z3 and Z2 respectively; is the transfer function from disturbance input to controlled output, G 11 , G12 They are δ f 、F yw Transfer function to the sideslip angle β, G 13 , G 14 They are δ f 、F yw Transfer function to yaw rate γ; G0 = [G 01 G 02 ] T is the transfer function from the controller output to the controlled output, G 01 , G 02 Respectively represent Δδ f Transfer function to the sideslip angle β and yaw rate γ of the center of mass.

[0067] S5.4. Solve the robust stability controller K(s) to make the closed-loop system stable and satisfy the following constraints:

[0068]

[0069] In the formula, and They are w=[β d γ d δ f F yw ] T Transfer function to Z1, Z2 and Z3; η is a constant.

[0070] 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.

[0071] 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 robust stability control method for an intelligent steer-by-wire vehicle, characterized in that: Here are the steps: S1. Establish a two-degree-of-freedom vehicle dynamics model under the conditions of small angle assumption and linear tire model; S2. According to the established two-degree-of-freedom vehicle dynamics model, the yaw rate and the sideslip angle of the vehicle under steady-state conditions are solved; S3, considering that the vehicle is restricted by the road adhesion conditions during actual driving, setting the control target for vehicle stability control; S4. Establish a reference model for robust controller design based on a two-degree-of-freedom vehicle dynamics model; S5. Design and solve the problem based on H2 / H ∞ A hybrid sensitivity controlled steer-by-wire vehicle robust stability controller is provided for performing robust stability control of a steer-by-wire vehicle.

2. The method for controlling robust stability of an intelligent steer-by-wire vehicle according to claim 1, characterized in that: The two-degree-of-freedom vehicle dynamics model under the small angle assumption and linear tire model conditions in S1 is as follows: In the formula, v x is the longitudinal velocity of the vehicle; γ is the yaw rate of the vehicle; β is the sideslip angle of the center of mass of the vehicle; m is the mass of the vehicle; I z is the moment of inertia of the vehicle around the Z axis; 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; k f is the front wheel cornering stiffness; k r is the rear wheel cornering stiffness; f is the front wheel steering angle resulting from driver input.

3. The method for controlling robust stability of an intelligent steer-by-wire vehicle according to claim 1, characterized in that: The yaw rate and the sideslip angle of the vehicle under steady-state conditions are solved in S2 as follows: In the formula, is the stability factor; L=a+b is the wheelbase of the vehicle.

4. The method for controlling robust stability of an intelligent steer-by-wire vehicle according to claim 1, characterized in that: The control objectives of the vehicle stability control in S3 are as follows: Where μ is the road adhesion coefficient; g is the gravitational acceleration; γ d is the reference yaw rate; β d is the reference center of mass sideslip angle.

5. The method for controlling robust stability of an intelligent steer-by-wire vehicle according to claim 1, characterized in that: The reference model for the robust controller design in S4 is as follows: In the formula, F yw is the lateral wind force; l yw is the distance from the side wind action point to the center of mass; Δδ f Additional front wheel steering angle for controller input.

6. The method for controlling robust stability of an intelligent steer-by-wire vehicle according to claim 1, characterized in that: The design steps of the robust stability controller for the steer-by-wire vehicle in the S5 are as follows: S5.

1. Select additional front wheel turning angle Δδ f As the control input, that is, u=[Δδ f ]; the vehicle's yaw rate γ and center of mass sideslip angle β are used as state variables, that is, x = [βγ] T ; In addition, the reference center of mass side slip angle β d , reference yaw rate γ d , the driver inputs the equivalent front wheel steering angle δ f and the side wind disturbance F yw As the interference input signal, that is, w = [β d γ d δ f F yw ] T The tracking error of the sideslip angle and yaw rate is used as the measurement output, i.e., y = [e1 e2] T =[Δβ Δγ] T =[β d -β γ d -γ] T ; Select z ∞ =[z ∞1 z ∞2 z ∞3 z ∞4 ] T =[β γ Δβ Δγ] T As the controlled system H ∞ Performance; Select z2 = [Δδ f ]H2 performance as the controlled system; S5.

2. Establishment based on H2 / H ∞ The state space of vehicle robust stability control with mixed sensitivity control is: In the formula, D 12 =[0] 4x1 ; C2 = [0] 1x2 ;D 21 =[0] 1x4 ;D 22 =[1] 1x1 ; S5.

3. Derive the generalized control object and closed-loop system of the steer-by-wire vehicle robust stability control based on the established state space: Where P(s) is the generalized control object; K(s) is the robust stability controller; Z1 = [Z ∞3 Z ∞4 ] T and Z3=[Z ∞1 Z ∞2 ] T is the output of the controlled system, where Z1 represents the target tracking performance and interference suppression performance of the controlled system, Z3 represents the robust stability and noise suppression performance of the controlled system; Z2 represents the size of the controller output; W1=diag{W 11 ,W 12 }、W2=diag{W 21 ,W 22 } and W3 represent the weighting functions of the three performances Z1, Z3 and Z2 respectively; is the transfer function from disturbance input to controlled output, G 11 , G 12 They are δ f 、F yw Transfer function to the sideslip angle β, G 13 , G 14 They are δ f 、F yw Transfer function to yaw rate γ; G0 = [G 01 G 02 ] T is the transfer function from the controller output to the controlled output, G 01 , G 02 Respectively represent Δδ f Transfer function to the sideslip angle β and yaw rate γ of the center of mass; S5.

4. Solve the robust stability controller K(s) to make the closed-loop system stable and satisfy the following constraints: In the formula, and They are w=[β d γ d δ f F yw ] T Transfer function to Z1, Z2 and Z3; η is a constant.

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