Magnetic-spring based energy harvesting from human motions: Design, modeling and experiments

•An electromagnetic harvester is designed for harvesting energy from human motion.•Structural parameter and magnetic field are analyzed for performance enhancement.•Dynamic model is established for theoretical analysis under different excitations.•Experimental results verify the effectiveness of the proposed device.•Proper structural parameters can improve the harvester’s performance. A tunable magnetic-spring based electromagnetic energy harvester is presented in this paper to harvest vibration energy from human motions. The harvester is modeled by Ansoft Maxwell software and the best way of magnetic stack is chosen according to the generated voltage from simulation. Dynamic model of the energy harvester is derived and corresponding theoretical and numerical analysis are performed to evaluate the performance of the proposed system. Experimental results under frequency-sweep excitation with different acceleration levels show that the harvester is promising to generate electricity for a broadband frequency range. In the experiments considering human motion, the impact between shoe and ground as well as the swing motion of leg are investigated by attaching the device to human lower-limb. Testing results under various motion speeds show that proper structural parameters such as equivalent mass and movement length can improve the performance of the harvester. Moreover, it is demonstrated that the swing motion of human lower-limb could enhance the performance of the proposed device, especially for higher motion speed.