Research Of Wireless Energy Transfer System Based On Piezoelectric Transducers

The ocean is the cradle of life,and it contains rich resources.The development and utilization of marine resources has become the inevitable development direction to solve the problem of global resource shortage.At present,only 5%of the seabed has been explored.On the other hand,changes in the nature of the ocean have an important impact on Earth’s climate and the social life of human beings.The effective development of marine resources and real-time monitoring of the marine environment are all based on the reliability,stability and continuity of the numerous underwater electrical devices.Therefore,how to power these underwater electronic systems in real time and ensure the reliability and uninterrupted nature of underwater monitoring has become one of the important research directions in the field of marine technology.Acoustic Wireless Energy Transfer(AWET)can achieve electricity-sound-electricity conversion through acoustic coupling which shows excellent characteristics such as no influence on seawater conductivity and no electromagnetic interference.And these characteristics make AWET considered as an important direction to solve the above problem,showing a great practical significance in the field of marine research.In his paper,the electrical equivalent model of piezoelectric transducers and the acoustic wave propagation model in underwater AWET system are studied and analyzed.In addition,the optimization of the performance and the improvement of energy conversion efficiency are also achieved.The main contributions of this thesis are listed as follows:1.Based on the theory of tissue-separated and metal-separated AWET,the composition and key issues of underwater AWET system are studied and analyzed in detail.The composition includes the basic structure of the system,the principle of piezoelectric transducer and its equivalent circuit model.The key issues include seawater acoustic channel characteristics,and acoustic transmission characteristics such as diffusion loss,absorption loss,and scattering loss.2.The electrical impedance matching method is studied under the equivalent circuit model of lead zirconate titanate(PZT)piezoelectric transducers.In order to improve the energy transfer efficiency,a power wave based synchronous complex conjugate matching method is introduced to electrically impedance match the transmitter and receiver transducers respectively.In addition,The traditional method and synchronous complex conjugate matching method are compared from the perspective of complexity and power conversion efficiency.3.Aiming at the voltage regulation in sound-electricity conversion,a design of receiving piezoelectric transducer with a multi-concentric annular series structure is proposed.The piezoelectric transducer discretizes the electrodes coated on the upper and lower surfaces into several independent concentric annular ones.Then the adjacent output electrode pairs are connected in series with each other to form a series structure of multiple output ends.This structure can greatly improve the open circuit output voltage of the transducer.Hence,the open circuit output voltage of the system can be adjusted and controlled.4.Based on the theoretical analysis work,an underwater AWET test platform with a certain scale is built.With this platform,the power transmission efficiency of the system under specified frequency,transducer structure and impedance matching method is analyzed,tested and verified.