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Coarse-Scale Secondary Actuator Positioning System For Hard Disk Drive Disclosure Number: IPCOM000015077D
Original Publication Date: 2002-May-17
Included in the Prior Art Database: 2003-Jun-20

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The coarse-scale actuator positioning system disclosed here is a subsystem that is completely independent of the standard actuator positioner. It can provide secondary backup verification of the reports from the primary systems or serve on equal terms as a direct safety latch. A magnetic Hall sensor is attached to the actuator structure in such a position that the magnetic flux from the actuator fixed magnets varies monotonically as the comb is rotated. The Hall sensor then provides a readout of voltage that is uniquely mapped to the position of the recording heads. This Hall sensor output voltage is then sampled by an analog-to-digital convertor channel that is part of the hard disk controller chip. The information provided by this Hall sensor system may be used in various ways, including incorporation into the overall servo software control scheme, as well as through a direct hardware emergency control line input into the voice coil motordriver circuit. The incremental cost of this position sensing system is just for the Hall sensor itself, in addition to the costs of mounting onto the actuator comb and wiring to the flex cable. All of the other components required for this system to function exist on today’s hard disk drives. The use of this system has several advantages, including the following: