Abstract: A control for a robotic actuator employs a position processor to determine the phase of a pair of electrooptically generated position signals as well as to keep track of the number of whole cycles of the position signals. Whole cycles are tracked using a prediction technique depending upon the continuity of position and velocity. A command processor employing the sensed position produces a velocity signal for driving the robotic actuator. When very slow motion is sensed, the response of the controller is appropriately reduced to maintain a velocity command signal generally in proportion to the motion.

Abstract: A robotic height sensor employs the defocussing of a spot of light to detect the motion of a probe contacting a reference object. The defocussing changes the electrical output of a photodetector which output is used to control a height drive mechanism. In a preferred embodiment of the invention, an intentional weakened portion of a shaft is provided for permitting limited lateral freedom of the shaft to accommodate minor irregularities in a workpiece.

Abstract: Air bearing pads for supporting a one-axis table in a granite bridge positioning apparatus on a thin film of air include machine-thinned sections for providing resilience to the pads in order to permit flexing sufficient to accommodate surface irregularities on the supporting surface. A single air pressure regulator provides a source of pressurized air to flow-control devices of a plurality of air bearing pads supporting a one-axis table. The individual flow-control devices adjust the flow of air to their respective air bearing pads to individually adjust the lift of the pads.

Abstract: A friction drive for a positioning table employs a friction drive bar centered along the axis of the positioning table and coupled to the positioning table through a flexure member which allows lateral translation of the friction drive bar with respect to the table. The shaft of a rigidly mounted servomotor is tightly pinched against the side of the friction drive bar by a pair of back-up rollers on a pivoted support bar anchored to the frame bearing against the off side of the servomotor shaft and a pressure roller, also mounted on an anchored pivoted support bar, bearing against the opposed side of the friction drive bar. The pair of back-up rollers and the pressure roller are resiliently urged together to firmly pinch the servomotor shaft and friction drive bar together. The anchored pivoted support bar carries through longitudinal forces to prevent deflection of the servomotor shaft.