Dynamic Study of MEMS Variable Capacitive Device for Power Harvesting

This work shows the complicated dynamic responses of the MEMS parallel plate capacitor for power harvesting resulting from the onset of rocking instability. Rocking instability or symmetry breaking is a relatively new area of study as it pertains to plate instability. It is important because the instability decreases the total amount of power that can be harvested especially when the tips of the moving plate make contact with the fixed plate. Two different designs characterized by the number of variable capacitors are studied. Power harvesting is achieved by the motion of a moving plate under external forces of vibration. The dynamics of the moving plate under sinusoidal excitations are obtained using numerical integration. We show that capacitive plates can become non-parallel due to the onset of rocking instability. Complicated dynamic phenomena including period doubling and chaos can occur. Consequently, the harvested power is greatly reduced when rocking instability occurs.Copyright © 2012 by ASME