Written-in error compensation method for coherent repeatable runout
AssigneeSeagate Technology LLC
InventorsReed David Hanson, John Christopher Morris, Thomas Christopher Zirps
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Abstract
The present invention recognizes that induced RRO is coherent, i.e., the RRO has a large degree of repeatability from track to track. The present invention is a zero acceleration profile (compensation) process that targets CRRO (Coherent RRO). A process of the present invention represents a considerable reduction in the factory calibration time compared to other compensation techniques currently used. The reduction in time is attributed to the fact that CRRO can be computed by averaging position error signals (PES) over multiple tracks as opposed to total RRO which is computed by averaging over multiple revolutions on the same track.
Claims20
A method of compensating for runout comprising the step of computing coherent repeatable runout by averaging position error signals over multiple tracks.
A method for compensating for runout of a storage device comprising steps of:
- determining coherent repeatable runout for a plurality of servos in a zone;
- storing compensation values corresponding to the coherent repeatable runout;
- and
- using the compensation values to compensate for the coherent repeatable runout.
A servo loop adapted to use compensation values, determined from sectors in different tracks, to compensate for coherent repeatable runout.
Dependencies are inferred from the claim text.