Research On Wearable Wireless Power Transfer System For Capsule Endoscope

Higher requirements for the energy supply mode of capsule endoscope are put forward since the function diversification and miniaturization of capsule endoscope have been developing,such as higher power,longer working hours and smaller volume-proportion.As an effective energy supply way,wireless power transfer(WPT)technology can provide continuous energy supply with high energy density for capsule endoscope.In addition,besides meeting the energy requirements,the volume-proportion of the receiving device is also one important factor.In this dissertation,a WPT system with a small volume-proportion receiver is developed,which includes a one-dimensional receiving coil(ODRC)structure and a three-dimensional transmitting coil(TDTC)structure.Firstly,after analyzing the characteristics of the current capsule endoscope,a scheme is proposed based on the present ODRC.The ODRC includes a capsule and a single-layer winding solenoid.Compared to button battery and three-dimensional receiving coil,the solenoid is of lighter weight and smaller volume,which facilitates the function diversification and miniaturization.To ensure that the ODRC can receive energy effectively in arbitrary directions,two TDTC structures that can generate the magnetic field with x,y,and z components have been designed.(1)A distributed transmitting coil array is proposed,which can depress the coupling between adjacent coils in the array.The analysis results demonstrate the present design.(2)In order to reduce the complexity of structure and feeding,another integrated TDTC structure is proposed.The transmitting coil is composed of three sets of coils arranged on the surface of human trunk,which can generate the magnetic field in three directions of x,y and z respectively,and has the advantages of simple structure and single-port feeding.Finally,two WPT systems are built,simulated and tested with the present ODRC structure and two TDTC structures,respectively.For the first system,the simulation is carried out in the air medium,and the results show that the system has good power transfer efficiency and stability.For the second system,simulation and experiment are carried out in the air medium and human(animal)tissues model respectively.The results show that the system has better power transfer efficiency and stability than the former one,and the minimum power(186mW)provided by the system can not only meet the basic requirements of a capsule endoscope,but also have margin to expand more functions.