CN-122009314-A - Method and system for identifying and eliminating return clearance of rack-and-pinion type active steering system

Abstract

The invention relates to the technical field of vehicle steering control, and discloses a method and a system for identifying and eliminating a return clearance of a rack-and-pinion type active steering system, which accurately trigger a reversing event by acquiring motor rotation angle, rotation speed and current signals in real time and setting double conditions of expected steering change and motor rotation speed lower than a threshold value on the premise of not adding additional hardware; in the gap elimination process, the abrupt change characteristic from a stable low value to a step-type rising of the motor current is used as an accurate judging time for completing the lamination of the gear and the rack, the current return gap value is estimated on line by calculating the angular displacement of the motor, and an adaptive updating mechanism is introduced to store and fuse multiple estimated values in a rolling way, so that the system can adapt to abrasion and temperature change. The invention realizes the automatic identification and compensation of the return clearance with low cost and high precision, remarkably improves the response speed and the control smoothness of steering reversing, and has the advantages of self-learning and strong robustness.

Inventors

• ZHANG YUKUN
• LIU CONGHAO
• HAO LIANG
• LIU YAN
• ZHAO DEYANG

Assignees

• 辽宁工业大学

Dates

Publication Date

20260512

Application Date

20260410

Claims (10)

1. 1. The method for identifying and eliminating the return clearance of the rack-and-pinion type active steering system is characterized by comprising the following steps of: Step S1, collecting a motor rotation angle, a motor rotation speed and a motor current in real time; Step S2, judging whether a reversing event occurs according to the steering control instruction; Step S3, when the commutation event is judged to occur, controlling the motor output torque to eliminate the return clearance; Step S4, in the process of eliminating the return clearance, judging whether the gear and the rack are attached or not by detecting the change characteristics of the motor current; And S5, when the bonding is judged to be completed, recording the motor angular displacement from the start of the reversing event to the bonding completion time, and estimating a return clearance value according to the motor angular displacement.
2. 2. The method of claim 1, wherein the determining in step S2 that the commutation event has occurred includes that the desired steering direction is not consistent with the current gear-on-side direction and the motor speed is below a preset speed threshold.
3. 3. The method according to claim 2, wherein the preset rotational speed threshold is 0.5% to 3%, or 5rpm to 10rpm, or 0.5 rad/s to 1rad/s of the rated rotational speed of the motor.
4. 4. The method according to claim 1, wherein the method for determining the fitting by detecting the change characteristic of the motor current in the step S4 is as follows: When the step-like rise of the motor current from a stable low baseline level is detected, and the current change rate exceeds a preset change rate threshold value, judging that the gear and the rack are completely attached; The current change rate is [ ] ) The calculated expression of (2) is: In which, in the process, As a rate of change of current with respect to time, In the event of a current flow, In order to be able to take time, Is a time variation approaching 0.
5. 5. The method of claim 4, wherein the predetermined rate of change threshold is greater than 10A/s when the current rate of change is [ ] ) When the number of the bonded articles is within the range of 30A/s to 200A/s, it is determined that bonding has occurred.
6. 6. The method according to claim 1, further comprising a step S6 for adaptively updating the backhaul gap, wherein the step S6 performs validity check on the backhaul gap value estimated in the step S5, and if the check is passed, stores the backhaul gap value in a data buffer with a fixed length, and calculates an updated backhaul gap value by using a data fusion algorithm using a plurality of historical valid estimated values in the data buffer for subsequent commutation compensation control.
7. 7. The method of claim 6, wherein the validity check includes determining whether the current estimate is within a predetermined multiple of the historical average.
8. 8. The method of claim 6, wherein the data buffer is a first-in first-out (FIFO) buffer having a length N that is a predetermined positive integer.
9. 9. The method of claim 6, wherein the data fusion algorithm comprises calculating a median of the buffer data, or calculating a weighted average of the buffer data.
10. 10. A rack and pinion active steering system comprising a motor, a rack and pinion mechanism, a motor controller and a processor, wherein the processor, when executing a computer program stored on a memory, is capable of controlling the motor to drive the rack and pinion mechanism by the motor controller to carry out the steps of the method according to any one of claims 1 to 9.

Description

Method and system for identifying and eliminating return clearance of rack-and-pinion type active steering system The invention relates to the technical field of vehicle steering control, in particular to a method and a system for identifying and eliminating a return clearance of a rack-and-pinion type active steering system. The gear rack type steering system in the background art is widely applied to steering mechanisms of various automobiles due to the advantages of simple structure, high transmission efficiency, clear road feel and the like. Particularly in the increasingly popular active steering system, the motor directly or auxiliary drives the gear to realize high-grade functions such as variable steering ratio, lane keeping assistance, automatic parking and the like, thereby greatly improving the operability, safety and comfort of the vehicle. In a specific production and life, a vehicle equipped with an active steering system generally includes a permanent magnet synchronous motor, a speed reducing mechanism, and a set of rack and pinion steering gear. When a driver turns a steering wheel or an automatic driving system to send a steering instruction, a whole vehicle controller or a steering system controller calculates a desired steering angle and torque and drives a motor to rotate. The output torque of the motor is amplified by the speed reducing mechanism and then drives the steering gear to rotate, and the gear teeth of the gear are meshed with the tooth grooves on the racks to convert the rotary motion into linear motion of the racks so as to push the wheels to steer. In order to pursue more accurate steering control and more natural driving hand feeling, an active steering system has extremely high requirements on the instantaneity and the accuracy of steering response. In an ideal situation, the rotation of the motor should maintain a strict linear correspondence with the displacement of the rack, i.e. a "gapless" transmission. However, limited by machining accuracy (e.g., tooth form errors, assembly tolerances), mechanical wear from long term use, and tooth flank clearance designed to reserve thermal expansion space, certain mechanical clearances must exist between the gear and rack, i.e., "return clearance". The presence of the return clearance presents a significant challenge to the performance of the active steering system, principally in the following respects: When the steering system is reversed, for example, the steering system is switched from left to right, the gear needs to cross the return clearance between the gear and the rack first, and then the gear and the tooth surface on the other side are attached again to transfer torque; in the short idle stroke stage, the rotation of the motor does not immediately cause the actual deflection of the wheels, so that obvious dead zone or hysteresis occurs in steering response; The driving hand feeling is discontinuous, and the control texture is influenced, namely, when a driver actively turns and goes through a reversing process, a return clearance can cause the moment of a steering wheel to generate a phenomenon of 'force release' or 'abrupt change' in a short time; In a third aspect, increasing system complexity or cost to address the problem of increased system complexity or cost, the prior art generally employs several schemes, but each has limitations: Mechanical level optimization, namely, reducing the return clearance by improving the machining precision of parts, optimizing the assembly process or adopting an elastic pre-tightening structure (such as spring compression), but high-precision machining means high manufacturing cost, and the pre-tightening structure can increase system friction, accelerate abrasion and possibly even cause heavy steering at low speed; The scheme of the hardware sensor can accurately compensate the gap, but obviously increases the hardware cost, the complexity of wiring harness arrangement and potential fault points of the system; the method has extremely high requirements on model precision, is difficult to adapt to gap parameter time-varying characteristics caused by mechanical abrasion, temperature change and the like, has great engineering realization difficulty and poor robustness; in view of the foregoing, a need exists for a new backhaul gap identification and cancellation method based on signal characteristics; Disclosure of Invention In the prior art, the problems of steering response delay, control precision reduction and discontinuous hand feeling caused by return clearance are difficult to be effectively solved on the premise of not increasing hardware cost and not depending on a complex model. Therefore, the key technical problem to be solved by the application is how to realize on-line and self-adaptive identification and elimination of the return clearance in the rack-and-pinion type active steering system by only utilizing the existing motor signals of the system under the condition th