Patent ID: 6710966
Filing Date: 2004-03-23
Classification: G11B

Abstract:
In a magnetic disk drive having a head disk assembly (HDA) including a rotating disk having distributed position information in a plurality of servo wedges for defining a plurality of concentric data tracks, a rotary actuator that pivots relative to a base and that carries a transducer that periodically reads the position information from the servo wedges, a voice coil motor (VCM) circuit that includes a voice coil motor that is coupled to the rotary actuator, the VCM circuit responding to a control effort signal that is periodically adjusted during a track-following operation based on the position information such that the transducer tends to follow a selected track, a method of adaptively reducing an effect of vibration during the track following operation comprising the steps of:generating a sensor signal that is responsive to a vibration to the disk drive that tends to cause the rotary actuator to move off-track; reading the position information from a current servo wedge to generate a measured position signal; generating a nominal position error signal based on a difference between the measured position signal and a target position signal; reading the sensor signal to generate a sensor value associated with the current servo wedge; modifying the sensor value based on a first adaptive-filter gain to generate a position error adjustment signal; adjusting the nominal position error signal with the position error adjustment signal to generate an adjusted position error signal; calculating a control effort signal based on the adjusted position error signal; outputting the control effort signal to the VCM circuit; and altering the first adaptive-filter gain based on the adjusted position error signal and the sensor value associated with the current servo wedge for use during a next servo wedge.