Bi-Stable cantilevered piezoelectric energy harvester using springs

Abstract

A cantilever is the most popular design used for a vibration based piezoelectric energy harvester due to its simple configuration. However, it has two critical problems; the system is significantly sensitive to an input excitation frequency and is not proper to a low frequency vibration environments, such as human motions. This research presents a new nonlinear cantilevered piezoelectric energy harvester which consists of a conventional cantilevered piezoelectric energy harvester and springs. By attaching springs, this system can have two stable states; one is deforming upwards and another is deforming downwards. The springs also make the frequency range which shows intense dynamics response lower. Electro-mechanical equations for the proposed system are derived using the Euler-Bernoulli beam theory and Kane's method. As a result, the system shows intense dynamic responses at the frequency range from 1 Hz to 7 Hz under the acceleration of 3 m/s2. The vibration of this frequency range (1 Hz ∼ 7 Hz) can be easily observed from the motion of human or animal, shaking of a tree by wind. In the future work, the acceleration data of human's foot when walking or running could be input to the Electro-mechanical equations to investigate the performance.