Analysis and Experimental Validation of a Piezoelectric Harvester with Enhanced Frequency Bandwidth

Abstract

The use of a single bimorph as a harmonic oscillator aimed at harvesting vibrational energy is not effective due to its inherent narrow frequency bandwidth stemming from the need to adjust the natural frequency of the harvester to the platform excitation frequencies. Therefore, the present research focuses on the development, manufacturing, and testing of an advanced system based on three bimorphs, capable of adjusting their natural frequencies using tip end masses, and interconnected by springs, thus enlarging the system’s bandwidth. An analytical model was developed for three bimorphs interconnected by two springs with three end masses. The model can predict the output generated voltage from each bimorph, and then the total output power is measured on a given outside resistor as a function of the material properties, the geometric dimensions of the vibrating beams, the end-masses, and the spring constants. The analytical model was then compared with data in the literature, yielding a good correlation. To further increase the reliability of the model, a test set-up was designed and manufactured that included three bimorphs with three end-masses connected by two springs. The system was excited using a shaker, and the output voltage was measured for each bimorph for various configurations. Then, the analytical model was tuned based on the test results by introducing two factors, the quality and the stiffness factors, and the predictions of the calibrated analytical model were compared with the experimental results, yielding a good correlation. The calibrated analytical model was then used to perform a comprehensive parametric investigation for two and three bimorphs systems, in which the influences of various parameters—like spring constant, mass value, thickness, and width and length of the bimorph and the substrate beam—on the output generated power were investigated. The main conclusion from this parametric investigation was that by correctly choosing the geometric sizes of the cantilevers, the adequate tip end masses, and the ratio between constants of the springs, the frequency bandwidth is expanded yielding a higher harvested power. Typical harvested power of the present designed system can reach up to 20 mW at the first natural frequency and up to 5 mW for the second natural frequency.

Tuning Techniques for Piezoelectric and Electromagnetic Vibration Energy Harvesters

“…Therefore, in practical applications, the increase of the effective operating frequency range of RVEHs is mandatory. In the literature, a number of papers describing control methods or architectures that are specifically designed with the aim of increasing the effective operating frequency range of RVEHs, has been proposed [87][88][89][90][91][92][93][94][95]. In particular, harvesters arrays, nonlinear harvesters, and mechanical tuning techniques (MTTs) are the most widely analyzed optimization methods.…”

Development of Piezoelectric Energy Harvester System through Optimizing Multiple Structural Parameters

“…In view of this, the application of piezoelectric energy harvesting technology in road engineering has been explored [10][11][12]. Piezoelectric transducer structures include the stack type [13,14], cymbal type [15], cantilever type [16,17] and flexible type [11]. Some of these structures have been tested in the laboratory and finite element analysis has been used to analyze the dynamic response of piezoelectric pavements [17,18].…”

Piezoelectric Energy Harvesting from Suspension Structures with Piezoelectric Layers

“…He et al presented vibration energy harvesters with a rolling steel ball inside a guiding channel as the proof mass and derived the mathematical model of the system [ 45 ]. Abramovich et al established an analytical model of three bimorphs with three end masses and obtained power levels up to 20 and 5 mW at the first and second natural frequencies, respectively [ 46 ]. Wang et al developed evaluation methods with an output capacity density indicator and obtained good agreement between simulations and analytical result [ 47 ].…”