Research On Piezoelectric-Electromagnetic Hybrid Energy Harvester

Currently,sensor nodes in wireless network are used extensively in everyday life,with the continuous development of Io T.These nodes are usually deployed in a large-range,scattered and complex environment,and powered by the traditional batt ery.The way of traditional power supply has many problems,such as short life,limited power,and frequent replacement,and has problems of difficulties in replacement and threat to life when the environment of sensor nodes is bad.Therefore,it is an effective solution to use the energy harvesting technology to convert energy in the environ.ment into electrical energy for continuously powering sensor nodes.Due to its advantages in working frequency band,harvesting efficiency and output power,piezoelectric-electromagnetic hybrid energy harvesters have attracted extensive attention in the field of energy harvesting.A novel piezo electric-electro magnetic hybrid energy harvest er was proposed based on the research of related work at home and abroad in this paper.This energy harvester can achieve the harvesting for ultra-low frequency vibration energy.A triangular amplification structure amplified input displacement and increased movement distance of magnets.The movement of magnets made piezoelectric cantilever beam to be released and adsorbed,achieving conversion of low-frequency excitation into high-frequency self-excited resonance.A closed magnetic circuit was designed for electromagnetic energy harvester with a.pair of mag nets and a soft mag netic core.The pair of magnets was placed side.by side in opposite polarity direction,causing the direction of magnetic flux in the coil to reverse by180°.In order to analyze and calcul ate the designed device,an equivalent mechani cal model was establi shed based on the designed device.According to this model,the output performance of this device has analyzed and calculated,the output voltage and current of piezo electric and electro magnetic energy harvesters have been derived,and the output power was obtained.According to these expressions,using MAT LAB for numerical analysis,obtained the relation ship between output voltage and output.power of piezo electric and electro magnetic energy harvesters and resistance.The numerical analysis results show that the output voltage.of piezo electric and electro magnetic energy harcester increases continuously,and finally reaches to 12.46 V and 4.45 V respectively,with the increase of load resist ance.However,as the load resistance increases,the output power of piezo electric and electro magnetic energy harvesters increases firstly,then reaches a peak,and finally decreases continuously.When the load resistances are 547k? and 2.24k?,the output power of both reaches 100.7?W and 1.59 m W,respectively.In order to verify the relia.bility of the designed energy harvester,an experiment.al prototype was fabricated,and an experiment al test.plat.form was set up.The experimental results of single press,cyclic press and capacitor charging were analyzed respectively.The experimental results show that under single press experiments,the piezoelectric cantilever beam generates a peak voltage of-18 V at the moment before release,and a peak voltage of20.57 V after release.After that,the instantaneous voltage of 23.4V is generated at the moment when the beam is absorbed again.For electromagnetic energy harvester,the back and forth movement of permanent magnets causes the induction coil to generate a positive voltage of 26.7V and a negative voltage of 11.3V.In cyclic press experiments at 5Hz,the maximum open-circuit peak-to-peak voltages generated by piezoelectric and electromagnetic energy harvesters are 40.39 V and 36.87 V,respectively.The optim al load resistan ce and the maximum output power of the piezo electric energy harvester are 398.7k?and 87.9?W,While the electromagnetic energy harvester's are 3.2k? and 2.173 m W,respectively.When charging a capacitor,the voltage charged by the piezoelectric energy harvester is less than that charged by the electromagnetic energy harvester in the same time,and the voltage charged by hybrid energy harvester is greater than that charged by either of the two,and less than the sum of the two.The above results indicate that the piezo electric-electro magnetic.hybrid energy harvest.er designed in this paper,has higher energy harvesting efficiency and output performance in the ultra-low frequency environment.Compared with a single energy harvester,this device has more advantages and great potential in various application fields.