Design and Testing of a Motor-Based Capsule Robot Powered by Wireless Power Transmission

This paper presents a motor-based capsule robot powered by wireless power transmission, a device with a small size of Φ 13 mm × 42 mm for exploring the intestinal tract. The active locomotion of the capsule robot is achieved with an inchworm mechanism, which consists of two expanding devices at both ends and a middle extensor. The expanding device features a large expanding diameter range of 13 to 29.9 mm by adopting a four-bar linkage and it is sealed by two O-rings. Based on the Hertz contact theory, the design parameters of the two O-rings (i.e., wire diameter, hardness, and compression ratio) were optimized, and the optimized O-rings caused 17.6% torque loss at most. To take full advantage of the space in the inchworm mechanism, a novel hollow-cylinder-like 3-D receiving coil was proposed, which employed a combined ferrite core and measured 6 mm in inner diameter, 12.9 mm in outer diameter, and 11.5 mm in length. By selecting appropriate numbers of turns for the 3-D coils, the output power fluctuation of the receiving coil was minimized within a range of 485.7 to 1459.2 mW. Finally, the system performance of the capsule robot was successfully tested in an ex vivo intestine using a fabricated prototype with inspection function.