An Impact-based Broadband Low-Frequency Electromagnetic Vibration Energy Harvester And Its Applications

Currently,most wireless sensor nodes are powered by traditional chemical batteries.Such disadvantages of the batteries as short lifespan,high maintenance costs and polluting environment limit the application.Converting the ambient energy into electricity to power wireless sensor node is an effective method to solve the problem.The vibration energy is a kind of green energy source,but the vibration in natural environments has the characteristics like low-level,low-frequency and wide bandwidth.Therefore,it is of great importance to study high efficiency method and structure to harvest environmental low-frequency vibration energy.In this thesis,a new structure of an impact-based electromagnetic vibration energy harvester(VEH)for harvesting low-frequency broadband vibration was proposed,and the theoretical model of the harvester was established.Based on the model,the influence of different parameters on the performance of the harvester was studied.Then the harvester was designed and fabricated.The electrical output performance of the VEH prototype was tested.Finally,the harvester was used to power a wireless temperature and humidity sensor node.The main work is as follows:(1)The advance and trend of electromagnetic VEH were analyzed and the method and structure of high efficiency for harvesting low-frequency and low-level vibration were summarized.(2)To harvest low-frequency and low-level vibration energy,a new impact-based electromagnetic VEH was proposed.The harvester includes the outer frame(consisting of base and coil bracket),the inner frame(consisting of magnet bracket,Spring and magnet)and rollers.(3)The theoretical model of the harvester was established.The effects of the diameter of the copper wire,the shape of the induction coil,the initial spacing between the mass block and the outer frame of the harvester,and the spring stiffness parameters on the output performance of the harvester were studied.And the harvesters were designed.(4)The prototypes of the harvester are fabricated and tested.Experiments show that under base excitation of 0.3g at 8.5Hz,the output power of the harvester reached the maximum value of 24.84 mW,the power bandwidth is 21.2% or 1.8 Hz,the power density is about 247.2?W/cm3.(5)Under base excitation of 0.3 g at 7.8 Hz,it took about 32 seconds for the harvester to charge an 10,000 ?F capacitor from 0V to 4.6V.A wireless temperature and humidity sensor node was driven by the harvester successfully.