Optimization and analysis of Helmholtz-like three-coil wireless power transfer system applied in gastrointestinal robots

Abstract

Wireless power transfer (WPT) systems based on magnetic resonance provides a possible method to supply energy for implantable medical devices, such as gastrointestinal robots and wireless capsule endoscopes. However, low power transfer efficiency (PTE) (most researches show it to be lower than 3%) and poor power received stability are the key limitation of WPT systems in such applications. Three-coil WPT systems are regarded as an effective method to improve the power transfer efficiency and power received of gastrointestinal robots. Thus, an analytical model of a three-coil inductive link was established in this paper. Then the power transfer efficiency of load coil was optimized by changing the coil turns and raising a novel coil configuration: a Helmholtz-like load coil. As a result, the power transfer efficiency and power deliver to load (PDL) of this three-coil WPT system are tremendously improved. To verify the proposed design, a prototype simulated the gastrointestinal robot working situation and it was implemented for an experimental test. The results obtained from the experimental test demonstrate that the proposed three-coil WPT system with 9 turns load coil and 40 turns receiving coil achieves a PTE of 4.32% and a PDL of 541.5 mW. Moreover, the best PTE attained by the novel Helmholtz-like load coil was 6.45% and the PDL was 845 mW.