A method for active return control of an electric power steering system
By using a two-stage active return torque calculation method and a lookup table and coefficient table to control EPS in stages, the problem that the active return control method of EPS cannot simultaneously take into account the return accuracy and calibration efficiency is solved. This achieves optimization of steering feel and stability under all working conditions and improves calibration efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHAANXI FAST AUTO DRIVE GRP CO LTD
- Filing Date
- 2025-12-30
- Publication Date
- 2026-07-21
AI Technical Summary
Existing EPS active alignment control methods cannot balance alignment accuracy and calibration efficiency, increasing calibration cycle and difficulty, relying on engineer experience, and affecting batch calibration efficiency.
A two-stage active self-centering torque calculation method is adopted. The EPS controller receives vehicle speed, steering wheel angle and hand force signals in real time. The system uses lookup tables and coefficient tables for staged control, including the first self-centering stage and the second self-centering stage. The coefficients are calculated and filtered to optimize the control process.
It achieves optimized steering feel and stability under all working conditions, reduces calibration workload, improves calibration efficiency, avoids vibration and overshoot, is applicable to simple calibration of the same type of vehicle, and ensures accurate return to center.
Smart Images
Figure CN121573063B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the automotive field and relates to electric power steering methods, specifically an active return-to-center control method for an electric power steering system. Background Technology
[0002] In recent years, electric power steering (EPS) systems have been widely used in automobiles, with almost all passenger cars now using them and commercial vehicles gradually adopting them as well. In the future, hydraulic power steering (HPS) and electro-hydraulic power steering (EHPS) will gradually be replaced. With the increasing popularity of EPS, people's demands for it are constantly rising, requiring fast dynamic response, good stability, and strong anti-interference capabilities.
[0003] Active self-centering is a fundamental function of EPS (Electric Power Steering). At low speeds, the vehicle experiences greater frictional torque, making insufficient self-centering easy. At high speeds, the large moment of inertia leads to overshooting during self-centering. To address the issues of insufficient self-centering at low speeds and overshooting at high speeds, researchers have proposed numerous control methods. Traditional methods primarily rely on looking up the self-centering torque in tables for different vehicle speeds. Currently, a more popular method is PID control, which uses closed-loop PID control of the steering wheel angle and angular velocity to manage the entire self-centering process.
[0004] Currently, there are many control methods for EPS active homing, and the control process is becoming increasingly complex. To some extent, these methods have solved the problems of insufficient homing at low speeds and overshooting at high speeds. However, new problems have also emerged, such as increased calibration cycles and difficulty, reliance on engineers' experience, and a significant impact on the efficiency of batch calibration of EPS. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide an active return-to-center control method for electric power steering systems, thereby solving the technical problem that existing EPS active return-to-center control methods cannot simultaneously achieve return-to-center accuracy and calibration efficiency.
[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0007] A method for calculating the active return torque of an electric power steering system, the electric power steering system including an EPS controller and a CAN bus TAS sensor connected to it, the electric power steering system obtaining a first return torque lookup table, a first return coefficient lookup table, a second return torque lookup table, and a second return coefficient lookup table through vehicle calibration experiments; based on the specific steps:
[0008] Step 1: The EPS controller receives the vehicle speed signal from the CAN bus and the steering wheel angle from the TAS sensor in real time. Steering wheel angular velocity and steering wheel hand force signals;
[0009] Step 2, based on the vehicle's current speed signal and steering wheel angle... The first positive torque is obtained by consulting the first positive torque lookup table. Based on the hand force signal and steering wheel angular velocity under the current operating conditions of the vehicle. The first positive coefficient is obtained by querying the first positive coefficient lookup table. ; the first positive torque With the first positive coefficient Multiplying them together yields the first stage of the return torque. ;
[0010]
[0011] Step 3: Determine if the vehicle's current operating condition simultaneously meets the following three conditions. If yes, proceed to Step 4; otherwise, adjust the first-stage return torque. As the total return torque ;
[0012]
[0013] Step 4: Adjust the steering wheel angle according to the vehicle's current operating conditions. By consulting the second positive torque lookup table based on the steering wheel angular velocity, the second positive torque can be obtained. The second positive coefficient is obtained by consulting the second positive coefficient lookup table based on the vehicle speed signal under the current operating conditions. ; the second return torque With the second positive coefficient Multiplying them together yields the second-stage return torque. ;
[0014]
[0015] Step 5, adjust the first stage return torque. Second stage return torque Adding them together, we get the total return torque. ;
[0016] .
[0017] This invention also includes the following technical features:
[0018] In steps 2 and 4, the first positive coefficient is respectively... Second positive coefficient Perform filtering.
[0019] Compared with the prior art, the beneficial technical effects of this invention are:
[0020] (I) In the first return-to-center stage, it is only necessary to clarify the two predetermined relationships of the first return-to-center stage and return the steering wheel to a general range, which reduces the workload of the traditional table lookup calibration method. In the second return-to-center stage, the second return-to-center torque is added, which can ensure that the return-to-center is in place and the return-to-center residual angle is small, realizing precise control of small angles. At this time, the angle and angular velocity are not large, and the calibrated torque is not large, which is easy to control and is not prone to shaking and overshoot. It overcomes the defects of the traditional fixed return-to-center torque strategy, which is too sensitive at high speed and insufficient return-to-center force at low speed. It realizes the optimization of steering feel and stability under all working conditions and solves the technical problem that the control method of EPS active return-to-center in the prior art cannot take into account both return-to-center accuracy and calibration efficiency.
[0021] (II) Although the two-stage active homing control method still relies on the traditional table lookup method, it has reasonably decomposed the homing process, reduced the calibration workload, and improved efficiency. Attached Figure Description
[0022] Figure 1 This is a flowchart of the method of the present invention;
[0023] Figure 2 This is a signal flow diagram for the EPS controller.
[0024] Figure 3 This is a graph showing the relationship between vehicle speed signal, steering wheel angle, and first return torque in this invention.
[0025] Figure 4 This is a diagram showing the relationship between the hand force signal, the steering wheel, and the first return coefficient in this invention.
[0026] Figure 5 This is a graph showing the relationship between the steering wheel angle, steering wheel angular velocity, and second return torque in this invention.
[0027] Figure 6 This is a graph showing the relationship between the vehicle speed signal and the second positive coefficient in this invention.
[0028] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation
[0029] It should be noted that, unless otherwise specified, all components in this invention are those known in the art.
[0030] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.
[0031] This invention provides a method for calculating the active return torque of an electric power steering (ESP) system. The ESP system includes an EPS controller and a CAN bus TAS sensor connected to it. The ESP system obtains a first return torque lookup table, a first return coefficient lookup table, a second return torque lookup table, and a second return coefficient lookup table through vehicle calibration experiments. The method specifically includes the following steps:
[0032] Step 1: The EPS controller receives the vehicle speed signal from the CAN bus and the steering wheel angle from the TAS sensor in real time. Steering wheel angular velocity and steering wheel hand force signals;
[0033] Step 2, based on the vehicle's current speed signal and steering wheel angle... The first positive torque is obtained by consulting the first positive torque lookup table. Based on the hand force signal and steering wheel angular velocity under the current operating conditions of the vehicle. The first positive coefficient is obtained by querying the first positive coefficient lookup table. ; the first positive torque With the first positive coefficient Multiplying them together yields the first stage of the return torque. ;
[0034]
[0035] Step 3: Determine if the vehicle's current operating condition simultaneously meets the following three conditions. If yes, proceed to Step 4; otherwise, adjust the first-stage return torque. As the total return torque ;
[0036]
[0037] Step 4: Adjust the steering wheel angle according to the vehicle's current operating conditions. By consulting the second positive torque lookup table based on the steering wheel angular velocity, the second positive torque can be obtained. The second positive coefficient is obtained by consulting the second positive coefficient lookup table based on the vehicle speed signal under the current operating conditions. ; the second return torque With the second positive coefficient Multiplying them together yields the second-stage return torque. ;
[0038]
[0039] Step 5, adjust the first stage return torque. Second stage return torque Adding them together, we get the total return torque. ;
[0040] .
[0041] In the above technical solution, in the first return-to-center stage, it is only necessary to clarify the two predetermined relationships of the first return-to-center stage and return the steering wheel to a general range, reducing the workload of the traditional table lookup calibration method. In the second return-to-center stage, the second return-to-center torque is added, which can ensure that the return-to-center is in place and the return-to-center residual angle is small, realizing precise control of small angles. At this time, the angle and angular velocity are not large, and the calibrated torque is not large, which is easy to control and less likely to cause shaking and overshoot. It overcomes the defects of the traditional fixed return-to-center torque strategy, which is too sensitive at high speed and insufficient return-to-center force at low speed. It achieves optimization of steering feel and stability under all working conditions and solves the technical problem that the existing EPS active return-to-center control method cannot take into account both return-to-center accuracy and calibration efficiency.
[0042] The calibration-obtained lookup tables for the first return torque, first return coefficient, second return torque, and second return coefficient are shown in Tables 1-4. Table 1 aims to return the steering wheel to a general angle range and does not require high precision. Tables 2 and 4 primarily prevent excessive second return torque, which could lead to overshoot at high speeds. For the same vehicle type, only one calibration is needed, significantly reducing the calibration workload and improving efficiency while maintaining a relatively consistent return-to-center effect. Smooth and rapid active return-to-center can be achieved using a simple control strategy and calibration. Table 3 shows an angle range of 0-100° and an angular velocity range of 0-3 rad / s, with a denser distribution for finer control. The second stage is an auxiliary stage; therefore, the second return torque... The numerical value is significantly smaller than the first return torque. .
[0043] Line charts corresponding to Tables 1 through 4, such as Figures 3-6 As shown in the figure, the trend of the corresponding predetermined relationship can be seen more clearly.
[0044] Table 1
[0045]
[0046] Table 2
[0047]
[0048] Table 3
[0049]
[0050] Table 4
[0051]
[0052] In steps 2 and 4, the first positive coefficient is respectively... Second positive coefficient Perform filtering.
[0053] In the above technical solutions, there may be situations where no active driver intervention or centering is required. However, due to potential hand force fluctuations or large changes in rate, a filtering process is needed to ensure a smooth transition of the coefficient. Even in boundary areas of some operating conditions, the coefficient will not abruptly change, avoiding the uneven centering caused by misjudgments of operating conditions in some control methods. Moreover, this table, after one calibration, is applicable to the same type of vehicle.
Claims
1. A method for calculating the active return torque of an electric power steering system, the electric power steering system comprising an EPS controller and a CAN bus TAS sensor connected thereto, wherein the electric power steering system obtains a first return torque lookup table, a first return coefficient lookup table, a second return torque lookup table, and a second return coefficient lookup table through vehicle calibration experiments; characterized in that, Based on the specific steps included: Step 1: The EPS controller receives the vehicle speed signal from the CAN bus and the steering wheel angle from the TAS sensor in real time. Steering wheel angular velocity and steering wheel hand force signals; Step 2, based on the vehicle's current speed signal and steering wheel angle... The first positive torque is obtained by consulting the first positive torque lookup table. Based on the hand force signal and steering wheel angular velocity under the current operating conditions of the vehicle. The first positive coefficient is obtained by querying the first positive coefficient lookup table. ; the first positive torque With the first positive coefficient Multiplying them together yields the first stage of the return torque. ; Step 3: Determine if the vehicle's current operating condition simultaneously meets the following three conditions. If yes, proceed to Step 4; otherwise, adjust the first-stage return torque. As the total return torque ; Step 4: Adjust the steering wheel angle according to the vehicle's current operating conditions. By consulting the second positive torque lookup table based on the steering wheel angular velocity, the second positive torque can be obtained. The second positive coefficient is obtained by consulting the second positive coefficient lookup table based on the vehicle speed signal under the current operating conditions. ; the second return torque With the second positive coefficient Multiplying them together yields the second-stage return torque. ; Step 5, adjust the first stage return torque. Second stage return torque Adding them together, we get the total return torque. ; 。 2. The method for calculating the active return torque of the electric power steering system as described in claim 1, characterized in that, In steps 2 and 4, the first positive coefficient is respectively... Second positive coefficient Perform filtering.
3. A computer-readable storage medium having computer program instructions stored thereon, characterized in that, When the program instruction is executed by the processor, it implements the method for calculating the active return torque of the electric power steering system as described in claim 1 or 2.
4. A chip, characterized in that, It includes a processor and an interface, the processor being used to read instructions to execute the method for calculating the active return torque of the electric power steering system of claim 1 or 2.