# US 10,311,905 B1 · Methods, devices, and systems for establishing fly-height parameters for hard disk drives

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- Number: US 10,311,905 B1
- Document ID: US10311905B1
- Status: Granted
- Kind: B1
- Application number: 15/937,261
- Filed: 2018-03-27
- Granted: 2019-06-04
- Earliest claimed: 2018-03-27
- Assignees: Seagate Technology LLC
- Applicants: Seagate Technology LLC
- Inventors: ChengYi Guo; Sheng Yuan Lin; Teck Khoon Lim; Teck Hoon Chua
- Web page: https://patentgrep.com/patent/US10311905B1

## CPC

- G11B 5/6011: {Control of flying height}
- G06N 3/0499: Feedforward networks
- G06N 3/08: Learning methods
- G06N 3/09: Supervised learning
- G11B 5/40: Protective measures on heads, e.g. against excessive temperature (G11B5/31 takes precedence; protection against wear G11B5/255 {; protective structure of the head: see under structures, e.g. G11B5/3106})
- G11B 5/455: Arrangements for functional testing of heads; Measuring arrangements for heads
- G11B 5/82: Disk carriers
- G11B 5/607: {using thermal means}
- G11B 5/6076: {Detecting head-disk contact}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- G06N: COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS

## Abstract

A method is disclosed for establishing a fly height parameter for a hard disc drive. The method includes receiving a set of testing data associated with the hard disc drive and subjecting the hard disc drive to a fly-height test at a first, nominal temperature to generate fly-height data. Based on the set of testing data and the fly-height data, the method includes predicting the hard disc drive's fly-height data for a fly-height test at a second temperature different from the first, nominal temperature. The method further includes establishing the fly-height parameter for the hard disc drive in response to the fly-height data and the predicted fly-height data.

## Claims

### Claim 1

A method for establishing a fly height parameter for a hard disc drive, the method comprising:
receiving a set of testing data associated with the hard disc drive;
subjecting the hard disc drive to a fly-height test while operating the hard disc drive at a first, nominal temperature to generate fly-height data;
based on the set of testing data and the fly-height data, predicting the hard disc drive's fly-height data for a fly-height test performed while operating the hard disc drive at a second temperature different from the first, nominal temperature; and
in response to the fly-height data and the predicted fly-height data, establishing the fly-height parameter for the hard disc drive.

### Claim 2 (depends on 1)

The method of claim 1, wherein the fly-height parameter is used to control a head-to-media spacing of a read/write head of the hard disc drive.

### Claim 3 (depends on 1)

The method of claim 1, wherein the fly-height parameter is used to control a heater current of a read/write head of the hard disc drive.

### Claim 4 (depends on 1)

The method of claim 1, wherein the fly-height parameter is a thermal clearance slope.

### Claim 5 (depends on 4)

The method of claim 4, wherein the thermal clearance slope is a linear slope of head-to-media spacing as a function of temperature.

### Claim 6 (depends on 1)

The method of claim 1, further comprising:
in response to the fly-height data and the predicted fly-height data, establishing the fly-height parameter for multiple zones of a magnetic recording disc.

### Claim 7 (depends on 1)

The method of claim 1, further comprising:
establishing a zone-by-zone curve of the predicted fly-height data; and
rejecting predicted fly-height data that are inconsistent with the established curve.

### Claim 8 (depends on 7)

The method of claim 7, wherein the established fly-height parameter is based only on non-rejected predicted fly-height data.

### Claim 9 (depends on 1)

The method of claim 1, further comprising:
in response to the fly-height data and the predicted fly-height data, establishing a plurality of fly-height parameters for the hard disc drive.

### Claim 10 (depends on 9)

The method of claim 9, further comprising:
in response to the fly-height data and the predicted fly-height data, establishing a fly height parameter for each read/write head of the hard disc drive.

### Claim 11 (depends on 1)

The method of claim 1, further comprising:
subjecting the hard disc drive to the plurality of tests to generate the set of testing data associated with the hard disc drive.

### Claim 12 (depends on 1)

The method of claim 1, wherein the step of establishing the fly-height parameter for the hard disc drive is performed using a trained artificial neural network to predict the hard disc drive's fly-height data.

### Claim 13 (depends on 12)

The method of claim 12, further comprising:
training an artificial neural network to predict the fly-height data for a fly-height test at the second temperature based on testing data including fly-height data from the fly-height test at the first, nominal temperature and fly-height data from a fly-height test at the second temperature.

### Claim 14 (depends on 1)

The method of claim 1, wherein the fly-height test involves causing head-to-disc contract, and wherein predicting the hard disc drive's fly-height data for the fly-height test at the second temperature does not involve causing head-to-disc contract.

### Claim 15 (depends on 1)

The method of claim 1, further comprising:
storing the established fly-height parameter to memory of the hard disc drive.

### Claim 16

A method for establishing a fly height parameter for a hard disc drive, the method comprising:
receiving a set of testing data associated with the hard disc drive;
receiving fly-height data associated with the hard disc drive and generated from a fly-height test performed at a first, nominal temperature;
based on the set of testing data and the fly-height data, predicting the hard disc drive's fly-height data for a fly-height test at a second temperature different from the first, nominal temperature;
establishing a curve of the predicted fly-height data;
generating modified predicted fly-height data by deleting predicted fly-height data that are outliers with the established curve; and
in response to the fly-height data and the modified predicted fly-height data, establishing the fly-height parameter for the hard disc drive.

### Claim 17 (depends on 16)

The method of claim 16, further comprising:
establishing a curve of the predicted fly-height data on a head-by-head basis;
generating modified predicted fly-height data, on a head-by-head basis, by deleting predicted fly-height data that are outliers with the established curves; and
in response to the fly-height data and the modified predicted fly-height data, establishing the fly-height parameter for the hard disc drive.

### Claim 18

A system for establishing a fly height parameter for a hard disc drive, the system comprising:
a computing device comprising a trained artificial neural network, a processor, and a memory, wherein
the computing device is configured to:
receive a set of testing data associated with the hard disc drive,
receive fly-height data associated with the hard disc drive and generated from a fly-height test performed at a first, nominal temperature,
compute fly-height data for a fly-height test at a second temperature using the trained artificial neural network, the received set of testing data, and the received fly-height data, and
compute a plurality of fly-height parameters for the hard disc drive based on at least the received fly-height data and the computed fly-height data.

### Claim 19 (depends on 18)

The system of claim 18, wherein the computing device is further configured to:
establish a trend of the computed fly-height data, and
generate modified predicted fly-height data by deleting predicted fly-height data that are outliers with the established curve.

### Claim 20 (depends on 19)

The system of claim 19, wherein the computing device is further configured to:
establish the fly-height parameter for the hard disc drive based on at least the modified predicted fly-height data.