Fixed Disk Subsystem Description; Control Electronics; Head Disk Assembly; Actuator - IBM Ultrastar 36LZX Specifications

3.0 Fixed disk subsystem description

3.1 Control electronics

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

3.2 Head disk assembly

The head disk assembly (HDA) is assembled in a clean room environment and contains disks, a spindle
motor, actuator assembly, and voice coil motor. 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.

3.3 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 load/unload zone
outside of the data area, where the actuator is locked.
Ultrastar 36LZX hard disk drive specifications
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