A steering angle redundancy control method and system for a dual-motor steer-by-wire system

Abstract

The application provides a steering angle redundancy control method and system for a double-motor steer-by-wire system, and the method comprises the following steps: acquiring a yaw rate of a vehicle, vehicle state parameters, a failure state of a steering motor and a desired steering angle, and performing filtering processing on the yaw rate and the vehicle state parameters; determining a steering wheel steering angle estimation value of the double-motor steer-by-wire system in the vehicle according to the filtered yaw rate and the vehicle state parameters; determining a total torque of the steering motor of the double-motor steer-by-wire system according to the desired steering angle and the steering wheel steering angle estimation value and by using an adaptive non-singular fast terminal sliding mode control mode; determining torque instruction values of each steering motor in the system according to the total torque of the steering motor and the failure state of the steering motor by using a dynamic distribution mode; and driving the double-motor steer-by-wire system to operate based on the torque instruction values of each steering motor. The technical scheme provided by the application realizes accurate control of the steering angle and has strong robustness.

Description

Technical Field

[0001] This application relates to the field of automotive steer-by-wire control, and more particularly to a method and system for redundancy control of steering angle in a dual-motor steer-by-wire system. Background Technology

[0002] In recent years, with the advancement of automotive intelligence and electrification technologies, autonomous vehicles have become a hot topic in the industry. Among these, steer-by-wire systems play a crucial role in path tracking and emergency obstacle avoidance in autonomous vehicles, and their performance directly impacts active safety and driving experience. Compared to traditional steering systems, steer-by-wire systems eliminate the mechanical connection between the steering wheel and the steering actuator, relying entirely on electrical signals for vehicle control, which facilitates the integration of chassis domain functions. However, the elimination of mechanical backup increases the probability of electromechanical system failure, placing higher demands on the functional safety of steer-by-wire systems.

[0003] As the power source for the steering system, the performance of the steering motor is crucial. If the steering motor fails, it will pose a serious threat to vehicle handling and driving safety. Therefore, in order to improve the reliability and safety of the system, ensure functional safety, and take into account the limitations of system structure and cost, a dual-motor redundant steer-by-wire system is often adopted.

[0004] Current fault-tolerant control methods for dual-motor steer-by-wire systems focus more on upper-level vehicle stability control and less on lower-level actuator-level steering angle control. Furthermore, dual-motor steer-by-wire systems inherently contain parameter uncertainties, such as uncertainties in system moment of inertia and damping, leading to lower control accuracy. Therefore, to achieve precise steering angle control even in the event of steering motor failure, a robust and highly accurate redundant steering angle control scheme for dual-motor steer-by-wire systems is urgently needed. Summary of the Invention

[0005] This application provides a method and system for redundant control of steering angle in a dual-motor steer-by-wire system, to at least solve the technical problem of low steering angle control accuracy in the event of steering motor failure.

[0006] The first aspect of this application proposes a method for redundant control of steering angle in a dual-motor steer-by-wire system, the method comprising:

[0007] The vehicle's yaw rate, vehicle state parameters, steering motor failure state, and desired steering angle are obtained, and the yaw rate and vehicle state parameters are filtered.

[0008] Based on the filtered yaw rate and the vehicle state parameters, the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is determined.

[0009] Based on the desired steering angle and the estimated steering wheel angle, and using adaptive non-singular fast terminal sliding mode control, the total torque of the steering motors in the dual-motor steer-by-wire system is determined.

[0010] The torque command value of each steering motor in the dual-motor steer-by-wire system is determined by dynamically distributing the total torque of the steering motors.

[0011] The dual-motor steer-by-wire system is driven to operate based on the torque command values ​​of each steering motor.

[0012] Preferably, the vehicle status parameters include:

[0013] At the current moment, the vehicle's center of gravity sideslip angle, vehicle mass, distance from the vehicle's center of gravity to the front axle, distance from the vehicle's center of gravity to the rear axle, vehicle longitudinal velocity, lateral stiffness of the front and rear tires, and vehicle's moment of inertia about the z-axis.

[0014] Furthermore, determining the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle based on the filtered yaw rate and the vehicle state parameters includes:

[0015] A two-degree-of-freedom vehicle model is constructed based on the filtered vehicle state parameters.

[0016] An unknown input observer is constructed based on the yaw rate of the vehicle after filtering.

[0017] Based on the two-degree-of-freedom vehicle model and the unknown input observer, the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is determined.

[0018] Furthermore, the formula for calculating the estimated steering wheel steering angle of the dual-motor steer-by-wire system in the vehicle is as follows:

[0019]

[0020] In the formula, B is the estimated value of the steering angle of the steering wheel. + Let B be the pseudo-inverse matrix of the second matrix. This represents the first derivative of the observed state variables obtained based on a two-degree-of-freedom vehicle model and an unknown input observer. Let A be the first derivative of the vehicle's yaw rate output by the system, and let A be the first matrix. Here are the estimated values ​​of the state variables, where, C f C represents the lateral stiffness of the front tire. r Let m be the lateral stiffness of the rear tire, m be the vehicle mass, and v be the lateral stiffness. xFor the longitudinal speed of the vehicle, l f l is the distance from the vehicle's center of gravity to the front axle. r I is the distance from the vehicle's center of gravity to the rear axle. z Let E be the vehicle's moment of inertia about the z-axis, and let x be a state variable, which includes the sideslip angle and yaw rate. E = -B(CB) T [CB(CB) T ] -1 E is the third matrix.

[0021] Furthermore, determining the total torque of the drive motors of the dual-motor steer-by-wire system based on the desired steering angle and the estimated steering wheel angle, using adaptive non-singular fast terminal sliding mode control, includes:

[0022] The steering angle control error of the steering wheel and the first derivative of the error are determined based on the desired steering angle and the estimated steering angle of the steering wheel.

[0023] Construct a non-singular terminal sliding surface based on the steering angle control error of the steering wheel and the first derivative of the error;

[0024] A Lyapukhov function is constructed based on the non-singular terminal sliding surface, and the parameter adaptive rate is obtained based on the Lyapukhov function.

[0025] The total torque of the steering motor in the dual-motor steer-by-wire system is determined based on the adaptive rate of the parameters.

[0026] Furthermore, the formula for calculating the parameter adaptation rate is as follows:

[0027]

[0028] In the formula, The first derivative of the estimated value of the uncertain part of the system, γ>0, where γ is the controller parameter, s is the sliding surface, and J eq The equivalent rotational inertia of the system, For mapping functions, Δ is the estimated value of the uncertain part of the system. max Δ represents the maximum value of the uncertain part of the system. min It represents the minimum value of the uncertain part of the system.

[0029] Furthermore, the step of determining the torque command value of each steering motor in the dual-motor steer-by-wire system using a dynamic allocation method based on the total torque of the steering motor and the failure state of the steering motor includes:

[0030] Using formula T m1 =0.5fT mThe torque command value of the first steering motor in the dual-motor steer-by-wire system is determined using the formula T. m2 =0.5(2-f)T m Determine the torque command value of the second steering motor in the dual-motor steer-by-wire system;

[0031] Among them, T m1 T represents the torque command value of the first steering motor in a dual-motor steer-by-wire system. m2 T represents the torque command value of the second steering motor in a dual-motor steer-by-wire system. m Let f be the total torque of the steering motor, and f be the failure state of the steering motor. f = 1 indicates that the steering motor is not failed, and f = 0 indicates that the steering motor has failed.

[0032] The second aspect of this application provides a redundancy control system for the steering angle of a dual-motor steer-by-wire system, comprising:

[0033] The acquisition module is used to acquire the vehicle's yaw rate, vehicle state parameters, steering motor failure state, and desired steering angle, and to filter the yaw rate and vehicle state parameters.

[0034] The first determining module is used to determine the estimated value of the steering wheel steering angle of the dual-motor steer-by-wire system in the vehicle based on the filtered yaw rate and the vehicle state parameters.

[0035] The second determining module is used to determine the total torque of the steering motor of the dual-motor steer-by-wire system based on the desired steering angle and the estimated steering wheel angle, and using an adaptive non-singular fast terminal sliding mode control method.

[0036] The third determining module is used to determine the torque command value of each steering motor in the dual-motor steer-by-wire system by means of dynamic allocation based on the total torque of the steering motor and the failure state of the steering motor.

[0037] The control module is used to drive the dual-motor steer-by-wire system based on the torque command values ​​of each steering motor.

[0038] Preferably, the vehicle status parameters include:

[0039] The current vehicle's center of gravity sideslip angle, vehicle mass, distance from the vehicle's center of gravity to the front axle, distance from the vehicle's center of gravity to the rear axle, vehicle longitudinal velocity, lateral stiffness of the front and rear tires, and vehicle's moment of inertia about the z-axis.

[0040] Furthermore, the first determining module is also used for:

[0041] A two-degree-of-freedom vehicle model is constructed based on the filtered vehicle state parameters.

[0042] An unknown input observer is constructed based on the yaw rate of the vehicle after filtering.

[0043] Based on the two-degree-of-freedom vehicle model and the unknown input observer, the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is determined.

[0044] The technical solutions provided by the embodiments of this application bring at least the following beneficial effects:

[0045] This application proposes a method and system for redundant control of steering angle in a dual-motor steer-by-wire system. The method includes: acquiring the vehicle's yaw rate, vehicle state parameters, steering motor failure state, and desired steering angle; filtering the yaw rate and vehicle state parameters; determining an estimated steering wheel angle of the dual-motor steer-by-wire system based on the filtered yaw rate and vehicle state parameters; determining the total torque of the steering motors in the dual-motor steer-by-wire system based on the desired steering angle and the estimated steering wheel angle, using adaptive non-singular fast terminal sliding mode control; determining the torque command value of each steering motor in the dual-motor steer-by-wire system using a dynamic allocation method based on the total torque of the drive motors and the steering motor failure state; and driving the dual-motor steer-by-wire system based on the torque command values ​​of each steering motor. The technical solution proposed in this application achieves precise steering angle control with strong robustness.

[0046] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0047] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0048] Figure 1 This is a flowchart illustrating a method for redundancy control of steering angle in a dual-motor steer-by-wire system according to an embodiment of this application;

[0049] Figure 2 This is a schematic diagram of a dual-motor steer-by-wire system according to an embodiment of this application;

[0050] Figure 3 This is an architecture diagram of a redundancy control method for steering angle in a dual-motor steer-by-wire system according to an embodiment of this application;

[0051] Figure 4This is a simulation diagram of steering wheel steering angle control under a steering motor failure in a step steering condition according to an embodiment of this application;

[0052] Figure 5 This is a simulation diagram of steering wheel steering angle control under a steering motor failure in a sinusoidal steering condition, according to an embodiment of this application.

[0053] Figure 6 This is a simulation diagram of steering wheel steering angle control under a steering motor failure in a double lane change operation, according to an embodiment of this application.

[0054] Figure 7 This is a simulation diagram of the steering wheel angle estimation at a vehicle speed of 40 km / h according to an embodiment of this application;

[0055] Figure 8 This is a simulation diagram of the steering wheel steering angle estimation at a vehicle speed of 60 km / h according to an embodiment of this application;

[0056] Figure 9 This is a structural diagram of a redundancy control system for a dual-motor steer-by-wire system according to an embodiment of this application. Detailed Implementation

[0057] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0058] This application proposes a method and system for redundant control of steering angle in a dual-motor steer-by-wire system. The method includes: acquiring the vehicle's yaw rate, steering motor operating data, and desired steering angle; filtering the yaw rate and steering motor operating data; determining an estimated steering wheel angle of the dual-motor steer-by-wire system based on the filtered yaw rate and steering motor operating data; determining the total torque of the drive motors of the dual-motor steer-by-wire system based on the desired steering angle and the estimated steering wheel angle, using adaptive non-singular fast terminal sliding mode control; determining the torque command value of each drive motor in the dual-motor steer-by-wire system based on the total drive motor torque using a dynamic allocation method; and driving the dual-motor steer-by-wire system based on the torque command values ​​of each drive motor. The technical solution proposed in this application achieves precise steering angle control with strong robustness.

[0059] The following description, with reference to the accompanying drawings, illustrates a method and system for redundancy control of steering angle in a dual-motor steer-by-wire system according to an embodiment of this application.

[0060] Example 1

[0061] Figure 1 The flowchart below shows a method for redundancy control of steering angle in a dual-motor steer-by-wire system according to an embodiment of this application. Figure 1 As shown, the method includes:

[0062] Step 1: Obtain the vehicle's yaw rate, vehicle status parameters, steering motor failure status, and desired steering angle, and then filter the yaw rate and vehicle status parameters.

[0063] In this embodiment of the disclosure, the vehicle status parameters include:

[0064] The current vehicle's center of gravity sideslip angle, vehicle mass, distance from the vehicle's center of gravity to the front axle, distance from the vehicle's center of gravity to the rear axle, vehicle longitudinal velocity, lateral stiffness of the front and rear tires, and vehicle's moment of inertia about the z-axis.

[0065] It should be noted that, as Figure 2 The diagram shows the structure of a dual-motor steer-by-wire system, specifically including a controller, a steering wheel assembly, and a steering actuator assembly. The controller receives signals from various sensors and outputs control commands to the road feeler motor and two steering drive motors. The steering wheel assembly, consisting of a steering wheel, steering column, and road feeler motor, simulates the steering resistance of the steer-by-wire system in real time and provides feedback to the driver. The steering actuator assembly, composed of two steering motors, a rack and pinion steering gear, steering tie rods, and steering wheels, is used to achieve vehicle steering. When both steering motors are functioning correctly, they share the steering load. If one steering motor fails, the other, functioning motor takes over the entire steering load.

[0066] Step 2: Determine the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle based on the filtered yaw rate and the vehicle state parameters.

[0067] In this embodiment of the disclosure, step 2 specifically includes:

[0068] A two-degree-of-freedom vehicle model is constructed based on the filtered vehicle state parameters.

[0069] An unknown input observer is constructed based on the yaw rate of the vehicle after filtering.

[0070] Based on the two-degree-of-freedom vehicle model and the unknown input observer, the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is determined.

[0071] The formula for calculating the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is as follows:

[0072]

[0073] In the formula, B is the estimated value of the steering angle of the steering wheel. + Let B be the pseudo-inverse matrix of the second matrix. This represents the first derivative of the observed state variables obtained based on a two-degree-of-freedom vehicle model and an unknown input observer. Let A be the first derivative of the vehicle's yaw rate output by the system, and let A be the first matrix. Here are the estimated values ​​of the state variables, where, C f C represents the lateral stiffness of the front tire. r Let m be the lateral stiffness of the rear tire, m be the vehicle mass, and v be the lateral stiffness. x For the longitudinal speed of the vehicle, l f l is the distance from the vehicle's center of gravity to the front axle. r I is the distance from the vehicle's center of gravity to the rear axle. z Let E be the vehicle's moment of inertia about the z-axis, and let x be a state variable, which includes the sideslip angle and yaw rate. E = -B(CB) T [CB(CB) T ] -1 E is the third matrix.

[0074] Specifically, a two-degree-of-freedom vehicle model is constructed, and the specific formula is as follows:

[0075]

[0076] y = Cx

[0077] In the formula, Let y be the first derivative of the system state variables, y be the yaw rate of the vehicle output by the system, and x = [β, ω]. r ] T β is the sideslip angle of the vehicle's center of gravity, ω r Let u = δ be the yaw rate of the vehicle. f δ f For the steering wheel angle of the steer-by-wire system, y = ω r .

[0078] The specific formula for constructing an observer with unknown input is as follows:

[0079]

[0080] In the formula, z is the observed state variable. for xThe estimators are N, L, and F, which are matrices that need to be determined.

[0081] The state estimation error and its first derivative are calculated using the following formula:

[0082]

[0083] In the formula, e represents the state estimation error. The first derivative of the state estimation error. Let I be the first derivative of the estimated state variables, W be the identity matrix, N be the first estimation matrix, L be the second estimation matrix, and F be the third estimation matrix.

[0084] The estimation error asymptotically converges to 0 if and only if the chosen matrices N,L,F satisfy the following condition:

[0085]

[0086] Offline solution for the undetermined matrices N, L, F of an unknown input observer.

[0087] The formula for calculating the estimated steering wheel angle of the steer-by-wire system is as follows:

[0088]

[0089] Where, E = -B(CB) T [CB(CB) T ] -1 E is the third matrix.

[0090] It should be noted that the calculation of the total torque in step 3 also includes:

[0091] The equivalent mathematical model of the dual-motor steer-by-wire system is constructed, and the specific formula is as follows:

[0092]

[0093] in,

[0094]

[0095] In the formula, J eq B is the equivalent rotational inertia of the system. eq For the system's equivalent damping, T z T is the system's steering resistance torque. d For the system's uncertain load torque, T eq T is the equivalent total motor torque of the system. m J is the total torque of the steering motor. f B is the moment of inertia of the steering wheel. f For steering wheel damping, Jm B is the moment of inertia of the steering motor. m For the steering motor damping, M r For the mass of the rack and pinion steering gear, B r G1 is the damping of the rack and pinion steering gear, G2 is the reduction ratio of the steering motor reducer, and r is the rotational angle transmission ratio from the rack to the steering wheel. p Let be the pitch circle radius of the pinion, f represent the failure state of the steering motor, f = 1 indicates the steering motor is not failed, f = 0 indicates the steering motor has failed, and ΔJ and ΔB represent the system uncertainty parameters. A unified representation of the uncertain parts of a system.

[0096] Step 3: Based on the desired steering angle and the estimated steering wheel angle, and using adaptive non-singular fast terminal sliding mode control, determine the total torque of the steering motors in the dual-motor steer-by-wire system.

[0097] In this embodiment of the disclosure, step 3 specifically includes:

[0098] The steering angle control error of the steering wheel and the first derivative of the error are determined based on the desired steering angle and the estimated steering angle of the steering wheel.

[0099] Construct a non-singular terminal sliding surface based on the steering angle control error of the steering wheel and the first derivative of the error;

[0100] A Lyapukhov function is constructed based on the non-singular terminal sliding surface, and the parameter adaptive rate is obtained based on the Lyapukhov function.

[0101] The formula for calculating the parameter adaptation rate is as follows:

[0102]

[0103] In the formula, The first derivative of the estimated value of the uncertain part of the system, γ>0, where γ is the controller parameter, s is the sliding surface, and J eq The equivalent rotational inertia of the system, For mapping functions, Δ is the estimated value of the uncertain part of the system. max Δ represents the maximum value of the uncertain part of the system. min It represents the minimum value of the uncertain part of the system.

[0104] The total torque of the drive motors of the dual-motor steer-by-wire system is determined based on the adaptive rate of the parameters.

[0105] Specifically, the online calculation of the steering wheel's steering angle control error and the first derivative of the error is performed using the following formula:

[0106]

[0107] Wherein, e1 is the steering angle control error of the steering wheel, and e2 is the first-order derivative of the steering angle control error of the steering wheel. is the first-order derivative of the steering angle control error of the steering wheel, and δ fd is the desired steering angle;

[0108] Construct a non-singular terminal sliding mode surface, and the specific formula is as follows:

[0109] s = ae1 + be2 + ce2 p / q

[0110]

[0111] Wherein, is the first-order derivative of the sliding mode surface, and a, b, c, k1, k2 are all parameters greater than zero, p and q are both positive odd numbers, and satisfy q < p < 2q, 0 < ε < 1, and ε is a preset coefficient.

[0112] Construct a Lyapunov function and design a parameter adaptation rate, and the specific formula is as follows:

[0113]

[0114] Wherein, γ > 0.

[0115] In order to prevent from being too large and causing the control input signal to be too large or situation, a mapping algorithm is adopted to correct the adaptation law, so that changes within [Δ min , Δ max :

[0116]

[0117] Online calculate the total torque of the steering motor, and the specific formula is as follows:

[0118]

[0119] T m = 2r p (T z + B eq )

[0120] Step 4: Determine the torque command values of each steering motor in the dual-motor by-wire steering system in a dynamically allocated manner according to the total torque of the steering motor and the failure state of the steering motor.

[0121] In the embodiment of the present disclosure, the specific content of the step 4 includes:

[0122] Using formula T m1 =0.5fT m The torque command value of the first steering motor in the dual-motor steer-by-wire system is determined using the formula T. m2 =0.5(2-f)T m Determine the torque command value of the second steering motor in the dual-motor steer-by-wire system;

[0123] Among them, T m1 T represents the torque command value of the first steering motor in a dual-motor steer-by-wire system. m2 T represents the torque command value of the second steering motor in a dual-motor steer-by-wire system. m The total torque of the drive motor is given by f, where f represents the failure state of the steering motor. f = 1 indicates that the steering motor is not failed, and f = 0 indicates that the steering motor has failed.

[0124] Step 5: Drive the dual-motor steer-by-wire system to operate based on the torque command values ​​of each steering motor.

[0125] Specifically, such as Figure 3 The diagram shown is an architecture diagram of the redundancy control method for steering angle in the dual-motor steer-by-wire system of the present invention.

[0126] Furthermore, the method of the present invention was simulated under the following conditions: step angle, sinusoidal angle, double lane change, vehicle speed of 40 km / h, and vehicle speed of 60 km / h. The simulation results are as follows: Figure 4-8 As shown, the method proposed in this invention achieves precise control of the steering angle and has strong robustness, wherein, as Figure 4 The figure shown is a simulation diagram of steering wheel steering angle control when a steering motor fails under a step angle condition. Figure 5 The figure shown is a simulation diagram of the steering wheel steering angle control when a steering motor fails under sinusoidal steering conditions. Figure 6 The figure shown is a simulation diagram of the steering wheel steering angle control when a steering motor fails under double lane change conditions. Figure 7 The image shown is a simulation diagram of the estimated steering wheel angle at a vehicle speed of 40 km / h. Figure 8 The figure shown is a simulation diagram of the estimated steering angle of the steering wheel at a vehicle speed of 60 km / h.

[0127] in, Figure 4 , 5In Figure 6, the vertical axis represents the steering wheel angle, Desire represents the desired steering wheel angle, ANSFT-SMRC represents the Adaptive Non-Singular Fast Terminal Sliding Mode Redundancy Control (ANSFT-SMRC), which is the control method proposed in this patent, and SMC represents Sliding Mode Control, which is used as a comparison method. For control methods, the more consistent the curve obtained by the control method is with the desired curve, the higher the control accuracy.

[0128] Figure 7 , 8 The vertical axis represents the steering wheel angle. CARSIM is the steering wheel angle curve obtained from the CARSIM vehicle dynamics simulation software. UIO is the steering wheel angle curve estimated by the unknown input observer. If UIO and CARSIM outputs are consistent, then UIO is considered to meet the estimation accuracy requirements.

[0129] Meanwhile, the present invention has the following advantages: 1. The non-singular fast terminal sliding mode steering angle redundancy control method proposed in this invention can ensure that the error converges within a finite time and has good control performance; 2. The adaptive rate proposed in this invention considers the system rotational inertia, damping and other parameters and system uncertainties in the dual-motor steer-by-wire system, thereby improving the robustness of the controller; 3. This invention provides an unknown input observer, which can accurately estimate the steering wheel steering angle by only knowing the vehicle yaw rate, without the need for expensive steering angle sensors, thereby reducing system cost.

[0130] In summary, the proposed method for redundant steering angle control in a dual-motor steer-by-wire system achieves precise and robust steering angle control at a low cost.

[0131] Example 2

[0132] Figure 9 This is a structural diagram of a redundancy control system for a dual-motor steer-by-wire system according to an embodiment of this application, as shown below. Figure 9 As shown, the system includes:

[0133] The acquisition module 100 is used to acquire the vehicle's yaw rate, vehicle state parameters, steering motor failure state, and desired steering angle, and to filter the yaw rate and vehicle state parameters.

[0134] The vehicle status parameters include:

[0135] The current vehicle's center of gravity sideslip angle, vehicle mass, distance from the vehicle's center of gravity to the front axle, distance from the vehicle's center of gravity to the rear axle, vehicle longitudinal velocity, lateral stiffness of the front and rear tires, and vehicle's moment of inertia about the z-axis.

[0136] The first determining module 200 is used to determine the estimated value of the steering wheel steering angle of the dual-motor steer-by-wire system in the vehicle based on the filtered yaw rate and the vehicle state parameters.

[0137] The formula for calculating the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is as follows:

[0138]

[0139] In the formula, B is the estimated value of the steering angle of the steering wheel. + Let B be the pseudo-inverse matrix of the second matrix. This represents the first derivative of the observed state variables obtained based on a two-degree-of-freedom vehicle model and an unknown input observer. Let A be the first derivative of the vehicle's yaw rate output by the system, and let A be the first matrix. Here are the estimated values ​​of the state variables, where, C f C represents the lateral stiffness of the front tire. r Let m be the lateral stiffness of the rear tire, m be the vehicle mass, and v be the lateral stiffness. x For the longitudinal speed of the vehicle, l f l is the distance from the vehicle's center of gravity to the front axle. r I is the distance from the vehicle's center of gravity to the rear axle. z Let E be the vehicle's moment of inertia about the z-axis, and let x be a state variable, which includes the sideslip angle and yaw rate. E = -B(CB) T [CB(CB) T ] -1 E is the third matrix.

[0140] The second determining module 300 is used to determine the total torque of the steering motor of the dual-motor steer-by-wire system based on the desired steering angle and the estimated steering wheel angle, and using an adaptive non-singular fast terminal sliding mode control method.

[0141] The third determining module 400 is used to determine the torque command value of each steering motor in the dual-motor steer-by-wire system by means of dynamic allocation based on the total torque of the drive motor and the failure state of the steering motor.

[0142] The control module 500 is used to drive the dual-motor steer-by-wire system to operate based on the torque command values ​​of each steering motor.

[0143] In this embodiment of the disclosure, the first determining module 200 is further configured to:

[0144] A two-degree-of-freedom vehicle model is constructed based on the filtered vehicle state parameters.

[0145] An unknown input observer is constructed based on the yaw rate of the vehicle after filtering.

[0146] Based on the two-degree-of-freedom vehicle model and the unknown input observer, the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is determined.

[0147] In this embodiment of the disclosure, the second determining module 300 is further configured to:

[0148] The steering angle control error of the steering wheel and the first derivative of the error are determined based on the desired steering angle and the estimated steering angle of the steering wheel.

[0149] Construct a non-singular terminal sliding surface based on the steering angle control error of the steering wheel and the first derivative of the error;

[0150] A Lyapukhov function is constructed based on the non-singular terminal sliding surface, and the parameter adaptive rate is obtained based on the Lyapukhov function.

[0151] The formula for calculating the parameter adaptation rate is as follows:

[0152]

[0153] In the formula, The first derivative of the estimated value of the uncertain part of the system, γ>0, where γ is the controller parameter, s is the sliding surface, and J eq The equivalent rotational inertia of the system, For mapping functions, Δ is the estimated value of the uncertain part of the system. max Δ represents the maximum value of the uncertain part of the system. min It represents the minimum value of the uncertain part of the system.

[0154] The total torque of the steering motor in the dual-motor steer-by-wire system is determined based on the adaptive rate of the parameters.

[0155] In this embodiment of the disclosure, the third determining module 400 is further configured to:

[0156] Using formula T m1 =0.5fT m The torque command value of the first steering motor in the dual-motor steer-by-wire system is determined using the formula T. m2 =0.5(2-f)T mDetermine the torque command value of the second steering motor in the dual-motor steer-by-wire system;

[0157] Among them, T m1 T represents the torque command value of the first motor in a dual-motor steer-by-wire system. m2 T represents the torque command value for the second motor in a dual-motor steer-by-wire system. m The total torque of the drive motor is given by f, where f represents the failure state of the steering motor. f = 1 indicates that the steering motor is not failed, and f = 0 indicates that the steering motor has failed.

[0158] In summary, the dual-motor steer-by-wire system with redundant steering angle control proposed in this embodiment achieves precise control of the steering angle with strong robustness and low cost.

[0159] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0160] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0161] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for redundant control of steering angle in a dual-motor steer-by-wire system, characterized in that, The method includes: The vehicle's yaw rate, vehicle state parameters, steering motor failure state, and desired steering angle are obtained, and the yaw rate and vehicle state parameters are filtered. Based on the filtered yaw rate and the vehicle state parameters, the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is determined. Based on the desired steering angle and the estimated steering wheel angle, and using adaptive non-singular fast terminal sliding mode control, the total torque of the drive motors of the dual-motor steer-by-wire system is determined. The torque command value of each steering motor in the dual-motor steer-by-wire system is determined by a dynamic allocation method based on the total torque of the steering motor and the failure state of the steering motor. The dual-motor steer-by-wire system is driven to operate based on the torque command values ​​of each steering motor. The formula for calculating the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is as follows: In the formula, This is an estimated value for the steering angle of the steering wheel. Let B be the pseudo-inverse matrix of the second matrix. This represents the first derivative of the observed state variables obtained based on a two-degree-of-freedom vehicle model and an unknown input observer. Let A be the first derivative of the vehicle's yaw rate output by the system, and let A be the first matrix. Here are the estimated values ​​of the state variables, where, , This refers to the lateral stiffness of the front tire. For the lateral stiffness of the rear tire, For vehicle quality, For the longitudinal speed of the vehicle, This is the distance from the vehicle's center of gravity to the front axle. This is the distance from the vehicle's center of gravity to the rear axle. Let be the moment of inertia of the vehicle about the z-axis. These are state variables, including the sideslip angle and yaw rate. E is the third matrix; The determination of the torque command value of each steering motor in the dual-motor steer-by-wire system using a dynamic allocation method based on the total torque of the steering motors and the failure state of the steering motors includes: Using formula The torque command value of the first steering motor in the dual-motor steer-by-wire system is determined using the formula. Determine the torque command value of the second steering motor in the dual-motor steer-by-wire system; in, This is the torque command value for the first steering motor in a dual-motor steer-by-wire system. This refers to the torque command value of the second steering motor in a dual-motor steer-by-wire system. This represents the total torque of the steering motor. This indicates a failure state of the steering motor. This indicates that the steering motor is not malfunctioning. This indicates that the steering motor has failed.

2. The method as described in claim 1, characterized in that, The vehicle status parameters include: At the current moment, the vehicle's center of gravity sideslip angle, vehicle mass, distance from the vehicle's center of gravity to the front axle, distance from the vehicle's center of gravity to the rear axle, vehicle longitudinal velocity, lateral stiffness of the front and rear tires, and vehicle's moment of inertia about the z-axis.

3. The method as described in claim 2, characterized in that, The step of determining the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle based on the filtered yaw rate and the vehicle state parameters includes: A two-degree-of-freedom vehicle model is constructed based on the filtered vehicle state parameters. An unknown input observer is constructed based on the yaw rate of the vehicle after filtering. Based on the two-degree-of-freedom vehicle model and the unknown input observer, the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is determined.

4. The method as described in claim 3, characterized in that, The step of determining the total torque of the steering motors in the dual-motor steer-by-wire system based on the desired steering angle and the estimated steering wheel angle, and using adaptive non-singular fast terminal sliding mode control, includes: The steering angle control error of the steering wheel and the first derivative of the error are determined based on the desired steering angle and the estimated steering angle of the steering wheel. Construct a non-singular terminal sliding surface based on the steering angle control error of the steering wheel and the first derivative of the error; A Lyapukhov function is constructed based on the non-singular terminal sliding surface, and the parameter adaptive rate is obtained based on the Lyapukhov function. The total torque of the steering motor in the dual-motor steer-by-wire system is determined based on the adaptive rate of the parameters.

5. The method as described in claim 4, characterized in that, The formula for calculating the parameter adaptation rate is as follows: In the formula, The first derivative of the estimated value of the uncertain part of the system. , For controller parameters, For sliding surface, The equivalent rotational inertia of the system, For mapping functions, , This is an estimate of the uncertain part of the system. This represents the maximum value of the uncertain part of the system. It represents the minimum value of the uncertain part of the system.

6. A steering angle redundancy control system for a dual-motor steer-by-wire system based on the steering angle redundancy control method of any one of claims 1-5, characterized in that, The system includes: The acquisition module is used to acquire the vehicle's yaw rate, vehicle state parameters, steering motor failure state, and desired steering angle, and to filter the yaw rate and vehicle state parameters. The first determining module is used to determine the estimated value of the steering wheel steering angle of the dual-motor steer-by-wire system in the vehicle based on the filtered yaw rate and the vehicle state parameters. The second determining module is used to determine the total torque of the steering motor of the dual-motor steer-by-wire system based on the desired steering angle and the estimated steering wheel angle, and using an adaptive non-singular fast terminal sliding mode control method. The third determining module is used to determine the torque command value of each steering motor in the dual-motor steer-by-wire system by means of dynamic allocation based on the total torque of the steering motor and the failure state of the steering motor. The control module is used to drive the dual-motor steer-by-wire system to operate based on the torque command values ​​of each steering motor; The formula for calculating the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is as follows: In the formula, This is an estimated value for the steering angle of the steering wheel. Let B be the pseudo-inverse matrix of the second matrix. This represents the first derivative of the observed state variables obtained based on a two-degree-of-freedom vehicle model and an unknown input observer. Let A be the first derivative of the vehicle's yaw rate output by the system, and let A be the first matrix. Here are the estimated values ​​of the state variables, where, , This refers to the lateral stiffness of the front tire. For the lateral stiffness of the rear tire, For vehicle quality, For the longitudinal speed of the vehicle, This is the distance from the vehicle's center of gravity to the front axle. This is the distance from the vehicle's center of gravity to the rear axle. Let be the moment of inertia of the vehicle about the z-axis. These are state variables, including the sideslip angle and yaw rate. E is the third matrix; The determination of the torque command value of each steering motor in the dual-motor steer-by-wire system using a dynamic allocation method based on the total torque of the steering motors and the failure state of the steering motors includes: Using formula The torque command value of the first steering motor in the dual-motor steer-by-wire system is determined using the formula. Determine the torque command value of the second steering motor in the dual-motor steer-by-wire system; in, This is the torque command value for the first steering motor in a dual-motor steer-by-wire system. This refers to the torque command value of the second steering motor in a dual-motor steer-by-wire system. This represents the total torque of the steering motor. This indicates a failure state of the steering motor. This indicates that the steering motor is not malfunctioning. This indicates that the steering motor has failed.

7. The system as described in claim 6, characterized in that, The vehicle status parameters include: The current vehicle's center of gravity sideslip angle, vehicle mass, distance from the vehicle's center of gravity to the front axle, distance from the vehicle's center of gravity to the rear axle, vehicle longitudinal velocity, lateral stiffness of the front and rear tires, and vehicle's moment of inertia about the z-axis.

8. The system as described in claim 7, characterized in that, The first determining module is further configured to: A two-degree-of-freedom vehicle model is constructed based on the filtered vehicle state parameters. An unknown input observer is constructed based on the yaw rate of the vehicle after filtering. Based on the two-degree-of-freedom vehicle model and the unknown input observer, the estimated steering wheel angle of the dual-motor steer-by-wire system in the vehicle is determined.

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