Control method and device for steer-by-wire system and vehicle

Abstract

The invention relates to a control method and device for a steer-by-wire system and a vehicle, and the method comprises the following steps: S1, applying a preset excitation signal to a steering system of the vehicle, and collecting the state data of the vehicle; s2, training and optimizing a preset model based on the state data of the vehicle to obtain an identification model; s3, acquiring driving state data of the driving vehicle in real time, and inputting the driving state data into the recognition model to recognize nonlinear friction force existing in a steer-by-wire system of the driving vehicle; s4, a compensation strategy of the running vehicle is determined according to the nonlinear friction force, and the expected output torque of a motor of the running vehicle is obtained according to the compensation strategy; and S5, the output torque of the motor of the running vehicle is adjusted in real time based on the expected output torque of the motor so as to offset the nonlinear friction force of the steer-by-wire system of the running vehicle. The non-linear friction force in the steer-by-wire system is recognized and effectively compensated, and the steering hand feeling in the steering process can be improved.

Description

Technical Field

[0001] This specification relates to the field of automotive steering technology, and in particular to a control method, device, and vehicle for a steer-by-wire system. Background Technology

[0002] With the future development of autonomous driving technology for intelligent vehicles, steer-by-wire systems, by replacing the mechanical connection between the steering wheel and wheels with electrical signals, offer advantages such as improved vehicle spatial layout flexibility and enhanced driving comfort. This also allows for flexible design and personalized customization of steering characteristics (such as steering ratio, damping, and return torque). However, while freeing drivers from mechanical constraints, the absence of a physical connection between the steering wheel and wheels means drivers can no longer directly perceive road conditions and vehicle dynamics through traditional methods.

[0003] Steering feel is the force feedback felt by the driver when operating the steering wheel, conveying important information about road conditions and tire grip. In a steer-by-wire system, this steering feel is actively simulated and generated by a force feedback motor at the steering wheel end, also known as a road feel motor. However, friction issues within the upper column assembly of the steer-by-wire system can severely affect the accuracy of the steering feel simulation. This internal friction primarily originates from components such as bearings, seals, and gear meshing. This friction is not simple Coulomb friction but possesses complex nonlinear and hysteretic characteristics, resulting in an uneven steering feel for the driver when operating the steering wheel. This reduces the driving experience and negatively impacts the vehicle's handling stability. Summary of the Invention

[0004] This specification provides a control method, device, and vehicle for a steer-by-wire system to solve the problem in the prior art where the internal friction of the steer-by-wire system affects the driver's steering feel during steering.

[0005] The following technical solution is adopted in this specification: A control method for a steer-by-wire system includes the following steps: S1: Apply a preset excitation signal to the vehicle's steering system and collect the vehicle's state data; S2: Train and optimize the preset model based on the vehicle's state data to obtain a recognition model; S3: Real-time acquisition of driving status data of the vehicle and input of the driving status data into the recognition model to identify the nonlinear friction force existing in the steer-by-wire system of the vehicle; S4: Determine the compensation strategy for the vehicle based on the nonlinear friction force, and obtain the desired output torque of the motor of the vehicle based on the compensation strategy; S5: Adjust the output torque of the motor of the vehicle in real time based on the desired output torque of the motor to counteract the nonlinear friction force of the steer-by-wire system of the vehicle.

[0006] Based on the aforementioned technical means, by identifying and effectively compensating for the nonlinear friction in the steer-by-wire system, the lag and unevenness in the steering feel can be reduced, thereby providing the driver with a more realistic, natural, and consistent force feedback experience. This not only enhances the responsiveness of the steering system but also allows the driver to perceive the vehicle status and road information more intuitively, further improving driving comfort and steering feel.

[0007] This method applies a preset excitation to the steering system and collects state data to train and optimize the recognition model. This enables the model to identify the current nonlinear friction force in real time during vehicle operation and dynamically adjust the motor output torque based on the real-time identified nonlinear friction force to counteract the impact of nonlinear friction force on the driver's steering feel during steering, ensuring the accuracy and timeliness of the compensation.

[0008] Furthermore, the preset model in S2 is the Bouc-Wen model.

[0009] Based on the aforementioned technical means, the internal friction of the steer-by-wire system has complex nonlinear and hysteretic characteristics. The Bouc-Wen model is a classic and efficient mathematical model for describing hysteretic nonlinear phenomena. Using the Bouc-Wen model as the preset model can more accurately characterize the dynamic hysteretic behavior of friction force as the steering wheel angle and steering speed change.

[0010] Furthermore, in step S2, specifically, based on the vehicle's state data, a particle swarm optimization algorithm is used to identify the parameters of the Bouc-Wen model to obtain the identification model.

[0011] Based on the aforementioned technical means, the Bouc-Wen model is parameter identified using the particle swarm optimization algorithm. This allows for the rapid and accurate automatic identification of a set of optimal Bouc-Wen model parameters from measured state data, thereby efficiently constructing a high-fidelity identification model. This improves the accuracy of the identification model in identifying nonlinear friction forces in drive-by-wire systems. Furthermore, the adaptive global search capability of the particle swarm optimization algorithm reduces reliance on initial parameter values ​​and manual parameter tuning experience, enhancing the robustness of the entire parameter identification process, even in the face of individual differences in friction characteristics caused by different vehicles and different wear conditions.

[0012] Furthermore, the vehicle status data in S1 includes: the torque of the vehicle's steering wheel, the steering angle of the vehicle's steering wheel, and the rotational speed signal of the vehicle's steering wheel.

[0013] Furthermore, the adjustment of the motor's output torque in step S5 specifically employs a multi-loop PID control method.

[0014] Furthermore, the multi-loop PID control method includes the following steps: S51: Obtain the current difference between the motor current corresponding to the desired output torque and the current motor current, perform PID control calculation on the current difference, and output a pulse width modulation drive signal. S52: Obtain the voltage difference between the motor voltage corresponding to the desired output torque and the current motor voltage, perform PID control calculation on the voltage difference, and output a voltage control signal; S53: Combine the pulse width modulation drive signal and the voltage control signal to adjust the output torque of the motor of the vehicle.

[0015] Based on the aforementioned technical means, the current loop uses PID to quickly and accurately control the motor torque (because electromagnetic torque is directly related to current), ensuring dynamic tracking capability of the desired torque. Simultaneously, a voltage loop is introduced, which, through PID control of the voltage difference, effectively compensates for the effects of motor back EMF and resistance changes, stabilizing the armature voltage and providing a good voltage environment for the stable operation of the current loop. By combining the pulse width modulation drive signal and the voltage control signal to adjust the output torque of the vehicle's motor, decoupling and coordinated control of the motor's electrical and mechanical variables are achieved. This results in a final output torque that not only responds quickly but also has high steady-state accuracy and strong anti-disturbance capability, thereby more stably counteracting nonlinear friction and improving the smoothness and consistency of steering feel.

[0016] Furthermore, the preset excitation signal includes a sine wave signal or a frequency sweep signal.

[0017] Based on the above technical means, sinusoidal signals can systematically excite the frictional hysteresis loop of the system in periodic reciprocating motion at different frequencies and amplitudes, fully demonstrating the nonlinear law of frictional force changing with sinusoidal motion; while sweep frequency signals can excite the system in a continuous frequency band, effectively covering different steering speed conditions from low speed to high speed, thereby obtaining the frictional response of the system under different dynamic conditions.

[0018] Furthermore, the compensation strategy in S4 specifically involves adjusting the desired output torque of the motor so that the desired output torque of the motor is positively correlated with the nonlinear friction force of the steer-by-wire system of the vehicle.

[0019] Based on the above technical means, in the specific implementation process, when the system identifies a large frictional force that hinders steering, the control strategy will calculate a larger expected output torque of the motor to generate an additional active torque in the opposite direction to offset the resistance; conversely, the same applies. From the strategy level, it is ensured that the compensation action can accurately output the expected output torque of the motor according to the nonlinear frictional force of the steer-by-wire system of the vehicle, making the compensation purpose clear and the logic clear.

[0020] Furthermore, a friction compensation control device for a steer-by-wire system is also provided, for implementing the aforementioned control method for a steer-by-wire system, the device comprising: The system includes a data acquisition module, a data processing module, and a control module, wherein the data processing module is communicatively connected to both the data acquisition module and the control module. The data acquisition module is used to collect the vehicle's status data and transmit the vehicle's status data to the data processing module; The data processing module is used to receive and process the vehicle's status data to obtain a compensation strategy, and convert the compensation strategy into a control signal and transmit it to the control module. The control module is used to receive the control signal and control the output torque of the vehicle's motor according to the control signal.

[0021] Based on the above technical means, the data acquisition module is responsible for accurately acquiring relevant data, the data processing module focuses on model building, friction identification and compensation strategy formulation, and the control module converts the compensation strategy into actual control signals to act on the power assist motor. Each module has a clear division of labor and works in concert. By collecting data in real time, identifying friction, and formulating and implementing compensation strategies, a closed-loop feedback system is formed, which can continuously adapt to various changes in the vehicle's driving process to ensure that the steering feel remains uniform at all times.

[0022] Furthermore, a vehicle is also provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the aforementioned control method for a steer-by-wire system.

[0023] The above-mentioned technical solutions adopted in this specification can achieve the following beneficial effects: 1. By identifying and effectively compensating for nonlinear friction in the steer-by-wire system, the lag and unevenness in steering feel can be reduced, thus providing the driver with a more realistic, natural and consistent force feedback experience. This not only enhances the responsiveness of the steering system but also allows the driver to perceive the vehicle status and road information more intuitively, further improving driving comfort and steering feel.

[0024] 2. This method applies a preset excitation to the steering system and collects state data to train and optimize the recognition model. This enables the recognition model to identify the current nonlinear friction force in real time during vehicle operation and dynamically adjust the motor output torque accordingly to counteract its influence, ensuring the accuracy and timeliness of the compensation. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of this specification and form part of this specification, illustrate exemplary embodiments and are used to explain this specification, but do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a flowchart illustrating the first embodiment of the present invention. Figure 2 This is a flowchart of the multi-loop PID control algorithm in this embodiment.

[0026] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent. To better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The same or similar reference numerals correspond to the same or similar components. The terms describing positional relationships in the drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this specification clearer, the technical solutions of this specification will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments in this specification without creative effort are within the scope of protection of this application.

[0028] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0030] In the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0031] In the embodiments of this application, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium.

[0032] In embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0033] The technical solutions provided in the various embodiments of this specification are described in detail below with reference to the accompanying drawings.

[0034] Example 1 like Figure 1 As shown, this embodiment provides a control method for a steer-by-wire system, including the following steps: S1: Apply a preset excitation signal to the vehicle's steering system and collect the vehicle's state data; In this embodiment, the vehicle's status data includes the steering wheel torque, the steering wheel angle, and the steering wheel rotation speed signal.

[0035] In this embodiment, the preset excitation signal includes a sine wave signal or a frequency sweep signal.

[0036] like Figure 1 As shown, in this embodiment, S2: The preset model is trained and optimized based on the vehicle's state data to obtain a recognition model; In this embodiment, the preset model is specifically the Bouc-Wen model.

[0037] In this embodiment, the Bouc-Wen model can accurately describe the nonlinear hysteresis characteristics, and its expression is as follows: , in, Represents the magnitude of macroscopic sliding friction. This indicates the influence of the stiffness of the interconnected protrusions at zero relative velocity during micro-slip. Controlling the shape of the hysteresis loop and the micro-sliding displacement, Controlling the smoothness of the transition curve from micro-sliding to macro-sliding, in order to The use of dimensionless variables instead of the sign function in traditional friction models allows the model to more accurately simulate the frictional characteristics of microscopic sliding processes. This indicates the steering wheel angle.

[0038] In this preferred embodiment, S2 specifically involves: using a particle swarm optimization algorithm to identify the parameters of the Bouc-Wen model based on the vehicle's state data, in order to obtain the identification model.

[0039] In this embodiment, the parameters in the model are used to identify the nonlinear characteristics of the Bouc-Wen model; they are not obtained directly and need to be identified.

[0040] In other embodiments, other methods can be used to identify the parameters of the Bouc-Wen model.

[0041] like Figure 1 As shown, in this embodiment, S3: Real-time acquisition of driving status data of the vehicle, and input of the driving status data into the recognition model to identify the nonlinear friction force existing in the steer-by-wire system of the vehicle; In this embodiment, the nonlinear friction force is specifically the internal friction of the upper column of the steering-by-wire system.

[0042] like Figure 1 As shown, in this embodiment, S4: determine the compensation strategy of the vehicle based on the nonlinear friction force, and obtain the desired output torque of the motor of the vehicle based on the compensation strategy.

[0043] In this embodiment, the compensation strategy in S4 is specifically as follows: adjust the desired output torque of the motor so that the desired output torque of the motor is positively correlated with the nonlinear friction force of the steer-by-wire system of the vehicle.

[0044] In this preferred embodiment, the principle of the compensation strategy is as follows: First, let's explain the principle of model-based compensation torque calculation. It mainly involves integrating the offline-identified nonlinear Bouc-Wen friction model into the control model of the steer-by-wire system. During actual operation, the current steering input (steering wheel angle, speed, etc.) is used to calculate the estimated value of the friction torque in real time using the Bouc-Wen model. This estimated value is the compensation torque that needs to be used to counteract the internal friction of the upper column of the steer-by-wire system.

[0045] Secondly, regarding the explanation of the compensation strategy, since steer-by-wire disconnects the mechanical link of the intermediate shaft, the road feel simulation of steer-by-wire will depend entirely on the torque simulation of the road feel motor (i.e., the motor on the steering column). The simulated torque of the road feel motor is generally divided into several parts: basic assist torque, self-centering torque, inertia compensation torque, friction compensation torque, etc. The nonlinear friction torque from this patent is incorporated into this multi-torque fusion. Weighting coefficients can be designed to distribute the components of each torque, ensuring that each component can work in coordination under different operating conditions, ultimately achieving the ideal road feel torque output from the road feel motor.

[0046] like Figure 1 As shown, in this embodiment, S5: The output torque of the motor of the driving vehicle is adjusted in real time based on the desired output torque of the motor to counteract the nonlinear friction force of the steer-by-wire system of the driving vehicle.

[0047] In this embodiment, the adjustment of the motor's output torque specifically employs a multi-loop PID (Proportion-Integral-Derivative) control method.

[0048] like Figure 2 As shown, in this embodiment, the multi-loop PID control method specifically includes the following steps: S51: Obtain the current difference between the motor current corresponding to the desired output torque and the current motor current, perform PID control calculation on the current difference, and output a pulse width modulation drive signal. S52: Obtain the voltage difference between the motor voltage corresponding to the desired output torque and the current motor voltage, perform PID control calculation on the voltage difference, and output a voltage control signal; S53: Combine the pulse width modulation drive signal and the voltage control signal to adjust the output torque of the motor of the vehicle.

[0049] In this embodiment, the current loop uses PID to quickly and accurately control the motor torque (because electromagnetic torque is directly related to current), ensuring dynamic tracking capability of the desired torque. Simultaneously, a voltage loop is introduced, which, through PID control of the voltage difference, effectively compensates for the effects of motor back EMF and resistance changes, stabilizing the armature voltage and providing a good voltage environment for the stable operation of the current loop. By combining the pulse width modulation drive signal and the voltage control signal to adjust the output torque of the vehicle's motor, decoupling and coordinated control of the motor's electrical and mechanical variables are achieved. This results in a final output torque that is not only responsive but also has high steady-state accuracy and strong anti-disturbance capability, thereby more stably counteracting nonlinear friction and improving the smoothness and consistency of steering feel.

[0050] In summary, this embodiment significantly reduces the lag and unevenness of steering feel by identifying and compensating for nonlinear friction in the steer-by-wire system, providing the driver with a more realistic, natural, and consistent force feedback experience, enhancing driving comfort and handling intuition. By applying preset excitation to the steering system and collecting state data, the recognition model is trained and optimized, enabling the model to identify the current nonlinear friction in real time during vehicle operation and dynamically adjust the motor output torque accordingly to counteract its effects, ensuring the accuracy and timeliness of the compensation.

[0051] Example 2 This embodiment is similar to Embodiment 1, and the same parts are described in Embodiment 2. The following description only focuses on the improved parts.

[0052] This embodiment provides a friction compensation control device for a steer-by-wire system, used to implement a control method for a steer-by-wire system as described in Embodiment 1. The device includes: The system includes a data acquisition module, a data processing module, and a control module, wherein the data processing module is communicatively connected to both the data acquisition module and the control module. The data acquisition module is used to collect the vehicle's status data and transmit the vehicle's status data to the data processing module; The data processing module is used to receive and process the vehicle's status data to obtain a compensation strategy, and convert the compensation strategy into a control signal and transmit it to the control module. The control module is used to receive the control signal and control the output torque of the vehicle's motor according to the control signal.

[0053] In this embodiment, the data acquisition module is responsible for accurately acquiring relevant data, the data processing module focuses on model building, friction identification, and compensation strategy formulation, and the control module converts the compensation strategy into actual control signals to act on the power assist motor. Each module has a clear division of labor and works in concert. By collecting data in real time, identifying friction, and formulating and implementing compensation strategies, a closed-loop feedback system is formed, which can continuously adapt to various changes during vehicle operation and ensure that the steering feel remains uniform at all times.

[0054] Example 3 This embodiment is similar to Embodiment 1, and the same parts are described in Embodiment 2. The following description only focuses on the improved parts.

[0055] This embodiment provides a vehicle, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. The processor executes the program to implement the control method for a steer-by-wire system described in Embodiment 1.

[0056] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A control method for a steer-by-wire system, characterized in that, Includes the following steps: S1: Apply a preset excitation signal to the vehicle's steering system and collect the vehicle's state data; S2: Train and optimize the preset model based on the vehicle's state data to obtain a recognition model; S3: Real-time acquisition of driving status data of the vehicle and input of the driving status data into the recognition model to identify the nonlinear friction force existing in the steer-by-wire system of the vehicle; S4: Determine the compensation strategy for the vehicle based on the nonlinear friction force, and obtain the desired output torque of the motor of the vehicle based on the compensation strategy; S5: Adjust the output torque of the motor of the vehicle in real time based on the desired output torque of the motor to counteract the nonlinear friction force of the steer-by-wire system of the vehicle.

2. The control method for a steer-by-wire system according to claim 1, characterized in that, The preset model in S2 is the Bouc-Wen model.

3. The control method for a steer-by-wire system according to claim 2, characterized in that, Specifically, in S2, based on the vehicle's state data, a particle swarm optimization algorithm is used to identify the parameters of the Bouc-Wen model in order to obtain the identification model.

4. The control method for a steer-by-wire system according to claim 3, characterized in that, The vehicle status data in S1 includes: the torque of the vehicle's steering wheel, the steering angle of the vehicle's steering wheel, and the speed signal of the vehicle's steering wheel.

5. The control method for a steer-by-wire system according to claim 1, characterized in that, The adjustment of the motor's output torque in S5 specifically employs a multi-loop PID control method.

6. A control method for a steer-by-wire system according to claim 5, characterized in that, The multi-loop PID control method includes the following steps: S51: Obtain the current difference between the motor current corresponding to the desired output torque and the current motor current, perform PID control calculation on the current difference, and output a pulse width modulation drive signal. S52: Obtain the voltage difference between the motor voltage corresponding to the desired output torque and the current motor voltage, perform PID control calculation on the voltage difference, and output a voltage control signal; S53: Combine the pulse width modulation drive signal and the voltage control signal to adjust the output torque of the motor of the vehicle.

7. The control method for a steer-by-wire system according to claim 1, characterized in that, The preset excitation signal in S1 includes a sine wave signal or a frequency sweep signal.

8. The control method for a steer-by-wire system according to claim 1, characterized in that, The compensation strategy in S4 specifically involves adjusting the desired output torque of the motor so that the desired output torque of the motor is positively correlated with the nonlinear friction force of the steer-by-wire system of the vehicle.

9. A friction compensation control device for a steer-by-wire system, characterized in that, For implementing a control method for a steer-by-wire system as described in any one of claims 1-8, the apparatus comprises: The system includes a data acquisition module, a data processing module, and a control module, wherein the data processing module is communicatively connected to both the data acquisition module and the control module. The data acquisition module is used to collect the vehicle's status data and transmit the vehicle's status data to the data processing module; The data processing module is used to receive and process the vehicle's status data to obtain a compensation strategy, and convert the compensation strategy into a control signal and transmit it to the control module. The control module is used to receive the control signal and control the output torque of the vehicle's motor according to the control signal.

10. A vehicle, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the program to implement a control method for a steer-by-wire system as described in any one of claims 1-8.

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