US 8,300,337 B2Granted

Disk drive and method for measuring clearance change in the disk drive

AssigneeHitachi Global Storage Technologies Netherlands B.V.

InventorsMasayuki Kurita, Kenji Kuroki, Kenichi Kuramoto, Yoshihiko Maeda

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Abstract

A method for measuring change of clearance between a head and a disk. The method includes reading a preliminarily written data string for clearance measurement on a disk to obtain a first measured value corresponding to a clearance, and writing a new data string for deterioration check onto the disk and reading the data string for deterioration check to obtain a second measured value corresponding to the clearance. The method also includes determining a deterioration of the data string for clearance measurement from a difference between the first measured value and the second measured value, measuring a clearance change using the data string for clearance measurement by a normal operation if the determination is that the data string for clearance measurement has not deteriorated, and measuring a clearance change by an operation different from the normal operation if the determination is that the data string for clearance measurement has deteriorated.

Claims18

Dependent claims

A method for measuring a change of a clearance between a head and a disk, said method comprising;

reading a preliminarily written data string for clearance measurement on a disk to obtain a first measured value of Kgrad corresponding to a clearance, said clearance determined by a first linear dependence on said first measured value of Kgrad;
writing a new data string for deterioration check onto said disk and reading said data string for deterioration check to obtain a second measured value of Kgrad corresponding to a second clearance, said second clearance determined by a second linear dependence on said second measured value of Kgrad;
determining a deterioration of said data string for clearance measurement from a difference between said first measured value of Kgrad and said second measured value of Kgrad;
measuring a clearance change using said data string for clearance measurement by a normal operation if said determination is that said data string for clearance measurement has not deteriorated;
measuring a clearance change by an operation different from said normal operation if said determination is that said data string for clearance measurement has deteriorated;
and
wherein Kgrad comprises a corrected tap value of an adaptive cosine filter implemented in a read/write channel of a hard-disk drive;
and
wherein said first linear dependence and said second linear dependence are characterized by coefficients having different values, said values of said coefficients stored in a non-volatile memory of said hard-disk drive.

6 more elements

A disk drive comprising:

a write element configured to write a new data string for deterioration check onto a disk;
a read element configured to read a preliminarily written data string for clearance measurement on said disk and said data string for deterioration check;
a moving mechanism that supports a head comprising said write element and said read element and configured to move said head in proximity to a recording surface of said disk;
and
a controller configured to control said moving mechanism and said head;
wherein said controller is configured to obtain a first measured value of Kgrad corresponding to a clearance based on read-back signals in said data string for clearance measurement, said clearance determined by a first linear dependence on said first measured value of Kgrad;
said controller is configured to obtain a second measured value of Kgrad corresponding to a second clearance based on read-back signals from said data string for deterioration check, said second clearance determined by a second linear dependence on said second measured value of Kgrad;
said controller is configured to determine a deterioration of said data string for clearance measurement by comparing said first measured value of Kgrad with said second measured value of Kgrad;
said controller is configured to measure a clearance change using said data string for clearance measurement by a normal operation if said determination is that said data string for clearance measurement has not deteriorated;
and, said controller is configured to measure a clearance change by an operation different from said normal operation if said determination is that said data string for clearance measurement has deteriorated;
and
wherein Kgrad comprises a corrected tap value of an adaptive cosine filter implemented in a read/write channel of a hard-disk drive;
and
wherein said first linear dependence and said second linear dependence are characterized by coefficients having different values, said values of said coefficients stored in a non-volatile memory of said hard-disk drive.

11 more elements

Dependencies are inferred from the claim text.