A road feel feedback torque control method based on steer-by-wire

Abstract

The present invention discloses a road feel feedback torque control method based on steer-by-wire, comprising the following steps: S1, establishing a model-based feedback torque designer; S2, obtaining a reference feedback torque through the feedback torque designer; S3, using the difference between the reference feedback torque and the actual feedback torque as a state variable; S4, establishing a high-order all-wheel drive system for the steering dynamics system, performing torque tracking controller control processing, achieving personalized steering feel through main torque and compensation torque, utilizing the HOFA method to convert the actual nonlinear SbW system into a linear all-wheel drive system, simplifying the controller design, and achieving high-precision tracking control of the steering feedback torque through the high-order all-wheel drive system controller, thereby improving the real-time performance of the system. The road feel feedback torque control method based on steer-by-wire provided by the present invention eliminates the nonlinearity of the actual system, improves control performance, and provides the driver with accurate and real-time steering feedback.

Description

Technical Field

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

[0002] With the rapid development of intelligent chassis technology, steer-by-wire (SbW) systems have achieved mechanical decoupling between the steering wheel and front tires. Steering commands are transmitted via electronic signals, and steering feedback torque cannot be directly transmitted to the driver. This prevents the driver from directly sensing road feedback, such as vibration caused by uneven road surfaces and wheel-to-ground friction. Therefore, reestablishing road perception has become a key issue in SbW system design. Existing road perception designs are mostly based on model- or data-driven approaches, but these approaches still face challenges in real-time performance and control accuracy. Summary of the Invention

[0003] In view of the above problems, a road feel feedback torque control method based on steer-by-wire is provided, which aims to solve the problems existing in the prior art.

[0004] The specific technical solutions are as follows:

[0005] A road feel feedback torque control method based on steer-by-wire comprises the following steps:

[0006] S1. Establish a model-based feedback torque designer;

[0007] S2. Obtain reference feedback torque through the feedback torque designer;

[0008] S3. The error value obtained by subtracting the reference feedback torque from the actual feedback torque is used as the state quantity;

[0009] S4. Establishing a high-order all-wheel drive system for the steering dynamics system and performing torque tracking controller control processing to obtain real-time and accurate tracking reference feedback torque;

[0010] S41. Establish a steering wheel dynamics model and a road feel motor dynamics model;

[0011] S42, converting the steering wheel dynamics model established in S41 into a nonlinear second-order all-wheel drive model;

[0012] S43. Design state feedback control law;

[0013] S44. Construct Lyapunov function and perform stability analysis;

[0014] The dynamic model in step S41 includes: the steering wheel is a typical dual-input system, which allows the driver to rotate the steering wheel by adjusting the arm impedance and provides the driver with necessary steering feedback. Assuming that the steering column is rigid, the steering wheel dynamic model can be expressed as follows:

[0015] Where, is the driver’s input torque; is the steering column moment of inertia; is the damping coefficient; is the steering wheel angle; is the Coulomb friction torque; is the torque measured by the torque and angle sensor;

[0016] It is expressed by the following formula:

[0017] Where, is the sensor stiffness coefficient; is the mechanical angle of the road sensor motor; is the reduction ratio of the road-sensing motor; is the steering wheel angle;

[0018] The road sense motor dynamics model is expressed by the following formula:

[0019] Where, is the motor output torque; is the motor moment of inertia; is the motor damping coefficient; is the Coulomb friction torque of the motor.

[0020] The above-mentioned road feel feedback torque control method based on steer-by-wire further has the following characteristics: the model-based feedback torque designer includes:

[0021] Main torque generation module: Generates a basic feedback torque map based on the rack feedback force and vehicle speed obtained from the extended state observer, and designs gain coefficients to correct the main torque;

[0022] Compensation torque generation module: selects damping torque, friction torque, inertia torque, soft limit torque and active return torque as compensation quantities;

[0023] The damping torque is simplified to compensate the steering wheel angular velocity by a variable damping coefficient with the vehicle speed as a variable to obtain the damping compensation torque;

[0024] The friction torque uses an improved Coulomb friction model to compensate for the friction torque of the steering wheel assembly;

[0025] The inertia moment is limited and compensated by using a saturation function;

[0026] The soft limit torque is designed to have a soft end interval, and the soft end torque gradually increases within the interval;

[0027] The active return torque is designed to perform dual closed-loop control of the steering wheel rotation angle and angular velocity, and an active return gain coefficient compensation design is performed;

[0028] Reference feedback torque Calculated by the following formula:

[0029] in, is the main feedback torque, is the active return torque, is the damping torque, is the friction torque, is the moment of inertia, is the soft limit torque.

[0030] The above-mentioned road feel feedback torque control method based on steer-by-wire also has the following characteristics: the main torque generation module includes: a rack feedback force estimation unit, which estimates the rack force in real time based on an extended state observer, and the rack and pinion dynamics model is expressed by the following formula:

[0031] Where, is the mass of the rack; is the frame damping coefficient; is the rack displacement; is the first-order derivative of the rack displacement; is the second-order derivative of the rack displacement; is the rack friction force; is the steering resistance of the rack; is the pinion radius; is the motor reduction ratio; Output torque for the steering motor;

[0032] Generate a two-dimensional map curve of the rack feedback torque based on the rack feedback force and vehicle speed. Use the current estimated rack force and current vehicle speed to look up the table in the map curve to obtain the accurate rack feedback torque. , get the basic feedback characteristics of the steering wheel;

[0033] According to the operation of the turning driver, when the driver releases the steering wheel under the action of the active self-aligning torque, the steering wheel tends to turn to the middle, the rack force decreases, and the sign is opposite to the active self-aligning torque. The main torque gain coefficient is introduced and obtained by the following formula:

[0034] Among them, | | is the absolute value of the torque measured by the torque and angle sensor, is the main moment dead zone node, The absolute value of the torque obtained by TAS when the main torque gain is the maximum, It is a function of the relationship between the main torque gain and the absolute value of the torque obtained by TAS based on the calibration parameters of the actual vehicle;

[0035] The main moment is calculated by the following formula:

[0036] in, is the rack feedback torque, is the main moment gain coefficient.

[0037] The above-mentioned road feel feedback torque control method based on steer-by-wire further has the following characteristics: the compensation torque generation module includes:

[0038] The active self-aligning torque generation unit generates self-aligning torque based on dual closed-loop control of steering wheel angle and angular velocity to ensure rapid steering wheel return. The active self-aligning torque is described by the following formula:

[0039] Outer ring angle control:

[0040]

[0041] Inner loop angular velocity control:

[0042] Where, is the steering wheel angle, is the steering wheel angular velocity, is the desired angular velocity, and are the proportional and integral coefficients of the angle loop, is the initial value of the active aligning torque, and are the proportional coefficient and integral coefficient of the angular velocity loop, For vehicle speed.

[0043] The active steering gain coefficient is introduced. When the driver actively steers, the active return torque is reduced to avoid hindering the driver's steering action. When the driver takes his hands off the steering wheel, the active return torque assists the driver's operation. The active steering gain coefficient is described by the following formula:

[0044] Where, is the dead zone node of the active aligning torque, is the absolute value of the torque obtained by TAS at the minimum active self-aligning torque, The active return torque is based on the actual vehicle calibration parameters and Function of the relationship between the absolute values ​​of the moments;

[0045] The active return compensation torque is calculated using the following formula:

[0046]

[0047] The damping torque generating unit dynamically adjusts the steering wheel damping torque according to the vehicle speed to limit the steering wheel speed and damping torque. Obtained by the following formula:

[0048] Where, It's the speed. is the damping coefficient that changes with vehicle speed and increases with increasing speed. is the angular velocity of the steering wheel.

[0049] The friction torque generation unit uses the improved Coulomb friction model to generate the friction torque in the same direction as the steering wheel movement. Obtained by the following formula:

[0050] Where, is the friction torque, is the Coulomb friction torque, is the gradient change coefficient;

[0051] The inertia moment generation unit generates inertia moment through the steering wheel angular acceleration to improve the steering wheel response performance. The description is as follows:

[0052] Where sat(·) is the saturation function, is the coefficient of inertia;

[0053] The soft end limit torque generating unit generates nonlinear increasing torque when the steering wheel approaches the mechanical limit position to simulate a comfortable limit feeling. Obtained by the following formula:

[0054] Where, is the starting angle of the soft end interval, is the soft end angle, and the soft end interval angle difference Δ =| |- , (Δ ) is the nonlinear soft end torque, is the maximum soft end torque.

[0055] The above-mentioned road feel feedback torque control method based on steer-by-wire further has the following characteristics: the steering wheel dynamics equation is converted into a nonlinear second-order all-wheel drive model including:

[0056] The second-order state-space equation is expressed as follows:

[0057] in are the two states of the SbW system, u= represents the control input, It is considered as a measurable disturbance measured by the sensor;

[0058] Combining the above, we can get the second-order full-drive model of the steering feedback torque system, which is expressed by the following formula:

[0059] in:

[0060] Meet all-wheel drive requirements .

[0061] The above-mentioned road feel feedback torque control method based on steer-by-wire further has the following characteristics: the state feedback control law includes:

[0062] Introduction The reference feedback torque obtained by the feedback torque designer is As Get about The error feedback system is expressed by the following formula:

[0063] in, To be Reference signal for tracking;

[0064] By adopting the parameterization method, the state feedback control law is designed and expressed by the following formula:

[0065]

[0066] Bringing the state feedback control law to the error feedback system, we get the final closed-loop system, which is expressed by the following formula:

[0067] .

[0068] In summary, the beneficial effects of this solution are:

[0069] The steer-by-wire (SbW) torque control method provided by this invention achieves personalized steering feel through the use of primary and compensating torques. The HOFA method transforms the actual nonlinear SbW system into a linear full-drive system, simplifying controller design. A high-order full-drive system controller enables high-precision tracking control of the steering feedback torque, improving the system's real-time performance. This steer-by-wire (SbW) torque control method eliminates the nonlinearity of the actual system, improving control performance and providing the driver with accurate and real-time steering feedback. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Schematic diagram of a flow chart of a method for controlling torque with road feel feedback based on steer-by-wire according to the present invention;

[0071] Figure 2 This is a structural block diagram of a feedback torque designer for a road feel feedback torque control method based on steer-by-wire according to the present invention;

[0072] Figure 3 This is a structural block diagram of a main torque generation module of a road feel feedback torque control method based on wire-controlled steering according to the present invention. DETAILED DESCRIPTION

[0073] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0074] 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.

[0075] The present invention will be further described below with reference to specific examples, but they are not intended to limit the present invention.

[0076] Figure 1 Schematic diagram of a flow chart of a method for controlling torque with road feel feedback based on steer-by-wire according to the present invention. Figure 2 This is a structural block diagram of a feedback torque designer for a road feel feedback torque control method based on steer-by-wire according to the present invention. Figure 3 This is a structural block diagram of a main torque generation module of a road feel feedback torque control method based on wire-controlled steering according to the present invention. Figure 1-Figure 3 As shown, the road feel feedback torque control method based on steer-by-wire provided in this embodiment includes the following steps:

[0077] S1. Establish a model-based feedback torque designer;

[0078] S2. Obtain reference feedback torque through the feedback torque designer;

[0079] S3. The error value obtained by subtracting the reference feedback torque from the actual feedback torque is used as the state quantity;

[0080] S4. Establish a high-order all-wheel drive system for the steering dynamics system and perform torque tracking controller control processing to obtain real-time and accurate tracking reference feedback torque.

[0081] In the above embodiment, the model-based feedback torque designer includes:

[0082] Main torque generation module: Generates a basic feedback torque map based on the rack feedback force and vehicle speed obtained from the extended state observer, and designs gain coefficients to correct the main torque;

[0083] Compensation torque generation module: selects damping torque, friction torque, inertia torque, soft limit torque and active return torque as compensation quantities;

[0084] The damping torque is simplified to compensate the steering wheel angular velocity by using a variable damping coefficient with the vehicle speed as the variable to obtain the damping compensation torque;

[0085] The friction torque uses an improved Coulomb friction model to compensate for the friction torque of the steering wheel assembly;

[0086] The inertia moment is limited and compensated by using saturation function;

[0087] The soft limit torque is designed in the soft end interval, and the soft end torque gradually increases within the interval;

[0088] Active return torque is used to design dual closed-loop control of steering wheel rotation angle and angular velocity, and active return gain coefficient compensation is designed;

[0089] Reference feedback torque Calculated by the following formula:

[0090] in, is the main feedback torque, is the active return torque, is the damping torque, is the friction torque, is the moment of inertia, is the soft limit torque.

[0091] In the above embodiment, the main torque generation module includes: a rack feedback force estimation unit, which estimates the rack force in real time based on the extended state observer. The gear rack dynamics model is expressed by the following formula:

[0092] Where, is the mass of the rack; is the frame damping coefficient; is the rack displacement; is the first-order derivative of the rack displacement; is the second-order derivative of the rack displacement; is the rack friction force; is the steering resistance of the rack; is the pinion radius; is the motor reduction ratio; Output torque for the steering motor;

[0093] Generate a two-dimensional map curve of the rack feedback torque based on the rack feedback force and vehicle speed. Use the current estimated rack force and current vehicle speed to look up the table in the map curve to obtain the accurate rack feedback torque. , get the basic feedback characteristics of the steering wheel;

[0094] According to the operation of the turning driver, when the driver releases the steering wheel under the action of the active self-aligning torque, the steering wheel tends to turn to the middle, the rack force decreases, and the sign is opposite to the active self-aligning torque. The main torque gain coefficient is introduced and obtained by the following formula:

[0095] Among them, | | is the absolute value of the torque measured by the torque and angle sensor, is the main moment dead zone node, The absolute value of the torque obtained by TAS when the main torque gain is the maximum, It is a function of the relationship between the main torque gain and the absolute value of the torque obtained by TAS based on the calibration parameters of the actual vehicle;

[0096] The main moment is calculated by the following formula:

[0097] in, is the rack feedback torque, is the main moment gain coefficient.

[0098] In the above embodiment, the compensation torque generating module includes:

[0099] The active self-aligning torque generation unit generates self-aligning torque based on dual closed-loop control of steering wheel angle and angular velocity to ensure rapid steering wheel return. The active self-aligning torque is described by the following formula:

[0100] Outer ring angle control:

[0101]

[0102] Inner loop angular velocity control:

[0103] Where, is the steering wheel angle, is the steering wheel angular velocity, is the desired angular velocity, and are the proportional and integral coefficients of the angle loop, is the initial value of the active aligning torque, and are the proportional coefficient and integral coefficient of the angular velocity loop, For vehicle speed.

[0104] The active steering gain coefficient is introduced. When the driver actively steers, the active return torque is reduced to avoid hindering the driver's steering action. When the driver takes his hands off the steering wheel, the active return torque assists the driver's operation. The active steering gain coefficient is described by the following formula:

[0105] Where, is the dead zone node of the active aligning torque, is the absolute value of the torque obtained by TAS at the minimum active self-aligning torque, It is a function of the relationship between the active aligning torque based on the actual vehicle calibration parameters and the absolute value of the torque obtained by TAS;

[0106] The active return compensation torque is calculated using the following formula:

[0107]

[0108] The damping torque generating unit dynamically adjusts the steering wheel damping torque according to the vehicle speed to limit the steering wheel speed and damping torque. Obtained by the following formula:

[0109] Where, It's the speed. is the damping coefficient that changes with vehicle speed and increases with increasing speed. is the angular velocity of the steering wheel.

[0110] The friction torque generation unit uses the improved Coulomb friction model to generate the friction torque in the same direction as the steering wheel movement. Obtained by the following formula:

[0111] Where, is the friction torque, is the Coulomb friction torque, is the gradient change coefficient;

[0112] The inertia moment generation unit generates inertia moment through the steering wheel angular acceleration to improve the steering wheel response performance. The description is as follows:

[0113] Where sat(·) is the saturation function, is the coefficient of inertia;

[0114] The soft end limit torque generating unit generates nonlinear increasing torque when the steering wheel approaches the mechanical limit position to simulate a comfortable limit feeling. Obtained by the following formula:

[0115] Where, is the starting angle of the soft end interval, is the soft end angle, and the angle difference between soft end intervals Δ =| |- , (Δ ) is the nonlinear soft end torque, is the maximum soft end torque.

[0116] In the above embodiment, step S4 further includes establishing a torque tracking controller, and establishing the torque tracking controller includes the following steps:

[0117] S41. Establish a steering wheel dynamics model and a road feel motor dynamics model;

[0118] S42, converting the steering wheel dynamics model established in S41 into a nonlinear second-order all-wheel drive model;

[0119] S43. Design state feedback control law;

[0120] S44. Construct Lyapunov function and perform stability analysis.

[0121] In the above embodiment, the dynamic model in step S41 includes: the steering wheel is a typical dual-input system, which allows the driver to rotate the steering wheel by adjusting the arm impedance and provides the driver with necessary steering feedback. Assuming that the steering column is rigid, the steering wheel dynamic model can be expressed as follows:

[0122] Where, is the driver’s input torque; is the steering column moment of inertia; is the damping coefficient; is the steering wheel angle; is the Coulomb friction torque; is the torque measured by the torque and angle sensor;

[0123] It is expressed by the following formula:

[0124] Where, is the sensor stiffness coefficient; is the mechanical angle of the road sensor motor; is the reduction ratio of the road-sensing motor; is the steering wheel angle;

[0125] The road sense motor dynamics model is expressed by the following formula:

[0126] Where, is the motor output torque; is the motor moment of inertia; is the motor damping coefficient; is the Coulomb friction torque of the motor.

[0127] It should be noted that the road sensing motor mentioned above is a permanent magnet synchronous motor.

[0128] In the above embodiment, converting the steering wheel dynamics equation into a nonlinear second-order all-wheel drive model includes:

[0129] The second-order state-space equation is expressed as follows:

[0130] in are the two states of the SbW system, u = represents the control input, It is considered as a measurable disturbance measured by the sensor;

[0131] Combining the above, we can get the second-order full-drive model of the steering feedback torque system, which is expressed by the following formula:

[0132] in:

[0133] Meet all-wheel drive requirements .

[0134] In the above embodiment, the state feedback control law includes:

[0135] Introduction The reference feedback torque obtained by the feedback torque designer is As Get about The error feedback system is expressed by the following formula:

[0136] in, To be Reference signal for tracking;

[0137] By adopting the parameterization method, the state feedback control law is designed and expressed by the following formula:

[0138]

[0139] Bringing the state feedback control law to the error feedback system, we get the final closed-loop system, which is expressed by the following formula:

[0140] .

[0141] In the above embodiment, step S44 includes:

[0142] According to the second-order full-drive model, the Lyapunov function is selected and expressed by the following formula:

[0143]

[0144] Prove stability:

[0145] V remains consistent and eventually bounded, and the closed-loop system is asymptotically stable.

[0146] The working principle adopts an SFT designer based on a model method and an SFT controller based on a high-order all-wheel drive (HOFA) system method. The SFT designer includes a main torque module and a compensation torque module obtained from the rack force vehicle speed map; the SFT controller includes establishing an SbW system model; the steering wheel model is converted into a HOFA model; the error value of the total expected road feel motor torque obtained by the designer and the actual feedback torque is obtained as the state quantity of the all-wheel drive system, and a parametric design is performed and the stability of the closed-loop system is proved. Compared with the existing technology, the SFT designer of the present invention combines multiple torque compensation factors of the steering system to provide the driver with a real, reliable and personalized steering feel.

[0147] The above are only preferred embodiments of the present invention and do not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the present invention specification should be included in the protection scope of the present invention.

Claims

1. A road feel feedback torque control method based on steer-by-wire, characterized by: The following steps are involved: S1. Establish a model-based feedback torque designer; S2. Obtain reference feedback torque through the feedback torque designer; S3. The error value obtained by subtracting the reference feedback torque from the actual feedback torque is used as the state quantity; S4. Establishing a high-order all-wheel drive system for the steering dynamics system and performing torque tracking controller control processing to obtain real-time and accurate tracking reference feedback torque; The step S4 further includes establishing a torque tracking controller, and the establishment of the torque tracking controller includes the following steps: S41. Establish a steering wheel dynamics model and a road feel motor dynamics model; S42, converting the steering wheel dynamics model established in S41 into a nonlinear second-order all-wheel drive model; S43. Design state feedback control law; S44. Construct Lyapunov function and perform stability analysis; The dynamic model in step S41 includes: the steering wheel is a typical dual-input system, which allows the driver to rotate the steering wheel by adjusting the arm impedance and provides the driver with necessary steering feedback. Assuming that the steering column is rigid, the steering wheel dynamic model can be expressed as follows: Where, T d is the driver’s input torque; J sw is the moment of inertia of the steering column; B sw is the damping coefficient; θ sw is the steering wheel angle; T fsw is the Coulomb friction torque; T s is the torque measured by the torque and angle sensor; T s It is expressed by the following formula: Where K sw is the sensor stiffness coefficient; θ m is the mechanical angle of the road sensor motor; G m is the reduction ratio of the road-sensing motor; θ sw is the steering wheel angle; The road sense motor dynamics model is expressed by the following formula: Where, T m is the motor output torque; J m is the motor's moment of inertia; B m is the motor damping coefficient; T fm is the Coulomb friction torque of the motor.

2. The method for controlling torque with road feel feedback based on steer-by-wire according to claim 1, characterized in that: The model-based feedback torque designer includes: Main torque generation module: Generates a basic feedback torque map based on the rack feedback force and vehicle speed obtained from the extended state observer, and designs gain coefficients to correct the main torque; Compensation torque generation module: selects damping torque, friction torque, inertia torque, soft limit torque and active return torque as compensation quantities; The damping torque is simplified to compensate the steering wheel angular velocity by a variable damping coefficient with the vehicle speed as a variable to obtain the damping compensation torque; The friction torque uses an improved Coulomb friction model to compensate for the friction torque of the steering wheel assembly; The inertia moment is limited and compensated by using a saturation function; The soft limit torque is designed to have a soft end interval, and the soft end torque gradually increases within the interval; The active return torque is designed to perform dual closed-loop control of the steering wheel rotation angle and angular velocity, and an active return gain coefficient compensation design is performed; Reference feedback torque T ref Calculated by the following formula: T ref =T main +T AR +T damp +T fric +T int +T se Among them, T main is the main feedback torque, T AR is the active self-aligning torque, T damp is the damping torque, T fric is the friction torque, T int is the moment of inertia, T se is the soft limit torque.

3. The method for controlling torque with road feel feedback based on steer-by-wire according to claim 2, characterized in that: The main torque generation module includes: a rack feedback force estimation unit, which estimates the rack force in real time based on the extended state observer. The gear rack dynamics model is expressed by the following formula: Where M r is the mass of the rack; B r is the frame damping coefficient; x r is the rack displacement; is the first-order derivative of the rack displacement; is the second-order derivative of rack displacement; F frm is the rack friction force; F rack is the steering resistance of the rack; r p is the radius of the pinion; G rm is the motor reduction ratio; T rm Output torque for the steering motor; Generate a two-dimensional map curve of the rack feedback torque based on the rack feedback force and vehicle speed, and look up the table in the map curve to obtain the accurate rack feedback torque T rack , get the basic feedback characteristics of the steering wheel; According to the operation of the turning driver, when the driver releases the steering wheel under the action of the active self-aligning torque, the steering wheel tends to turn to the middle, the rack force decreases, and the sign is opposite to the active self-aligning torque. The main torque gain coefficient is introduced and obtained by the following formula: Among them, |T S | is the absolute value of the torque measured by the torque and angle sensor, T rz is the main moment dead zone node, T rm is the absolute value of the torque obtained by TAS when the main torque gain is the largest, fr(|T s |) is a function of the relationship between the main torque gain and the absolute value of the torque obtained by TAS based on the actual vehicle calibration parameters; The main moment is calculated by the following formula: T main =T rack ·k main Among them, T rack is the rack feedback torque, k main is the main moment gain coefficient.

4. The method for controlling torque with road feel feedback based on steer-by-wire according to claim 3, characterized in that: The compensation torque generating module includes: The active self-aligning torque generation unit generates self-aligning torque based on dual closed-loop control of steering wheel angle and angular velocity to ensure rapid steering wheel return. The active self-aligning torque is described by the following formula: Outer ring angle control: Inner loop angular velocity control: Where θ sw is the steering wheel angle, is the steering wheel angular velocity, is the desired angular velocity, k p,out and k i,out are the proportional and integral coefficients of the angle loop, T ar is the initial value of the active aligning torque, k p,in and k i,in are the proportional coefficient and integral coefficient of the angular velocity loop, v veh is the vehicle speed; The active steering gain coefficient is introduced. When the driver actively steers, the active return torque is reduced to avoid hindering the driver's steering action. When the driver's hands are off the steering wheel, the active return torque assists the driver's operation. The active steering gain coefficient is described by the following formula: Where, T arz is the dead zone node of the active aligning torque, T arm is the absolute value of the torque obtained by TAS at the minimum active self-aligning torque, f ar (|T S |) is a function of the relationship between the active aligning torque based on the actual vehicle calibration parameters and the absolute value of the torque obtained by TAS; The active aligning torque is calculated using the following formula: T AR =T ar ·k ar The damping torque generating unit dynamically adjusts the steering wheel damping torque according to the vehicle speed to limit the steering wheel speed. The damping torque T damp Obtained by the following formula: Where C damp (v veh ) is the damping coefficient that changes with vehicle speed and increases with increasing speed. is the steering wheel angular velocity; The friction torque generation unit uses the improved Coulomb friction model to generate the friction torque consistent with the direction of steering wheel movement. The friction torque T fric Obtained by the following formula: Where, T fric is the friction torque, T coul is the Coulomb friction torque, a coul is the gradient change coefficient; The inertia moment generation unit generates inertia moment through the steering wheel angular acceleration to improve the steering wheel response performance. The inertia moment T int The description is as follows: Where sat(·) is the saturation function, k int is the coefficient of inertia; The soft end limit torque generating unit generates a nonlinear increasing torque when the steering wheel approaches the mechanical limit position to simulate a comfortable limit feeling. The soft end torque T se Obtained by the following formula: Where θ sta is the starting angle of the soft end interval, θ se is the soft end angle, and the angle difference between soft end intervals Δθ se =|θ sw |-θ sta , f se (Δθ se ) is the nonlinear soft end torque, T max is the maximum soft end torque.

5. The method for controlling torque with road feel feedback based on steer-by-wire according to claim 1, characterized in that: The steering wheel dynamics equation is converted into a nonlinear second-order all-wheel drive model including: The second-order state-space equation is expressed as follows: in are the two states of the SbW system, u=T m represents the control input, It is considered as a measurable disturbance measured by the sensor; Combining the above, we can get the second-order full-drive model of the steering feedback torque system, which is expressed by the following formula: in: The all-wheel drive condition det B≠0 is met.

6. The method for controlling torque with road feel feedback based on steer-by-wire according to claim 5, characterized in that: The state feedback control law includes: Introducing z=x * -x form, the reference feedback torque T obtained by the feedback torque designer ref As x2 * The error feedback system about z2 is obtained and expressed by the following formula: Among them, x * ∈R is the reference signal to be tracked by x; By adopting the parameterization method, the state feedback control law is designed and expressed by the following formula: Bringing the state feedback control law to the error feedback system, we get the final closed-loop system, which is expressed by the following formula:

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