The second edition of this monograph provides a systematic treatment of the design of modern hard disk drive servo systems updated with the latest research results to reflect recent improvements in spindle speed and bit density and other changes in this fast-moving field. In particular, it focuses on the applications of some newly developed results in control theory, i.e., robust and perfect tracking control and composite non-linear feedback control which are suitable for track following and seeking respectively. Emphasis is placed on hard disk drive servo systems with single- or dual-stage actuation using a voice-coil-motor actuator enhanced in the latter case by the addition of a micro-actuator providing faster responses and therefore higher bandwidth in track following. Other issues such as modeling and compensation of nonlinearities and friction in microdrives, disturbance rejection and resonance compensation are also addressed.

The techniques and applications involved include:

• time- and frequency domain methods for system identification;
• physical effect approaches for parameter identification;
• linear systems tools;
• linear control techniques (PID, H2, H-infinity, and other robust control methods);
• classical nonlinear control techniques (time-optimal, proximate time-optimal, and mode switching control);
• composite nonlinear feedback (CNF) control;
• complete single- and dual-stage hard disk drive servo systems;
• time- and frequency domain properties of hard disk drive servo systems;
• design of piezoelectric actuator systems;
• modeling and compensation of nonlinearities and friction inmicrodrives.

Hard Disk Drive Servo Systems will be of great value to practicing engineers in the hard disk and CD-ROM drive industries and to researchers in areas related to servo systems. The Linear Systems and CNF MATLABA(R) toolkits used to develop many of the results in this book can be downloaded from Professor Chena (TM)s website.

The series Advances in Industrial Control aims to report and encourage technology transfer in control engineering. The rapid development of control technology has an impact on all areas of the control discipline. New theory, new controllers, actuators, sensors, new industrial processes, computer methods, new applications, new philosophies , new challenges. Much of this development work resides in industrial reports, feasibility study papers and the reports of advanced collaborative projects. The series offers an opportunity for researchers to present an extended exposition of such new work in all aspects of industrial control for wider and rapid dissemination. Hard disk drive systems are ubiquitous in today's computer systems and the technology is still evolving. There is a review of hard disk drive technology and construction in the early pages of this monograph that looks at the characteristics of the disks and there it can be read that: "bit density... continues to increase at an amazing rate", "spindle speed... the move to faster and faster spindle speeds continue", "form factors... the trend...is downward... to smaller and smaller drives", "performance... factors are improving", "redundant arrays of inexpensive disks... becoming increasingly common, and is now seen in consumer desktop machines", "reliability... is improving slowly... it is very hard to improve the reliability of a product when it is changing rapidly" and finally "interfaces... continue to create new and improved standards... to match the increase in performance of the hard disks themselves".