A Three-Dimensional Orthogonal Receiving Coil for In Vivo Microrobot Wireless Power Transmission Systems

Approaches to studying electromagnetic induction in weak coupling have recently received attention in robotics since they could be used to supply energy to robots, allowing robots to diagnose and treat diseases in the human body. A three-dimensional orthogonal receiving coil connected in parallel, with a size of 13 mm x 13 mm x 13 mm, for an intestinal examination microrobot is designed in this article. Based on the defined attitude functions, we build and verify the stability and effectiveness of the proposed coil model through both analytical calculation and simulation analysis. In addition, to supply enough power to the microrobot, the number of turns of the receiving coil is optimized, considering both the electrical coil parameters and the limited space inside the robot. Then, an evaluation of the proposed 3D orthogonal receiving coil is presented in the bench tests. The results show that the power transmission efficiency can reach as high as 9.6%, with 1271 mW. This paper also uses a curved pipe to simulate the robot's movement with the designed coil in the tortuous intestine. The average speed is 0.97 mm/s, with the path covering 180 degrees. The experiments illustrate the excellent performance of the wireless power transmission, even when the positions of the two induction coils are constantly changing.