Importance

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Abstract

In a data recording disk file, a digital servo control system generates an estimate of the sinusoidal function representative of the dominant component of nonrepeatable runout (NRRO) and derives from this function a NRRO signal to add to the digital control signal to eliminate the NRRO component from the head position error signal (PES). The estimate of the sinusoidal function is made from the measured PES and from predetermined constants representative of known disk file physical parameters. In the preferred embodiment, a new estimate of the sinusoidal function, and accordingly a NRRO signal derived from the newly estimated function, is made during every PES sample time during track following. During track seeking the estimate of the NRRO sinusoidal function is not updated during PES sampling; rather the NRRO signal is derived from the last estimate of the sinusoidal function. With the present invention the effect of NRRO on the PES, such as that caused by drive motor bearing inaccuracies, is essentially cancelled, thereby improving the read/write operations of the disk file.

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First Claim