Sampled-Data Output-Feedback Tracking Control for Interval Type-2 Polynomial Fuzzy Systems

In this paper, we investigate the stability and performance of the interval type-2 (IT2) polynomial fuzzy-model-based tracking control system, formed by an IT2 polynomial fuzzy model and an IT2 polynomial fuzzy controller, based on the output feedback and sampled-data structure. IT2 fuzzy sets are employed to capture the uncertainties of the nonlinear plant. Furthermore, considering the digital implementation of control strategy and only the system outputs are available, the IT2 polynomial fuzzy controller is of discrete time and output-feedback type. Both membership-function-independent and membership-function-dependent stability analysis, with the consideration of $H_\infty$ performance index, are conducted to develop stability conditions in terms of sum-of-square based on Lyapunov stability theory. The information of membership functions, system states, and sampling process are included in the stability analysis for the relaxation of stability conditions. Simulation examples are presented to verify the effectiveness of the proposed tracking control approach.