Disk drive to estimate repeatable runout (RRO) based upon on an optimal mean square estimation (MSE) learning method
AssigneeWestern Digital Technologies, Inc.
InventorsMin Chen, Li Yi
Life of this patent
Estimating the term…
Abstract
Disclosed is a method of estimating repeatable runout (RRO) for a disk drive. The method includes: determining a plurality of position error signal (PES) values for a plurality of servo wedges of a track of a disk; and estimating repeatable runout (RRO) in the PES values for the servo wedges of the track by averaging determined PES values over a pre-determined number of revolutions of the disk of the disk drive and scaling the averaged PES values by a pre-determined ratio of the variance of non-repeatable runout (NRRO) to the variance of an optimal estimation of the RRO for the disk drive.
Claims14
A method of estimating repeatable runout (RRO) for a disk drive comprising:
- determining a plurality of position error signal (PES) values for a plurality of servo wedges of a track of a disk;
- and
- estimating repeatable runout (RRO) in the PES values for the servo wedges of the track by averaging determined PES values over a pre-determined number of revolutions of the disk of the disk drive and scaling the averaged PES values by a pre-determined ratio of the variance of non-repeatable runout (NRRO) to the variance of an optimal estimation of the RRO for the disk drive, wherein the RRO value is governed by an equation:
- R
-
- R
- ^
-
- O
- =
- 1
- n
- +
- r
-
-
- ∑
- i
- =
- 1
- n
-
-
- PES
-
-
- (
- n
- )
- ;
- wherein n is a number of revolutions of the disk of the disk drive, PES(n) is a summed PES value for the plurality of servo wedges of the track at an n-th revolution, and r is the pre-determined ratio of the variance of NRRO to the variance of the optimal estimation of the RRO for the disk drive.
A disk drive to estimate repeatable runout (RRO), the disk drive comprising:
- a disk including at least one track having a plurality of servo wedges;
- a moveable head;
- and
- a servo controller for controlling the position of the moveable head to perform track following on the plurality of servo wedges of the track and to measure a plurality of position error signal (PES) values, the servo controller to:
- determine a plurality of position error signal (PES) values for a plurality of servo wedges of the track of the disk;
- and
- estimate repeatable runout (RRO) in the PES values for the servo wedges of the track by averaging determined PES values over a pre-determined number of revolutions of the disk of the disk drive and scaling the averaged PES values by a pre-determined ratio of the variance of non-repeatable runout (NRRO) to the variance of an optimal estimation of the RRO for the disk drive, wherein the RRO value is governed by an equation:
- R
-
- R
- ^
-
- O
- =
- 1
- n
- +
- r
-
-
- ∑
- i
- =
- 1
- n
-
-
- PES
-
-
- (
- n
- )
- ;
- wherein n is a number of revolutions of the disk of the disk drive, PES(n) is a summed PES value for the plurality of servo wedges of the track at an n-th revolution, and r is the pre-determined ratio of the variance of NRRO to the variance of the optimal estimation of the RRO for the disk drive.
Dependencies are inferred from the claim text.