Vibration control of a novel tube scanner using piezoelectric strain-induced voltage

Piezoelectric tube scanners are widely used in nanopositioning applications such as in scanning probe microscopy. Capacitive or inductive sensors are used to provide feedback to improve bandwidth and accuracy of these tube scanners. However, these sensors contain certain noise densities which restrict the bandwidth of the closed loop system if nanometer resolution is required. The use of piezoelectric strain-induced voltage as a measurement signal has been recently proposed to provide feedback with a noise profile of up to three orders of magnitude better than capacitive sensors. This technique uses a quadrant of the electrode for actuation and the opposite quadrant for sensing. The major drawbacks of this arrangement are that the travel range of the tube is reduced by half and the tube is not driven symmetrically; thus the tube is not a collocated system. In this article, a novel electrode pattern of a tube scanner which addresses the above issues and allows for simultaneous actuation and sensing is presented. By using the piezoelectric strain voltage as measurement, an Integral Resonant Control (IRC) method combined with a feedforward inversion technique is implemented to achieve high-speed and accurate scanning performances of the tube.