A HYBRID PD-FUZZY CONTROLLER FOR ATOMIC FORCE MICROSCOPES

This paper presents two fuzzy-based controllers designed to scan non-contact atomic force microscopes (AFM) over a specimen surface. Firstly, we develop a conventional fuzzy controller to achieve asymptotic probe lip tracking for bounded tip trajectories. Secondly, a hybrid PD-fuzzy controller is designed for the same purpose where the PD gains are tuned online by means of fuzzy logic. Finally, we compare the efficacy and requirements of the two controllers and compare their results to those of other recently proposed controllers for the same purpose. We show improved performance using both of our controllers; the most significant advantage being increased controller bandwidth and thus faster AFM scan rates. However, the PD-fuzzy controller is found to impose more realistic actuation demands on the plant than the Fuzzy controller.