Resistive and reactive loads’ influences on highly coupled piezoelectric generators for wideband vibrations energy harvesting

Abstract

One of the main challenges in energy harvesting from ambient vibrations is to find efficient ways to scavenge the energy, not only at the mechanical system resonance, but on a wider frequency band. Instead of tuning the mechanical part of the system, as usually proposed in the state of the art, this paper develops extensively the possibility to tune the properties of the harvester using the electrical interface. Due to the progress in materials, piezoelectric harvesters can exhibit relatively high electromechanical coupling: hence, the electrical part can now have a substantial influence on the global parameters of the piezoelectric system. In order to harness the energy efficiently from this kind of generator on a wide frequency band, not only the electrical load's effect on the harvester's damping should be tuned, but also its effect on the harvester's stiffness. In this paper, we present an analytical analysis of the influences of the resistive and reactive behavior of the electrical interface on highly coupled piezoelectric harvesters. We develop a normalized study of the multiphysic interactions, reducing the number of parameters of the problem to a few physically meaningful variables. The respective influence of each of these variables on the harvesting power has been studied and led us to the optimal electrical damping expression and the influences of the damping and of the coupling on the equivalent admittance of the piezoelectric energy harvester (PEH). Finally, we linked these normalized variables with real reactive load expressions, in order to study how a resistive, capacitive and inductive behaviors could affect the global performances of the system. The theoretical analysis and results are supported by experimental tests on a highly coupled piezoelectric system (" = 23%). Using an adequate tuning of a RC load at each frequency, the maximum harvested power (11) under a small acceleration amplitude of 0.5. 0" is reach over a 14Hz large frequency band around 105Hz which has been predicted by the model with less than 5% error.

Strongly coupled piezoelectric cantilevers for broadband vibration energy harvesting

“…Where , are the equivalent mass and stiffness matrix, , the coupling and forcing vectors and the piezoelectric material clamped capacitance. Their expressions for parallel electrical connection are given in equations (30) to (34)…”

“…Once the mode shapes and their second derivatives are determined, we obtain the analytical expressions of the equivalent parameters of the system (29) by substituting them in (30) to (34). The coefficients of each matrix and vector are finally expressed in equations (50) to (53).…”

“…For the systems that have sufficiently large 2 and ( 2 ≥ 2), ' shows, for optimal resistive loads (R), two maxima ( ′ = ) separated by a less interesting low in the curve which can be raised thanks to optimal combinations of resistance and capacitance loads (R and C) [34] (Figure 1). Because banks of capacitors cannot be easily integrated in a circuit, strategies that involve non-linear electrical techniques [35] have recently been developed to optimize the harvested power in the [ 1 , 1 ] bandwidth and even beyond with the SC-SECE [10] and the FT-SECE [9] techniques.…”

Analytical Modeling and Validation of a Preloaded Piezoceramic Current Output

“…Since an efficient energy harvesting system is the optimum design of different components, the selection of interface circuit elements is particularly important. Morel et al studied the influence of the resistive, capacitive and inductive behavior in a piezoelectric energy harvesting system and derived a simplified model [ 20 ], and they also manufactured an extra low energy consumption integrated interface to achieve >91% efficiency of energy harvesting under shocks and 94% under periodic excitations [ 21 ]. Their studies have the potential to improve the interface-circuit parameter coupling for the current output model.…”

Disturbance observer–based terminal sliding mode control for effective performance of a nonlinear vibration energy harvester

“…In linear systems, if value of the excitation frequency is far from the system natural frequency, the amplitude of the response will remarkably decrease. Improving the power density and frequency bandwidth of vibration energy harvesting systems will certainly enable to address more applications (Lefeuvre et al, 2017; Liao and Sodano, 2010; Morel et al, 2019). Hence, many researchers tried to exploit nonlinear behaviour to overcome this issue by widening the frequency bandwidth.…”