Preloaded freeplay wide-bandwidth low-frequency piezoelectric harvesters

We propose a technique for increasing the bandwidth of resonant low-frequency (<100 Hz) piezoelectric energy harvesters based on the modification of the clamped boundary condition of cantilevers, termed here as preloaded freeplay boundary condition. The effects of the preloaded freeplay boundary condition are quantified in terms of the fundamental frequency, frequency response, and power output for two beam configurations, namely, classical cantilevered bimorph piezoelectric energy harvester and zigzag unimorph piezoelectric energy harvester. A comparative analysis was performed between both the harvesters to empirically establish the advantages of the preloaded freeplay boundary condition. Using this approach, we demonstrate that the coupled degree-of-freedom dynamics results in an approximate 4-7 times increase in half-power bandwidth over the fixed boundary condition case.