CN-121973234-A - High-precision positioning control method and system for moment motor for robot joint

CN121973234ACN 121973234 ACN121973234 ACN 121973234ACN-121973234-A

Abstract

The invention relates to the technical field of robot control, in particular to a high-precision positioning control method and system for a torque motor for a robot joint. The method comprises the steps of obtaining operation data of a robot joint, performing direct current removal processing to obtain a ripple current sequence, performing variation modal decomposition on the ripple current sequence to obtain a plurality of intrinsic modal components, evaluating frequency domain dispersion indexes of the intrinsic modal components, determining phase locking confidence coefficients of the intrinsic modal components according to a motor polar groove matching relation and a mechanical angle position to remove external fluctuation interference, determining a dynamic compensation gain coefficient by combining the frequency domain dispersion indexes and the phase locking confidence coefficients, and performing reverse torque compensation on a torque motor based on the dynamic compensation gain coefficient. The invention solves the technical problems of drifting of torque motor cogging torque along with working conditions and error compensation of interference, and improves the positioning stability of the robot joint during low-speed operation.

Inventors

WU HAONAN
ZHOU JIANHUA
CHEN MAOWU

Assignees

常州多维电气股份有限公司

Dates

Publication Date: 20260505
Application Date: 20260330

Claims (10)

1. A high-precision positioning control method of a torque motor for a robot joint is characterized by comprising the following steps: acquiring operation data of a robot joint, and performing DC removal processing on the operation data to obtain a ripple current sequence reflecting current ripple characteristics; performing variation modal decomposition on the ripple current sequence to obtain a plurality of intrinsic modal components, and evaluating the frequency domain dispersion index of each intrinsic modal component according to the distribution condition of the spectrum energy of each intrinsic modal component relative to the center frequency; According to the motor polar groove matching relation and the mechanical angle position of the robot joint, extracting the instantaneous phase sequence of each intrinsic mode component, analyzing the correlation of the instantaneous phase sequence and the theoretical cogging torque phase sequence in the time dimension, and determining the phase locking confidence coefficient of each intrinsic mode component so as to eliminate external fluctuation interference; and determining a dynamic compensation gain coefficient by combining the frequency domain dispersion index and the phase locking confidence coefficient, and executing reverse torque compensation on the torque motor based on the dynamic compensation gain coefficient.
2. The method for high-precision positioning control of a torque motor for a robot joint according to claim 1, wherein the step of acquiring the operation data of the robot joint comprises the steps of acquiring a mechanical angle position of the motor by using an absolute value encoder and acquiring a torque current component of the motor by using a current sensor.
3. The high-precision positioning control method for the torque motor for the robot joint according to claim 1, wherein the step of performing DC removal processing on the operation data to obtain a ripple current sequence reflecting current ripple characteristics comprises the steps of setting a sliding window, calculating a torque current component mean value in the sliding window, and taking a difference value between an acquired torque current component and the torque current component mean value as the ripple current sequence.
4. The method for high-precision positioning control of a robot joint torque motor according to claim 1, wherein the step of evaluating the frequency domain dispersion index of each eigenmode component includes performing frequency domain transformation on each eigenmode component to obtain a spectral energy distribution, wherein the spectral energy is concentrated near a center frequency, and the smaller the value of the frequency domain dispersion index is, the lower the corresponding frequency domain dispersion is.
5. The method for high-precision positioning control of a torque motor for a robot joint according to claim 1, wherein the determining of the theoretical cogging torque phase sequence comprises calculating a spatial harmonic order of the cogging torque based on a pole pair number and a slot number of the motor, and determining the theoretical cogging torque phase sequence based on the spatial harmonic order and a mechanical angle position.
6. The method for high-precision positioning control of a torque motor for a robot joint according to claim 5, wherein the analyzing the correlation of the instantaneous phase sequence and the theoretical cogging torque phase sequence in the time dimension to obtain the phase locking confidence comprises: calculating phase difference distribution between the instantaneous phase sequence and the theoretical cogging torque phase sequence; And evaluating the directional consistency of the phase difference distribution on the unit circle by using a vector synthesis method, if the directional consistency of the phase difference distribution is the same, judging the corresponding eigenmode component as a torque component locked with the motor position, giving high phase locking confidence, and if the phase difference distribution is in a random divergence state, judging the corresponding eigenmode component as external interference, and giving low phase locking confidence.
7. The method for high-precision positioning control of a robot joint torque motor according to claim 1, wherein the determining a dynamic compensation gain factor comprises: Constructing an adaptive evaluation model taking the phase locking confidence coefficient and the frequency domain dispersion index as input variables; And according to the signal reliability determined by the self-adaptive evaluation model, the dynamic compensation gain coefficient approaches to a maximum value when the intrinsic mode component is judged to be an effective cogging torque component, and the dynamic compensation gain coefficient attenuation approaches to a minimum value when the intrinsic mode component is judged to contain external interference or noise.
8. The method for high-precision positioning control of a moment motor for a robot joint according to claim 7, wherein the performing reverse torque compensation on the moment motor based on the dynamic compensation gain coefficient comprises selecting an eigenmode component with highest phase locking confidence as an object to be compensated, performing intensity adjustment on a time domain waveform of the object to be compensated by using the dynamic compensation gain coefficient, generating reverse compensation current, and superposing the reverse compensation current into a current loop of the moment motor.
9. The method for high-precision positioning control of a robot joint torque motor according to claim 1, further comprising calculating center frequencies of the eigenmode components before evaluating frequency domain dispersion indexes of the eigenmode components, and removing eigenmode components whose center frequencies exceed a cogging torque characteristic frequency range.
10. A high-precision positioning control system for a robot joint torque motor, characterized by comprising a processor and a memory, wherein the memory stores computer program instructions that, when executed by the processor, implement a high-precision positioning control method for a robot joint torque motor according to any one of claims 1-9.

Description

High-precision positioning control method and system for moment motor for robot joint Technical Field The invention relates to the technical field of robot control. More particularly, the invention relates to a high-precision positioning control method and system for a torque motor of a robot joint. Background Along with the increasing popularization of the application of cooperative robots and precision assembly robots, in order to eliminate the problems of backlash errors and mechanical compliance caused by the traditional speed reducers, more and more robot joints begin to adopt a torque motor direct driving technology, and the motors generally have high pole pair numbers, can output larger torque in a low-speed state, and meet the dynamic response requirement of the robot joints. However, the inherent cogging torque of the torque motor is a main obstacle affecting the positioning accuracy of the direct-drive joint, and is derived from the periodic change of magnetic permeability between the rotor permanent magnet and the stator cogging, and can cause motor rotation speed fluctuation and positioning jitter under the common low-speed creeping or high-precision positioning maintaining working condition of the robot joint, thereby seriously affecting the processing accuracy and the terminal stability. At present, the traditional compensation scheme mostly adopts a preset table look-up method, namely reverse offset is carried out according to a torque waveform of a factory test, but the preset compensation table is usually static and is difficult to adapt to mechanical abrasion or magnetic drift after a robot runs for a long time, meanwhile, a robot joint can be subjected to various dynamic interferences such as load change, environmental vibration and the like when a task is executed, the existing frequency domain analysis technology is difficult to accurately separate a cogging torque component fixed along with the position from a mixed interference signal changing along with time, and the technical limitation easily causes error compensation, causes system oscillation and limits high-precision performance of the robot joint under a complex working condition. Disclosure of Invention In order to solve the technical problems that the torque motor compensation scheme lacks self-adaptability and external fluctuation interference cannot be accurately stripped, the invention provides schemes in the following aspects. In a first aspect, the invention provides a high-precision positioning control method of a torque motor for a robot joint, comprising the steps of obtaining operation data of the robot joint, and performing DC removal processing on the operation data to obtain a ripple current sequence reflecting current ripple characteristics; performing variation modal decomposition on the ripple current sequence to obtain a plurality of intrinsic modal components, and evaluating the frequency domain dispersion index of each intrinsic modal component according to the distribution condition of the spectrum energy of each intrinsic modal component relative to the center frequency; According to the motor polar groove matching relation and the mechanical angle position of the robot joint, extracting the instantaneous phase sequence of each intrinsic mode component, analyzing the correlation of the instantaneous phase sequence and the theoretical cogging torque phase sequence in the time dimension, and determining the phase locking confidence coefficient of each intrinsic mode component so as to eliminate external fluctuation interference; and determining a dynamic compensation gain coefficient by combining the frequency domain dispersion index and the phase locking confidence coefficient, and executing reverse torque compensation on the torque motor based on the dynamic compensation gain coefficient. According to the invention, a variation modal decomposition technology is combined with a phase verification based on physical properties through a data-driven real-time analysis strategy, so that the limitation of a traditional static table lookup method is broken, the cogging torque characteristic fixed along with the position can be automatically learned and purified from complex current data, the problem that compensation parameters fail due to motor aging or thermal drift is solved, more importantly, accurate decoupling of cogging torque components and external interference is realized under a dynamic working condition, and the positioning stability and control precision of the robot joint during low-speed operation are improved. Preferably, the acquiring of the operation data of the robot joint comprises acquiring a mechanical angle position of the motor by using an absolute value encoder and acquiring a torque current component of the motor by using a current sensor. Preferably, the DC removing processing is performed on the operation data to obtain a ripple current sequence reflecting the current ripple characteri