TUNING THE RESONANCE FREQUENCY OF A PIEZOELECTRIC VIBRATION BASED ENERGY HARVESTER USING AN ELECTROMAGNETIC FORCE

Abstract eng:
Vibration based energy converters employing piezoelectric thin films have gained popularity in recent years. Most of these harvesters are designed to work at resonance in order to maximize the output power. Therefore, they are usually manufactured to have resonance frequencies that match the excitation frequencies of the operating environment. However, in some cases, there is a mismatch between the resonance and excitation frequencies due to manufacturing tolerances and varying excitation frequency. These deviations can affect the performance of the harvester. There are different methods to broaden the operational frequency of the harvesters [1-3]. In this paper an adaptively tuned piezoelectric vibration based energy harvesting system based on the use of electromagnetic force is proposed. The main motivation is to control the resonance frequency of the piezoelectric harvester with the electromagnetic force in order to maximize the harvested power. The idea is demonstrated in a bimorph piezoelectric harvester which is located between two electromagnets. The nonlinear governing differential equation of motion is derived based on Euler Bernoulli theory, and solved to obtain the dynamic solutions. The results show that by controlling the amount of electrical current passes through the coils of electromagnets, the resonance frequency of the harvester can be tuned to give a high amplitude response over a wide range of frequencies, and shows the great potential of this system.

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