US 6,122,133 A · Hybrid method of determining a fractional track position of a read transducer in a hard disk drive

Abstract

A method used to implement a sampled servo control system in a magnetic disk drive for generating a fractional track portion of a position error signal to correctably maintain the alignment of a read transducer (or associated write transducer) relative to a centerline of one of a plurality of a concentric data tracks upon a rotating data storage disk. The system uses a hybrid approach of determining a fractional track position by using a two-burst algorithm when possible and using a multi-burst algorithm only when necessary. The system is particularly suited to determining fraction track position when jogging a relatively narrow magnetoresistive read transducer with a servo pattern normally useful only for wider transducers, namely a pattern of four angularly sequential servo bursts A, B, C, D that are 100% of a track pitch in width and are arranged in quadrature. In this context, the preferred system reads all four 100% servo bursts and then uniquely selects between a two-burst algorithm and a four-burst algorithm to generate a fractional track position relative to a two-burst centerline (A/B or C/D) or a four-burst centerline (N-Q or N+Q). In general, the servo system selects between the two-burst and the four-burst algorithms based on the transducer's passing through a two-burst zone or a four-burst zone, which preferably overlap, as determined from the relative burst amplitudes of all four servo bursts. When operating at a position in which the zones overlap, the preferred system is biased to select the zone corresponding to the algorithm used during the immediately previous servo sample in order to add stability.

Claims31

Dependent claims

A method for repeatedly determining a fractional track position of a read transducer in a sampled servo disk drive for maintaining alignment of the read transducer relative to a centerline of one of a plurality of concentric data tracks upon a rotating data storage disk, comprising the steps of:

reading a plurality of angularly sequential servo bursts that are differently radially spaced with respect to a concentric data track;
calculating a first fractional track position using a first algorithm based on a first plurality of the angularly sequential servo bursts;
determining whether to retain the first fractional track position;
and
calculating a second fractional track position using a second algorithm based on a second greater plurality of the servo bursts if the first fractional track position is not retained.

2 more elements

A disk drive generating a fractional track position signal, comprising:

a base;
a data disk having a plurality of concentric data tracks;
a transducer head assembly including a read transducer;
a sampled servo control system for moving the transducer head over the data disk relative to the concentric data tracks;
a plurality of angularly sequential servo bursts on the data disk comprising four angularly sequential servo bursts A, B, C, D that are each 100% of a track pitch in width and are radially arranged in a 100% quadrature servo pattern wherein two of the servo bursts A, B are equally radially disposed on either side of a "normal" two-burst centerline A/B that is substantially aligned with the centerline of a concentric data track and two of the servo bursts C, D are equally radially disposed on either side of a "quadrature" two-burst centerline C/D that is substantially offset from the centerline of the concentric data track by 50% of a track pitch;
two-burst means for calculating a fractional track position with a first algorithm using only two of the four servo bursts A, B or C, D;
four-burst means for calculating a fractional track position with a second algorithm using all four servo bursts A, B, C, D;
means for dividing a repeating portion of the 100% quadrature servo pattern into a plurality of two-burst zones in which the fractional track position is calculable by the two-burst algorithm using only two bursts and a plurality of four-burst zones in which the fractional track position is calculable by the four-burst algorithm using all four bursts;
means for determining which zone was read by the read transducer based on relative values of the four servo bursts A, B, C, D;
and
means for selecting between the two-burst and four-burst means for calculating the fractional track position based on which zone was determined to be read by the read transducer.

8 more elements

A method of determining a fractional track position of a read transducer in a disk drive using a repeating pattern of four angularly sequential servo bursts A, B, C, D that are radially arranged in a 100% quadrature servo pattern wherein two of the servo bursts A, B are equally radially disposed on either side of a "normal" two-burst centerline A/B that is substantially aligned with the centerline of a concentric data track and two of the servo bursts C, D are equally radially disposed on either side of a "quadrature" two-burst centerline C/D that is substantially offset from the centerline of the concentric data track by 50% of a track pitch, the method comprising the steps of:

reading four servo bursts A, B, C, D for use in calculating a two-burst fractional track position relative to a two-burst centerline and in calculating a four-burst fractional track position relative to a four-burst centerline;
using a two-burst fractional track position to position the read transducer if the two-burst fractional track position is less than a limit value;
and
using a four-burst fractional track position to position the read transducer if the two-burst fractional track position is greater than the limit value.

1 more element

Dependencies are inferred from the claim text.

Hybrid method of determining a fractional track position of a read transducer in a hard disk drive

Life of this patent

Hybrid method of determining a fractional track position of a read transducer in a hard disk drive

Life of this patent

Abstract

Claims31