Study Of Right-angle Piezoelectric Cantilever System For Vibrational Energy Harvesting

This paper presents theoretical analysis and experiments on novel right-anglepiezoelectric cantilever for vibrational energy harvesting.This paper firstly proposes a right angle piezoelectric cantilever for energy harvesting,as well as the concept of using torque to smooth the strain distribution of the piezoelectriccantilever and improve its performance. In this device, an auxiliary cantilever with proofmass is attached to a piezoelectric cantilever and forms a right angle with it; it is one of themost efficient devices currently available to smooth the strain distribution of apiezoelectric cantilever. In addition, dynamic analysis based on the Rayleigh-Ritzmethods for piezoelectric cantilever was proposed, and novel methods of forcedisplacement impedance method was proposed to analyze the force and momentdistribution in the right angle cantilever excited by inertia force, and directly demonstratedthe principle of strain smooth effect of the torque in right angle cantilever, this principlecan be used to further improve the performance of right angle cantilever. Straindistributions of three models were examined by ANASYS at the resonant frequencies,respectively, which prove the strain smoothen effect of a torque directly. ANASYS resultsshowed that the auxiliary beam would provide an extremely large torque and smoothen thestrain distribution of the main beam in the longitude direction at the first resonantfrequencies, thus uniform strain distribution may obtained.In the experiment, three models of right angle cantilever were fabricated with thesame main beam but different stiffness auxiliary beam, and all the auxiliary beams havehalf the length of the main beam. When the auxiliary beam has stiffness0.02times of thatof the main beam, the piezoelectric element attached at the main beam has an extremelyuniform strain distribution in longitude direction, and its Relatively Utilization Efficiency(RUE) is93%at the resonant frequency; at the same time the RUE of a traditionalpiezoelectric cantilever is50%. Experiments also showed that the RUE of a right anglepiezoelectric cantilever increase as the stiffness of the auxiliary beam decrease. And the frequency response of RUE also confirms the concept of torque applied principle.Furthermore, experiment also shows the voltage output and the power output vs frequency.The data prove the advantage of a strain smoothened piezoelectric cantilever and provedthe concept indirectly.