Importance

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Abstract

A learning control unit is provided between a feedback calculating unit and a driving unit. When a period for one medium rotation period is assumed to be T.sub.L, an unknown drive current function Irepeat(t) which repeats for a period of time from a start time t=0 for one medium rotation period to an end time t=T.sub.L is obtained by a learning algorithm as an approximated function I repeat(t) that is approximately presumed by a set of the heights C.sub.i of N rectangular functions having interval numbers i=0.about. (N-1) whose time widths are obtained by dividing the period for one medium rotation period into N intervals. After the learning, a learning control signal I repeat is outputted synchronously with the medium rotation and a feed-forward control is performed. The learning control unit can be provided between a position signal detecting unit and a feedback calculating unit and can learn a position function TESrepeat(t) as an approximated function TES repeat(t) in a similar manner.

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First Claim