Research On Piezoelectric-Electromagnetic Hybrid Energy Harvesting Technology For Environmental Energy

With the popularity of low-power devices,wireless sensor networks(WSNs)improve the efficiency of information acquisition and processing.However,the contradiction between the device size and standby time is becoming more significant.Both the working life of the node and the difficulty of replacing the power supply pose great challenges to the existing technology.In recent years,the rise of energy harvesting(EH)technology provides a reasonable and feasible solution for this problem.The devices for environmental EH have huge potential and application prospects.In this thesis,now available vibration EH technology was collated and analyzed,in the meantime,a novel hybrid piezoelectric-electromagnetic energy harvester was proposed to collect the mechanical energy generated by flow-induced vibration.The specific work is as follows:(1)The advantages and disadvantages of WSNs were analyzed.The development status and principles of EH technology were introduced.The theory of flow-induced vibration,the related mathematical models and the existing energy harvesters were described.(2)A piezoelectric-electromagnetic hybrid energy harvester was designed and fabricated to collect the mechanical energy generated by flow-induced vibration.The energy density of the prototype was 98.88?W/cm~3.It consisted of supporting structure,coupling structure,PZT bimorph,coil,magnet and management circuit.As a basic part,the supporting structure provided fixed points for other parts.The coupling structure was attached to the free end of the PZT bimorph and the magnet is mounted on it.The harvester converted the kinetic energy of fluid into electrical energy by flow-induced vibration and then stored the energy in a capacitor through the management circuit.(3)The physical process during the harvester worked were simulated and analyzed by COMSOL Multiphysics software.It mainly included three contents:simulation of fluid-structure interaction,frequency response of piezoelectric cantilever beam,vibration analysis of magnetic-spring structure.The results of the numerical simulations were used to guide the actual design.(4)A variety of mass blocks were used to test the frequency response of the PZT in order to study the optimal range of weight.Altium Designer software was used to design a circular planar coil.The coil can be superimposed according to the system requirements to increase the energy harvesting efficiency.A magnetic-spring harvester was fabricated and its output characteristics verified the feasibility of scavenging low-frequency vibration energy.And a method of hybrid EH was proposed in the thesis.(5)The coupling structures were designed by SolidWorks software and fabricated by 3D-printing.The cross-section shapes of these cylinders included circle,polygon,airfoil and so on.The experiments of output performance were carried out in a wind tunnel.And the vibration responses of different cylindrical structures were analyzed.(6)The circuit based on LTC3588-1 was used to manage piezoelectric energy,and the circuit based on LTC3108-1 was used to manage electromagnetic energy.The managemet circuit realized the storage and utilization of energy and it was tested in a wind tunnel.