Luã G. Costa

Mechanical energy harvesting has increasing scientific and technological interests due to novel energetic challenges. A critical issue in classical cantilever-based mechanical energy harvesting systems is the lack of multidirectional energy conversion capabilities and, due to that, deviations from the excitation source can drastically reduce their performance. This limitation has led to the development of energy harvesters with attached pendula, serving as a direction coupling mechanism. Nevertheless, the pendulum structure itself can act as an energy absorber, drastically reducing the harvester performance in certain scenarios. In order to overcome this issue, a hybrid multidirectional pendulum-based energy harvester has been introduced by the authors. The hybrid transduction integrates a piezoelectric element to capture energy from the principal direction and an electromagnetic transducer to harness rotational energy from the pendulum. This paper presents an in-depth analysis of the hybrid multidirectional pendulum-based energy harvester using a nonlinear dynamics perspective to evaluate the energy harvesting performance. A reduced-order model is proposed to represent the essential characteristics of such systems. A parametric analysis using a nonlinear dynamics perspective is carried out to map the system dynamics and performance. The emergence of complex and rich dynamics is observed, including chaos and hyperchaos. Results reveal the most and least effective combinations of structural parameters in terms of energy conversion. Additionally, the dynamical responses and patterns associated with high performance are identified. These responses are often characterized by a blend of irregular complex behaviors, coupled with a mix of oscillatory and rotational patterns of motion, resulting in wider bandwidth systems.

This work presents a hybrid multidirectional mechanical energy harvester to enhance the performance of a cantilever-based harvester when subjected to multidirectional excitations. The multidirectional capabilities are achieved by employing a pendulum structure. Hybrid transduction is provided by combining a piezoelectric element and an electromagnetic transducer. A reduced-order model is presented based on the electromechanical Lagrangian formulation, and numerical analyses are performed to characterize the system behavior. A comparison based on energy harvesting performance is established among the novel multidirectional hybrid energy harvester (MHEH), the classical piezoelectric harvester (CPEH), and a multidirectional piezoelectric harvester (MPEH). Results show that the addition of the pendulum alone indeed provides multidirectional capabilities, but the overall performance can be reduced in some scenarios since it works as an energy absorber. This limitation is overcome by the hybridization strategy of the MHEH, by incorporating an electromagnetic transducer into the pendulum support. Overall, a significant improvement is achieved in all scenarios by utilizing the hybrid system.

Nature provides abundant ambient mechanical energy in the form of vibration, sound, wave, wind, and biomechanical energy, which can be harvested to power electronic systems. Smart materials-based mechanical energy harvesting systems have attracted increasing attention over the past two decades due to their advantageous characteristics such as high power density, simple design, and scalability. Nevertheless, the design of compact and high-performing systems remains a challenge. This work deals with the analysis of a compact multistable dual-beam nonlinear energy harvester that can be configured for different stability layouts. By using a nonlinear dynamics analysis framework and suitable tools, a qualitative performance characterization of the harvester for each stability configuration is conducted. Results show that multistable characteristics associated with a softer inner beam characteristic and higher excitation levels are related to complex phenomena and can greatly enhance performance.

The use of smart materials as transducers in mechanical energy harvesting systems has gained significant attention in recent years. Despite the numerous proposed solutions in the literature, challenges still exist in terms of their implementation within limited spaces while maintaining optimal performance. This paper addresses these challenges through the concepts of compactness and space-efficient design, as well as the incorporation of nonlinear characteristics and additional degrees-of-freedom. A multistable dual beam nonlinear structure featuring two magnetic interactions and two piezoelectric transducers is presented. A reduced order model with 2-degrees-of-freedom is established based on the harvester structure in order to capture the essential qualitative characteristics of the system. Stability analysis demonstrates that the combination of two nonlinear magnetic interactions furnish unprecedented multistable characteristics to this type of harvester. A framework using a nonlinear dynamics perspective is established to analyze multistable systems based on energy harvesting purposes. Different dynamical and stability characteristics are determined by the differences in the system stiffness ratio. Parametric analyses are carried out classifying regions of high performance in the external excitation parameter space. These regions are associated with rich and complex dynamics. Finally, a comprehensive comparison is conducted between the proposed harvester and the classical bistable harvester, revealing improvements in performance across nearly all relevant conditions. These findings highlight the enhanced capabilities of the proposed harvester design, solidifying its potential of application in diverse energy harvesting scenarios.