Patent ID: 7265931

Claim:
A servo system for a hard disk drive that controls track alignment of a transducer head relative to a desired tracking location using at least two measurements, (a) a first measurement made from servo data position error signals (PES) read from a rotatable disk by the transducer head; and (b) a second measurement made from a feed forward signal indicative of a disturbance applied to the hard disk drive, the second measurement being used to control the track alignment only when the servo system determines that use of the second measurement will likely reduce track alignment error, wherein the servo system determines that use of the second signal will likely reduce the track alignment error when a threshold is exceeded, the threshold being determined from a computer model enabling comparison of predicted PES amounts with and without the use of the second signal, wherein the feed forward signal comprises two or more of the following: an accelerometer signal provided from the accelerometer sensing movement of the disk; a first spindle motor speed indication signal provided from a frequency of servo markers passing the transducer head as read from the disk rotated by the spindle motor; a second spindle motor speed indication signal provided from a back emf signal received from a winding of the spindle motor; and a voice control motor (VCM) movement indication signal provided from a back emf signal received from a winding of the VCM.