Electroglas, Inc.

General Signal Corporation

Tex M Dudley

William J Cornwell

William H Lee

An apparatus and method for positioning a wafer holding platform by moving it along a first set of axes concurrently through a path measured along a second set of axes. An apparatus of the present invention comprises a motor system to move the wafer holding stage and a motion control system to control the path of the wafer holding stage. The motor system constrains the wafer holding stage to a first two axes of movement, and the motion control system controls the path along a second two axes of movement. The first two axes and second two axes are located at angles from one another. The distance a wafer on the wafer holding stage is to be moved is measured along the second two axes. A method comprises constraining the movement of a wafer holding stage to a first and a second movement axes and controlling a path of the wafer holding stage along a third and a fourth movement axis. The present invention increases the speed of the wafer holding platform, thereby decreasing the time needed to test a wafer.

Method and apparatus for motion control

Movable (a head) and stationary (a stator) members are disposed in contiguous relationship. First magnetizable and non-magnetizable zones are alternately disposed on the stator in a particular direction. Second magnetizable and non-magnetizable zones are alternately disposed on the head in the particular direction. The zones on the head and the stator face each other and have substantially equal spacings. First means are associated with the head for producing magnetic fluxes in the magnetizable zones in the head and stator in a particular pattern to obtain incremental relative movements between the head and the stator on a vectorial basis in the particular direction. Second means are associated with the head for compensating for hysteresis effects in the magnetizable zones in the head and stator. The second means may produce magnetic flux of alternating polarity and decaying amplitude near the end of each incremental movement of the head relative to the stator. Means are provided for indicating the position of the head relative to the stator in the particular direction at each instant. Means are included for obtaining the production by the first means of magnetic fluxes at each position to provide corrections in the incremental movement of the head relative to the stator in the particular direction at that position.

System for linear motor control

A positioning apparatus includes a platen and a head independently movable relative to the platen. First and second coils having a particular phase relationship are disposed relative to each other on the head are independently energized to produce first and second electromagnetic forces. These electromagnetic forces have varying characteristics for moving the head relative to the platen and constant characteristics for maintaining the head in a substantially fixed relationship to the platen. Abrupt changes from the variable to the constant characteristics of the applied electromotive forces allow inertial forces to impart a decaying oscillation of the head about the positional origin determined by the constant characteristics of the applied electromotive force. Oscillation of the head relative to the platen produces first and second back-electromotive force sinusoids in the first and second coils, respectively. Means is provided for detecting the first back-electromotive force sinusoid to produce a damping signal with characteristics similar to the characteristics of the second back-electromotive force sinusoid. This damping signal can be introduced to the second coil to damp the second back-electromotive force sinusoid and inhibit the oscillations of the head.

Growing community of inventors

Palo Alto, CA, United States of America

Tex M Dudley