An EPS control strategy based on double closed loop of steering system motion

Abstract

The application discloses an EPS control strategy based on a double closed loop of steering system motion, which is composed of a steering system rotation angle position control module, a steering system angular velocity limit value module and a steering system rotation angle velocity control module. sw The steering system rotation angle position control module inputs the difference between the expected steering wheel rotation angle and the actual steering wheel rotation angle δ The steering system angular velocity limit value module limits the expected steering wheel angular velocity through a calibrated steering system angular velocity limit value characteristic field. According to the steering wheel rotation angle and the vehicle speed during steering, the steering system angular velocity is determined, the steering system angular velocity limit value module is designed, the return speed is changed with the vehicle speed, and the return performance under various working conditions is more in line with the expectation of the driver.

Description

Technical Field

[0001] This invention relates to the field of electric power steering technology, and in particular to an EPS control strategy based on a dual closed-loop motion control system for the steering system. Background Technology

[0002] Electric power steering (EPS) systems use an electric motor to provide steering assistance, reducing the driver's effort during steering and thus improving vehicle handling and comfort. Compared to traditional hydraulic power steering systems, EPS is widely used in modern automobiles due to its higher energy efficiency and faster response. For vehicle steering, high-quality steering return performance can improve driving comfort.

[0003] Chinese invention patent CN107161208A discloses an active return-to-center control method for an automotive electric power steering system. This method implements active return-to-center control by establishing a Simulink model. The steering angle and torque signals obtained from torque and angle sensors are used as system inputs. When the torque signal is less than a calibrated torque threshold, no return-to-center operation is performed; when it is greater than or equal to the threshold, return-to-center control begins. The final return-to-center torque is used as the system output. This invention employs dual PI control, resulting in higher accuracy for active return-to-center control. However, this control method requires a significant amount of calibration work.

[0004] Chinese invention patent CN116788347A discloses an active self-centering control method and an electric power steering system. The method includes: acquiring actual vehicle data, including actual vehicle speed and actual steering wheel angle; acquiring a first target self-centering speed and a smoothed second target self-centering speed based on the actual vehicle speed and the actual steering wheel angle; and performing active self-centering control based on the second target self-centering speed. This method can achieve a balance between minimizing the residual self-centering angle after the steering wheel passes the center position and avoiding sudden changes in steering torque after the steering wheel passes the center position. However, this control method does not consider the relationship between the self-centering speed and vehicle speed changes during the self-centering process, making it difficult for the self-centering effect to meet the driver's psychological expectations. Summary of the Invention

[0005] The purpose of this invention is to study the relationship between the return-to-center speed and vehicle speed in current electric power steering (EPS) vehicles, thereby obtaining the steering return-to-center speed desired by the driver. To address the aforementioned problems, this invention proposes an EPS control strategy based on a dual closed-loop steering system motion, which makes the vehicle's return-to-center speed vary with vehicle speed, thus improving the vehicle's return-to-center quality.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An EPS control strategy based on a dual closed-loop motion of the steering system consists of a steering system angular position control module, a steering system angular rate limit module, and a steering system angular rate control module.

[0008] Steering system angle position control module: Uses a PID controller to perform closed-loop control of the steering system angle position, inputting the desired steering wheel angle. and actual steering wheel angle The difference is used to obtain the desired steering wheel angular velocity. This ensures that the driver's intentions are accurately executed;

[0009] Steering system angular rate limit module: ensures that the driver cannot turn too fast when turning outwards, preventing the car from entering an unstable state; at the same time, it ensures that the return speed of the steering wheel when returning to center is within the driver's psychological safety zone, preventing the driver from feeling uncomfortable;

[0010] Steering system angular rate control module: After determining the desired limit steering wheel angular rate, a PID controller is used to perform closed-loop control of the steering system angular rate, inputting the desired limit steering wheel angular rate. and actual steering wheel angular velocity The difference is used to obtain the desired compensation torque. This enables the vehicle to steer precisely, improving its stability and comfort.

[0011] As a further technical solution of the present invention: the steering system angular rate limit module is jointly determined by vehicle steering stability constraints and driver comfort constraints, and is a characteristic field jointly determined by vehicle speed and steering wheel angle.

[0012] As a further technical solution of the present invention: the steering system angular rate control module achieves control by adjusting the parameters of the dual-loop PID and the steering system angular rate limit value. Control to ensure return-to-center speed characteristics and steering compensation torque. With steering wheel torque The difference is the steering assist torque. .

[0013] As a further technical solution of the present invention, it includes the following steps:

[0014] Step 1: Input the steering wheel angle and speed signals, and obtain the steering wheel angular velocity through the steering system angle position control module;

[0015] Step 2: Calibrate the characteristic field of the steering system's angular rate limit;

[0016] Step 3: After determining the desired steering system angular rate limit, the desired compensation torque is obtained through the steering system angular rate control module. Power limiting control is performed using the PID output saturation circuit. The steering system's operating power is limited based on the rated power of the vehicle's power steering motor to prevent the motor from failing to provide the required assistance.

[0017] Step 4: After obtaining the steering compensation torque, the difference between the steering compensation torque and the steering wheel torque is the steering assist torque.

[0018] As a further technical solution of the present invention: step two specifically includes:

[0019] Step 1: With the actual vehicle traveling at longitudinal speeds of 0 km / h, 10 km / h, and 20 km / h, rotate the steering wheel to 0°, 30°, 60°, and so on, with a sampling interval of 30° until the maximum steering wheel angle at which the car does not become unstable at that speed.

[0020] Step 2: At longitudinal speeds of 40km / h, 60km / h, and 80km / h, rotate the steering wheel to 0°, 10°, 30°, ... with a sampling interval of 10° until the maximum steering wheel angle at which the car does not become unstable at that speed.

[0021] Step 3: At longitudinal speeds of 100km / h and 120km / h, rotate the steering wheel to 0°, 5°, 10°... with a sampling interval of 5° until the maximum steering wheel angle at which the car does not become unstable at that speed.

[0022] Step 4: Release the steering wheel input torque and return the steering wheel to the center area;

[0023] Step 5: Collect data on steering wheel return speed at different longitudinal speeds and different steering wheel angles;

[0024] Step 6: Obtain the steering system angular rate limit through the above steps.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. This invention solves the problem that the return-to-center control strategy of electric power steering system can make the return-to-center speed change with the vehicle speed, thereby improving the return-to-center quality of the vehicle.

[0027] 2. This invention determines the steering system angular rate based on the steering wheel angle and vehicle speed during steering. By designing a steering system angular rate limit module, the return speed varies with the vehicle speed, making the return performance under various working conditions more in line with the driver's expectations. Attached Figure Description

[0028] Figure 1This is a schematic diagram of the EPS control strategy implementation scheme based on the dual closed loop motion of the steering system described in this invention;

[0029] Figure 2 This is a diagram of the steering system angle position control architecture described in this invention;

[0030] Figure 3 This is a diagram of the steering system angle rate control architecture described in this invention. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figures 1-3 As shown, an EPS control strategy based on a dual closed-loop steering system motion comprises a steering system angle position control module, a steering system angle rate limit module, and a steering system angle rate control module. The steering system angle position control module receives the desired steering wheel angle as input. and actual steering wheel angle The difference is used to obtain the desired steering wheel angular velocity; the steering system angular rate limit module limits the desired steering wheel angular velocity through the calibrated steering system angular rate limit characteristic field; after determining the desired limit steering wheel angular velocity, the steering system angular rate control module uses a PID controller to perform closed-loop control of the steering system angular rate, inputting the desired limit steering wheel angular velocity. and actual steering wheel angular velocity The difference is used to obtain the desired compensation torque. Steering compensation torque With steering wheel torque The difference is the steering assist torque. This enables the vehicle to steer precisely.

[0033] Table 1: Symbol Parameter Description Table

[0034]

[0035] Step 1: Input the steering wheel angle and speed signals, and obtain the steering wheel angular velocity through the steering system angle position control module.

[0036] Step 2: Calibrate the steering system's angular rate limit characteristic field, as follows:

[0037] (1) At longitudinal speeds of 0 km / h, 10 km / h, and 20 km / h, the steering wheel is turned to 0°, 30°, 60°, etc., with a sampling interval of 30° until the maximum steering wheel angle at which the car does not become unstable at that speed;

[0038] (2) At longitudinal speeds of 40km / h, 60km / h, and 80km / h, the steering wheel is turned to 0°, 10°, 30°, etc., with a sampling interval of 10° until the maximum steering wheel angle at which the car does not become unstable at that speed;

[0039] (3) At longitudinal speeds of 100km / h and 120km / h, the steering wheel is turned to 0°, 5°, 10°... with a sampling interval of 5° until the maximum steering wheel angle at which the car does not become unstable at that speed;

[0040] (4) Remove the steering wheel input torque and return the steering wheel to the center area;

[0041] (5) Collect data on steering wheel return speed under different longitudinal speeds and different steering wheel angles.

[0042] The steering system angular rate limit is obtained through the above steps.

[0043] Step 3: After determining the desired steering system angular rate limit, the desired compensation torque is obtained through the steering system angular rate control module. Power limiting control is performed using the PID output saturation circuit. The steering system's operating power is limited based on the rated power of the vehicle's power steering motor to prevent the motor from failing to provide the required assistance.

[0044] Step 4: After obtaining the steering compensation torque, the difference between the steering compensation torque and the steering wheel torque is the steering assist torque.

[0045] It should be understood that although the steps in the flowcharts of the various embodiments of the present invention are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the various embodiments may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least a portion of the sub-steps or stages of other steps.

[0046] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0047] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An EPS control strategy based on a dual closed-loop motion control system for steering systems, characterized in that, It consists of a steering system angle position control module, a steering system angle rate limit module, and a steering system angle rate control module; Steering system angle position control module: Uses a PID controller to perform closed-loop control of the steering system angle position, inputting the desired steering wheel angle. and actual steering wheel angle The difference is used to obtain the desired steering wheel angular velocity. This ensures that the driver's intentions are accurately executed; Steering system angular rate limit module: ensures that the driver cannot turn too fast when turning outwards, preventing the car from entering an unstable state; at the same time, it ensures that the return speed of the steering wheel when returning to center is within the driver's psychological safety zone, preventing the driver from feeling uncomfortable; Steering system angular rate control module: After determining the desired limit steering wheel angular rate, a PID controller is used to perform closed-loop control of the steering system angular rate, inputting the desired limit steering wheel angular rate. and actual steering wheel angular velocity The difference is used to obtain the desired compensation torque. This enables the vehicle to steer precisely, improving its stability and comfort. It also includes the following steps: Step 1: Input the steering wheel angle and speed signals, and obtain the steering wheel angular velocity through the steering system angle position control module; Step 2: Calibrate the characteristic field of the steering system's angular rate limit; Step 3: After determining the desired steering system angular rate limit, the desired compensation torque is obtained through the steering system angular rate control module. Power limiting control is performed using the PID output saturation circuit. The steering system's operating power is limited based on the rated power of the vehicle's power steering motor to prevent the motor from failing to provide the required assistance. Step 4: After obtaining the steering compensation torque, the difference between the steering compensation torque and the steering wheel torque is the steering assist torque; Step two specifically includes: Step 1: With the actual vehicle traveling at longitudinal speeds of 0 km / h, 10 km / h, and 20 km / h, rotate the steering wheel to 0°, 30°, 60°, and so on, with a sampling interval of 30° until the maximum steering wheel angle at which the car does not become unstable at that speed. Step 2: At longitudinal speeds of 40km / h, 60km / h, and 80km / h, rotate the steering wheel to 0°, 10°, 30°, ... with a sampling interval of 10° until the maximum steering wheel angle at which the car does not become unstable at that speed. Step 3: At longitudinal speeds of 100km / h and 120km / h, rotate the steering wheel to 0°, 5°, 10°... with a sampling interval of 5° until the maximum steering wheel angle at which the car does not become unstable at that speed. Step 4: Release the steering wheel input torque and return the steering wheel to the center area; Step 5: Collect data on steering wheel return speed at different longitudinal speeds and different steering wheel angles; Step 6: Obtain the steering system angular rate limit through the above steps.

2. The EPS control strategy based on a dual closed-loop motion control of the steering system according to claim 1, characterized in that, The steering system angular rate limit module is determined by both vehicle steering stability constraints and driver comfort constraints, and is a characteristic field determined by vehicle speed and steering wheel angle.

3. The EPS control strategy based on a dual closed-loop motion control of the steering system according to claim 1, characterized in that, The steering system angular rate control module adjusts the parameters of the dual-loop PID controller and the steering system angular rate limit value to achieve [control / control]. Control to ensure return-to-center speed characteristics and steering compensation torque. With steering wheel torque The difference is the steering assist torque .

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