Observer-Based Sampled-Data Controller in Saturated Systems via Composite Nonlinear Feedback

Abstract

Employing composite nonlinear feedback idea, an observer-based digital controller is addressed for continuous-time systems with input nonlinearity and disturbance. To achieve the regulation purpose, the equivalent discrete-time equations are obtained via discretization. The gains of the digital integral controller are specified such that the input–output relationship becomes strictly positive real for the closed-loop structure. Such a test condition will be verified through checking the feasibility of a linear matrix inequality. Having ensured the positive realness, the transient responses are surprisingly improved by adding suitable nonlinear feedback terms. The results are used in some constrained systems to exhibit the effectiveness of the presented mechanism over the similar one.