Road feeling feedback control method based on steer-by-wire high-order all-drive model

Abstract

The invention discloses a road feeling feedback control method based on a steer-by-wire high-order all-drive model, and the method comprises the following steps: S1, determining a main torque and a compensation torque, and superposing the main torque and the compensation torque to obtain a reference torque; s2, a vehicle control unit (VCU) determines a current front wheel angle and a current reference feedback torque according to a current vehicle state, and establishes a kinetic equation of an HW module and a kinetic equation of a road feeling motor; and S3, according to the kinetic model in the step S2, a control-oriented second-order state space model of the SbW system is obtained, the sensitivity of the control system to interference is reduced by using a sliding mode, and the inherent chatter and vibration possibility in SMC application is reduced by using an HOFA method, so that the overall system performance of the HOFA-SMC and the manipulation comfort of a driver are improved. The road feeling feedback control method based on the steer-by-wire high-order all-drive model has the effect of improving the controllability, comfort and stability of the electric vehicle under various road conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle control algorithms, and in particular to a road feel feedback control method based on a steer-by-wire high-order all-wheel drive model. Background Art

[0002] Electrification and intelligence are the development trends of modern automobile chassis. Therefore, traditional mechanical connections in automobile chassis systems are increasingly being replaced by electronic signals. In traditional steering systems, steering resistance is transmitted to the handwheel through mechanical components such as the frame and steering shaft to produce steering feel, which is related to steering resistance in real time. However, in steer-by-wire (SbW) vehicles, the handwheel and road wheel are mechanically separated. The driver's steering command is transmitted to the motor through an electrical signal, and the motor drives the road wheel. This mechanical decoupling eliminates most of the steering feel that usually occurs in traditional vehicles, but also improves the vehicle's fuel efficiency and maneuverability, while providing greater flexibility and customization for drivers with different driving modes and preferences.

[0003] While SbW systems offer many advantages over conventional steering systems, one of their main challenges is creating the right steering feel for the driver. Ensuring a real-time correlation between steering feel and steering resistance, as well as the realism of the steering experience, is critical to driver safety and comfort.

[0004] Common road-sensing motor torque control methods in the prior art include: open-loop control, PID control, anti-disturbance control, sliding mode control, etc. However, most of these control methods have obvious problems such as insufficient robustness, complex implementation, and difficulty in parameter adjustment. Among them, sliding mode control (SMC) has the characteristics of being insensitive to uncertain disturbances and changes in system parameters. Therefore, the design of the sliding mode control rate is very important, and new methods need to be designed to reduce the inherent vibration and jitter of the sliding mode. Summary of the invention

[0005] In view of the above problems, a road feel feedback control method based on a high-order all-wheel drive model of steer-by-wire is provided, aiming to solve the problems existing in the prior art.

[0006] The specific technical solutions are as follows: A road feel feedback control method based on a high-order all-wheel drive model of steer-by-wire comprises the following steps: S1, determining the main torque and the compensation torque, and superimposing the main torque and the compensation torque to obtain a reference torque; S2, the vehicle control unit (VCU) determines the current front wheel angle and the current reference feedback torque according to the current vehicle state, establishes the dynamic equation of the HW module and the dynamic equation of the road sense motor; S3, according to the dynamic model in step S2, obtain a control-oriented second-order state space model of the SbW system; S4, converting the second-order state space model in step S3 into a nonlinear second-order full-drive model of HW; S5, transforming the second-order full-drive model in step S4 into an error feedback system; S6. Establishing an equivalent control law according to the error feedback system; S7. Proof of stability.

[0007] The above-mentioned road feel feedback control method based on the high-order all-wheel drive model of wire control steering also has the following characteristics: the compensation torque includes active return torque , to ensure that the steering wheel returns to the neutral position smoothly without overshooting when the driver actively releases his hands; soft limit torque , since the SbW system has a variable gear ratio, the system was developed to limit the steering wheel angle range to ensure safety; it also includes damping torque , friction torque and inertia torque ; Overall reference torque as a road feel source It is expressed as follows: .

[0008] The above-mentioned road feel feedback control method based on the high-order all-wheel drive model of wire control steering also has the following characteristics: the dynamic equation of the HW module is: ; Where: It represents the torque applied by the driver by adjusting the arm resistance on the hand wheel; Indicates the moment of inertia of the handwheel steering column; is the hand wheel damping coefficient; is the hand wheel angle; represents the equivalent Coulomb friction torque of the steering column; is the torque measured by the TAS sensor; The dynamic equation of the road sensing motor is: ; Where: Represents the output electromagnetic torque of the road sensing motor; Indicates the motor's moment of inertia; is the motor damping coefficient; Represents the equivalent Coulomb friction torque between the road sensing motor and the reduction mechanism.

[0009] The above-mentioned road feel feedback control method based on the high-order all-wheel drive model of wire control steering also has the following characteristics: the second-order state space model is: ; Where: is the state quantity of the steering system, and the input quantity is , is a mature friction model, and subsequent experiments have shown that it has a significant impact on control performance. Usually considered as a measurable disturbance measured by a sensor, .

[0010] The above-mentioned road feel feedback control method based on the high-order all-wheel drive model of steer-by-wire also has the following characteristics: the second-order all-wheel drive model: ; ; ; ; Where: and is a known nonlinear function, is included and The total disturbance of .

[0011] The above-mentioned road feel feedback control method based on the high-order all-wheel drive model of steer-by-wire also has the following characteristics: the error feedback system is: ; ; ; ; A new sliding function based on the FAS method is designed as follows: .

[0012] The above-mentioned road feel feedback control method based on the high-order all-wheel drive model of steer-by-wire also has the following characteristics: the equivalent control law is: ; According to the equivalent control law, the closed-loop dynamic equation is obtained as follows: ; Right now, ; in, .

[0013] In summary, the beneficial effects of this scheme are: In the road feel feedback control method based on the steer-by-wire high-order all-wheel drive model provided by the present invention, the control system's sensitivity to interference is reduced by using a sliding mode, and the possibility of inherent flutter and vibration in SMC applications is reduced by using the HOFA method, thereby improving the overall system performance of HOFA-SMC and the driver's handling comfort. The road feel feedback control method based on the steer-by-wire high-order all-wheel drive model provided by the present invention has the effect of improving the controllability, comfort and stability of electric vehicles under various road conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flow chart of a road sense feedback control method based on a high-order all-wheel drive model of steer-by-wire according to the present invention; Figure 2 A control principle diagram of a road sense feedback control method based on a high-order all-wheel drive model of steer-by-wire according to the present invention; Figure 3 The present invention is a road sense composition diagram of a road sense feedback control method based on a high-order all-wheel drive model of steer-by-wire. DETAILED DESCRIPTION

[0015] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0017] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0018] Figure 1 Schematic diagram of a flow chart of a road sense feedback control method based on a high-order all-wheel drive model of steer-by-wire according to the present invention. Figure 2 This is a control principle diagram of a road sense feedback control method based on a high-order all-wheel drive model of steer-by-wire according to the present invention. Figure 3 : is a road sense composition diagram of a road sense feedback control method based on a high-order all-wheel drive model of steer-by-wire according to the present invention, such as Figure 1-Figure 3 As shown, the road sense feedback control method based on the high-order all-wheel drive model of wire control provided in this embodiment includes the following steps: S1, determining the main torque and the compensation torque, and superimposing the main torque and the compensation torque to obtain a reference torque; S2, the vehicle control unit (VCU) determines the current front wheel angle and the current reference feedback torque according to the current vehicle state, establishes the dynamic equation of the HW module and the dynamic equation of the road sense motor; S3, according to the dynamic model in step S2, obtain a control-oriented second-order state space model of the SbW system; S4, converting the second-order state space model in step S3 into a nonlinear second-order full-drive model of HW; S5, transforming the second-order full-drive model in step S4 into an error feedback system; S6. Establishing an equivalent control law based on the error feedback system; S7. Proof of stability.

[0019] In the above embodiment, the compensation torque includes the active return torque , to ensure that the steering wheel returns to the neutral position smoothly without overshooting when the driver actively releases his hands; soft limit torque , since the SbW system has a variable gear ratio, the system was developed to limit the steering wheel angle range to ensure safety; it also includes damping torque , friction torque and inertia torque ; Overall reference torque as a road feel source It is expressed as follows: .

[0020] In the above embodiment, the dynamic equation of the HW module (handwheel module) is: ; Where: It represents the torque applied by the driver by adjusting the arm resistance on the hand wheel; Indicates the moment of inertia of the handwheel steering column; is the hand wheel damping coefficient; is the hand wheel angle; represents the equivalent Coulomb friction torque of the steering column; is the torque measured by the TAS sensor; The dynamic equation of the road sense motor is: ; Where: Represents the output electromagnetic torque of the road sensing motor; Indicates the motor's moment of inertia; is the motor damping coefficient; Represents the equivalent Coulomb friction torque between the road sensing motor and the reduction mechanism.

[0021] It should be noted that due to its advantages of small torque fluctuation and low noise, a permanent magnet synchronous motor is used to provide the driving torque, and the servo drive works in a torque control mode. The dynamic equation of the road sensing motor end needs to ignore the current loop characteristics.

[0022] In the above embodiment, the second-order state space model is: ; ; Where: is the state quantity of the steering system, and the input quantity is , is a mature friction model, and subsequent experiments have shown that it has a significant impact on control performance. Usually considered as a measurable disturbance measured by a sensor, .

[0023] In the above embodiment, the second-order full-drive model: ; ; ; ; Where: and is a known nonlinear function, is included and The total disturbance of .

[0024] In the above embodiment, the error feedback system is: ; ; ; ; A new sliding function based on the FAS method is designed as follows: .

[0025] It should be noted that in the process of transforming the second-order full-drive model into an error feedback system, To be The reference signal to be tracked is ; Where: represents a positive scalar.

[0026] In the above embodiment, once the sliding mode occurs, an equivalent control law can be established, and the equivalent control law is: ; Substituting the equivalent control law into the error feedback system, the closed-loop dynamic equation can be obtained as follows: ; Right now, ; in, .

[0027] It should be noted that by constructing the sliding mode Lyapunov function and proving its stability, it can be obtained that the convergence of the closed-loop system in step 7 can reach the sliding mode surface and stay on the sliding mode surface in a finite time; For a given positive scalar As long as the sliding surface is designed as the new sliding mode function in step 6, the state trajectory of the closed-loop system can be driven to the sliding mode surface in a finite time by the following SMC law: superior: ; The choice of Lyapunov function is as follows: ; The compensation torque equation in step S1 is: ; In step S2 The calculation formula is: ; Where: is the stiffness coefficient of the angular torque sensor; Indicates the mechanical angle of the road sensor motor. Indicates the reduction ratio of the road-sensing motor reducer. It is worth noting that is consistent with the definition of SFT, and It is the torque actively applied by the driver and cannot be directly controlled by the road sensing motor.

[0028] In step S4, it is assumed that ,and is bounded, satisfies , then the output equation of the controlled output can be expressed as: ; In step S6, select: ; in, , is a positive scalar, choose , Obviously, the eigenvalues ​​of the matrix F are and .

[0029] For any selected , all matrices and a non-singular matrix All meet the following requirements: ; in, is an arbitrary parameter matrix satisfying ,matrix The characteristic value of and .

[0030] It can be seen that as long as the matrix is ​​selected Stable, then the closed-loop system is stable. Obviously, the degrees of freedom of the control system are determined by the parameter matrix and Determined, in addition, the matrix is Hurwitz to ensure the asymptotic convergence of the system.

[0031] Working principle, high-order full drive (HOFA) system method, which is a control-oriented system model, usually characterized as full drive, different from the system model based on the control method based on the first-order state space theory, most nonlinear systems can be converted into HOFA systems through physical modeling or mathematical derivation. After obtaining the HOFA model, the measurable nonlinear terms can be easily eliminated to obtain a stable linear closed-loop system. In addition, more design freedom is provided to achieve additional system requirements. Therefore, combining SMC (sliding film control) with HOFA theory can significantly improve the system's anti-interference ability. This method aims to reduce the control system's sensitivity to interference by using sliding mode, and use the HOFA method to reduce the possibility of inherent flutter and vibration in SMC applications, thereby improving the overall system performance of HOFA-SMC and the driver's handling comfort.

[0032] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A road feel feedback control method based on a high-order all-wheel drive model of steer-by-wire, characterized in that: The following steps are involved: S1, determining the main torque and the compensation torque, and superimposing the main torque and the compensation torque to obtain a reference torque; S2, the vehicle control unit determines the current front wheel angle and the current reference feedback torque according to the current vehicle state, establishes the dynamic equation of the HW module and the dynamic equation of the road sense motor; S3, according to the dynamic model in step S2, obtain a control-oriented second-order state space model of the SbW system; S4, converting the second-order state space model in step S3 into a nonlinear second-order full-drive model of HW; S5, transforming the second-order full-drive model in step S4 into an error feedback system; S6. Establishing an equivalent control law according to the error feedback system; S7. Proof of stability.

2. The road feel feedback control method based on a high-order all-wheel drive model of steer-by-wire according to claim 1, characterized in that: The compensation torque includes an active return torque , to ensure that the steering wheel returns to the neutral position smoothly without overshooting when the driver actively releases his hands; soft limit torque , since the SbW system has a variable gear ratio, the system was developed to limit the steering wheel angle range to ensure safety; it also includes damping torque , friction torque and inertia torque ; Overall reference torque as a road feel source It is expressed as follows: 。 3. The road feel feedback control method based on a steer-by-wire high-order all-wheel drive model according to claim 2, characterized in that: The dynamic equation of the HW module is: ; Where: It represents the torque applied by the driver by adjusting the arm resistance on the hand wheel; Indicates the moment of inertia of the handwheel steering column; is the hand wheel damping coefficient; is the hand wheel angle; represents the equivalent Coulomb friction torque of the steering column; is the torque measured by the TAS sensor; The dynamic equation of the road sensing motor is: ; Where: Represents the output electromagnetic torque of the road sensing motor; Indicates the motor's moment of inertia; is the motor damping coefficient; Represents the equivalent Coulomb friction torque between the road sensing motor and the reduction mechanism.

4. The road feel feedback control method based on a steer-by-wire high-order all-wheel drive model according to claim 3, characterized in that: The second-order state-space model is: ; Where: is the state quantity of the steering system, and the input quantity is , is a mature friction model, and subsequent experiments have shown that it has a significant impact on control performance. Usually considered as a measurable disturbance measured by a sensor, .

5. The road feel feedback control method based on a steer-by-wire high-order all-wheel drive model according to claim 4, characterized in that: The second-order full-drive model: ; ; ; ; Where: and is a known nonlinear function, is included and The total disturbance of .

6. The road feel feedback control method based on a steer-by-wire high-order all-wheel drive model according to claim 5, characterized in that: The error feedback system is: ; ; ; ; A new sliding function based on the FAS method is designed as follows: .

7. The road feel feedback control method based on a steer-by-wire high-order all-wheel drive model according to claim 6, characterized in that: The equivalent control law is: ； According to the equivalent control law, the closed-loop dynamic equation is obtained as follows: ; Right now, ; in, .

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