Chapter List

6.1 Introduction

The prevalent trend in hard disk design is towards smaller hard disks with increasingly larger capacities. This implies that the track width has to be smaller, leading to lower error tolerance in the positioning of the head. The controller for track following has to achieve tighter regulation in the control of the servomechanism. Current HDDs use a combination of classical control techniques, such as lead-lag compensators, PID compensators, and notch filters. These classical methods can no longer meet the demand for HDDs of higher performance. Thus, many control approaches have been tried, such as LQG and/or LTR approach (see, e.g., [18, 19]), and adaptive control (see, e.g., [28]) and so on.

The purpose of this chapter is to use the results of the RPT control method of Chapter 3 and the CNF control technique of Chapter 5 to carry out the design of track-following controllers for an HDD with a single VCM actuator. We first obtain a model of the VCM actuator and then cast the overall track-following control system design into an RPT design framework. A second-order dynamic measurement feedback controller is then designed to achieve robust and perfect tracking for any step reference. Our controller is theoretically capable...