Controlling the tip-sample force of contact mode atomic force microscopes using PI-like fuzzy control technique

In this study, a PI-like fuzzy logic controller is designed to accommodate the nonlinear behaviors in the constant tip-deflection systems for contact mode AFM. By exploiting the fuzzy logic structure of the controller, heuristic knowledge is incorporated and results in a non-linear controller with improved transient performance over traditional PI controllers. Using the proposed controller allows the cantilever tip to track sample surface rapidly and accurately. The rapid tracking response facilitates us to observe high aspect ratio micro structure accurately and quickly. Additionally, continuously manual gain tuning by trial and error in commercial AFMs is alleviated. In final, the proposed PI-like fuzzy controller shows better performance than traditional PI controllers.