Data Recording Instrument Company Limited

Cambrian Consultants, Inc.

Francis P Hammond

Martyn A Lewis

A method and apparatus are disclosed for providing continuous position information in a position servo system having position information signals 162, 164 coming from encoder 160 and which provide indirect position information over selected ranges, and a reference position information signal 153 coming from transducer 140 and which provides reference position information at discrete intervals. In the preferred embodiment, the distances between selected positions of two position information signals are combined, and in response to position offset information obtained from the reference position signal 153, thereafter used in selecting which of the position information signals 162, 164 will be used for determining position information. The position determination techniques are further employed in positioning the transducer apparatus 140 relative to a rotating storage medium 142 through the use of an externally commutated positioning apparatus, such as motor 100, under control of a processing element 30. A control method is combined with the positioning method and apparatus which includes an initial determination of salient parameters associated with the apparatus (such as the commutation points of the motor 100 with respect to its end stops, and the amplitude of the two signals 162, 164). Positioning of the transducing apparatus 140 is achieved through a plurality of control modes which are responsive to the determined parameters. In addition, the accuracy with which the position of the transducing apparatus 140 is determined varies among the modes with the remaining distance yet to traverse to a desired destination position.

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Cheshire, United Kingdom

Francis P Hammond