Mechanism, theory and application research of a rotating electromagnetic energy harvester suitable for multi-directional excitation

Energy harvesting in multi-directional excitation for human wearable devices is a challenge. A rotating electromagnetic energy harvester (REMEH) based on an eccentric rotor structure is proposed in this paper. Two poles of the magnets in the REMEH are alternately arranged in a ring. The electrical output characteristics of the energy harvester are analyzed through theoretical, numerical simulation and experimental testing methods based on the establishment of magnetic flux density models, the coil induced voltage, and the excitation direction of the eccentric rotor structure. Theoretical analysis and experimental results show that the design of the eccentric rotor structure is well adapted to multi-directional and irregular excitation. The circular staggered arrangement of the magnets effectively increases the output voltage and output power. The results show that the average output power increases slowly when the walking speed increases from 1 to 3 km h-1, and the average output power increases substantially when the walking speed increases from 3 to 5 km h-1. When the walking speed is 1 and 3 km h-1, the average output power is 0.439 and 0.638 mW, respectively. At a walking speed of 5 km h-1, the average output power increases rapidly to 1.68 mW, corresponding to a power density of 16.59 μW g-1. This high-performance energy harvester can provide effective power supply for wearable devices or low-powered sensors.