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Reduction of acoustic noise during VCM open loop control

IP.com Disclosure Number: IPCOM000015335D
Original Publication Date: 2001-Dec-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Abstract

Disclosed is a method to reduce acoustic noise of hard disk drive during VCM open loop control. Problem As for the hard disk drive which utilize "Head load/unload function", VCM is driven with open loop control on occasion of confirmation whether the actuator is stopped on the ramp or not, or calibration before loading. In cases of these, the mechanical parts are vibrated because VCM current is changed with rectangle form. It is major cause of acoustic noise during load/unload operation. Solution The cause of acoustic noise when VCM is driven with open loop control, is large change of current with rectangle form. The rectangle form is constituted by many fourier elements, and resonance frequency of mechanical parts is included in them. Therefore the method of driving the VCM is changed in order that VCM is driven with sine curve because it is constituted by only one fourier element. Fig. 1 shows the difference of traditional and new method of driving VCM current when VCM current is changing from Ia to Ib. Amplitude is set as difference of Ia and Ib, and frequency is set as suitable one which is out of resonance of mechanical parts. The RRO table is used for generating sine curve.

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Reduction of acoustic noise during VCM open loop control

Disclosed is a method to reduce acoustic noise of hard disk drive
during VCM open loop
control.

Problem
As for the hard disk drive which utilize "Head load/unload function",
VCM is driven with
open loop control on occasion of confirmation whether the actuator is
stopped on the ramp
or not, or calibration before loading. In cases of these, the
mechanical parts are vibrated
because VCM current is changed with rectangle form. It is major cause
of acoustic noise
during load/unload operation.

Solution
The cause of acoustic noise when VCM is driven with open loop control,
is large change of
current with rectangle form. The rectangle form is constituted by many
fourier elements,
and resonance frequency of mechanical parts is included in them.
Therefore the method of driving the VCM is changed in order that VCM
is driven with sine
curve because it is constituted by only one fourier element.

Fig. 1 shows the difference of traditional and new method of driving
VCM current when VCM
current is changing from Ia to Ib. Amplitude is set as difference of
Ia and Ib, and frequency
is set as suitable one which is out of resonance of mechanical parts.
The RRO table is used
for generating sine curve.

Traditional method New method

Ib

Ia

Ib

Ia

current

VCM

VCM

current

Time Time

Fig. 1

Effectiveness
The sound power during load/unload operation was measured at

1

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acoustic chamber.
Fig. 2 is...