The Discrete-Time Sliding Mode Control with Computation Time Delay for Repeatable Run-Out Compensation of Hard Disk Drives

T H Yan,B He,X S Xu,X D Chen

doi:10.1155/2013/505846

Abstract

The presented is a study on the problem of disturbance rejection, specifically the periodic disturbance, by applying discrete-time sliding mode control method. For perturbations such as modeling errors and external disturbances, their compensation is formulated using the designed sliding mode control. To eliminate the effect of these perturbations, the convergence rate between the disturbance and their compensation has been shaped by an additional parameter. Decoupling of the resultant perturbation estimation dynamics from the closed loop dynamics is achieved. Computation time delay is also presented to address the perturbation effects. The approach developed ensures the robustness of the sliding mode dynamics to parameter uncertainties and exogenous disturbances, in addition to the complete rejection of the periodic disturbance component. Satisfactory simulation results as well as experimental ones have been achieved based on a fast servo system of a modern hard disk drive to illustrate the validity of the controller for repeatable run-out (RRO) compensation.

Highlights

One of the most attractive features of the variable structure system (VSS) with sliding mode is its invariance and robustness to perturbations including modeling errors and external disturbances
This paper presents a discrete-time sliding mode controller with an additional parameter to adjust the convergence rate for improving the perturbation compensation, and based on the spirit of [22], the effects of computation time delay are considered for complete disturbances compensation
The control desk consists of the laser Doppler vibrometer (LDV), an hard disk drive (HDD), and a PC installed with the DSpace

Summary

Introduction

One of the most attractive features of the variable structure system (VSS) with sliding mode is its invariance and robustness to perturbations including modeling errors and external disturbances. Since discrete-time sliding mode control has been developed for guaranteeing the asymptotic stability of uncertain sampled-data systems, as well as to reducing the chattering phenomenon that arises when the controller was implemented on a digital computer, the computation time delay should be considered in the discrete-time sliding mode structure for improving the system performance. This paper presents a discrete-time sliding mode controller with an additional parameter to adjust the convergence rate for improving the perturbation compensation, and based on the spirit of [22], the effects of computation time delay are considered for complete disturbances compensation.

Preliminaries

Discrete-Time Sliding Mode Control Design

Application to a Hard Disk Drive

Experimental Results

Conclusions