Control of a Digital Galvanometer Scanner Using a Discrete-Time Sliding-Mode Variable-Structure Controller Based on a Decoupled Disturbance Compensator

Guangsheng Chen,Yunlong Wang

doi:10.3390/app11219788

Guangsheng Chen, Yunlong Wang

Open Access

https://doi.org/10.3390/app11219788

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Abstract

Laser processing plays an important role in industrial manufacturing, in which a galvanometer scanner (GS) functions as the core component of the laser processing equipment. With the development of the digital system, the GS based on the digital system finds a broader range of potential application. In order to address the slow step-responses of a GS with disturbance and parameter perturbation, the mathematical model of the motor of the GS is derived and a discrete-time sliding-mode variable-structure controller (DSVC) based on a decoupled disturbance compensator (DDC) (DSVC+DDC) is designed. The step-response performance of a GS is the key factor affecting the quality evaluation of laser processing. Experiments are conducted on the step responses of the motor of the GS on a digital experimental platform. The experiment results show that when guaranteeing a steady-state error within 20 urad and an overshoot of less than 5%, the rise time for step-responses in 1% and 10% of the whole stroke is 1 and 2 ms, decreasing by 23% and 58% compared with the reference performance index, which indicates the effectiveness of the proposed method. The proposed approach can not only compensate for the external disturbance online and improve the step-response speed of the GS, but also relax the traditionally assumed limit of the upper bound of external disturbance to the limit of the change rate of external disturbance, which reduces the difficulty of a practical application. This method has great significance for further applications in high precision machining.

Highlights

Laser processing, with advantages such as its being contactless, fast, and noiseless, has become a key technique in industrial production and automation [1]
Using the torque-equilibrium method to obtain the torque coefficient of the motor and the identification method for motor parameters proposed by Kaan Erkorkmaz et al [15], the relevant parameters of the experimental platform were obtained (Table 2)
A discrete-time sliding-mode variable-structure controller (DSVC)+decoupled disturbance compensator (DDC) is designed to address the slow step-responses of a galvanometer scanner (GS) with disturbance and parameter perturbation

Summary

Introduction

With advantages such as its being contactless, fast, and noiseless, has become a key technique in industrial production and automation [1]. (CTI) in the United States have launched excellent two-dimensional (2-d) and three-dimensional (3-d) GSs. The driver of traditional GSs is generally controlled by an analogue driver board. The driver of traditional GSs is generally controlled by an analogue driver board This can provide a favorable control effect, the performance and polyfunctionality of the system are limited due to the relatively fixed control structure and a finite number of fixed parameters. When system parameters change due to variations of the scanning angle and temperature as well as the aging of parts, the fixed parameters cannot be adjusted . These limitations, can be overcome by the digital control of the driver [2]

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