A black gauze cap-shaped bistable energy harvester with a movable design for broadening frequency bandwidth

A black gauze cap-shaped bistable energy harvester (abbreviated as the BGCBEH) with a movable design is raised to broaden frequency bandwidth. The proposed BGCBEH is composed of two harvesting units which like the ancient Chinese cap wings. Under lower frequency vibrations, they can not only reciprocate in the horizontal direction, but also vibrate in the vertical direction. Each harvesting unit can realize adaptive potential by reciprocating sliding of cap wings, and achieving inter-well oscillation to get more energy, which are verified by theoretical analyzing and numerical simulating. Under harmonic excitation, the energy obtained by BGCBEH is greater than that by unmovable bistable energy harvester (abbreviated as the UBEH) within 69.7% of the given frequency bandwidth. The energy acquisition frequency domain is broadened by 373.8% and the corresponding rms voltage is increased by 81%. Under random excitation, the rms voltage of the proposed BGCBEH is increased by 396.4% compared to that of the UBEH. The proposed design is further verified by the experiments. Under harmonic excitation, the energy obtained by BGCBEH is greater than that by the UBEH within 71% of the given frequency bandwidth. The energy acquisition frequency domain is broadened by 44% and the corresponding rms voltage is increased by 111.1%. Under random excitation, the rms voltage of the proposed BGCBEH is increased by 81.7% compared to that of the UBEH, and this increase is distributed over the entire frequency domain. The experimental results are greatly consistent with those observed in the above numerical simulating. The output can be further improved when the sum of movable distance and initial magnetic spacing are optimized. The proposed BGCBEH is expected to be applicable to the early-stage warning and accurate detection of passive acceleration due to its snap-through amplitude response characteristics, which needs to be further explored.