Modeling and experimental verification of proof mass effects on vibration energy harvester performance

Abstract

An electromechanically coupled model for a cantilevered piezoelectric energy harvester with a proof mass is presented. Proof masses are essential in microscale devices to move device resonances towards optimal frequency points for harvesting. Such devices with proof masses have not been rigorously modeled previously; instead, lumped mass or concentrated point masses at arbitrary points on the beam have been used. Thus, this work focuses on the exact vibration analysis of cantilevered energy harvester devices including a tip proof mass. The model is based not only on a detailed modal analysis, but also on a thorough investigation of damping ratios that can significantly affect device performance. A model with multiple degrees of freedom is developed and then reduced to a single-mode model, yielding convenient closed-form normalized predictions of device performance. In order to verify the analytical model, experimental tests are undertaken on a macroscale, symmetric, bimorph, piezoelectric energy harvester with proof masses of different geometries. The model accurately captures all aspects of the measured response, including the location of peak-power operating points at resonance and anti-resonance, and trends such as the dependence of the maximal power harvested on the frequency. It is observed that even a small change in proof mass geometry results in a substantial change of device performance due not only to the frequency shift, but also to the effect on the strain distribution along the device length. Future work will include the optimal design of devices for various applications, and quantification of the importance of nonlinearities (structural and piezoelectric coupling) for device performance.

Experimental and theoretical studies on piezoelectric energy harvesting from low-frequency ambient random vibrations

“…Since the excitation frequency and the fundamental frequency of the harvester is identical in this test, the differences between analytical and experimental results is higher than when these two frequencies are different (that is not represented here). 21 As can be seen in Figure 10(b), the voltage output of the harvester increases with a sharp slop at relatively low electrical loads and then reaches to a saturated point, and Figure 10(c) represents that the current output will decrease by increasing resistive load that is in agreement with what the theory predicts. Figure 11 shows the comparison between the analytical and the experimental investigation of voltage FRF with the presence of optimum resistive load.…”

Nanoscale ferroelectric switching behavior at charged domain boundaries studied by angle-resolved piezoresponse force microscopy

“…Ferroelectric materials have attracted widespread interest in various applications such as nonvolatile memories, RF identification tags, and energy harvesters. [1][2][3] When any system is miniaturized, the domain structure associated with ferroelectric properties becomes important. Thus, fundamental studies of domain structure and polarization switching phenomena at the nanometer scale are highly demanding.…”

Dynamic energy harvesting performance of two Polyvinylidene Fluoride piezoelectric flags in parallel arrangement in an axial flow

“…Further information of (1) can be found in [13,14]. Equations (2) and (3) have been widely used in several applications, including [12,15,16], whose validity has been verified. Using the parameters in TABLE I, we investigate the dynamic energy harvesting performance of two piezoelectric flags in various separation distance H s .…”