Investigation to the influence of additional magnets positions on four-magnet bi-stable piezoelectric energy harvester

To enhance the harvesting performance of a bi-stable piezoelectric energy harvester (BEH), this work proposes a four-magnet BEH (FBEH). FBEH consists of a piezoelectric cantilever beam with a tip magnet, a fixed magnet and two movable magnets. The two movable magnets relative to the fixed magnet can move in both horizontal and vertical directions. A nonlinear distributed parameter model of FBEH is derived through the Hamilton principle. The effects of the excitation frequency and amplitude as well as the horizontal and vertical gap on the harvesting performance are mainly investigated by using the bifurcation diagram, phase diagram, Poincaré map and output power. Numerical simulations demonstrate that the proposed FBEH decreases the potential barrier and creates a higher than typical bi-stable one when subjected to lower excitation amplitudes and frequencies.