Research On Magnetostrictive Vibration Harvester With Double-stage Rhombus Amplification Mechanism

With the advent of the Internet of things era,the power consumption of more and more microelectronics equipment has gradually dropped toμW.These microelectronic devices are often installed in sophisticated locations where human disassembly is difficult.The limited energy storage capacity of the conventional chemical batteries that supply them and the environmental hazards of their subsequent disposal have attracted a lot of scholarly attention.From this,the concept of self-powered microelectronic devices is gradually appearing in the public eye,i.e.the design of a harvester to efficiently convert waste vibrational energy from nature into electrical energy.This allows it to replace conventional lithium batteries for the continuous supply of power to low-power electronic devices.The random direction and weakness of the environmental vibrations limit the ability of the harvester to capture and transform the vibrational energy.A mechanical amplification drive mechanism is therefore introduced,combined with a magnetostrictive energy core harvester section,to capture the low frequency waste vibration energy in the environment.The mechanical-magnetic-electric energy conversion is achieved through the coupling properties between the Villari effect and the Faraday electromagnetic induction effect.A magnetostrictive vibration energy harvester with a double-stage rhombus amplification mechanism has been designed.Based on a conventional harvester,a double-stage rhombus amplification mechanism is introduced to enhance the performance of the harvester under low frequency excitation.Firstly,a double-stage rhombus amplification mechanism is proposed with the objective of maximizing the amplification ratio and ensuring safety.A series of studies and analyses are carried out for the type of amplification mechanism,beam type and number of beams.A mathematical model of the force amplification ratio of the double-stage rhombus amplification mechanism is established based on the Euler-Bernoulli beam theory,so as to analyze the variation law of the amplification ratio with the dimensional parameters.The single-objective genetic algorithm is also used to optimize the analysis and design of the dimensional parameters.The validity of the amplification ratio and the feasibility of the safety factor are verified by finite element analysis.Secondly,the pick-up coils and pre-magnetization layout of the energy conversion section are studied and analyzed.The winding length of the coils and the enameled wire parameters are determined.Simulations are then carried out to determine the optimum pre-magnetization layout and number of permanent magnets for the Terfenol-D rod.Finally,a comprehensive experimental study of the designed harvester shows that the double-stage rhombus amplification mechanism can amplify the initial force by a factor of 15.5.The output voltage of the harvester with an optimal pre-magnetization layout is 13 times higher than without pre-magnetization.Through FFT spectrum analysis,the fundamental frequency of the harvester is determined to be 34 Hz,and the second and third order natural frequency is 170Hz and 341 Hz respectively.Combined with the point measurement method,the optimal operating frequency of the harvester is determined to be 30 Hz.Moreover,the output voltage frequency response and output power characteristics of the prototype are investigated by applying different forms of external excitation to it.The experimental results show that the open-circuit voltage is 252 m V,the output power is 1.056 m W,and the vibration harvesting capability is 41.4μW/N when the prototype is subjected to 20.5-25.5 N under 30 Hz continuous excitation with an 8Ωload resistor.And under random excitation,the open circuit voltage and output power reached 2.92 V and 266 m W respectively.Under simulated bus seat excitation,the prototype produced peak voltage of 1.06-1.51 V when the excitation level is 2.2-4.9 m/s~2.Eventually,a real power supply test is carried out using the prototype,and it is subjected to 30Hz continuous excitation and successfully powers the display of the temperature sensor.