Analysis and design of U-shaped wireless power transfer system for humanoid robots

Wireless power transfer (WPT) has played a vital role in many fields. However, two significant challenges are the various misalignments and electromagnetic safety of the system. This paper proposes an effective U-shaped wireless charging system for humanoid robots. The charging region of the system consists of a rotation area and a parallel area, allowing the receiver coil to be installed in humanoid robots at different attitudes. The system increases the installation flexibility and wireless charging freedom. Meanwhile, this design leads to a low leakage magnetic flux density in the zone around the system. To describe the model of the proposed WPT system, a calculation formula for the electrical parameters of the system is derived. In particular, the mutual inductance of the two coupled structures at an arbitrary attitude can be predicted. The parameters of the system are determined after performing the optimization procedure. The system is simulated, fabricated, and tested. Results show that the system has stronger robustness in the three power supply regions. In addition, the measurement efficiency is established between 34.69 and 42.12%. In addition, the characteristics of the system under angular and longitudinal misalignments are studied. The above results are used to examine the feasibility and validity of the proposed model.