A steering force control method for a steer-by-wire system

Abstract

The present invention belongs to the field of automotive technology, and in particular relates to a steering force feel control method for a steer-by-wire system. The method comprises a friction and hysteresis characteristics identification module for a steer-by-wire system operating mechanism, a nonlinear friction compensation module, and a steering force feel closed-loop control module. The friction and hysteresis characteristics identification module for the steer-by-wire system operating mechanism identifies the dry friction characteristics of a steer-by-wire steering wheel; the nonlinear friction compensation module compensates for the nonlinear friction of the steer-by-wire steering wheel through open-loop compensation; and the steering force feel closed-loop control module ensures that the steering hysteresis characteristics of the steer-by-wire system after open-loop compensation have a steering force feel that matches the driver's driving experience, thereby making the steer-by-wire system more in line with the driver's expectations. The present invention utilizes closed-loop control of the steering wheel friction hysteresis characteristics to ensure that the steer-by-wire system after open-loop compensation has steering hysteresis characteristics that match the driver's driving experience, thereby improving the motion quality of the steer-by-wire system.

Description

Technical Field

[0001] The present invention relates to the field of automobile technology, and in particular to a steering force sense control method for a steer-by-wire system. Background Art

[0002] With the rapid development of the automotive industry, steer-by-wire systems have become a key technology in modern vehicles. Compared to traditional mechanical steering systems, steer-by-wire systems eliminate the physical connection between the steering wheel and wheels, improving steering comfort, allowing for greater flexibility in vehicle interior design, and expanding possibilities for vehicle layout and cabin design. However, in practical applications, these systems face numerous challenges. The nonlinear friction and hysteresis characteristics of the steer-by-wire control mechanism, which often do not meet driver expectations, impact the steer-by-wire system's dynamic response. Existing control strategies rarely consider the hysteresis characteristics caused by the nonlinear friction of steer-by-wire systems, resulting in steering force feel that does not meet driver expectations and making it difficult to accurately and real-timely correct for the nonlinear friction of steer-by-wire systems. While methods such as adaptive control and sliding mode control have mitigated the impact of friction on system performance to some extent, their compensation effectiveness under different operating conditions remains limited, making accurate and real-time correction of nonlinear friction difficult to achieve.

[0003] Invention patent CN118358650A discloses a method for designing personalized steering feel for a steer-by-wire system. The method includes traditional steering feel design, customizable personalized steering feel design, and steer-by-wire steering wheel compensation torque design. Specifically, through the steer-by-wire steering wheel compensation torque design, there is no need to install a dynamic torque sensor. Only a small number of vehicle parameters are required to customize the steering wheel feedback torque for a single driver, meeting the driver's safety and comfort requirements. However, the invention does not consider the poor hysteresis characteristics caused by the nonlinear friction force of the steer-by-wire system, which results in the steering force feeling not meeting the driver's expectations, making it difficult to achieve accurate real-time correction of steer-by-wire dry friction.

[0004] Invention patent CN117002610A provides a force control method for a steer-by-wire system. This method calculates a target force torque reflecting road feel by calculating the error between the virtual position of the steering actuator and the actual position of the steering control mechanism. This ensures that the target force torque does not disappear due to the target steering torque control strategy. Furthermore, by properly setting the gain of the target steering torque controller, the error between the actual steering position of the steering actuator and the target steering position can be maintained at an acceptable level. However, this force control method does not consider the impact of the steering hysteresis characteristics of the steer-by-wire system on steering force feel, making it difficult to obtain the steering force feel desired by the driver during steering.

[0005] Therefore, compensating for nonlinear friction in steer-by-wire systems and correcting steering hysteresis to provide the driver with a desired steering feel have become key technical requirements for improving system response accuracy, enhancing the driving experience, and enhancing safety. Based on this, the present invention proposes a steering feel control method for a steer-by-wire system. This method aims to compensate for nonlinear friction in the system and correct steering hysteresis to provide the driver with a desired steering feel, thereby improving the responsiveness and stability of the steer-by-wire system. Summary of the Invention

[0006] (1) Technical problems solved

[0007] In view of the deficiencies in the prior art, the present invention provides a method for controlling steering force sense in a steer-by-wire system, which solves the problems raised in the above-mentioned background technology.

[0008] (2) Technical solution

[0009] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0010] A steering force feel control method for a steer-by-wire system comprises a friction and hysteresis characteristic identification module of a steer-by-wire system operating mechanism, a nonlinear friction compensation module, and a steering force feel closed-loop control module. The steering force feel control method for a steer-by-wire system comprises the following steps:

[0011] Step 1: Obtain the current steering wheel hysteresis characteristic curve by identifying the friction and hysteresis characteristics of the steering-by-wire system control mechanism , is the steering wheel torque, is the steering wheel angle, is the longitudinal speed of the car, the steps are as follows:

[0012] Fix the force-measuring steering wheel at an appropriate position on the steering wheel and adjust it to be coaxial with the original steering wheel so that it can accurately measure the steering wheel angle, steering wheel angular velocity and torque when the steering wheel is turned;

[0013] Ensure that the data acquisition system is operating normally and connected to the computer;

[0014] Turn the force-measuring steering wheel to the 0° position, rotate the steering wheel counterclockwise to the left limit at a low speed of 50°±10° / s, a medium speed of 150°±10° / s, and a high speed of 250°±10° / s, and then rotate the steering wheel clockwise to the right limit. Then, rotate the steering wheel counterclockwise to the 0° position and record the steering wheel torque changes using the steering wheel force sensor.

[0015] Repeat the above experiment five times and record the data;

[0016] The steering wheel angle and the corresponding steering wheel torque data are recorded by the steering wheel force sensor, thereby determining the curve of steering wheel torque and steering wheel position, that is, the steering wheel hysteresis curve;

[0017] Step 2: Compensate for nonlinear friction of the steering mechanism of the steer-by-wire system. The steps are as follows:

[0018] The result obtained in step 1 Curve data processing: The curve is divided into two sections, the upward curve and the downward curve. The average value of five groups of experimental data is taken as the upward curve for the clockwise nonlinear compensation characteristic, and the downward curve for the counterclockwise nonlinear compensation characteristic. Thus, the nonlinear characteristics of clockwise and counterclockwise steering are obtained.

[0019] According to the nonlinear characteristics of clockwise and counterclockwise steering, a steering wheel dry friction nonlinear compensation curve is formulated, that is, the nonlinear friction compensation torque under different steering wheel speeds and vehicle speeds;

[0020] According to the compensation table, the current motor compensation torque is obtained, the compensation characteristics are obtained, and the dry friction of the steering wheel is compensated;

[0021] Step 3: Steering force closed-loop control of the steer-by-wire system. The steps are as follows:

[0022] After performing open-loop compensation on the steering wheel, in order to make the steering hysteresis characteristics of the wire-controlled steering wheel consistent with the steering force felt by the driver, a corresponding steering hysteresis characteristic is formulated as a reference input;

[0023] Through the PID controller, the friction hysteresis torque is closed-loop controlled according to the steering hysteresis characteristics and the current actual steering motor torque, and the steering motor compensation torque is output;

[0024] The steering motor compensation torque signal is transmitted to the steering motor. Since the formulated steering hysteresis characteristic has a good steering force feel, the steering hysteresis characteristic of the wire control steering system can meet the steering force feel of the driving feeling.

[0025] Furthermore, the friction and hysteresis characteristics of the steering mechanism of the steer-by-wire system are identified through experimental methods. Secondly, the friction hysteresis torque of the nonlinear characteristics of the steering mechanism of the steer-by-wire system is compensated through open-loop compensation. Finally, a closed-loop control method is adopted to ensure that the steering force feel of the steer-by-wire system after open-loop compensation is consistent with the driver's driving feel.

[0026] Furthermore, the friction and hysteresis characteristics identification module of the steering-by-wire system operating mechanism identifies the dry friction characteristics of the steering-by-wire steering wheel.

[0027] Furthermore, the nonlinear friction compensation module compensates for the nonlinear friction of the wire-controlled steering wheel through open-loop compensation.

[0028] Furthermore, the steering force closed-loop control module enables the steering hysteresis characteristic of the steer-by-wire system after open-loop compensation to have a steering force that conforms to the driver's driving feeling, making the steer-by-wire system more consistent with the driver's driving feeling.

[0029] Furthermore, by compensating dry friction during the steering process with the torque of the torque motor, the influence of nonlinear dry friction on the steering force feel is reduced, and then the steering hysteresis characteristics are corrected to make it consistent with the driver's steering force feel.

[0030] (3) Beneficial effects

[0031] Compared with the prior art, the present invention provides a method for controlling steering force in a steer-by-wire system, which has the following beneficial effects:

[0032] The present invention adopts closed-loop control of the steering wheel friction hysteresis characteristics, so that the wire-controlled steering system after open-loop compensation has a steering hysteresis characteristic that conforms to the driver's driving feel, improves the steering feel of the wire-controlled steering system, solves the problem of nonlinear dry friction of the kingpin of the steering wheel at different positions caused by manufacturing and installation errors such as poor lubrication of the limit mechanism and slight axis deviation during motor installation of the wire-controlled steering system operating mechanism, and provides a dynamic compensation method for steering torque. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the system principle of the present invention;

[0034] Figure 2 Schematic diagram of the measured hysteresis characteristic curve before nonlinear friction correction of the steer-by-wire system of the present invention;

[0035] Figure 3 Schematic diagram of the target steering force characteristic curve of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] Example

[0038] like Figure 1-3 As shown, an embodiment of the present invention provides a steering force feel control method for a steer-by-wire system, which comprises a friction and hysteresis characteristic identification module of a steer-by-wire system operating mechanism, a nonlinear friction compensation module, and a steering force feel closed-loop control module. The steering force feel control method for a steer-by-wire system includes the following steps:

[0039] Step 1: Obtain the current steering wheel hysteresis characteristic curve by identifying the friction and hysteresis characteristics of the steering-by-wire system control mechanism , is the steering wheel torque, is the steering wheel angle, is the longitudinal speed of the car, the steps are as follows:

[0040] Fix the force-measuring steering wheel at an appropriate position on the steering wheel and adjust it to be coaxial with the original steering wheel so that it can accurately measure the steering wheel angle when the steering wheel is turned ( ), steering wheel angular velocity ( ) and torque;

[0041] Ensure that the data acquisition system is operating normally and connected to the computer;

[0042] Turn the force-measuring steering wheel to the 0° position, rotate the steering wheel counterclockwise to the left limit at a low speed of 50°±10° / s, a medium speed of 150°±10° / s, and a high speed of 250°±10° / s, and then rotate the steering wheel clockwise to the right limit. Then, rotate the steering wheel counterclockwise to the 0° position and record the steering wheel torque changes using the steering wheel force sensor.

[0043] Repeat the above experiment five times and record the data;

[0044] The steering wheel angle and the corresponding steering wheel torque data are recorded by the steering wheel force sensor, thereby determining the curve of steering wheel torque and steering wheel position, that is, the steering wheel hysteresis curve;

[0045] Step 2: Compensate for nonlinear friction of the steering mechanism of the steer-by-wire system. The steps are as follows:

[0046] The result obtained in step 1 Curve data processing: The curve is divided into two sections, the upward curve and the downward curve. The average value of five groups of experimental data is taken as the upward curve for the clockwise nonlinear compensation characteristic, and the downward curve for the counterclockwise nonlinear compensation characteristic. Thus, the nonlinear characteristics of clockwise and counterclockwise steering are obtained.

[0047] According to the nonlinear characteristics of clockwise and counterclockwise steering, a steering wheel dry friction nonlinear compensation curve is formulated, that is, the nonlinear friction compensation torque under different steering wheel speeds and vehicle speeds;

[0048] In this step, the steering wheel hysteresis curve measured in step 1 is decomposed into a clockwise nonlinear curve and a counterclockwise nonlinear compensation curve according to clockwise and counterclockwise steering. The nonlinear compensation curves for clockwise and counterclockwise steering are the nonlinear friction compensation characteristics of the steering wheel. According to the current steering direction and steering wheel angle, the motor friction compensation torque is obtained from the nonlinear compensation curves.

[0049] Step 3: Steering force closed-loop control of the steer-by-wire system. The steps are as follows:

[0050] After performing open-loop compensation on the steering wheel, in order to make the steering hysteresis characteristics of the wire-controlled steering wheel consistent with the steering force felt by the driver, a corresponding steering hysteresis characteristic is formulated as a reference input;

[0051] Through the PID controller, the friction hysteresis torque is closed-loop controlled according to the steering hysteresis characteristics that meet the driver's driving feeling and the current actual steering motor torque, and the desired steering motor compensation torque is output;

[0052] The steering motor compensation torque signal is transmitted to the steering motor. Since the formulated steering hysteresis characteristic has a good steering force feel, the steering hysteresis characteristic of the wire control steering system can meet the steering force feel of the driving feeling.

[0053] Figure 3 The upper curve is used for left turns and the lower curve is used for right turns. The hysteresis curve after compensation in step 2 is a linear curve, resulting in poor steering feel. To achieve a good steering feel, the center line is the set steering feel curve. By setting a personalized hysteresis torque, the steer-by-wire system has steering hysteresis characteristics that suit the driver's driving feel.

[0054] In some embodiments, the friction and hysteresis characteristics of the steering mechanism of the steer-by-wire system are identified through experimental methods; secondly, the friction hysteresis torque of the nonlinear characteristics of the steering mechanism of the steer-by-wire system is compensated through open-loop compensation; finally, a closed-loop control method is used to ensure that the steering force feel of the steer-by-wire system after open-loop compensation is consistent with the driver's driving feel.

[0055] In some embodiments, the friction and hysteresis characteristics identification module of the steering mechanism of the steer-by-wire system identifies the dry friction characteristics of the steer-by-wire steering wheel.

[0056] In some embodiments, the nonlinear friction compensation module compensates for the nonlinear friction of the steering-by-wire wheel through open-loop compensation.

[0057] In some embodiments, the steering force closed-loop control module enables the steering hysteresis characteristic of the steer-by-wire system after open-loop compensation to have a steering force that meets the driver's driving feeling, making the steer-by-wire system more in line with the driver's expectations.

[0058] In some embodiments, by the torque motor torque ( ) compensates for dry friction during steering, reduces the impact of nonlinear dry friction on steering force feel, and then corrects the steering hysteresis characteristics to make it consistent with the driver's steering force feel.

[0059] The left limit position and the right limit position in the above text refer to the left extreme position of the steering wheel and the right extreme position of the steering wheel.

[0060] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A steering force control method for a steer-by-wire system, comprising a friction and hysteresis characteristics identification module for a steer-by-wire system control mechanism, a nonlinear friction compensation module, and a steering force closed-loop control module, characterized in that: The steering force sense control method of the steer-by-wire system comprises the following steps: Step 1: Obtain the current steering wheel hysteresis characteristic curve by identifying the friction and hysteresis characteristics of the steering-by-wire system control mechanism , is the steering wheel torque, is the steering wheel angle, is the longitudinal speed of the car, the steps are as follows: Fix the force-measuring steering wheel at an appropriate position on the steering wheel and adjust it to be coaxial with the original steering wheel so that it can accurately measure the steering wheel angle, steering wheel angular velocity and torque when the steering wheel is turned; Ensure that the data acquisition system is operating normally and connected to the computer; Turn the force-measuring steering wheel to the 0° position, rotate the steering wheel counterclockwise to the left limit at a low speed of 50°±10° / s, a medium speed of 150°±10° / s, and a high speed of 250°±10° / s, and then rotate the steering wheel clockwise to the right limit. Then, rotate the steering wheel counterclockwise to the 0° position and record the steering wheel torque changes using the steering wheel force sensor. Repeat the above experiment five times and record the data; The steering wheel angle and the corresponding steering wheel torque data are recorded by the steering wheel force sensor, thereby determining the curve of steering wheel torque and steering wheel position, that is, the steering wheel hysteresis curve; Step 2: Compensate for nonlinear friction of the steering mechanism of the steer-by-wire system. The steps are as follows: The result obtained in step 1 Curve data processing: The curve is divided into two sections, the upward curve and the downward curve. The average value of five groups of experimental data is taken as the upward curve for the clockwise nonlinear compensation characteristic, and the downward curve for the counterclockwise nonlinear compensation characteristic. Thus, the nonlinear characteristics of clockwise and counterclockwise steering are obtained. According to the nonlinear characteristics of clockwise and counterclockwise steering, a steering wheel dry friction nonlinear compensation curve is formulated, that is, the nonlinear friction compensation torque under different steering wheel speeds and vehicle speeds; According to the compensation table, the current motor compensation torque is obtained, the compensation characteristics are obtained, and the dry friction of the steering wheel is compensated; Step 3: Steering force closed-loop control of the steer-by-wire system. The steps are as follows: After performing open-loop compensation on the steering wheel, in order to make the steering hysteresis characteristics of the wire-controlled steering wheel consistent with the steering force felt by the driver, a corresponding steering hysteresis characteristic is formulated as a reference input; Through the PID controller, the friction hysteresis torque is closed-loop controlled according to the steering hysteresis characteristics and the current actual steering motor torque, and the steering motor compensation torque is output; The steering motor compensation torque signal is transmitted to the steering motor. Since the formulated steering hysteresis characteristic has a good steering force feel, the steering hysteresis characteristic of the wire control steering system can meet the steering force feel of the driving feeling.

2. The method for controlling steering force feel of a steer-by-wire system according to claim 1, characterized in that: The friction and hysteresis characteristics of the steer-by-wire system's control mechanism are identified experimentally. Secondly, the friction hysteresis torque of the steer-by-wire system's nonlinear characteristics is compensated through open-loop compensation. Finally, a closed-loop control method is used to ensure that the open-loop compensated steer-by-wire system provides a steering force feel that matches the driver's driving feel.

3. The method for controlling steering force feel of a steer-by-wire system according to claim 1, characterized in that: The friction and hysteresis characteristic identification module of the steering-by-wire system operating mechanism identifies the dry friction characteristics of the steering-by-wire wheel.

4. The method for controlling steering force feel of a steer-by-wire system according to claim 1, characterized in that: The nonlinear friction compensation module compensates for the nonlinear friction of the wire-controlled steering wheel through open-loop compensation.

5. The method for controlling steering force feel of a steer-by-wire system according to claim 1, characterized in that: The steering force closed-loop control module enables the steering hysteresis characteristic of the steer-by-wire system after open-loop compensation to have a steering force that conforms to the driver's driving feeling, making the steer-by-wire system more consistent with the driver's driving feeling.

6. The method for controlling steering force feel of a steer-by-wire system according to claim 1, characterized in that: By compensating the dry friction during the steering process with the torque of the torque motor, the influence of nonlinear dry friction on the steering force feel is reduced, and then the steering hysteresis characteristics are corrected to make it consistent with the driver's steering force feel.

Images