US 7,009,804 B2Granted

Method and apparatus for micro-actuator stroke sensitivity calibration in a hard disk drive

AssigneeSamsung Electronics Co., Ltd.

InventorsVinod Sharma, Hyung Jai Lee

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Abstract

A sinusoidal signal is added to the notch filtered micro-actuator control signal stimulating the micro-actuator. The voice coil control signal is notch filtered to remove the frequency component of the sinusoidal signal before it stimulates the voice coil motor. The micro-actuator control signal is notch filtered to remove the frequency component of the sinusoidal signal before it stimulates the micro-actuator. The response of the system is measured as the Position Error Signal (PES), for the magnetic head moved by the micro-actuator. The measured PES is then demodulated at the frequency of the sinusoidal signal to create a measured amplitude. The stroke sensitivity is then calculated from the measured amplitude and amplitude of the sinusoidal stimulus. The frequency of the sinusoidal signal and notch filters is essentially the same, chosen away from significant excitation frequencies and outside the bandwidth of the servo system. The invention includes using multiple frequencies, as well as various formulas for the stroke sensitivity. The invention may be applied to more than one micro-actuator within the hard disk drive to create a stroke sensitivity for each micro-actuator, a combination, or for all micro-actuators. The invention includes the method implemented using a servo-controller, as well as the program system for the servo-controller, at least partly implementing the method.

Claims23

Dependent claims

A method of calibrating at least one micro-actuator in a hard disk drive, comprising the steps of:

notch filtering a micro-actuator control signal at a frequency to create a notch filtered micro-actuator signal;
adding a sinusoidal signal at said frequency to said notch filtered micro-actuator control signal to stimulate said micro-actuator;
notch filtering a voice coil control signal at said frequency to create a notch filtered voice coil control signal to stimulate said voice coil;
demodulating a PES signal based upon said sinusoidal signal to create a response amplitude at said frequency;
decouple filtering of said micro-actuator control signal to create a decoupling micro-actuator feedback signal;
removing said PES signal and said decoupling micro-actuator feedback signal to direct control of said voice coil motor;
and
calculating a stroke sensitivity based upon said response amplitude;
wherein said sinusoidal signal has a stimulus amplitude at said frequency;
wherein said micro-actuator is coupled with a magnetic head in a head gimbal assembly following a track on a rotating disk surface;
wherein said magnetic head follows said track in response to a voice coil motor through stimulation of a voice coil and in response to said micro-actuator;
and
wherein said PES signal is based upon said magnetic head following a track on said rotating disk surface in response to said notch filtered voice coil control signal and to said notch filtered micro-actuator control signal;
wherein said frequency is outside a bandwidth of a servo system in said hard disk drive, and away from any significant excitation resonance of said servo system;
wherein said servo system includes control of said voice coil motor, and of said micro-actuator through said head gimbal assembly positioning said magnetic head to follow said track and respond with said PES signal.

12 more elements

An apparatus for calibrating at least one micro-actuator in a hard disk drive, comprising:

means for notch filtering a micro-actuator control signal at a frequency to create a notch filtered micro-actuator signal;
means for adding a sinusoidal signal at said frequency to said notch filtered micro-actuator control signal to stimulate said micro-actuator;
means for notch filtering a voice coil control signal at said frequency to create a notch filtered voice coil control signal to stimulate said voice coil;
means for demodulating a PES signal based upon said sinusoidal signal to create a response amplitude at said frequency;
means for decouple filtering of said micro-actuator control signal to create a decoupling micro-actuator feedback signal;
means for removing said PES signal and said decoupling micro-actuator feedback signal to direct control of said voice coil motor;
and
means for calculating a stroke sensitivity based upon said response amplitude;
wherein said sinusoidal signal has a stimulus amplitude at said frequency;
wherein said micro-actuator is coupled with a magnetic head in a head gimbal assembly following a track on a rotating disk surface;
wherein said magnetic head follows said track in response to a voice coil motor through stimulation of a voice coil and in response to said micro-actuator;
and
wherein said PES signal is based upon said magnetic head following a track on said rotating disk surface in response to said notch filtered voice coil control signal and to said notch filtered micro-actuator control signal;
wherein said frequency is outside a bandwidth of a servo system in said hard disk drive, and away from any significant excitation resonance of said servo system;
wherein said servo system includes control of said voice coil motor, and of said micro-actuator through said head gimbal assembly positioning said magnetic head to follow said track and respond with said PES signal.

12 more elements

Dependencies are inferred from the claim text.