# US 9,437,231 B1 · Data storage device concurrently controlling and sensing a secondary actuator for actuating a head over a disk

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 9,437,231 B1
- Document ID: US9437231B1
- Status: Granted
- Kind: B1
- Application number: 14/865,858
- Filed: 2015-09-25
- Granted: 2016-09-06
- Earliest claimed: 2015-09-25
- Assignees: Western Digital Technologies, Inc.
- Applicants: Western Digital Technologies, Inc.
- Inventors: Timothy A. Ferris; Jaesoo Byoun
- Web page: https://patentgrep.com/patent/US9437231B1

## CPC

- G11B 5/5565: {system adaptation for compensation of variations of physical parameters, e.g. temperature}
- G11B 5/5526: {Control therefor; circuits, track configurations or relative disposition of servo-information transducers and servo-information tracks for control thereof (G11B5/556 takes precedence)}
- G11B 5/5552: {using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means}
- G11B 5/5582: {system adaptation for working during or after external perturbation, e.g. in the presence of a mechanical oscillation caused by a shock}
- 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)

## Abstract

A data storage device is disclosed comprising a voice coil motor (VCM) and a secondary actuator configured to actuate a head over a disk. A control signal is applied to the secondary actuator while processing a sensor signal generated by the secondary actuator. A vibration signal is generated based on the sensor signal, wherein the vibration signal is a high-pass signal.

## Claims

### Claim 1

A data storage device comprising:
a disk;
a head;
a voice coil motor (VCM) and a secondary actuator configured to actuate the head over the disk;
a sensor capacitor proportional to a capacitance of the secondary actuator; and
control circuitry configured to:
apply a control signal to the secondary actuator and concurrently process a sensor signal generated by the secondary actuator; and
generate a vibration signal based on the sensor signal and the sensor capacitor, wherein a capacitance of the sensor capacitor is at least two times less than a capacitance of the secondary actuator.

### Claim 2 (depends on 1)

The data storage device as recited in claim 1, wherein the vibration signal has a cut-off frequency between ten percent and ninety percent of a bandwidth of a control loop for controlling the secondary actuator.

### Claim 3 (depends on 1)

The data storage device as recited in claim 1, wherein:
a control loop for controlling the secondary actuator has a high-pass response; and
the vibration signal has a cut-off frequency above a cut-off frequency of the high-pass response of the control loop for the secondary actuator.

### Claim 4 (depends on 1)

The data storage device as recited in claim 1, wherein the vibration signal has a cut-off frequency higher than a cut-off frequency of a response of a control loop for controlling the VCM.

### Claim 5 (depends on 1)

The data storage device as recited in claim 1, wherein the control circuitry is further configured to:
generate a sensor current proportional to a current applied to the secondary actuator due to the control signal;
estimate a capacitive voltage of the secondary actuator based on the sensor current; and
generate the vibration signal based on a difference between the sensor signal and the estimated capacitive voltage.

### Claim 6 (depends on 5)

The data storage device as recited in claim 5, wherein the control circuitry is further configured to estimate the capacitive voltage of the secondary actuator by applying the sensor current to the sensor capacitor.

### Claim 7 (depends on 6)

The data storage device as recited in claim 6, wherein the control circuitry is further configured to adapt a gain of the sensor capacitor based on the sensor signal and the estimated capacitive voltage.

### Claim 8 (depends on 7)

The data storage device as recited in claim 7, wherein the control circuitry is further configured to:
low pass filter a difference between the sensor signal and the estimated capacitive voltage to generate a low-pass signal; and
adapt the gain of the sensor capacitor based on the low-pass signal.

### Claim 9 (depends on 1)

The data storage device as recited in claim 1, wherein the control circuitry is further configured to generate a feed-forward compensation signal applied to the secondary actuator based on the vibration signal.

### Claim 10

A data storage device comprising:
a disk;
a head;
a voice coil motor (VCM) and a secondary actuator configured to actuate the head over the disk; and
control circuitry configured to:
measure a position of the head over the disk;
generate a control signal based on the measured position of the head;
apply the control signal to the secondary actuator;
process a sensor signal generated by the secondary actuator;
generate a sensor current proportional to a current applied to the secondary actuator due to the control signal;
estimate a capacitive voltage of the secondary actuator by applying the sensor current to a sensor capacitor that is proportional to a capacitance of the secondary actuator;
generate a vibration signal based on a difference between the sensor signal and the estimated capacitive voltage; and
adapt a gain of the sensor capacitor based on the control signal and the estimated capacitive voltage.

### Claim 11 (depends on 10)

The data storage device as recited in claim 10, wherein the control circuitry is further configured to:
low pass filter a difference between the sensor signal and the estimated capacitive voltage to generate a low-pass signal; and
adapt the gain of the sensor capacitor based on the low-pass signal.

### Claim 12 (depends on 10)

The data storage device as recited in claim 10, wherein a capacitance of the sensor capacitor is at least two times less than the capacitance of the secondary actuator.

### Claim 13 (depends on 10)

The data storage device as recited in claim 10, wherein the control circuitry is further configured to generate a feed-forward compensation signal applied to the secondary actuator based on the vibration signal.

### Claim 14

A method of operating a data storage device, the method comprising:
actuating a head over a disk using a voice coil motor (VCM) and a secondary actuator;
applying a control signal to the secondary actuator and concurrently process a sensor signal generated by the secondary actuator; and
generating a vibration signal based on the sensor signal, wherein the vibration signal has a cut-off frequency between ten percent and ninety percent of a bandwidth of a control loop for controlling the secondary actuator.

### Claim 15 (depends on 14)

The method as recited in claim 14, wherein:
the control loop for controlling the secondary actuator has a high-pass response; and
the vibration signal has a cut-off frequency above a cut-off frequency of the high-pass response of the control loop for the secondary actuator.

### Claim 16 (depends on 14)

The method as recited in claim 14, wherein the vibration signal has a cut-off frequency higher than a cut-off frequency of a response of a control loop for controlling the VCM.

### Claim 17 (depends on 14)

The method as recited in claim 14, further comprising:
generating a sensor current proportional to a current applied to the secondary actuator due to the control signal;
estimating a capacitive voltage of the secondary actuator based on the sensor current; and
generating the vibration signal based on a difference between the sensor signal and the estimated capacitive voltage.

### Claim 18 (depends on 17)

The method as recited in claim 17, further comprising estimating the capacitive voltage of the secondary actuator by applying the sensor current to a sensor capacitor that is proportional to a capacitance of the secondary actuator.

### Claim 19 (depends on 18)

The method as recited in claim 18, further comprising adapting a gain of the sensor capacitor based on the sensor signal and the estimated capacitive voltage.

### Claim 20 (depends on 19)

The method as recited in claim 19, further comprising:
low pass filtering a difference between the sensor signal and the estimated capacitive voltage to generate a low-pass signal; and
adapting the gain of the sensor capacitor based on the low-pass signal.

### Claim 21 (depends on 18)

The method as recited in claim 18, wherein a capacitance of the sensor capacitor is at least two times less than the capacitance of the secondary actuator.

### Claim 22 (depends on 14)

The method as recited in claim 14, further comprising generating a feed-forward compensation signal applied to the secondary actuator based on the vibration signal.

### Claim 23

A method of operating a data storage device, the method comprising:
actuating a head over a disk using a voice coil motor (VCM) and a secondary actuator;
measuring a position of the head over the disk;
generating a control signal based on the measured position of the head;
applying the control signal to a secondary actuator configured to actuate the head over the disk;
processing a sensor signal generated by the secondary actuator;
generating a sensor current proportional to a current applied to the secondary actuator due to the control signal;
estimating a capacitive voltage of the secondary actuator by applying the sensor current to a sensor capacitor that is proportional to a capacitance of the secondary actuator;
generating a vibration signal based on a difference between the sensor signal and the estimated capacitive voltage; and
adapting a gain of the sensor capacitor based on the control signal and the estimated capacitive voltage.

### Claim 24 (depends on 23)

The method as recited in claim 23, further comprising:
low pass filtering a difference between the sensor signal and the estimated capacitive voltage to generate a low-pass signal; and
adapting the gain of the sensor capacitor based on the low-pass signal.

### Claim 25 (depends on 23)

The method as recited in claim 23, wherein a capacitance of the sensor capacitor is at least two times less than the capacitance of the secondary actuator.

### Claim 26 (depends on 23)

The method as recited in claim 23, further comprising generating a feed-forward compensation signal applied to the secondary actuator based on the vibration signal.

### Claim 27

Control circuitry configured to control a voice coil motor (VCM) and a secondary actuator to actuate a head over a disk, the control circuitry configured to:
apply a control signal to the secondary actuator and concurrently process a sensor signal generated by the secondary actuator; and
generate a vibration signal based on the sensor signal, wherein the vibration signal has a cut-off frequency between ten percent and ninety percent of a bandwidth of a control loop for controlling the secondary actuator.

### Claim 28 (depends on 27)

The control circuitry as recited in claim 27, wherein:
the control loop for controlling the secondary actuator has a high-pass response; and
the vibration signal has a cut-off frequency above a cut-off frequency of the high-pass response of the secondary actuator.

### Claim 29 (depends on 27)

The control circuitry as recited in claim 27, wherein the vibration signal has a cut-off frequency higher than a cut-off frequency of a response of a control loop for controlling the VCM.

### Claim 30 (depends on 27)

The control circuitry as recited in claim 27, wherein the control circuitry is further configured to:
generate a sensor current proportional to a current applied to the secondary actuator due to the control signal;
estimate a capacitive voltage of the secondary actuator based on the sensor current; and
generate the vibration signal based on a difference between the sensor signal and the estimated capacitive voltage.

### Claim 31 (depends on 30)

The control circuitry as recited in claim 30, wherein the control circuitry is further configured to estimate the capacitive voltage of the secondary actuator by applying the sensor current to a sensor capacitor that is proportional to a capacitance of the secondary actuator.

### Claim 32 (depends on 31)

The control circuitry as recited in claim 31, wherein the control circuitry is further configured to adapt a gain of the sensor capacitor based on the sensor signal and the estimated capacitive voltage.

### Claim 33 (depends on 32)

The control circuitry as recited in claim 32, wherein the control circuitry is further configured to:
low pass filter a difference between the sensor signal and the estimated capacitive voltage to generate a low-pass signal; and
adapt the gain of the sensor capacitor based on the low-pass signal.

### Claim 34 (depends on 31)

The control circuitry as recited in claim 31, wherein a capacitance of the sensor capacitor is at least two times less than the capacitance of the secondary actuator.

### Claim 35 (depends on 27)

The control circuitry as recited in claim 27, wherein the control circuitry is further configured to generate a feed-forward compensation signal applied to the secondary actuator based on the vibration signal.

### Claim 36

Control circuitry configured to control a voice coil motor (VCM) and a secondary actuator to actuate a head over a disk, the control circuitry configured to:
measure a position of the head over the disk;
generate a control signal based on the measured position of the head;
apply the control signal to the secondary actuator;
process a sensor signal generated by the secondary actuator;
generate a sensor current proportional to a current applied to the secondary actuator due to the control signal;
estimate a capacitive voltage of the secondary actuator by applying the sensor current to a sensor capacitor that is proportional to a capacitance of the secondary actuator;
generate a vibration signal based on a difference between the sensor signal and the estimated capacitive voltage; and
adapt a gain of the sensor capacitor based on the control signal and the estimated capacitive voltage.

### Claim 37 (depends on 36)

The control circuitry as recited in claim 36, wherein the control circuitry is further configured to:
low pass filter a difference between the sensor signal and the estimated capacitive voltage to generate a low-pass signal; and
adapt the gain of the sensor capacitor based on the low-pass signal.

### Claim 38 (depends on 36)

The control circuitry as recited in claim 36, wherein a capacitance of the sensor capacitor is at least two times less than the capacitance of the secondary actuator.

### Claim 39 (depends on 36)

The control circuitry as recited in claim 36, wherein the control circuitry is further configured to generate a feed-forward compensation signal applied to the secondary actuator based on the vibration signal.