Method and apparatus for unloading head from disk before a shock

Details Method and apparatus for unloading head from disk before a shock Method and apparatus for unloading head from disk before a shock

1997-12-08

2000-08-08

Sniezek, Andrew L.

Dynamic magnetic information storage or retrieval

Automatic control of a recorder mechanism

Controlling the head

360 7804, G11B 2102

Patent

active

061010626

ABSTRACT:
A method and apparatus for detecting harmful motion of a disk drive system to avoid a head crash. The motor spin current in the hard disk drive is used as a sensor to detect acceleration of the disk drive corresponding to a tipping or falling condition. In normal operation, the disk stack angular velocity (measured in revolutions per minute or RPM) is constantly monitored so that the disk drive control system can generate timing signals allowing the controller to accurately locate data addresses on the rotating disks. Disk stack RPM is accurately controlled at a constant value by a suitable feedback control loop which measures RPM and adjusts motor drive current to maintain the desired RPM. The rapidly rotating disk stack acts as a gyro system whose angular momentum resists any change in direction. In the event of a change in orientation of the disk drive such as that initiated by tipping or falling, gyroscopic forces are generated which act to increase friction of the bearings supporting the rotating disk stack resulting in a decrease in disk stack angular velocity. The change of disk stack RPM is detected by the normal feedback control loop electronics and an error signal can be generated to cause actuator park or unload action before impact of the falling disk drive occurs.

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"Quiescent Active Retract System For Disk File", IBM Technical Disclosure Bulletin, vol. 39 No. 11, Nov. 1996, p. 181.

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