Abstract
The nonlinear energy harvester has become a hot topic due to its broad bandwidth and lower resonant frequency. Based on the preliminary test and analyses in our previous work, further analyses and tests on the influence of parameters, including the nonlinear magnetic force of the hybrid energy harvesting structure on its output performance under harmonic excitation, are performed in this paper, which will provide powerful support for structural optimization. For designing a nonlinear piezoelectric-electromagnetic hybrid energy harvester, the state equation of electromechanical coupling, the harmonic response and average output power, voltage, and current of a nonlinear hybrid energy harvester under harmonic excitation are derived by the harmonic balance method. The effects of the excitation acceleration and the external load on the output performance of the nonlinear hybrid energy harvester are verified through experimental tests. The results showed that the output power of the nonlinear hybrid energy harvester increases with the increase in the acceleration of harmonic excitation, and the increase is affected by external load. When the piezoelectric-electromagnetic hybrid harvester operates at the optimal load and the resonant frequency, the average output power reaches its maximum value and the increase of the load of the piezoelectric unit makes the resonant frequency of the energy harvesting system increase. Compared with linear harvesting structures, the nonlinear hybrid harvester has better flexibility of environmental adaptability and is more suitable for harvesting energy in low-frequency environments.
Highlights
Vibration energy harvesters can convert vibration energy into electrical energy by piezoelectric, electromagnetic, and electrostatic mechanisms
Broader bandwidth and lower resonant frequency are two main challenges when the harvester is used in practice [7,8,9,10]
ConcAluccsoiordnisng to the results shown in Figure 10, the output power of the nonlinear energy harvester is Alacrcgoerrdtihnagn ttohattheof etlheectrcoomrreescphoanndicinalg cloinueparlinegneergqyuahtiaornvesotefr.thUendPeEr-EthMe shaymberidexchiatartvioenster, theacecxelperreastisoionn, tsheofouthtpeuvtipborawtieorsn arreesp0.o4n4saen, dou0.t4pmutWv,orletaspgeec,ticvuerlrye.nDt,ueantod tpheownoenrlionfeathr emnagonnelitnicear hyfborricde,entheergryeshoanravnetstferrequunednecryhaorfmthoenicnoenxlciinteaatironenweregrye dhearrivveesdte.rTdheecoreuatspeudt, cahnadracthteerirsetsicosnoanf tthe nofnreliqnueeanrchyyobfrtidhehlainrveaersteenreurgnydehrarhvaersmteornaincdexthceitantoionnlinweaerreenaelsrogysthuadriveedstbeyr atrheemexepaseurirmedentotablete1s1t9ing
Summary
Vibration energy harvesters can convert vibration energy into electrical energy by piezoelectric, electromagnetic, and electrostatic mechanisms. Where y..(t) is the excitation acceleration; me is the equivalent mass of the vibration system; cm and k are the damping coefficient and linear stiffness of the vibration system, respectively; Rp and Rm are the load resistance of the PE and EM energy harvesting unit, respectively; Cp is the equivalent capacitance of the PE layer; Vp is the output voltage of the PE energy harvesting unit; Iem is the output current of the EM energy harvesting unit; Rc and Lc refers to the resistance and inductance of coils; and θ and ge are the PE and EM transfer factors, respectively These parameters are dependent on the material constants and the design of the energy harvester, which can be derived by standard model analysis. The output current of the electromagnetic energy harvesting unit is: Iem
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