Design and Implementation of Robust Controllers on a Novel MEMS Force Sensor

This study presents the design and implementation of Adaptive and H-innity Controllers on the Electro-thermal force sensor. The novel microelectromechanical system (MEMS) sensor has a mechanism that permits tuning of the deviceâĂŹs mechanical sti ness and has been used for the characterization of micro-cantilever and biological tissues. The performance of this device was examined at di erent sti ness adjustment and actuation voltages. The result of the experiment showed as the actuation force which is a function of actuation voltage was increased, the displacement of the actuator also increased, indicating that the device's stiffness can be adjusted based on this mechanism. The displacement of the sensor's probe is characterized by nonlinearities and uncertainties. To eliminate these effects which could cause instability and limit the operation of this device, two robust controllers were synthesized and implemented on the system. First. Model Reference Adaptive Controller (MRAC) based on MIT rule was implemented on the system by varying the adaptation gain from 0.5 to 3.0. It was observed that these suitable Adaptation gain caused the system output to approximate its reference model, hence dynamic performance was maintained in the presence of unpredictable and immeasurable variations. Finally, H innity controller was synthesized and implemented on this system. The performance of the controller in closed-loop with the system guaranteed robustness, good performance in terms of reference tracking and high disturbance rejection. Thus, providing high stability with respect to operating conditions. The MEMS force sensor considered in this study has proven to be a future invaluable device for MEMS and biological applications.