Omnidirectional and Efficient Wireless Power Transfer System for Logistic Robots

The WPT system for logistic robots has the problems of large fluctuation of charging power and low efficiency due to the change of its position. Based on the principle of parity time symmetry, an omnidirectional and efficient wireless power transfer system for logistic robots is proposed. Firstly, the coupling coefficient of two planar spiral coils in different relative positions in space are studied. Then, a time-varying coupled-mode model of the WPT system based on the offset angle of the receiver coil is established, and its working principle and characteristics are analyzed. As long as the coupling coefficient satisfies certain conditions, the output power and efficiency of the system are always keeping constant. Finally, the proposed model is experimentally verified. The measured results show that the WPT system proposed can realize stable 150W power transfer with constant transmitting efficiency of more than 90% for a logistic robot within a confined three-dimensional space around the charging station, which are provided to further verify the correctness of theoretical analysis.