Floating Coil Design for Enhanced Angular Misalignment Tolerance in WPT Systems

This paper presents a novel floating receiver (Rx) coil system designed to address angular misalignment challenges in static and quasi-static wireless power transfer (WPT) applications. Unlike conventional solutions that rely on multiple coils, active alignment control, or complex compensation networks, the proposed system leverages a liquid medium to achieve passive self-alignment, ensuring stable power transfer efficiency (PTE) under extreme angular misalignment conditions. By integrating the Rx coil with a low-permittivity, low permeability liquid, the system passively adjusts its orientation to align with the transmitter (Tx) magnetic field, maintaining efficient inductive coupling. Theoretical analysis, numerical simulations, and experimental validation are conducted across various Tx-Rx configurations, including planar circular coils and Helmholtz coils. Results demonstrate that the floating Rx system maintains high PTE even at misalignment angles up to 180°, significantly outperforming conventional setups without liquid integration. The proposed approach eliminates the need for additional alignment mechanisms while improving misalignment tolerance. It is a promising solution for angularly unstable applications such as robots and autonomous underwater vehicles (AUVs). This work offers a new perspective on enhancing the adaptability of WPT systems and paves the way for further exploration of liquid-integrated passive alignment techniques.