An enhanced tunable rotational energy harvester with variable stiffness system for low-frequency vibration

An enhanced tunable rotational energy harvester for low-frequency vibration is proposed. It consists of a rotational vibrating system and a translating proof mass suspended by wire. The active tuning of the resonant frequency is implemented using the serial connection control of spiral springs, which is named here as a variable stiffness system. The concept, design, and implementation for the proposed device are presented. The numerical simulation and the vertical shaker test are performed, respectively, and the results showed that the proposed energy harvester could effectively generate the electricity under the low-frequency vibration and readily change its natural frequency as well.