A Wireless Air Flow Monitoring Node Based On Micro Piezoelectric Energy Harvester

Conventional batteries, due to their drawbacks such as large size, the need to bereplaced or recharged regularly, and pollution to the environment, can’t meetrequirements of the wireless sensor network. Micro energy technology, capable ofconverting environmental energy into electrical energy, is an ideal solution to power thewireless sensor network. Wind energy, renewable and clean, is almost ubiquitous in theenvironment. In recent years, micro wind energy harvesters have become one ofresearch hotpots all over the world. However, there are few research results on thewireless sensor node based on micro wind energy harvesters; therefore, the relatedresearch has important academic value and exemplary function.Aiming at requirements of the meteorological observation and health monitoring ofcoal mines/tunnels, this dissertation designed a wireless air flow monitoring node basedon micro piezoelectric energy harvester. On the basis of our previous studies, aself-powered wireless wind energy monitoring node was devised. According to thewind-induced vibration mechanism and piezoelectric effect, two micro wind energyharvesters were manufactured. They jointly form this node, and one of them acts as anenergy provider and the other measures the wind speed by its vibration frequency. Theresearch activities mainly include:(1) Summarized and analyzed the current research actuality and development trendof the wireless sensor node that is based on the micro energy harvester, and proposedthe design scheme of self-powered wireless air flow monitoring node.(2) Completed the structure design and assembled prototypes of the piezoelectricenergy harvester with a resonant cavity structure, and completed the process design andmanufactured the micromachining structure of MEMS air flow measurement unit.(3) Designed a detection circuit for the energy harvester to detect the frequencyand wind speed, which is realized by a microcontroller MSP430F149and a wirelesstransmission-reception module nRF24L01.(4) Made a power management circuit to power the micro controller circuit, whichis composed of the chip LTC3588-1and the regulator LT3009and able to convert theAC output of energy harvester to DC.(5) The experimental results show that the self-powered wireless air flowmonitoring node can transmit the data of the measured wind speed every80s, at12m/s, and its sensitivity is1.86Hz/(m/s). In addition, the resonant frequency of the MEMSwind speed measurement unit will shift12Hz at10.2m/s, and the sensitivity is1.18Hz/(m/s).