| In today’s society,the rapid growth of emerging markets such as “Internet +”,Internet of Things,smart cities,automotive electronics,mobile communications,smart manufacturing and artificial intelligence has promoted the rapid development of wireless sensor networks.However,the power supply problem of wireless sensor network nodes(WSNs)poses a new challenge to the global energy system.The micro-energy technology that efficiently acquires and converts environmental energy has become an enabling technology for WSNs to provide reliable and reliable power supply.How to further realize the efficient acquisition and conversion of environmental kinetic energy and improve environmental adaptability has become the focus of research in this field.Aiming at the problem that the output performance and operating frequency bandwidth of the micro piezo vibration energy harvester(PVEH)are difficult to meet the application requirements in the practical process,this thesis proposed a new structure of miniature broadband PVEH with trapezoidal cantilever beam array based on the multi-mode array extension method and the collision-limiting nonlinear extension method.The theoretical models for the electromechanical coupling and band expansion of the broadband PVEH with trapezoidal cantilever beam array were systematically established and solved.The main influencing factors of the performance of the trapezoidal piezoelectric cantilever beam based on AlN film were analyzed,and the structural parameters of the device were designed and optimized.The research on AlN film and 3D microstructure-compatible processing technology was carried out,and the processing flow of the device was formulated.A prototype of a miniature broadband PVEH based on a trapezoidal cantilever beam array was successfully developed.The optimized load voltage,optimized output power and operating bandwidth of the prototype developed under acceleration excitation of 0.5g can reach 6.73 V,10.06 μW and 5.8 Hz,respectively,which effectively improves the output performance and expands the operating frequency bandwidth.The main work of the thesis:(1)The domestic and international research status,trend and existing problems of PVEH in theoretical model,piezoelectric material,structural design,processing technology and frequency band expansion were systematically analyzed.The research objectives and research contents of this thesis were determined.(2)Based on multi-mode array extension method and collision-limiting nonlinear extension method,a new structure of miniature broadband PVEH with trapezoidal cantilever beam array was proposed.A single-degree-of-freedom bidirectional coupled lumped parameter model,bidirectional coupled distribution parameter model based on Euler-Bernoulli beam theory,bidirectional coupling distributed parameter model based on Timoshenko beam theory and Hamilton’s principle of the unequal section piezoelectric cantilever beam unit were established and analyzed,and the derived theoretical models were verified by ANSYS finite element simulation.(3)The electromechanical model of the nonlinear bidirectional coupled lumped parameter was established for the collision limiting band of the unequal section piezoelectric cantilever beam unit,and the nonlinear electromechanical model was constructed and analyzed.Then the electrical output of the limiting structure unit under the collision limit excitation was theoretically analyzed.(4)The axial stress distribution of piezo layers of differently shaped unequal section piezoelectric cantilever beams was studied.The main factors affecting the performance of trapezoidal piezoelectric cantilever beam units were systematically analyzed.The main technical indexes and overall optimization ideas of the trapezoidal piezoelectric cantilever beam unit were determined.Based on the established theoretical model,the structural parameters and limiting height of the broadband PVEH were optimized.(5)The crystal structure,mechanism and influencing factors of crystal orientation,and preparation methods of AlN piezoelectric films were analyzed.The process flow chart layout and layout design of trapezoidal piezoelectric cantilever array unit was completed,and a prototype of broadband PVEH based on trapezoidal cantilever beam array was successfully developed.(6)The test method of broadband PVEH based on trapezoidal cantilever beam array was studied,and the vibration performance test platform was built.The relevant parameters and electrical output performance of the device were tested and analyzed. |
