Biography
Enrollment Date: 2013
Graduation Date：2016
Degree：M.S.
Defense Date：2016.05.30
Advisors：Xiang Xie
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Wireless Power Transfer for Implantable Medical Applications
Abstract:
With the development of microelectronics technology, the implantable medical applications has been developed rapidly. The function of implantable medical applications is becoming more and more complicated, power supply problem become the bottleneck problem of its development. Wireless power transfer (WPT) technology is a feasible solution. This paper is aimed at the design of WPT system for wireless capsule endoscopy application and designed a high-efficiency and omnidirectional WPT system under the stringent space restriction, considering the changing position and posture of the capsule in the working process. This paper focuses on the design of energy transmitting coil in vitro and the energy receiving coil in capsule, the related design technology can be directly applied to other implantable medical applications.
A combined transmitting coil is designed for the capsule moving arbitrarily in the digestive tract (GI) during the working process. Such transmitting coil select different working pattern according to the position of capsule. This mechanism ensures high worst case efficiency of capsule as well as good homogeneity of magnetic field distribution in the whole working area.
Due to the arbitrary movement of the capsule in GI, three-dimensional orthogonal receiving coil structure is chosen to realize omnidirectional energy harvesting. Besides, in order to improve the efficiency of energy transfer and considering capsule’s shape as well as other influence factors, a rectangle shape ferrite core is adopted in receiving coil. Through comprehensive consideration of the effective permeability of magnetic core, magnetic core loss, metal loss and so on, a high-efficiency energy receiving coil is designed.
This paper set up an energy transmission experiment platform to test the energy transmitting and receiving coil we designed. The works and innovations about transmitting coil and receiving coil in this thesis are as follows:
Firstly, a combined transmitting coil structure is proposed, such structure ensures high coupling coefficient between transmitting coil and receiving coil, as well as the consistency of magnetic field distribution.
Secondly, a method to design a high-efficiency and omnidirectional energy receiving coil is proposed by optimizing the coupling coefficient of WPT system and the quality factor of the receiving coil, which includes the choice of coil structure, magnetic core material and shape, wire type, wire diameter, turn numbers of winding, operating frequency and so on.
Finally, an omnidirectional receiving coil is designed according to the design method proposed above. The final wireless power transfer system is designed and the DC-DC transfer efficiency is at least 3.92% in the whole work process of the capsule.