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Loop control of active damping for HDD

IP.com Disclosure Number: IPCOM000014346D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 3 page(s) / 170K

Publishing Venue

IBM

Abstract

1. Idea of disclosure Disclosed is a new reliable head load/unload servo control method for HDDs with Active Damping/Control using the active damping loop gain control. Active damping/control has been used to eliminate gain of the major mode (butterfly mode), that limits servo bandwidth, by actively damping and

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Loop control of active damping for HDD

1. Idea of disclosure Disclosed is a new reliable head load/unload servo control method for HDDs with Active Damping/Control using the active damping loop gain control. Active damping/control
has been used to eliminate gain of the
major mode (butterfly mode), that limits
servo bandwidth, by actively damping and
stiffening the mode. The active
damping/control technique requires that
the sensor location being chosen such
that the sensor signal is in phase with
all major modes. However, this may not
be achievable for some condition like
head suspension being on a ramp for head
load/unload purpose. Because the actuator
resonance mode will be changed due to
touching HGA Load/Unload Tabs to Ramp.
Fig. 1 shows the fundamental
description for active damping control
and Fig.2 shows the head suspension and
actuator structure for Head load/unload
type hard disk drive.

Fundamentals of Active Damping

Sensor should detect coil sway deformation. Sensor signal should be in phase with all major modes. Phase control in active damping loop can stabilize/damp high frequency out-of-phase modes .

OBJECTIVE: OBJECTIVE Increase servo bandwidth through reducing gain and increasing frequency of flexible modes actively .

Fig.1 Fundamentals of Active Damping

Digital Servo

+

+

Current VCM

PES

Active damping stiffening & mass-reducing

Driver

Actuator

- d * strain rate - s * strain + m * rate of strain rate [+ Phase Shift Effects]

(analog circuit)

Sensor Signal (strain)

1

...