Nonlinear bi-stable energy harvester from human motion

A nonlinear bi-stable energy harvester from the human motion is proposed to solve the problem that the frequency bandwidth of traditional linear piezoelectric energy harvesters is narrow and it is hard to match with human motions. The harvester considers the characteristics of the human leg's motion and improves the energy harvesting efficiency by using the acceleration caused by leg swings and their impacts on the ground. An electromechanical model of nonlinear energy harvesters is derived based on the Hamilton principle and human motion signals. A portable nonlinear energy harvesting device is designed based on the characteristics of the human motion, and dynamic characteristics of linear, nonlinear mono-stable and bi-stable oscillators are realized by adjusting the position of magnets. Numerical simulations based on real human leg's vibration data show that the proposed harvester achieves the large amplitude inter-well oscillation and generates more energy from the human motion. Experimental results under various motion speeds verify the great advantage of the nonlinear bi-stable energy capture technology, and the efficiency of the proposed electromechanical model. The average output power of the bi-stable system reaches a maximum value of 23.2 μW when the motion speed is 8 km/h.