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.

中文翻译：

---

一种双向多级WPT系统的多自由度耦合机制

对于无线电源传输（WPT）技术在机器人手臂中的应用，需要为跨多个手臂关节的每个手臂设备提供灵活的电源。但是，关节的转动和负载的变化会导致各级输出电压的波动。为了保证稳定的输出电压，提出了一种双向多级WPT（BM-WPT）方法为多个负载提供能量。提出了碗耦合结构和三维正交环形线圈排列，以减少对关节旋转的耦合变化。每级采用特殊的谐振拓扑设计，无论能量传输方向如何，都可以在每一级上自由注入或输出能量。这种拓扑结构还可以降低输出电压随负载变化的灵敏度。