A Coupling Mechanism With Multidegree Freedom for Bidirectional Multistage WPT System

For the application of wireless power transfer (WPT) technology in robot arm, it is necessary to provide flexible power supply for each arm device across multiple arm joints. However, rotation of the joints and the variation of the loads will lead to the fluctuation of the output voltage at each stage. To guarantee stable output voltage, a bidirectional multistage WPT (BM-WPT) method is proposed to provide energy for multiple loads. A bowl-coupling structure and three-dimensional orthogonal ring coil arrangement are proposed to reduce coupling variation against joint rotation. With a special resonant topology design for each stage, energy can be injected or output freely on each stage regardless of energy transfer direction. This topology can also reduce the sensitivity of the output voltages with the variation of the loads. The simulation and experimental results have verified the effectiveness of the proposed method and the coupling mechanism.