Fixed Disk Subsystem Description; Control Electronics; Head Disk Assembly; Actuator - IBM DDRS-39130 - Ultrastar 9.1 GB Hard Drive Specifications

2.0 Fixed Disk Subsystem Description

2.1 Control Electronics

The drive is electronically controlled by a microprocessor, several logic modules, digital/analogue modules,
and various drivers and receivers. The control electronics perform the following major functions:
Conducts a power-up sequence and calibrates the servo.
Monitors various timers for head settling, servo failure, etc.
Analyzes servo signals to provide closed loop control. These include position error signal and estimated
velocity.
Controls the voice coil motor driver to align the actuator onto a desired position.
Monitors the actuator position and determines the target track for a seek operation.
Constantly monitors error conditions of the servo and takes corresponding action if an error occurs.
Controls starting, stopping, and rotating speed of the spindle.
Controls and interprets all interface signals between the host controller and the drive.
Controls read write accessing of the disk media, including defect management and error recovery.
Performs self-checkout (diagnostics).

2.2 Head Disk Assembly

The head disk assembly (HDA) is assembled in a clean room environment and contains a disk and actuator
assembly. Air is constantly circulated and filtered when the drive is operational. Venting of the HDA is
accomplished via a breather filter.
The spindle is driven directly by a brushless, sensorless DC drive motor. Dynamic braking is used to stop the
spindle quickly.

2.3 Actuator

The read/write heads are mounted in the actuator. The actuator is a swing-arm assembly driven by a voice
coil motor. A closed-loop positioning servo controls the movement of the actuator. An embedded servo
pattern supplies feedback to the positioning servo to keep the read/write heads centered over the desired
track.
The actuator assembly is balanced to allow vertical or horizontal mounting without adjustment.
When the drive is powered off, the actuator automatically moves the head to a dedicated landing zone
outside of the data area, where the actuator is locked.
Copyright IBM Corp. 1997
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