ABSTRACT
This chapter introduces a new method that applies the N-delay control theory to the feedforward controller design in the Two-Degrees-of-Freedom control system (TDOF). In the TDOF control scheme, feedforward controllers are introduced in addition to the feedback controller. During short track-seeking control in hard disk drives (HDD), it is effective to use unified control methods which work for both track-seeking and track-following. HDDs are used in various products such as notebook computers, digital audio players, and flat-screen televisions. A short-span seek control system and a long-span seek control system are realized by a new digital control design approach for low acoustic noise. HDDs have two track-seeking control modes, namely, the short-span seek control mode where the seek distance is less than one hundred tracks and the long-span seek control mode where the seek distance is more than one hundred tracks.
