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Optimal Design of 6.78 MHz Wireless Power Transfer System for Robot Arm

This paper presents a 2-hop wireless power transfer (WPT) system for the robot-arm application. The proposed WPT system consists of the class-E inverter on the transmitter side and a class-D rectifier on the receiver side. We obtain the analytical model of the WPT system for obtaining the class-E ZVS/ZDS conditions. The model includes the detailed physical information of the coil, namely coil diameter, height, wire thickness, winding turn number, and so on. Therefore, it is possible to optimize the WPT system for the theoretical highest power-delivery efficiency under the robot-arm coil-space restriction. The circuit experiment showed quantitative agreements with the theoretical predictions, which proved the validity of the proposed design method. The experimental prototype achieved 78.0 % power-delivery efficiency at 6.78 MHz operating frequency and 39.3 W output power.