Performance test and improvement of piezoelectric torsionalactuators

Abstract

This paper presents the design, test and improvement of a newlydeveloped piezoelectric torsional actuator which generates large angulardisplacement using piezoceramics and a torsion bar. Because the proposedpiezoelectric torsional actuator can generate torsional displacement,directly invoking the shear mode of the piezoelectric material, nocomplicated additional mechanism is needed. The electrodes are formed froma cylindrical piezoceramic poled along the axial direction and divided intosix segments that are arranged radially and bonded to each other in oppositepoling directions with conductive adhesive. The key to designing such an actuatoris to match the torsional resonant frequency of the actuator with theexcitation frequency. Finite element analysis for the piezoelectric actuatoris performed to find the torsional resonant mode; an experimentalinvestigation in terms of electrical impedance and torsional displacementmeasurement was conducted to verify the mode. As a result a maximum angulardisplacement of 0.18° was measured. To magnify the torsionaldisplacement, a torsion bar was attached on top of the actuator. Thus, thetorsional displacement was magnified by a factor of three. A resonancedecrease due to the added mass of the torsion bar was observed and atheoretical investigation was performed using a two degrees of freedomlumped model.