Feedback Scheme Based on Fuzzy Control for Shear Force Control

Fuzzy control is a practical alternative for a variety of challenging control applications, since it provides a convenient method for constructing nonlinear controllers via the use of heuristic information (1). In this work, we propose a novel technique to control the tip-sample distance in a scanning near field optical microscope (SNOM) using fuzzy control. The fuzzy controller design assumes only one input signal defined as the difference of the sampled signal (tuning fork-tip) and the reference signal, which are compared through designed software. This signal is used as the rule-base of the fuzzy logic controller. A basic data acquisition is used as interface to manipulate the fuzzy controller as feedback scheme in the positioning system (piezoelectric bimorph) for the shear force control. The approach curve of the shear-force measurement of the bimorph piezo was obtained using this scheme. In conclusion, this approach can be viewed as simple and reliable as feedback scheme based on fuzzy control for shear force control in a SNOM.