Steering force sensing control method for steer-by-wire system

Abstract

The invention belongs to the technical field of automobiles, and particularly relates to a steering-by-wire system steering force sensing control method which is composed of a friction and hysteresis characteristic identification module of a steering-by-wire system control mechanism, a nonlinear friction compensation module and a steering force sensing closed-loop control module. A friction and hysteresis characteristic identification module of the steer-by-wire system control mechanism identifies dry friction characteristics of a steer-by-wire wheel; the non-linear friction compensation module compensates non-linear friction force of the steer-by-wire wheel in an open-loop compensation mode; the steering force sensing closed-loop control module enables the steering hysteresis characteristic of the steer-by-wire system after open-loop compensation to have the steering force sensing conforming to the driving feeling of a driver, and steer-by-wire better conforms to the expectation of the driver. The steering wheel friction hysteresis characteristic closed-loop control is adopted, so that the steer-by-wire system after open-loop compensation has the steering hysteresis characteristic conforming to the driving feeling of a driver, and the motion quality of the steer-by-wire system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of automobiles, 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 automobile industry, the steer-by-wire system has gradually become one of the important technologies of modern automobiles. Compared with the traditional mechanical steering system, the steer-by-wire system eliminates the physical connection between the steering wheel and the wheel, improves the steering comfort, makes the vehicle interior design more flexible, and provides more possibilities for vehicle layout and cockpit design. However, in practical applications, the system faces many challenges. The nonlinear friction of the steer-by-wire system control mechanism and the hysteresis characteristics that do not meet the driver's expectations affect the dynamic response performance of the steer-by-wire system. The existing control strategies rarely consider the poor hysteresis characteristics caused by the nonlinear friction of the steer-by-wire system, which leads to the problem that the steering force does not meet the driver's expectations, and it is difficult to achieve accurate real-time correction of the nonlinear friction of the steer-by-wire system. Although methods such as adaptive control and sliding mode control have alleviated the impact of friction on system performance to a certain extent, their compensation effects under different working conditions are still limited, and it is difficult to achieve accurate real-time correction of nonlinear friction.

[0003] Invention patent CN118358650A discloses a personalized steering feel design method for a wire-controlled steering system, which includes a traditional steering feel design, a customizable personalized steering feel design, and a wire-controlled steering wheel compensation torque design. Among them, through the wire-controlled steering wheel compensation torque design, there is no need to install a dynamic torque sensor, and only a small amount of vehicle parameters are required to customize the personalized steering wheel feedback torque for a single driver to meet the driver's safety and comfort requirements. However, the invention does not take into account the poor hysteresis characteristics caused by the nonlinear friction force of the wire-controlled steering system, which leads to the problem that the steering force does not meet the driver's expectations, and it is difficult to achieve accurate real-time correction of the wire-controlled steering dry friction.

[0004] Invention patent CN117002610A provides a force control method for a wire-controlled steering system. The target force torque reflecting the road feel is calculated by the error between the virtual position corresponding to the steering actuator and the actual position of the steering control mechanism, ensuring that the target force torque will not disappear due to the control strategy of the target steering torque; at the same time, by reasonably 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, the force control method of the invention does not consider the influence of the steering hysteresis characteristics of the wire-controlled steering system on the steering force, and it is difficult to obtain the steering force that the driver expects when steering.

[0005] Therefore, compensating for the nonlinear friction in the steer-by-wire system and correcting the steering hysteresis characteristics so that the driver can obtain the desired steering force feel have become key technical requirements for improving system response accuracy, improving driving experience and enhancing safety. Based on this, the present invention proposes a steering force feel control method for a steer-by-wire system, which aims to compensate for the nonlinear friction in the system; at the same time, the steering hysteresis characteristics are corrected so that the driver can obtain the desired steering force feel, thereby improving the response performance and stability of the steer-by-wire system. Summary of the invention

[0006] 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides a steering force sense control method for a steer-by-wire system, which solves the problems raised in the above-mentioned background technology.

[0007] (II) Technical solution In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions: A steering force control method for a wire-controlled steering system, comprising a friction and hysteresis characteristic identification module of a wire-controlled steering system operating mechanism, a nonlinear friction compensation module and a steering force closed-loop control module, the wire-controlled steering system steering force control method comprising 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 of 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 rotational torque when the steering wheel is turned; Ensure that the data acquisition system is functioning properly and connected to the computer; Turn the force-measuring steering wheel to the 0° position, and 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 counterclockwise to the 0° position. Record the steering wheel torque change through the steering wheel force sensor. Repeat the above experiment five times and record the data; The data of the steering wheel angle and the corresponding steering wheel torque are recorded by the steering wheel force sensor, so as to determine the curve of the steering wheel torque and the steering wheel position, namely the steering wheel hysteresis curve; Step 2: Nonlinear friction compensation of the steering mechanism of the wire control system, the steps are as follows: The obtained in step 1 Curve data processing: The curve is divided into two sections, an upward curve and a downward curve. The average value of five groups of experimental data is taken. The upward curve is the clockwise nonlinear compensation characteristic, and the downward curve is 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; The current compensation torque of the motor is obtained according to the compensation table, 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 the steering wheel is open-loop compensated, in order to make the steering hysteresis characteristics of the wire-controlled steering wheel consistent with the steering force sense of the driver, the corresponding steering hysteresis characteristics are formulated as reference input; Through the PID controller, according to the steering hysteresis characteristics and the current actual steering motor torque, the friction hysteresis torque is closed-loop controlled to output the steering motor compensation torque; The steering motor compensation torque signal is transmitted to the steering motor. Since the formulated steering hysteresis characteristic has a good steering force sense, the steering hysteresis characteristic of the wire control steering system can meet the steering force sense of the driving feeling.

[0008] Furthermore, the friction and hysteresis characteristics of the steering mechanism of the wire-controlled steering system are identified through experimental methods; secondly, the friction hysteresis torque of the nonlinear characteristics of the steering mechanism of the wire-controlled steering system is compensated through open-loop compensation; finally, a closed-loop control method is adopted to make the steering force feel of the wire-controlled steering system after open-loop compensation consistent with the driver's driving feel.

[0009] Furthermore, 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 steering wheel.

[0010] Furthermore, the nonlinear friction compensation module compensates for the nonlinear friction of the steering-by-wire wheel by means of open-loop compensation.

[0011] Furthermore, the steering force sense closed-loop control module enables the steering hysteresis characteristic of the steer-by-wire system after open-loop compensation to have a steering force sense that meets the driver's driving feeling, so that the steer-by-wire system is more in line with the driver's driving feeling.

[0012] Furthermore, by compensating the dry friction during the steering process with the torque of the torque motor, the influence of the nonlinear dry friction on the steering force is reduced, and then the steering hysteresis characteristic is corrected to meet the driver's steering force feeling.

[0013] (III) Beneficial effects Compared with the prior art, the present invention provides a steering force control method for a steer-by-wire system, which has the following beneficial effects: The present invention adopts closed-loop control of the friction hysteresis characteristics of the steering wheel, so that the wire-controlled steering system after open-loop compensation has a steering hysteresis characteristic that meets the driving feeling of the driver, improves the steering feeling of the wire-controlled steering system, solves the problem of nonlinear friction of the kingpin at different positions of the steering wheel caused by manufacturing and installation errors such as poor lubrication of the limit mechanism and slight eccentricity 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

[0014] Figure 1 It is a schematic diagram of the system principle of the present invention; Figure 2 It is a schematic diagram of the measured hysteresis characteristic curve before nonlinear friction correction of the wire control steering system of the present invention; Figure 3 It is a schematic diagram of the target steering force characteristic curve of the present invention. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0016] Example like Figure 1-3 As shown, a steering force sense control method for a wire-controlled steering system proposed in an embodiment of the present invention is composed of a friction and hysteresis characteristic identification module of a wire-controlled steering system operating mechanism, a nonlinear friction compensation module and a steering force sense closed-loop control module. The steering force sense control method for a wire-controlled steering system includes 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 the appropriate position of 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; Ensure that the data acquisition system is functioning properly and connected to the computer; Turn the force-measuring steering wheel to the 0° position, and 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 counterclockwise to the 0° position. Record the steering wheel torque change through the steering wheel force sensor. Repeat the above experiment five times and record the data; The data of the steering wheel angle and the corresponding steering wheel torque are recorded by the steering wheel force sensor, so as to determine the curve of the steering wheel torque and the steering wheel position, namely the steering wheel hysteresis curve; Step 2: Nonlinear friction compensation of the steering mechanism of the wire control system, the steps are as follows: The obtained in step 1 Curve data processing: The curve is divided into two sections, an upward curve and a downward curve. The average value of five groups of experimental data is taken. The upward curve is the clockwise nonlinear compensation characteristic, and the downward curve is 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; 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 of 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 curve. Step 3: Steering force closed-loop control of the steer-by-wire system. The steps are as follows: After the steering wheel is open-loop compensated, in order to make the steering hysteresis characteristics of the wire-controlled steering wheel consistent with the steering force sense of the driver, the corresponding steering hysteresis characteristics are formulated as reference input; Through the PID controller, according to the steering hysteresis characteristics that meet the driver's driving feeling and the current actual steering motor torque, the friction hysteresis torque is closed-loop controlled to output the desired steering motor compensation torque; The steering motor compensation torque signal is transmitted to the steering motor. Since the formulated steering hysteresis characteristic has a good steering force sense, the steering hysteresis characteristic of the wire control steering system can meet the steering force sense of the driving feeling.

[0017] Figure 3The left turn is the upper curve, and the right turn is the lower curve. The hysteresis curve after compensation in step 2 is a linear curve, and the steering force is poor. In order to have a good steering force, the middle line is the set steering force curve. By setting the personalized hysteresis torque size, the wire control steering system has a steering hysteresis characteristic that meets the driver's driving feeling.

[0018] In some embodiments, the friction and hysteresis characteristics of the steering mechanism of the wire-controlled steering system are identified through experimental methods; secondly, the friction hysteresis torque of the nonlinear characteristics of the steering mechanism of the wire-controlled steering system is compensated through open-loop compensation; finally, a closed-loop control method is adopted to make the steering force feel of the wire-controlled steering system after open-loop compensation consistent with the driver's driving feel.

[0019] 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.

[0020] In some embodiments, the nonlinear friction compensation module compensates for the nonlinear friction of the steering-by-wire wheel by means of open-loop compensation.

[0021] 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 sense that meets the driver's driving feeling, so that the steer-by-wire system better meets the driver's expectations.

[0022] In some embodiments, by using the torque of the torque motor ( ) 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.

[0023] 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.

[0024] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is 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 can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A steering force control method for a steer-by-wire system, comprising a friction and hysteresis characteristic identification module of a steer-by-wire system operating mechanism, a nonlinear friction compensation module and a steering force closed-loop control module, characterized in that: The steering force control method of the wire control steering 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 of 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 rotational torque when the steering wheel is turned; Ensure that the data acquisition system is functioning properly and connected to the computer; Turn the force-measuring steering wheel to the 0° position, and 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 counterclockwise to the 0° position. Record the steering wheel torque change through the steering wheel force sensor. Repeat the above experiment five times and record the data; The data of the steering wheel angle and the corresponding steering wheel torque are recorded by the steering wheel force sensor, so as to determine the curve of the steering wheel torque and the steering wheel position, namely the steering wheel hysteresis curve; Step 2: Nonlinear friction compensation of the steering mechanism of the wire control system, the steps are as follows: The obtained in step 1 Curve data processing: The curve is divided into two sections, an upward curve and a downward curve. The average value of five groups of experimental data is taken. The upward curve is the clockwise nonlinear compensation characteristic, and the downward curve is 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; The current compensation torque of the motor is obtained according to the compensation table, 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 the steering wheel is open-loop compensated, in order to make the steering hysteresis characteristics of the wire-controlled steering wheel consistent with the steering force sense of the driver, the corresponding steering hysteresis characteristics are formulated as reference input; Through the PID controller, according to the steering hysteresis characteristics and the current actual steering motor torque, the friction hysteresis torque is closed-loop controlled to output the steering motor compensation torque; The steering motor compensation torque signal is transmitted to the steering motor. Since the formulated steering hysteresis characteristic has a good steering force sense, the steering hysteresis characteristic of the wire control steering system can meet the steering force sense of the driving feeling.

2. The method for controlling steering force sense of a steer-by-wire system according to claim 1, characterized in that: 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, the closed-loop control method is adopted to make the steering force feel of the steer-by-wire system after open-loop compensation consistent with the driver's driving feeling.

3. The method for controlling steering force sense 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 sense 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 by means of open-loop compensation.

5. The method for controlling steering force sense 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 wire-controlled steering system after open-loop compensation to have a steering force sense that meets the driver's driving feeling, so that the wire-controlled steering is more in line with the driver's driving feeling.

6. The method for controlling steering force sense 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 is reduced, and then the steering hysteresis characteristics are corrected to make it consistent with the driver's steering force.

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