Optimization of a 6.78-MHz Inductive Power Transfer System for Unmanned Aerial Vehicles

This article presents an optimization of a 6.78-MHz inductive power transfer (IPT) system for unmanned aerial vehicles (UAVs). First, in order to mitigate the impact of the misalignment between the transmitting coil and the receiving coil on the output power and system efficiency, a homogeneous-flux transmitting coil was developed. The optimal allocation of turns of the transmitting coil for generating a homogeneous magnetic field was obtained using a built magnetic field and mutual inductance model combined with an optimization algorithm. In addition, an analytical eddy-current loss model of the air-core inductors was developed. Through the iterative processes for proximity-effect loss, the resistance modeling of the spiral and helical coils is improved, with errors of 7.1% and 4.9%, respectively. Then, the parameters of all the air-core inductors used in the study were optimized using the built loss model and optimization algorithm with various design considerations. Finally, a 6.78-MHz 200-W IPT system with a homogeneous-flux transmitting coil was demonstrated. The proposed system exhibited high-misalignment-tolerance and high-efficiency characteristics, maintaining an output power of approximate 200 W and an efficiency of 89% with a 25-mm lateral misalignment.