Reduction of seek-time (the time for the magnetic head to start to move and settle on the desired track) is an important R & D item for a hard disk drive together with increase of memory density. In an usual hard disk drive, position control of the head is divided in three modes, velocity control, transient control and track-following control modes. The reduction of the seek-time in the transient control mode depends directly on control method and it is most important to develop a control method to reduce the time for the head to settle on the track in this mode. A conventional hard disk drive uses analog control servo method but the reduction of the seek time by analog servo method is limited.
We digitize the head position control and apply dead-beat control method to reduce the settling time of the head. The dead-beat control is sensitive to the fluctuation of the system constants, therefore, we use the adaptive control scheme to the system. In the paper, characteristics of the proposed system are studied by a numerical simulation and an experiment. It is demonstrated that the settling time of the head on the track is reduced by a factor of more than two comparing with conventional analog servo method.
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