Electromagnetic x-y-theta precision positioner

Abstract

Mounting a position sensor equipped planar armature, in operative juxtaposition to a stator, by a spring colonnade basket of flexure columns, provides a low-friction precision X-Y-Theta positioner which has computer control of operations with feedback of actual position for closed loop servo operation. The spring colonnade basket provides freedom of motion in the X, Y and Theta (rotation about an axis mutually perpendicular to X and Y) dimensions without static friction present in sliding or rolling motions. The armature, which carries a gripper or other end effector and is free to move only within its own plane, is positioned by a motor made up of the armature and a stator mounted on a support platform. The stator is made up of a pair of U-shaped permanent magnets, each having U-shaped pole pieces mounted orthogonally to each other, at 45 degree angles to the axis of the magnet, so that each electromagnet controls motive power in both X and Y dimensions. Imbalances in the vector sums of the motive power of the electromagnets produces torque which provides Theta motion. Position sensors are mounted on the armature and stator. Position sensing signals are fed back to a computer for use in operations including repositioning The computer can vary the compliance of the flexure columns by adjusting the motor control currents as a function of a compliance variable.