Stability Analysis of Electrostatically Actuated Resonators With Delayed Feedback Controller

In this work we investigate the stability of parallel-plate electrostatic MEMS resonators using a delayed feedback controller. Two case studies are investigated: a capacitive sensor made of cantilever beams with a proof mass at their tip and a clamped-clamped microbeam. Dover-cliff integrity curves and basin-of-attraction analysis are used for the stability assessment of the frequency response of the resonators for several scenarios of positive and negative gain in the controller. It is found that, in the case of a positive gain, a velocity or a displacement feedback controller can be used to effectively enhance the stability of the resonators. This is confirmed by an increase in the area of the safe basin of attraction and in shifting the Dover-cliff curve upward. On the other hand, it is shown that a negative gain can significantly weaken the stability of the resonators. This can be of useful use in MEMS for actuation applications, such as in the case of capacitive switches, to lower the activation voltage of these devices and to ensure their trigger under all initial conditions.