Qume Corporation

Frank W Lin

Mei S Sze

A digital servo system adapted for use in a dual mode coarse-fine servo system to control a movable member from a starting position to an at rest destination position. The digital servo generates a pulse train in response to varying space phase cyclic analog position signal A from an encoder coupled to the movable member. Each cycle of an analog position signal represents a small incremental amount of movement by the movable member. The pulse train provides a change in its state in time with the varying position signals. In the preferred embodiment, eight changes occur per cycle. The pulse train is integrated to provide a velocity signal which is compared with a command velocity signal.

Digital servo system

A dual mode servo-system providing improved motion characteristics and improved noise immunity. A relatively movable member is driven by control signals derived from actual velocity feedback signals during coarse mode operation. At the beginning of fine mode operation the actual velocity signal is sampled and used to generate a synthetic velocity signal used to control motion of the member during final deceleration, along with an actual position feedback signal, the synthetic velocity signal having a decreasing magnitude tailored to a particular application. At a predetermined maximum time period, after detent of the member, a time out circuit re-inserts the actual velocity feedback signal. Control signals for the driven member are also derived from the actual motor current by integrating the motor current, the integrated current signals being used to control motion of the member during coarse mode operation only. During fine mode operation, the member is controlled by an actual position feedback signal and an actual velocity signal derived from the position signal.

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San Jose, CA, United States of America

Frank W Lin