Stable Wireless Power Transmission for a Capsule Robot With Randomly Changing Attitude

Wireless power transmission (WPT) for a capsule robot (CR) has always been a challenging issue because the unpredictable CR attitude can destabilize the induced power of the receiving coil onboard the CR. This article proposes a new WPT system for stably powering the CR, and it mainly consists of a rotatable two-dimensional transmitting coil (R2DTC), a one-dimensional receiving coil (1DRC), and an attitude detection module (ADM). The R2DTC can excite a uniform and directional alternating magnetic field (AMF) covering the CR workspace, and the AMF amplitude and direction are controllable in the 3-D space. The 1DRC has a shape of thin-walled ring, for ease of being used as a CR outer shell. The ADM is fixed together with the 1DRC; it can detect the 1DRC attitude in real time and is implemented in a compact size. Referring to the 1DRC attitude, the R2DTC can regulate the AMF to stabilize the 1DRC induced power. This article presents design and implementation details of the WPT system, as well as experiments for its performance evaluation. The R2DTC is verified to supply stable power of 500 mW to the attitude-changing 1DRC at most cases, with a transfer efficiency ranging from 8.15% to 13.53%.