Method and disk drive for improving head position accuracy during track following through real-time identification of external vibration

1. Field of the Invention The present invention may be embodied in a method and a disk drive for improving head position accuracy during track following through real-time identification of external vibration. A selected track is followed using a servo control loop having a nominal gain and being responsive to position error signal samples generated based on a difference between head position samples and a reference head position value. A spectral power value within a predetermined frequency band is determined from a sequence of the position error signal samples. If a property of the spectral power value exceeds a threshold, the gain of the servo control loop is increased within the predetermined frequency band to attenuate the effect of external vibration on the position of the head over the selected track during track following.