Vibration Harvesters with Mechanical Weak Coupling and Their Equivalent Circuit Model

To obtain a large power output by using MEMS vibratory energy harvesters, multiple devices can be used with connected together and their output synchronized. In this study, a butterfly-shaped harvester composed of two cantilever harvesters with weak mechanical coupling is proposed. For the fabricated test device, synchronized vibration of the two cantilevers as both wings of butterfly shape is successfully observed and the power output was doubled in the experiments. The mechanical coupling between the cantilevers is discussed by using equivalent circuit model. Based on the model, the devices with an additional mass to enhance the synchronization were fabricated and evaluated. The experimental results agree well with the calculation.