Magnetic disk apparatus

A magnetic disk apparatus which comprises an information recording/reproducing medium, a head for recording or reproducing information on or from said information recording/reproducing medium, an actuator for moving said head on said information recording/reproducing medium, and an extraction circuit for extracting a head position signal from the information read out from said information recording/reproducing medium by means of said head, wherein an operating signal is generated for controlling said actuator so that a head position indicated by said head position signal extracted by said extracting circuit coincides with a given target position,

• said magnetic disk apparatus further comprising a positioning control apparatus for performing a positioning control of said head,
• said positioning control apparatus comprising:
• error detecting means for deriving difference between said given target position and said head position in terms of an error signal,
• a compensator receiving as input thereto said error signal from said error detecting means for thereby generating said operating signal by carrying out phase compensation for stabilizing a vibration mode existing in an under-control object which is comprised of said actuator, said head and said extraction circuit, and
• a resonance filter to which said operating signal outputted from said compensator is inputted, said resonance filter having a resonance frequency at or in the vicinity of a given frequency at which positioning accuracy is to be enhanced, the output of said resonance filter being added to said head position signal.