Linear tables equipped with air bearings exhibit very low bearing friction. For this reason, it is not easy to attain a resting position or uniform displacement. In the development made by PTB, the linear table is displaced by means of two voice coil drives which work in the opposite direction to each other. Hereby, one electromagnetic actuator generates a constant pretension against which the second actuator displaces the table. This concept allows the stable operation of the air stage by an analogue controller. Especially the noise vertical to the direction of displacement is low (< 1 nm); this makes these tables particularly well suited for applications in roughnessmeasuring or form-measuring devices.
andreas.barthel