Vibration-based Piezoelectric Harvesters Research Articles

Analytical modeling and validation of multi-mode piezoelectric energy harvester

Abstract Energy consumption of electronic devices continues to reduce dramatically, enabling the ambient energy harvesting devices as a solution for powering the wireless sensor nodes (WSNs), micro-electromechanical systems and portable electronics. Over the years, vibration-based piezoelectric harvesting has been emerged as a potential technology to recharge/replace chemical batteries in WSNs. A conventional linear piezoelectric energy harvester (PEH) cannot meet the requirement of broadband vibration resources as it generates useful power only in a narrow bandwidth near the resonant frequency. Several techniques such as passive/active resonance tuning, array of harvester beams, nonlinear designs and multi-degree-of-freedom energy harvesters have been investigated. This paper proposes a generalized multi-mode PEH (MPEH) accompanied with analytical modeling, which generates multiple close peaks of voltage output from low amplitude broadband and low frequency ambient vibration sources. The proposed MPEH comprises of a main cantilevered beam bonded with a patch of piezoelectric layer and attached with multiple branches with tip masses at their free ends. The useful bandwidth and the number of peaks for the MPEH could be tuned conveniently by varying multiple branches and tip masses. The proposed MPEH offers high design flexibility in tuning geometric parameters for achieving target frequencies and generates high power density. The mathematical modeling of generalized MPEH under transverse harmonic base vibrations is presented and the dynamic equations of the multi-modal harvester system are obtained following the Lagrangian method. The derived distributed parametric model of MPEH is more accurate than lumped parametric models of PEHS presented in the literature. The accuracy of the proposed analytical model is validated by two examples with numerical simulation and experimental results. It is shown that the multi-mode PEH has potential to generate sufficient power output from broadband vibration sources to sustain low-power electronic devices.

A concept for energy harvesting from quasi-static structural deformations through axially loaded bilaterally constrained columns with multiple bifurcation points

A major obstacle limiting the development of deployable sensing and actuation solutions is the scarcity of power. Converted energy from ambient loading using piezoelectric scavengers is a possible solution. Most of the previously developed research focused on vibration-based piezoelectric harvesters which are typically characterized by a response with a narrow natural frequency range. Several techniques were used to improve their effectiveness. These methods focus only on the transducer’s properties and configurations, but do little to improve the stimuli from the source. In contrast, this work proposes to focus on the input deformations generated within the structure, and the induction of an amplified amplitude and up-converted frequency toward the harvesters’ natural spectrum. This paper introduces the concept of using mechanically-equivalent energy converters and frequency modulators that can transform low-amplitude and low-rate service deformations into an amplified vibration input to the piezoelectric transducer. The introduced concept allows energy conversion within the unexplored quasi-static frequency range (≪1 Hz). The post-buckling behavior of bilaterally constrained columns is used as the mechanism for frequency up-conversion. A bimorph cantilever polyvinylidene fluoride (PVDF) piezoelectric beam is used for energy conversion. Experimental prototypes were built and tested to validate the introduced concept and the levels of extractable power were evaluated for different cases under varying input frequencies. Finally, finite element simulations are reported to provide insight into the scalability and performance of the developed concept.