Research On Some Key Technologies For Multi-direction Piezoelectric Vibration Energy Harvesting

With the development of microelectro-mechanical technology and precision manufacturingtechnology, modern mechanical and electrical products increasingly miniaturized and humanity andits application is widespread day by day. At present, the energy supply of microelectro-mechanicalproducts mainly depend on the chemical battery. Developing new energy of long life, cleanenvironment and miniaturization has become one of the key technical problems to be solved becauseof the large volume, limited life and environmental pollution of chemical battery. Beginning with thedevelopment of the micro power supply technology, a comparison has been performed about theenergy conversion and application of the micro batteries. The piezoelectric energy harvester based onambient vibration energy sources will be the most promising micro power sources due to its highenergy density, clean, reliable work and easy miniaturization and so on. The theoretical calculation,finite element simulation, optimization and experiment of the multi-direction piezoelectric vibrationenergy harvesters were investigated in the article in order to make up the unidirection of theharvesters proposed by the researchers.The most notable characteristic of the multi-direction piezoelectric vibration energy harvesters is itsdirection. Based on the structures of the single direction piezoelectric vibration energy harvesters, twotypes of novel multi-direction piezoelectric vibration energy harvesters were proposed and the twotypes of harvesters are cube-type multi-direction piezoelectric vibration energy harvester anddandelion-type multi-direction piezoelectric vibration energy harvester respectively. The structureanalysis, calculation and experiment were focused on the cube-type multi-direction piezoelectricvibration energy harvester.The Rainbow shape piezoelectric transducer which is the key element of the cube-typemulti-direction piezoelectric vibration energy harvester was studied for scavenging vibration energyfirstly. Based on the force analysis, a dynamics theory modal of the Rainbow shape piezoelectrictransducer is built to analysis the vibration mode of the transducer. According to the elastic mechanicstheory and piezoelectricity theory, a modal was built to analysis the electric energy of the Rainbowshape piezoelectric transducer and the analysis results would be helpful for the optimization design ofthe transducer. Based on the piezoelectricity theory and the energy conversion principle, a theorymodal was built to analysis the electromechanical coupling coefficient of the Rainbow shapepiezoelectric transducer and the analysis results can be helpful for the application of the transducer.With the aim to study the performance of the cube-type multi-direction piezoelectric vibration energy harvester, the kinetic theory modal of the cube-type multi-direction piezoelectric vibrationenergy harvester was built based on the synthesis and decomposition principle of the vibration. Therelationship between the structural parameters of the cube-type multi-direction piezoelectric vibrationenergy harvester and the resonant frequency of the harvester was simulated followed. Based on thecircuit principle, the load power theory modal of the cube-type multi-direction piezoelectric vibrationenergy harvester was built to study the electromechanical coupling effect between the harvester andthe energy storage circuit. The relationship between the load power and the external excitationconditions, structure parameters and the load was simulated followed. Finally, the energy conversionefficiency theory modal of the cube-type multi-direction piezoelectric vibration energy harvester wasbuilt and the numerical simulation was performed based on the modal. The above researches provideimportant theoretical basis for the evaluation of the cube-type multi-direction piezoelectric vibrationenergy harvester.The experiment was performed to test and verificate the power generation of the cube-typemulti-direction piezoelectric vibration energy harvester. First, according to the experimentalrequirement, a prototype of multi-direction environmental vibration simulation platform wasmanufactured to satisfy the experimental needs. Secondly, the experiment was performed to test thepower generation of the cube-type multi-direction piezoelectric vibration energy harvester. The resultsshow that the load power of the cube-type multi-direction piezoelectric vibration energy harvesterapproaches to0.139mW when the external excitation frequency is136Hz and the excitationdirection along Y direction. As the external excitation direction changes, the maximum load power ofthe cube-type multi-direction piezoelectric vibration energy harvester is0.28mW and the directionselectivity of the harvester is weaker. This will be helpful for harvesting multi-direction ambientvibration energy.In order to study the performance of the dandelion-type multi-direction piezoelectric vibrationenergy harvester, preliminary exploration of the power generation was performed. Based on themechanics theory and piezoelectricity theory, a modal was developed to calculate the open voltageand electric energy of the cantilever piezoelectric power generation structure and the numericalsimulation of the theory modal was performed. The load voltage and the load power theory modal ofthe dandelion-type multi-direction piezoelectric vibration energy harvester was developed to study therelationship between the load power and the external excitation conditions, shape parameters and theload resistance. With the aim to test and evaluate the power generation of the dandelion-typemulti-direction piezoelectric vibration energy harvester, a prototype was made and the correspondingexperimental system was built. The experimental results show that the load power of thedandelion-type multi-direction piezoelectric vibration energy harvester approaches to0.68mW when the external excitation frequency is141Hz and the excitation direction along Y direction. As theexternal excitation direction changes, the maximum load power of the dandelion-type multi-directionpiezoelectric vibration energy harvester is also0.68mW. However, the results fluctuate largely. Thatis to say, the direction selectivity of the dandelion-type multi-direction piezoelectric vibration energyharvester is strong and it is not conducive to harvest multi-direction ambient vibration energy.