A Multi-period Sliding Mode Repetitive Control Method for CNC Machine Tool Linear Motor Based on Disturbance Compensation

Abstract

The invention discloses a disturbance compensation-based multi-period sliding mode repetitive control method of a linear motor of a numerically-controlled machine tool, and aims to solve the problem on precision control of a periodic signal by a linear motor servo system of an XY platform of the numerically-controlled machine tool. For a plurality of periodic disturbances having a known period length, a plurality of periodic disturbances having an unknown period length and non-periodic disturbances during the operation of the motor servo system, the control method provided by the invention uses a quadratic difference compensation technology of multi-period equivalent disturbances to realize effective suppression of the non-periodic disturbances and the periodic disturbances having the unknown period length, and uses a multi-period learning method to completely compensate the plurality of periodic disturbances having the known period length, thereby realizing precise position tracking of the linear motor of the numerically-controlled machine tool. According to the disturbance compensation-based multi-period sliding mode repetitive control method, a novel reaching law is created, soas to avoid a flutter phenomenon; a reference track is allowed to be formed by superposing a plurality of periodic signals having different period lengths; and the control method provided expands theapplication range of the existing same type of technical methods.

Description

technical field [0001] The invention relates to the fields of repetitive control technology and sliding mode control technology, in particular to a multi-period sliding mode repetitive control method for linear motors of numerically controlled machine tools. Background technique [0002] Traditional CNC machine tools are driven by rotary motors, and the transmission link is relatively complicated. This rotary motor servo system has the disadvantages of large transmission error, large mechanical noise and low transmission efficiency; at the same time, it is difficult for the rotary motor servo system to provide large feed speed and acceleration. In order to overcome the shortcomings of the traditional feed system, CNC machine tools directly driven by permanent magnet linear motors have emerged one after another. This type of machine tool does not need to install intermediate transmission links, the layout is relatively simple, and it has fast dynamic response speed, high cont...

AI Technical Summary

Problems solved by technology

[0005] 1. Most of the existing linear motor repetitive control methods are designed based on the frequency domain, and there are few linear motor control methods for CNC machine tools based on the time domain.

[0006] 2. The invention patent with the publication number CN101976042A only uses a single-cycle learning method to compensate for disturbances. When there are multiple disturbances with different cycles in the linear motor system, this single-cycle learning method tends to converge slowly when implemented, and Requires more storage space

For example, when there is an interfering signal with a period of 6s and 7s superimposed in the system, the common period of the interfering signal is 42s (42 is the least common multiple of 6 and 7), much larger than 6s and 7s; if single-period sliding mode repetitive control The device needs at least 42 / T s storage unit (T s is the sampling period), and the repeating controller needs the historical data of the previous period, and there is a control time lag of one period; therefore, the system switching function does not start to converge until at least one control period (42s), and the periodic disturbance suppression is very slow and high memory usage

[0007] 3. The invention patent application with the publication number CN109358502A provides a discrete multi-cycle linear motor repetitive control method, which has the following disadvantages: First, the adopted reaching law design scheme is in the form of discontinuous switching, which leads to the method In actual application, there may be discontinuity of the control quantity; secondly, this method is only applicable to the situation where there are periodic disturbances in the system with known cycle lengths, which limits its scope of application, because the actual CNC machine tool During the operation of the linear motor system, there are often periodic disturbances with known period lengths, periodic disturbances with unknown period lengths, and non-periodic disturbances at the same time; third, this method requires the number of periodic signals contained in the disturbance is equal to the number of periods contained in the reference signal, which also limits the scope of use of the method

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