Displacement Sensing by Piezoelectric Transducers in High-Speed Lateral Nanopositioning

This paper deals with the characterization of piezoelectric ceramic type sensors integrated in a compact high-speed 2-DOF nano-positioner to measure large signal stage displacement. Such transducers are very attractive because they provide measurements in a wide frequency bandwidth with low noise, they do not require bulky electronic modules and are cost effective compared to traditional sensors. The transducers are installed in series with piezoelectric actuators and thick ceramic insulators are incorporated between them to reduce the cross-talk. The sensor provides accurate position measurements as long as the nano-positioner displacement is within the sensing bandwidth. This is verified by large amplitude sinusoidal excitations of the nano-positioner along both x - and y -axes within the sensor bandwidth. The sensor can also measure the displacement in response to a single tone sinusoid at frequencies well above the dominant imaginary zeros of the interaction force, which is beyond the sensor bandwidth. Experimental measurements are compared with those obtained using a LASER interferometer sensor. The results allow obtaining precise calibration factors of the piezoelectric ceramic transducers with respect to the input frequencies and accurate displacement/voltage transfer characteristics for closed loop control purposes.