A tutorial on controls for disk drives

This paper presents a tutorial overview of control technology disk drive technology. The first part of the paper motivates interest in this technology by showing industry trends for increases in data storage density, total capacity of disk drives shipped, and cost per megabyte. The paper then discusses the basics of disk drive technology including the fundamentals of longitudinal magnetic recording and the function of several important disk drive components. The first part concludes by discussing the impact of the thermal stability of magnetic domains on track density. The second part covers the fundamental aspects of the control problem, such as sources of disturbances and noise, and defines many of the standard terms used to describe phenomena related to the servo problem in disk drives. The paper then discusses how the industry addresses these problems to obtain good performance