Publications

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We report that an investigation is carried out for the purpose of simultaneously controlling a base-excited dynamical system and enhancing the effectiveness of a piezoelectric energy harvesting absorber. Amplitude absorbers are included to improve the energy harvested by the absorber with the possibility of activating broadband resonant regions to increase the operable range of the absorber. This study optimizes the stoppers’ ability for the energy harvesting absorber to generate energy by investigating asymmetric gap and stiffness configurations. Medium stiffnesses of 5 x 10⁴ N/m and 1 x 10⁵ N/m show significant impact on the primary system’s dynamics and improvement in the level of the harvested power for the absorber. A solo stopper configuration when the gap distance is 0.02m improves 29% in peak power and 9% in average power over the symmetrical case. Additionally, an asymmetric stiffness configuration when one of the stiffnesses is 1 x 10⁵ N/m and a gap size of 0.02m indicates an improvement of 25% and 8% for peak and average harvested power, respectively, and the second stopper’s stiffness is 5 x 10³ N/m. Hard stopper configurations shows improvements with both asymmetric cases, but not enough improvements to outperform the system without amplitude stoppers.

Tuned mass dampers are a common method implemented to control structure’s vibrations. Most tuned-mass dampers only transfer the mechanical energy of the primary system to a secondary system, but it is desirable to convert the primary systems’ mechanical energy into usable electric energy. This study achieves this by using a piezoelectric energy harvester as a tuned-mass damper. Additionally, this study focuses on improving the amount of energy harvested by including amplitude stoppers. Mechanical stoppers have been investigated to sufficiently widen the response of piezoelectric energy harvesters. Furthermore, magnetic stoppers are compared to the mechanical stopper’s response. A nonlinear reduced-order model using Galerkin discretization and Euler-Lagrange equations is developed. The goal of this study is to maximize the energy harvested from the absorber without negatively affecting the control of the primary structure.

A popular technique to control dynamical systems is the implementation of tuned-mass dampers. Most tuned-mass dampers only transfer the mechanical energy of the primary system to a secondary system, but it is desirable to convert the primary systems’ mechanical energy into usable electric energy. A piezoelectric energy harvester is used in this study. Furthermore, amplitude stoppers are included to possibly generate a broadband region by causing a nonlinear interaction. Mechanical stoppers have been investigated to sufficiently widen the response of piezoelectric energy harvesters. The effectiveness of the stoppers type is also investigated by comparing magnetic stoppers to mechanical stoppers. A nonlinear reduced-order model using Galerkin discretization and Euler-Lagrange equations is developed. The goal of this study is to maximize the energy harvested from the absorber without negatively affecting the control of the primary structure.

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In this study, model derivations are carried out of a dynamical system under base excitations with a piezoelectric energy harvesting absorber as the tuned-mass-damper. Additionally, amplitude stoppers are included to the absorber in order to create a broadband resonant response, increasing the window of operational use for energy harvesting and system's control. This study is unique in the fact that the energy harvester is coupled to the source of its excitation. A nonlinear reduced-order model is developed using Euler–Lagrange principle and the Galerkin method to accurately estimate the energy harvesting absorber's displacement, harvested power, and the oscillating response of the primary structure. The nonlinear interaction of the energy harvesting absorber and the amplitude stoppers are the focus of this study, where an in-depth investigation of bifurcation points of the primary structure and energy harvesting absorber responses is performed. Due to a transfer of energy between the primary structure and the absorber, it is shown that a soft stopper with stiffness $5 \times {10^3}\,{\text{N}}\;{{\text{m}}^{ - 1}}\,$ has great control of the primary structure with 60% of the uncontrolled amplitude being reduced, as well as an increase of the harvested energy. Medium stoppers with small initial gaps size and hard stoppers do not control the primary structure and show a decrease in the energy harvesting capabilities due to the activation of the nonlinear contact-impact interactions. Finally, these stoppers also generate aperiodic regions due to the possible presence of grazing bifurcations.

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