The Parametric Impact Analysis Of Magnetically Bistable Cantilever Piezoelectric Energy Harvester

In order to overcome the limitations of conventional batteries,which require regular replacement,and provide wireless sensors and micro-electronic components with a constant supply of electricity effectively for a long time.In recent decades,researchers have been working on piezoelectric energy harvesters,which capture energy from environmental vibrations through piezoelectric effects of materials.Piezoelectric energy harvesting technology itself has experienced the development from the early linear,resonant,narrowband and monostable state to the present nonlinear,nonresonant,broadband and multistable state.The magnetic bistable cantilever piezoelectric harvester studied in this paper is a kind of multistable piezoelectric energy harvester with wide frequency bandwidth based on magnetic nonlinearity.The main research contents and innovation points of this paper are as follows:1.Based on euler-bernoulli beam hypothesis and Galerkin method,the motion differential equation of a nonlinear multi-stable piezoelectric energy harvesting system is established by using the generalized Hamilton variational principle of force and electricity coupling,and transformed into an ordinary differential equation through variational processing.Considering that the external excitation is harmonic excitation,the analytical expressions of displacement,voltage and power of the bistable piezoelectric energy harvester(BPH)are obtained by harmonic balance method.The effects of potential well characteristics(potential well depth and width)and initial conditions on the performance of the harvester are studied.The results show that:The properly designed magnet distance(horizontal distance d and vertical distance h)can change the potential well characteristics,so as to improve the performance of the harvester.The appropriate initial conditions can induce the nonlinear energy harvester to overcome the potential barrier and enter the interwell motion of the high energy orbit,so as to improve the efficiency of energy harvesting device.2.The dynamic equation of bistable piezoelectric energy harvester with elastic magnifier(BPH+EM)is established by generalized Hamilton variational principle.Considering harmonic excitation,the analytical solution of displacement,voltage and power of BPH+EM is obtained by harmonic balance method.By using the proposed analytical solution,how to enlarge the frequency bandwidth and improve the efficiency in BPH+EM system is discussed,and the influence law of elastic magnifier mass and spring stiffness on the dynamic performance of BPH+EM is studied.For BPH+EM,both the elastic magnifier mass and spring stiffness have optimal values.Reasonable selection of these two parameters can improve the energy conversion efficiency,widen the working frequency bandwidth and reduce the excitation starting threshold that generates large interwell motion.It is theoretically proved that BPH+EM degenerates into BPH when the spring stiffness reaches infinity,the energy harvesting effect of BPH+EM is lower than that of BPH when the magnifier mass goes to infinity or the spring stiffness goes to zero but not equal to zero.The numerical results verify the correctness of the theoretical results.3.When the external excitation is periodic,the change rules of maximum displacement,frequency bandwidth and starting threshold of BPH and BPH+EM at different excitation frequency,excitation intensity,linear coefficient,nonlinear coefficient,potential well width,potential well depth and initial conditions are compared.The effects of various parameters on the performance of BPH and BPH+EM were obtained,and it is also found that BPH+EM is more suitable for low frequency and weak excitation,while BPH is more suitable for high frequency and strong excitation.4.When the external excitation is random,the dynamic responses of BPH and BPH+EM under different excitation intensity,excitation standard deviation and initial conditions are compared.It is found that the efficiency of BPH+EM is better than that of BPH.Even when the external excitation is periodic+random mixed excitation,the advantage of BPH+EM is still obvious.