Narrow bandwidth is the major challenge to today’s vibration-based energy harvesters. Compared with other broadband approaches that involve moving parts and control electronics, a double-mass piezoelectric cantilever beam provides a simple and reliable solution to widen the effective bandwidth as a vibration energy harvester. In this article, a continuum model of a double-mass lead zirconate titanate cantilever subject to sinusoidal base excitation is presented. First, the undamped equation of motion along with boundary and transition conditions is derived from Hamilton’s principle, followed by modal analysis that determines the eigenfunctions and natural frequencies. Next, the coupled electromechanical equations for sinusoidal base excitation are obtained. The output voltage and relative displacement are solved analytically. The frequency response function and mode shapes predicted by the model are validated against experiments.

The dynamic response of parametrically excited microbeam arrays is governed by nonlinear effects which directly influence their performance. To date, most widely used theoretical approaches, although opposite extremes with respect to complexity, are nonlinear lumped-mass and finite-element models. While a lumped-mass approach is useful for a qualitative understanding of the system response it does not resolve the spatio-temporal interaction of the individual elements in the array. Finite-element simulations, on the other hand, are adequate for static analysis, but inadequate for dynamic simulations. A third approach is that of a reduced-order modeling which has gained significant attention for single-element microelectromechanical systems (MEMS), yet leaves an open amount of fundamental questions when applied to MEMS arrays. In this work, we employ a nonlinear continuum-based model to investigate the dynamic behavior of an array of N nonlinearly coupled microbeams. Investigations focus on the array's behavior in regions of its internal one-to-one, parametric, and several internal three-to-one and combination resonances, which correspond to low, medium and large S. Gutschmidt ( ) DC-voltage inputs, respectively. The nonlinear equations of motion for a two-element system are solved using the asymptotic multiple-scales method for the weakly nonlinear system in the afore mentioned resonance regions, respectively. Analytically obtained results of a two-element system are verified numerically and complemented by a numerical analysis of a three-beam array. The dynamic behavior of the twoand three-beam systems reveal several in-and outof-phase co-existing periodic and aperiodic solutions. Stability analysis of such co-existing solutions enables construction of a detailed bifurcation structure. This study of small-size microbeam arrays serves for design purposes and the understanding of nonlinear nearestneighbor interactions of medium-and large-size arrays. Furthermore, the results of this present work motivate future experimental work and can serve as a guideline to investigate the feasibility of new MEMS array applications.

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A nonlinear continuum model is used to investigate the dynamic behavior of an array of N nonlinearly coupled microbeams. Investigations concentrate on the region below the array's first pull-in instability, which is shown to be governed by several internal three-to-one and combination resonances. The nonlinear equations of motion for a two-element system are solved using the asymptotic multiple-scales method for the weak nonlinear system. The analytically obtained periodic response of two coupled microbeams is numerically evaluated by a continuation technique and complemented by a numerical analysis of a three-element array which exhibits quasi-periodic responses and lengthy chaotic transients. This study of small-size microbeam arrays serves for design purposes and the understanding of nonlinear nearest-neighbor interactions of medium- and large-size arrays.

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High efficiency in cruising is a determining factor in developing tuna-mimetic robots. So far, a number of tuna-like robots have been made. Nevertheless, the University of Canterbury has developed its own tuna-like robot called UC-Ika 1 to investigate and to accordingly improve the swimming performance of the biomimetic swimming robots. In order to do so, the propulsion system of a tuna with respect to its thrust and resistive forces is studied. Following that, the fish robot is designed and fabricated considering the tuna propulsion system. The robot is then tested several times to investigate its swimming performance. Comparison of the speed and efficiency of UC-Ika 1 with those of other tuna-like robots shows a promising improvement of cruising performance of UC-Ika 1.