Planar Free-Positioning Wireless Power Transfer System for Industrial and Automotive Robotic Applications

Enabling wireless power transfer (WPT) over a large area has been proposed for charging moving devices. One of the main challenges in large-area WPT systems is the fluctuations of efficiency and power at certain receiver positions or orientations, which necessitates the implementation of complex receiver tracking and control algorithms. In this article, we propose a planar three-coil receiver structure that inherently enables free-positioning movements in the transmitting area without any complex control or need for receiver position tracking. The results show that the proposed new receiver structure ensures almost constant dc–dc efficiency of approximately 85% throughout the full WPT area. The coil design guidelines are provided together with an optimization of 44% ferrite materials used in the WPT transmitter without affecting the performance. Finally, experimental results are presented to validate the proposed solution.