Modeling the Contact Interface of Ultrasonic Power Transfer System Based on Mechanical and Electrical Equivalence

An ultrasonic power transfer (UPT) system consists of piezoelectric transducers attached onto a coupling media, and power is transferred through a contact interface between the transducer and medium. This paper proposes an equivalent model that characterizes the mechanisms of power transfer across contact interfaces with the metallic coupling medium. A full impedance analysis of systems with structural links and contact interfaces is conducted to develop the contact model based on the equivalence between mechanical and electrical characteristics. A mutual component representing the interacting mechanical impedance is proposed for the contact model. One practical structurally combined UPT system and two other systems with different contact levels are built using 28 kHz Langevin-type piezoelectric transducers attached to aluminum plates. It was found that the experimental results show a good agreement with the analytical results using the proposed model for both the structural and contact models. Finally, the power transfer capability of systems with structural and contact interfaces is compared using the proposed model.