Voltage driven parallel-plate electrostatic actuators suffer from an operation range limit of 30% of the electrostatic gap; this has restrained their application in microelectromechanical systems (MEMS). In this paper, the travel range of an electrostatic actuator made of a micro-cantilever beam above a fixed electrode is extended quasi-statically to 90% of the capacitor gap by introducing a voltage regulator (controller) circuit designed for low frequency actuation. The voltage regulator reduces the actuator input voltage, and therefore the electrostatic force, as the beam approaches the fixed electrode so that balance is maintained between the mechanical restoring force and the electrostatic force. The low-frequency actuator also shows evidence of high order superharmonic resonances that are observed here for the first time in electrostatic actuators.

The dynamics of a close-loop electrostatic MEMS resonator, proposed as a platform for ultra sensitive mass sensors, is investigated. The parameter space of the resonator actuation voltage is investigated to determine the optimal operating regions. side each of the potential wells and around both wells. The optimal region in the parameter space for mass sensing purposes is determined. In that region, steadystate chaotic attractors develop and spend most of the time in the safe lower well while occasionally visiting the upper well. The robustness of the chaotic attractors in that region is demonstrated by studying their basins of attraction. Further, regions of large dynamic amplification are also identified in the parameter space. In these regions, the resonator can be used as an efficient long-stroke actuator.

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A voltage regulator is developed to extend the operation range of a electrostatic actuator using a displacement feedback. The feedback actuator system can be used for continuous position tracking of step, ramp, or harmonic voltage signals. The electrostatic actuator is composed of a micro-cantilever beam electrode above a fixed electrode. The voltage difference between the two electrodes is regulated by the controller to maintain the balance between mechanical and electrostatic forces at large beam deflections, thereby increasing the actuation range. Simulated closed loop system responses with experimentally identified parameters are presented and show the actuation can reach up to 85% of the gap in the static response with an input voltage of less than 12 V. Experimental results show that the controller properly functions and prevents the beam from experiencing pull-in. A close agreement is found between the simulated and measured closed loop model dynamic responses.

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