Modeling and characterization of a bimorph impedance transducer

In this paper, a bimorph impedance transducer (BIT), which is utilized as a simultaneous actuator and sensor for mechanical impedance measurement, is modeled and analytically characterized. A four-pole model is constructed to correlate the desired translational mechanical impedance with the measured electrical impedance. From the four-pole model, two set functions are defined to describe the system dynamics of the transducer. Closed-form expressions for these functions are then derived based on piezoelectric constitutive equations and beam theory. Besides producing accurate predications, as verified by a series of experiments, the analytical studies provide strong physical insight into the interaction between the transducer and the external load applied to it. Through two examples, it is found that the analytical solutions are also useful in improving the actuation efficiency and sensing capability of a BIT.