Precision x-y positioner

Abstract

Suspending an armature on a parallelopiped basket of flexure springs, with a lateral effect cell position sensor and an X-Y source of motive power, provides a precision X-Y positioner with minimum static friction and with feedback of actual position for closed loop servo operation under computer control. The armature is arranged for X-Y motion within its own plane, and is arranged to carry a gripper, cutting tool, or other end effector. The parallelopiped basket includes a stator, a first set of flexure springs, a flexure spring carrier mounted on the first set of flexure springs, a second set of flexure springs mounted on the flexure spring carrier, and the armature mounted on the second set of flexure springs in turn mounted on the carrier. The basket suspends the armature with freedom of motion in the X and Y dimensions without static friction associated with sliding or rolling motions. Motive power to reposition the armature to the desired X-Y coordinates is provided by a positioning motor made up of a pair of U-shaped permanent magnets each having coil-wrapped U-shaped pole pieces mounted orthogonally to each other. Once the armature is positioned, flux differentials applied to teeth on the armature oppose any forces tending to move the armature from the desired X-Y coordinates. Armature position sensing is by LED on the armature and a lateral effect cell, mounted on the stator, which feeds back sensing signals to a computer to form a servo loop. The computer can vary the compliance of the flexure springs by adjusting the motor control signals as a function of a compliance variable.