A Two-Dimensional Equivalent Circuit Model of Ultrasonic Power Transfer Systems Considering Losses and Transducer Misalignment

Ultrasonic power transfer (UPT) is a promising wireless power transfer technique with great development potential. Establishing an accurate model that describes the transmission process of the system is crucial for designing an UPT system. When the thickness of the piezoelectric transducer cannot be neglected compared to its diameter, considering vibrations in both thickness and radial directions can improve the model accuracy. Moreover, losses in the system during transmission was overlooked in the existing two-dimensional equivalent circuit model. In addition, slight radial misalignment in a practical UPT system can affect the transmission performance. In this article, we propose a 2-D equivalent circuit model of UPT systems that takes into account both losses and radial misalignment for cylindrical piezoelectric transducers, which is derived based on a two-port network and validated by comparing the system input impedance, input power, output power, and efficiency from the model and experiment. The results demonstrate that without radial misalignment of piezoelectric transducers, the proposed equivalent circuit model improved the accuracy significantly as compared with the existing 1-D and 2-D models. The derivation and incorporation of the radial misalignment matrix in the model also shows an accurate representation of the system and the consistent results from the proposed model and experiment are obtained showing the same trend of system performance with varying radial misalignment. The developed equivalent circuit model lays the foundation for accurate analysis, design, control, and optimization of UPT systems.