Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Patent
1994-06-30
1997-08-05
Sniezek, Andrew L.
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
360 60, 318601, 318635, G11B 2102
Patent
active
056548400
ABSTRACT:
A disk drive for operating in an environment in which the drive is subject to physical shock includes a circuit which senses movement of a transducer head support arm which result from a shock's rotational component. The rotational shock is detected as a residual BEMF signal in the drive's VCM coil winding. The residual signal is extracted from much larger position control signals that are applied to the VCM winding during normal system operation by providing circuits that simulate the VCM winding voltage caused by the position control signal and subtracting the outputs of the simulation circuits from the actual VCM coil winding voltage. This eliminates the normal operating components and leaves a residual signal that represents only the small portion of the VCM BEMF signal that results from the rotational shock. A threshold circuit compares the shock BEMF signal to a predetermined threshold. If the BEMF signal exceeds the threshold, disk drive write operations are aborted. An active calibration system is also employed that regularly updates both the simulated resistance and simulated inductance to null out the effects of temperature, design and aging tolerances.
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Edwards John R.
Patton Charles R.
Sareen Anil
Cullen Larry T.
Sniezek Andrew L.
Western Digital Corporation
Young, Esq. Leo J.
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