Hybrid Energy Harvesting System M. Amin Karami1, Paulo S. Varoto2 and Daniel J. Inman3 This paper focuses on experimental nonlinear vibration analysis of the proposed hybrid energy harvester. A nonlinear energy harvesting structure is proposed to convert ambient vibrations to the electrical energy using the piezoelectric and electromagnetic mechanisms. A repelling magnetic force is introduced to the system to both reduce the resonant frequency of the system and increase the frequency bandwidth by making the vibrations nonlinear. The paper is the continuation of a previous work by the authors in which the vibrations of the harvester was analytically characterized. Both mono-stable and bi-stable situations are studied. Depending on the level of excitations the bi-stable system can exhibit oscillations about each of its equilibriums, chaotic vibrations or the limit cycle oscillations (LCO) over both of the equilibriums. The proper design of the harvester allows the system to perform Limit Cycle Oscillations in response to moderate base excitations. The paper discusses the experimental results on electro-mechanical vibrations and the energy generation of the nonlinear hybrid harvester at different magnetic force levels, excitation frequencies and excitation levels. Introduction Energy harvesting is the act of scavenging small amounts of power from the ambient energy in the environment. This paper focuses on energy harvesting from vibrations. Such ambient energy can come from bridge vibrations, tire motion or the human heart beating. The minute energy can power up sensor nodes and therefore reduce the wiring complications or eliminate the need of changing batteries frequently. For more information on general energy harvesting the reader may refer to [1-6]. During the past two years nonlinear energy harvesting has received substantial attention. The nonlinearity can be natural (for example the nonlinear material properties of the piezoelectric substance [7] ) or can be synthetic. If in addition to 1 ICTAS Doctoral Scholar and PhD candidate, Department of Engineering Science and Mechanics, Virginia Tech, Blacksburg VA, 24061, karami@vt.edu 2 Professor on Mechanical Engineering, Universidade de São Paulo, São Paulo, Brazil, varoto@sc.usp.br 3 George R. Goodson Professor, Center for Intelligent Material Systems and Structures, Department of Mechanical Engineering, Virginia Tech, Blacksburg VA, 24061, dinman@vt.edu T. Proulx (ed.), Modal Analysis Topics, Volume 3, Conference Proceedings of the Society for Experimental Mechanics Series 6, 461 DOI 10.1007/978-1-4419-9299-4_38, © The Society for Experimental Mechanics, Inc. 2011 Experimental Study of the Nonlinear
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