A simulation of the performance of a self-tuning energy harvesting cantilever beam

Abstract

A vibration energy harvester is typically a cantilever beam made up of one or two layers of piezoelectric material that is clamped at one end to a vibrating host structure. The harvester is typically tuned to the frequency of the ambient vibration to ensure maximum power generation. One method to ensure that the system stays tuned in the presence of a varying frequency is to attach a mass to the cantilever and apply a control system to adjust its position along the cantilever according to the ambient frequency. This paper presents a simulation of the performance of such a system, based on a distributed parameter electromechanical model of the sliding-mass beam. A variety of control systems are used to adjust the position of the movable mass during operation and are compared for their efficacy in maintaining resonance over a varying excitation frequency. It was found that the resonance frequency of a bimorph cantilever VEH (Vibration Energy Harvester) could be successfully tuned over a wide frequency range. Moreover, it is also found that much of the voltage output reduction at higher frequencies could be compensated for by a separate control system used to adjust the capacitor load.