Composite disturbance-observer-based control and H∞ control for time-delay systems with nonlinear perturbations

This paper considers the problem of composite disturbance-observer-based control (DOBC) and H_∞ control for time-delay systems with nonlinear perturbations. The external disturbance is supposed to be generated by an exogenous system with time delay. After designing the corresponding disturbance observer and controller, we obtain a complex closed-loop time-delay system. Based on the LMI technologies and Lyapunov stability theory, we ensure the asymptotical stability and a prescribed H_∞ level of the obtained closed-loop system, which means the disturbance rejection and guarantees asymptotical stability and a prescribed H_∞ level of the considered time-delay system with nonlinear perturbations. Finally, simulation illustrates the effectiveness of the proposed methods.