Structural frequency response function acquisition via electric impedance measurement of surface-bonded piezoelectric sensor /actuator

Abstract

This paper presents a new technique for acquiring structural Frequency Response Function (FRF) via measurement of electric of a piezoceramic (PZT) patch bonded to a structure. The PZT patch, when driven by an ac voltage, behaves like an actuator as well as a sensor through its interaction with the host structure. The electric thus obtained carries the information of the structural signature. Through a generic multi-input model governing the electromechanical interaction of PZT actuators with structure, the structural FRF can be extracted from measured electric impedance. Both the point FRF of single location and the transfer FRF between two locations on a structure can be obtained. The concept of measuring the coupled impedance of two PZT sensors is presented and used to derive the transfer FRF of the structure. The effect of actuator stiffening to the structure and its removal from the measured FRF is addressed. The technique is proven to be an efficient and low cost approach to acquiring structural FRF. Because of the negligible mass load and stiffening effect of the solid state transducer, the approach is more appropriate for the system identification of light and flexible structures.