Implementing Both a Disturbance Observer and a Repetitive Controller for Track Following in a HDD With Emphasis on the Disturbance Observer Design

It is important to provide good tracking for a hard disk drive actuator, since good tracking can allow us to minimize the track pitch and thus increase the data storage capacity of a hard disk drive. Repeatable disturbances, such as disk vibration, and non-repeatable disturbances, such as shocks, are major problems in tracking control of a hard disk drive. It has been shown that a combination of a disturbance observer and a repetitive controller can effectively solve these two problems. In this research, these two controllers are implemented on a real computer hard disk drive, and design of the disturbance observer is emphasized.