Torsional micro-actuators have found variety of applications in optical switches, displays, interferometry, spectroscopy, aberration correction and biomedical imaging. The objective of this paper is to present a sophisticated fuzzy controller to stabilize the tilt angle of a torsional micro-actuator within and beyond its pull-in limit. To do so, a 2-DOF model which takes into account both rotational and translational DOFs of the actuator is considered. Using an energy approach based on Lagrange equation, the Ordinary Differential Equations (ODEs) governing the dynamic behavior of the system are derived. In the next step, the effects of voltage and damping in vertical direction on the pull-in limit are studied. According to the sense obtained from these studies, some linguistic laws and their relevant fuzzy IF-THEN rules are extracted. Using the famous combination of singleton fuzzifier, product inference engine and center average de-fuzzifier, along with the developed fuzzy IF-THEN rules as the heart of fuzzy system, the fuzzy controller is designed. The suggested controller is tested for a sample micro-actuator. The simulation results show that the actuator is able to follow the step command either within or beyond its pull-in limit with acceptable overshoot and settling time. The qualitative and quantitative knowledge resulting from this effort is expected to enable the analysis, خptimization and synthesis of torsional micro-actuators for improved dynamic performance.

Keywords