4.7 Servo Control

(1) Write/read recovery

This area is used to absorb the write/read transient and to stabilize the AGC.

(2) Servo mark

This area generates a timing for demodulating the gray code and position- demodulating the servo A to D by detecting the servo mark.

(3) Gray code (including index bit)

This area is used as cylinder address. The data in this area is converted into the binary data by the gray code demodulation circuit

(4) Servo A, servo B, servo C, servo D

This area is used as position signals between tracks and the IDD control at on- track so that servo A level equals to servo B level.

(5) PAD

This area is used as a gap between servo and data.

4.7.4 Actuator motor control

The voice coil motor (VCM) is controlled by feeding back the servo data recorded on the data surface. The MPU fetches the position sense data on the servo frame at a constant interval of sampling time, executes calculation, and updates the VCM drive current.

The servo control of the actuator includes the operation to move the head to the reference cylinder, the seek operation to move the head to the target cylinder to read or write data, and the track-following operation to position the head onto the target track.

(1) Operation to move the head to the reference cylinder

The MPU moves the head to the reference cylinder when the power is turned. The reference cylinder is in the data area.

When power is applied the heads are moved from the inner circumference shunt zone to the normal servo data zone in the following sequence:

a)Micro current is fed to the VCM to press the head against the inner circumference.

b)Micro current is fed to the VCM to move the head toward the outer circumference.

c)When the servo mark is detected the head is moved slowly toward the outer circumference at a constant speed.

C141-E104-02EN

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Fujitsu MHM215OAT, MHM200AT, MHM2100AT, MHL2300AT manual Actuator motor control
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MHM215OAT, MHM200AT, MHL2300AT, MHM2100AT specifications

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