High efficiency energy harvesting device with magnetic coupling for resonance frequency tuning

Abstract

Wireless sensors are becoming extremely popular for their ability to be employed in hostile and inaccessible locations to monitor various parameters of importance, and vibration energy harvesting shows great potential in powering these sensor networks. For efficient operation the device should operate in resonance at the environmental excitation frequency and hence requires a frequency tuning mechanism. Recently efforts have been attempted to broaden the frequency range of energy harvesting devices, but in terms of power density an efficient design methodology is lacking. In this work, a tunable energy harvesting device with high efficiency and power density is presented. The technique involves two single DOF's cantilever beams which are coupled in a novel fashion by means of magnetic force for resonance frequency tuning. Here the magnetic force acts as a variable stiffness coupling the two cantilever beams, allowing one to alter the corresponding resonance frequencies of the cantilever beams. Magnetic force of attraction and repulsion can be used to achieve the magnetic coupling and can increase the overall stiffness of either of the cantilever beams while decreasing the others. The total power output of the device is found to be between 180 μW to 320 μW.