Robust Current Control of Voice Coil Motor in Tip-Tilt Mirror Based on Disturbance Observer Framework

Abstract

In this paper, a control methodology based on the disturbance observer (DOB) framework is proposed to improve the current dynamic characteristic and the robustness of the voice coil motor (VCM) in the tip-tilt mirror. It is shown that the open-loop current characteristic is a third-order plant, which is influenced obviously by both the electrical and mechanical uncertainties under different environment temperatures. Although the traditional PID control is helpful to improve the current dynamics, it is not able to provide enough robustness. Therefore, a new control methodology based on DOB is proposed. The plant model is simplified from third-order to first-order by considering the back-electromotive force (EMF) as the disturbance. The perturbation of the electrical parameters is compensated by the inner-loop of the DOB framework, and the perturbation of the mechanical parameters is compensated by suppressing the back-EMF. Moreover, new sufficient conditions for robust stability are presented in the control method based on H ∞ algorithm. Compared with the traditional researches, the upper bound of the uncertainties is calculated directly in this paper. Therefore, the ranges of the electrical parameters are very clear according to the Qfilter. Based on the stability conditions, new design guidelines for the DOB-based robust current control for induction motor are also presented. Experiment results are given to show the design details and the superiority of the proposed control method.

Overview of Position Servo Control Technology and Development of Voice Coil Motor

“…However, because the robust control system generally does not work in the optimal state, the steady-state accuracy of the system is poor. Therefore, robust control is especially suitable for those systems with large variation range of uncertain factors and small stability margin [44]- [46]. In [47], H∞ robust control is used to solve the problem of assembly errors in the center of mass and force of VCM; In [48], robust control is used to reduce the impact of load resonance changes; some scholars also propose to use robust control to solve the problem uncertain external disturbance [49]- [51] and the problem of uncertain system model [52], thereby improving the stability and tracking effect of the system.…”

Adaptive control of fast steering mirror with high acceleration trajectory

“…On the other hand, research often assumes that the model of the FSM system is immutable, thus identifying the system as a transfer function and proposing control algorithms based on that transfer function [4]. Practical experiments show that both flexure and motors, after operating for a period under harsh motion conditions such as high temperatures, can cause changes in parameters like resistance, inductance [6], and stiffness, leading to a deterioration in the control quality of the system when using only the initial controller.…”

Improved particle swarm optimisation tuned PID position control of voice coil semi-active electrohydraulic damper

“…Simple structural design and reliability over a wide range of operating conditions made the PID control a popular choice in the current control of VCAs. 19 However, lack of robustness during nonlinear conditions is a major drawback of PID control in hydraulic systems 20 and VCA's. 21 The performance of the PID control depends on the three adjustable control gains such as proportional, integral, and derivative.…”