Fuzzy-enhanced Dual-loop Control Strategy for Precise Nanopositioning

Vibration problems are inherent to most precisionpositioning systems. These systems are lightly damped andhighly susceptible to mechanical resonance at any suddenchange in the voltage applied to the nanopositioning platform.These systems also exhibit nonlinearity, such as hysteresis andcreep. The traditional approach uses a combination of dampingcontrollers and tracking controllers to deal with nonlinearityand resonance respectively. The classical approach is based onsole use of the integral controller (l) or proportional integral(PI) as a tracking controller to treat nonlinearity; this paperemploys a hybrid feedback scheme, using the fuzzy logic con-troller as a correction tracking controller in in conjunction withthe conventional tracking controllers. The damping controllersutilised in this work to damp the mechanical resonance of thenanopositioning platform are the Integral Resonant Controller(IRC), the Positive Velocity and Position Feedback (PVPF),and the Positive Position Feedback Controller (PPF). Theproposed fuzzy logic controller delivers improved dynamictracking performance characteristics with less vibration incomparison with the conventional tracking method because thefuzzy logic controller can handle nonlinearity and vibrationvia its rules and membership functions. The use of fuzzyGaussian membership function can alleviate the appearanceof mechanical resonance.