Unknown input observer design for T-S fuzzy systems with time-varying bounded delays

The paper discusses the design of functional observers with unknown inputs for nonlinear systems described by Takagi-Sugeno fuzzy models and time-varying bounded delays. The considered system extends previous works by considering a T-S model with time bounded delays and unknown inputs. The main innovative idea behind the design of the functional observer is that the unknown inputs are present in both the state and output equations, and bounds on the delays maybe used to reduce conservatism. The observer design and analysis are based on the Lyapunov-Krasovskii stability theory, and the resulting observer convergence conditions are formulated in terms of linear matrix inequalities (LMIs), which can be numerically and symbolically solved using YALMIP/MATLAB toolbox. In the final section of the paper, some examples are provided to demonstrate the application of this approach.