Design of an adaptive sliding mode controller with a sliding mode Luenberger observer for the MEMS capacitive plates

Uncertain parameters in a MEMS tunable capacitor, as one of the fundamental elements in a MEMS AC voltage reference source (VRS) structure, is an important issue for acquisition of a rigorous voltage in the VRS output. The output is mostly supposed to be destroyed by harmful disturbance and noise. Even though the manufacturers make attempts to build MEMS tunable capacitor with desired characteristics in thorough compliance with the initial major design, uncertainties in the parameters inescapably do exist in manufacturing process on the ground of deficiencies in various procedures. This paper mainly remarks an adaptive sliding mode controlling design with a sliding mode Luenberger observer and its application for a MEMS tunable capacitor. The control design is done considering matched and unmatched terms of uncertainties and disturbance. The advantageous outcome is that the VRS could be generating a stable precise regulated output voltage owing to correct distance adjustment of the capacitor charged plates. The design exploits the sliding mode observer to get rid of extra usage of plate position measurement in the control structure. The controller alleviates the system output of the matched and unmatched disturbance which could exist dynamically because of cross stiffness and damping in addition to other inertial and electrostatic disturbing forces. The matched uncertainties, such as stiffness and damping change, might appear due to variation in fabrication procedures or working condition. The simulation yields are satisfactory and depict a persuasive tracking performance as well as regulation about the pull-in point.