Adaptive Sliding Mode Controller Design for a Tunable Capacitor Susceptible to Unknown Upper-Bounded Uncertainties and Disturbance

Abstract

Uncertainty in physical parameters of a tunable MEMS capacitor, as the main element of MEMS AC voltage reference (VRS), is a significant matter to be regarded in order to obtain a precise output voltage which could be ruined by disturbance and noise. Even though many attempts are done to make MEMS tunable capacitor with desired precise physical characteristics and improve accuracy of values in physical parametric properties, parametric uncertainties inevitably transpire in manufacturing process due to shortcomings in micromachining procedures. Not only does this paper take into account design of a PI adaptive sliding mode controller and its application for the MEMS AC VRS in such a way that it is competent of producing a stable precise regulated output voltage in the presence of uncertainties and exogenous disturbance, but also it conquers both terms of matched and unmatched uncertainties and disturbance which their upper bounds are limited but not known. The matched and unmatched disturbance may emerge in the device dynamics because of cross-talk, inertial coercions and electrostatic disturbing forces. The matched uncertainties, such as change in stiffness and damping factors, may exist because of alteration in manufacturing process or even operational situations. The simulation yields in the article are very convincing that the controller design has demonstrated a persuasive tracking performance and has resulted in a well regulation about the pull-in working point.