Electric power steering system, control method and storage medium

Abstract

The invention discloses an electric power steering system which comprises a steering wheel, a steering machine and an EPS processing module, the EPS processing module is connected with the steering wheel to obtain a steering angle signal and a steering torque signal of the steering wheel, and the EPS processing module is connected with the steering machine to obtain an actual steering angle signal of the steering machine. The EPS processing module obtains a vehicle speed signal through a CAN bus. The electric power steering system is simple in switching logic, high in working stability, capable of guaranteeing good return performance and good in steering hand feeling.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile steering technology. BACKGROUND

[0002] The existing EPS control strategy usually adopts multi-mode switching mechanism such as assist control, damping control and return control, for example, the disclosure with the authorized announcement number CN114889688A and the authorized announcement date August 12, 2022, and the patent name of the steering damping control method based on the automobile EPS, the disclosed steering damping control method based on the automobile EPS, the vehicle is equivalent to a second-order system, the system time domain response function of the vehicle under the step input of the steering angle and the preset calibration atlas are used to calculate the output of the damping control.

[0003] The similar assist control mode has the following problems: 1. Complex mode switching logic: it needs to rely on multiple parameter thresholds such as vehicle speed, steering wheel angle, torque, etc. to judge, which has great calibration difficulty and long development cycle; 2. Inconsistent steering feel: the steering wheel torque and the vehicle steering motion intensity (such as lateral acceleration and steering wheel angle) lack a direct corresponding relationship, resulting in significant differences in driver experience under different working conditions; 3. Insufficient return performance: the traditional return control relies on vehicle speed parameterization adjustment, which is difficult to dynamically adapt to complex road conditions, and the return speed does not match the driver's expectation. SUMMARY

[0004] The technical problem to be solved by the present application is to realize an electric power steering system with unified EPS control through a motion double closed-loop control (position closed-loop + rate closed-loop) and a steering intensity feedback mechanism.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is: an electric power steering system, the steering system includes a steering wheel, a steering machine and an EPS processing module, the EPS processing module is connected to the steering wheel to obtain the steering wheel steering angle signal and the steering torque signal, the EPS processing module is connected to the steering machine to obtain the actual steering angle signal of the steering machine, and the EPS processing module obtains the vehicle speed signal through the CAN bus.

[0006] The EPS processing module has a steering system steering angle position control module for inputting the difference between the expected steering wheel angle and the actual angle, generating an initial expected angular velocity through a PID controller, the expected steering wheel angle is obtained from the steering wheel steering angle signal, and the actual angle difference is obtained from the actual steering angle signal of the steering machine.

[0007] The EPS processing module includes a steering system angular rate limit module, which dynamically calibrates the angular rate limit characteristics based on vehicle speed to limit the steering wheel angular velocity, and simultaneously adjusts the return-to-center speed according to vehicle speed. The return-to-center speed decreases as vehicle speed increases. The EPS processing module has a steering strength feedback module, which combines the steering torque signal and the vehicle speed signal, and calculates the desired steering motion intensity in real time through the vehicle chassis dynamic steady-state inverse characteristic mapping table. When the vehicle speed is lower than the set threshold, the table is looked up based on the steering wheel angle; when the vehicle speed is higher than the set threshold, the table is looked up based on the lateral acceleration.

[0008] The EPS processing module has an equivalent resistance torque compensation module, which is used to generate an equivalent steering resistance torque at the pinion based on the difference between the actual and the desired pinion angle, combined with the inverse dynamic dynamic characteristics of the steering system, and to perform closed-loop control through the target assist torque.

[0009] The steering wheel angle signal is collected by a steering wheel angle sensor on the steering wheel shaft, and the vehicle speed signal is collected by a vehicle speed sensor.

[0010] A control method for an electric power steering system includes the following steps: Step 1: Collect driver steering data in real time, including steering wheel angle δ. sv Vehicle speed v, steering wheel torque T sv ; Step 2: Obtain the desired steering motion intensity or desired lateral acceleration based on the steering data; Step 3: Based on the desired steering motion intensity or desired lateral acceleration, the desired angular velocity ω0 is output by the position closed-loop PID; Step 4: The rate closed-loop PID generates a compensation torque Ta based on the difference between the desired angular velocity and the actual angular velocity; Step 5: After superimposing the compensation torque Ta with the equivalent resistance torque, output the target current of the motor.

[0011] In step 3, the initial desired angular velocity ω0 is corrected to the desired angular velocity ω1 by the angular rate limit module.

[0012] The inverse dynamic characteristics of the vehicle chassis were calibrated through real vehicle tests, and a mapping table between the steering wheel angle and the pinion angle was constructed. The inverse dynamic characteristics of the steering system were calibrated through real vehicle tests, and a mapping table between the pinion angle and the equivalent resistance torque was constructed.

[0013] A storage medium, the storage medium being a computer-readable storage medium for storing software program code, the software program code being a control method for executing the electric power steering system.

[0014] The electric power steering system of this invention features a simplified switching logic, high operational stability, excellent self-centering performance, and good steering feel. Attached Figure Description

[0015] The following is a brief explanation of the content represented by each figure in this specification: Figure 1 This is a block diagram illustrating the principle of an electric power steering system. Detailed Implementation

[0016] The following description, with reference to the accompanying drawings, details the specific implementation of the present invention, including the shape and structure of each component, the relative positions and connections between the parts, the function and working principle of each part, the manufacturing process, and the operation and use methods, to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0017] This invention relates to an automotive electric power steering (EPS) system based on a dual-loop motion control mechanism and steering strength feedback. This optimizes the unified control of steering assist, damping, and self-centering performance, thereby improving steering feel and stability. The entire system achieves unified EPS control through dual-loop motion control (position closed loop + rate closed loop) and a steering strength feedback mechanism.

[0018] The EPS processing module includes the following functional modules: 1. Steering system angle position control module: Input the difference between the desired steering wheel angle and the actual steering angle, and the PID controller will generate the initial desired angular velocity to ensure accurate execution of the driving intention; 2. Steering system angular rate limit module: Based on the dynamic calibration of the vehicle speed angular rate limit characteristic field, the steering wheel angular velocity is limited to prevent high-speed steering instability. At the same time, the return speed is adjusted according to the vehicle speed to meet the driver's psychological expectations. The limit characteristic field is based on the dynamic calibration of the vehicle speed, and the return speed decreases as the vehicle speed increases.

[0019] 3. Steering strength feedback module: By combining steering wheel torque and vehicle speed, the desired steering motion intensity (low speed corresponds to steering wheel angle, high speed corresponds to lateral acceleration) is calculated in real time through the vehicle chassis dynamics steady-state inverse characteristic mapping table, ensuring a linear relationship between torque and motion intensity; 4. Equivalent resistance torque compensation module: Based on the difference between the actual and desired pinion angle, and combined with the inverse steady-state characteristics of the steering system dynamics, an equivalent steering resistance torque is generated at the pinion. Finally, closed-loop control is achieved through the target assist torque. The steering wheel torque is mapped to the desired steering motion intensity (δ) using the inverse steady-state characteristics of the vehicle chassis dynamics.p or a r ).

[0020] The electric power steering (EPS) system comprises multiple vehicle controller units. All these units are connected to the vehicle controller via the vehicle's CAN network. The vehicle controller processes and arbitrates its own data before sending the final result out through the CAN network. Specifically, the EPS processing module connects to the steering wheel to obtain steering angle and torque signals. It also connects to the steering gear to obtain the actual steering angle signal. The EPS processing module acquires the vehicle speed signal via the CAN bus. The steering wheel angle signal is collected by a steering wheel angle sensor on the steering shaft, and the vehicle speed signal is collected by a vehicle speed sensor.

[0021] The EPS processing module of the electric power steering system includes a storage medium, which is a computer-readable storage medium for storing software program code used to execute the control method of the electric power steering system. The control method of the electric power steering system includes the following steps: Step 1: Real-time acquisition of steering wheel angle δ sv Vehicle speed v, steering wheel torque T sv ; Step 2: Calculate the desired steering motion intensity (δ) using the steering strength feedback module. p Or lateral acceleration a r ); Step 3: The position closed-loop PID outputs the initial desired angular velocity ω0, which is then corrected to ω1 by the angular rate limit module; Step 4: The rate closed-loop PID generates a compensation torque T based on the difference between ω1 and the actual angular velocity. a The target current of the motor is output after superimposing the equivalent resistance torque; Calibration method: The inverse characteristics of chassis dynamics (steering wheel angle - pinion angle mapping) and steering system dynamics (pinion angle - equivalent resistance torque mapping) are calibrated through real vehicle tests to ensure model accuracy. That is, the steady-state inverse characteristics of chassis dynamics are calibrated through real vehicle tests to construct a mapping table of steering wheel angle and pinion angle, and the inverse characteristics of steering system dynamics are calibrated through real vehicle tests to construct a mapping table of pinion angle and equivalent resistance torque. The execution parameters can be obtained by looking up the table based on the real-time state values. The operation method is simple and reliable, and different mapping tables can be pre-set according to different vehicle models, resulting in higher matching degree.

[0022] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. An electric power steering system, characterized in that: The steering system includes a steering wheel, a steering gear, and an EPS processing module. The EPS processing module is connected to the steering wheel to obtain steering wheel steering angle signals and steering torque signals. The EPS processing module is connected to the steering gear to obtain steering gear actual steering angle signals. The EPS processing module obtains vehicle speed signals through the CAN bus.

2. The electric power steering system according to claim 1, characterized in that: The EPS processing module has a steering system angle position control module, which is used to input the difference between the desired steering wheel angle and the actual angle, and generate an initial desired angular velocity through a PID controller. The desired steering wheel angle is obtained from the steering wheel angle signal, and the actual angle difference is obtained from the steering gear actual angle signal.

3. The electric power steering system according to claim 2, characterized in that: The EPS processing module has a steering system angular rate limit module, which is used to dynamically calibrate the angular rate limit characteristics according to the vehicle speed, limit the steering wheel angular rate, and adjust the return speed according to the vehicle speed. The return speed of the angular rate limit characteristics decreases as the vehicle speed increases.

4. The electric power steering system according to claim 3, characterized in that: The EPS processing module has a steering strength feedback module, which combines the steering torque signal and the vehicle speed signal, and calculates the desired steering motion intensity in real time through the vehicle chassis dynamic steady-state inverse characteristic mapping table. When the vehicle speed is lower than the set threshold, the table is looked up based on the steering wheel angle; when the vehicle speed is higher than the set threshold, the table is looked up based on the lateral acceleration.

5. The electric power steering system according to claim 4, characterized in that: The EPS processing module has an equivalent resistance torque compensation module, which is used to generate an equivalent steering resistance torque at the pinion based on the difference between the actual and the desired pinion angle, combined with the inverse dynamic dynamic characteristics of the steering system, and to perform closed-loop control through the target assist torque.

6. The electric power steering system according to any one of claims 1-5, characterized in that: The steering wheel angle signal is collected by a steering wheel angle sensor on the steering wheel shaft, and the vehicle speed signal is collected by a vehicle speed sensor.

7. A control method for an electric power steering system, characterized in that, Includes the following steps: Step 1: Collect driver steering data in real time, including steering wheel angle δ. sv Vehicle speed v, steering wheel torque T sv ; Step 2: Obtain the desired steering motion intensity or desired lateral acceleration based on the steering data; Step 3: Based on the desired steering motion intensity or desired lateral acceleration, the desired angular velocity ω0 is output by the position closed-loop PID; Step 4: The rate closed-loop PID generates a compensation torque Ta based on the difference between the desired angular velocity and the actual angular velocity; Step 5: After superimposing the compensation torque Ta with the equivalent resistance torque, output the target current of the motor.

8. The electric power steering system according to claim 7, characterized in that: In step 3, the initial desired angular velocity ω0 is corrected to the desired angular velocity ω1 by the angular rate limit module.

9. The electric power steering system according to claim 7 or 8, characterized in that: The inverse dynamic characteristics of the vehicle chassis were calibrated through real vehicle tests, and a mapping table between the steering wheel angle and the pinion angle was constructed. The inverse dynamic characteristics of the steering system were calibrated through real vehicle tests, and a mapping table between the pinion angle and the equivalent resistance torque was constructed.

10. A storage medium, said storage medium being a computer-readable storage medium for storing software program code, characterized in that: The software program code is used to execute the control method of the electric power steering system as described in any one of claims 7-9.

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