Embeddable induced strain actuator using a framed 3-3 piezoceramic stack: modeling and characterization

In an earlier SPIE paper, we described the development of a strain actuator consisting of a thin, co-fired, multilayered, PZT stack mounted within a titanium frame. The frame concept was designed to facilitate integration of the piezoceramic stack into a composite material during the fabrication process. The frame preloads the stack in compression, protects it during material fabrication and most importantly, provides an efficient shear transfer path to the surrounding host material. Because the piezoceramic stack power requirements are quite high, a special amplifier was also designed to meet the high current and voltage requirements. In this paper we focus on assessing the performance of the framed stack actuator for a variety of loading conditions. The calibration procedure uses a specially designed apparatus which loads the framed stack with a variety of impedances ranging from very compliant to very stiff. The mechanical power generated by the stack is measured directly in terms of the force transmitted to these loads along with their displacement. Electrical power is measured directly in terms of electrical current and voltage and is also computed in terms of the electrical admittance of the stack. Results show that the actuator is most efficient when a nearly matched impedance condition exists between the framed stack and its corresponding load.