Compensation for repeatable runout error
AssigneeSeagate Technology LLC
InventorsKyle K. Eddy, John C. Morris
Life of this patent
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Abstract
A disc drive having a servo loop for positioning a head over a disc includes a servo controller which generates a servo control signal in response to a received position error signal. An actuator, coupled to the servo controller, moves the head in response to the servo control signal. A sensor, located in the head, senses servo information located on the disc and produces a servo signal therefrom. The servo signal is combined with a reference signal to produce the position error signal. A compensation storage device stores decimated compensation values and a servo compensator expands the decimated compensated values and injects the expanded compensation values into the servo loop.
Claims18
A storage device having a servo loop comprising:
- a servo compensator adapted to expand decimated compensation values that are to be used in the servo loop;
- wherein the servo compensator includes an R-fold expander with R greater than 1.
A method of compensating for repeatable runout errors in a storage device, comprising steps of:
- (a) determining a sequence of compensation values;
- (b) reducing the number of compensation values in the sequence by performing an R-fold decimation oh the compensation values with R greater than 1;
- (c) expanding the reduced number of compensation values;
- and
- (d) compensating a servo loop in the storage device based upon the expanded compensation values.
A servo controller for use in a disc storage system, the storage system of the type having a sensor configured to sense servo information on a disc surface and provide a servo signal and an actuator configured to position the sensor over the disc surface in response to a servo control signal, the servo controller comprising:
- a reference signal input to receive a reference signal indicative of a desired sensor position over the disc surface;
- a position error signal related to a difference between the reference signal and the servo signal;
- stored decimated servo compensation values;
- and
- a servo compensator configured to expand the decimated servo compensation values and inject servo compensation values into the servo control signal;
- wherein the servo compensator includes an R-fold expander with R greater than 1.
Dependencies are inferred from the claim text.