Controlling dynamic pull-in escape in electrostatic MEMS

In this work, we present modeling and experimental data for controlling the dynamic pull-in and the escape-from-potential-well phenomena for a capacitive MEMS device using phase control technique. The device is actuated with a DC voltage superimposed to an AC harmonic voltage. An inevitable escape band of frequencies, where a MEMS resonator is forced to pull-in, is simulated theoretically and found experimentally. To enhance the stability of the MEMS device, a second weak AC signal with a specific phase shift is superimposed to the original AC excitation to be used as the control signal. It is found that this type of control signal can effectively shrink the escape tongue near the primary resonance of the capacitive device, thereby enhancing its stability. A numerical scheme (shooting technique) for finding periodic motion and investigating its stability using Floquet theory is used to simulate the device behavior. Comparison is then made between the simulation results and the obtained experimental data.