Robust unified Observer-based Fuzzy Controller of Perturbed Uncertain Multivariable Systems

This paper aims to design an observer-based fuzzy adaptive tracking control for perturbed multivariable nonlinear systems having an uncertain model under the additional constraints that the state vector is not available for measurement. In this output-feedback control scheme, to accurately and quickly construct the unmeasured states, a robust high-gain observer is constructed. The latter, which is characterized by a unified design function for the correction term, represents a large class of linear or nonlinear observers such as high-gain observers, (non-smooth or smooth) sliding mode observers. To overcome uncertainties in the system’ mathematical model, an adaptive fuzzy logic-based control approach is employed. Unknown fuzzy parameters are robustly updated via a new proportional-integral law improved by a σ -modification term. The corresponding stability analysis is performed via a Lyapunov type method.