Fuzzy-Enhanced Dual-Loop Control Strategy for Precise Nanopositioning

Abstract

Vibration problems are inherent to most precision positioning systems. These systems are lightly damped and highly susceptible to mechanical resonance at any sudden change in the voltage applied to the nanopositioning platform. These systems also exhibit nonlinearity, such as hysteresis and creep. The traditional approach uses a combination of damping controllers and tracking controllers to deal with nonlinearity and resonance respectively. The classical approach is based on sole use of the integral controller (l) or proportional integral (PI) as a tracking controller to treat nonlinearity; this paper employs a hybrid feedback scheme, using the fuzzy logic controller as a correction tracking controller in in conjunction with the conventional tracking controllers. The damping controllers utilised in this work to damp the mechanical resonance of the nanopositioning platform are the Integral Resonant Controller (IRC), the Positive Velocity and Position Feedback (PVPF), and the Positive Position Feedback Controller (PPF). The proposed fuzzy logic controller delivers improved dynamic tracking performance characteristics with less vibration in comparison with the conventional tracking method because the fuzzy logic controller can handle nonlinearity and vibration via its rules and membership functions. The use of fuzzy Gaussian membership function can alleviate the appearance of mechanical resonance.