Hard disk drive which uses the back EMF of the actuator to detect shocks
US5654840A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 30, 1994 |
| Grant date | Aug 5, 1997 |
| Priority date | — |
| Expiry date | Jun 30, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B5/5565
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.