Dynamic reduction of track shape errors in disc drives
AssigneeSeagate Technology LLC
InventorGabor Szita
Life of this patent
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Abstract
The invention eliminates relative and absolute track shape errors by writing zero acceleration path (ZAP) correction factors into the servo sectors during track propagation. A servo track guide zone is written to the disc. ZAP correction factors are written to the guide zone and self-propagating servo writing commences. The ZAP correction factors are determined in only two disc revolutions per track. The read element follows track k, a previously written track, and the write element writes servo marks for track k+1 during a write revolution. The position signal is monitored and recorded in order to estimate the shape of track k+1 according to the inverse transformation method during a correction revolution.
Claims19
A method for writing a servo track to a data storage disc in a data storage device, the data storage device having an actuator arm located adjacent to the disc that traverses a surface of the disc, a transducer head attached to the actuator arm, the transducer head having a read element and a write element, the method comprising steps of:
- a) writing a servo track k on the disc;
- b) reading the servo track k with the read element;
- c) determining an estimated track shape of the servo track k;
- d) writing the estimated shape of the servo track k as a zero acceleration path (“ZAP”) correction factor within the servo track k;
- e) following servo track k corrected by the ZAP correction factor for track k with the read element;
- f) writing a servo track k+1 with the write element while simultaneously monitoring and recording a position of the read element relative to the surface of the disc;
- g) computing an estimated shape of the servo track k+1 from the position of the read element obtained in writing step (f);
- h) aligning the read element over the servo track k+1;
- i) applying the estimated shape of the servo track k+1 as a ZAP correction factor for the servo track k+1;
- j) following servo track k+1 corrected by the ZAP correction factor for track k+1 with the read element;
- and,
- k) monitoring a ZAP corrected read element position over the servo track k+1.
An apparatus for writing a servo track to a data storage disc in a data storage device, the data storage device having an actuator arm located adjacent to the disc that traverses a surface of the disc, the actuator arm having a travel-limit-stop, a read/write head attached to the actuator arm, the read/write head having a read element and a write element, and a servo controller for positioning the read/write head relative to the surface of the disc, the apparatus comprising:
- a controller operable to direct the read element to retrieve information from the disc, direct the write element to store information to the disc, determine an estimated shape of a servo track k located on the disc, determine an estimated shape of a servo track k+1 located on the disc, determine one or more track shape correction factors for each track, write the track shape correction factors to one or more servo sectors of each track, compute an estimated path of the read element over servo track k+1, and compute a final estimated shape of the servo track k+1 based on a weighted average of the estimated shape of servo track k+1 and the estimated path of the read element over servo track k+1.
Dependencies are inferred from the claim text.