Robust constrained control for a class of uncertain systems based on disturbance observer

In this paper, the robust control problem is investigated for a class of uncertain systems with control input constraints based on disturbance observers. The disturbance observer is developed to estimate the compounded disturbance integrating the unknown external disturbance with the influence of control input constraints which is closely generated by an exogenous system. The design parameter of the disturbance observer is achieved by solving linear matrix inequality (LMI). Using the approximation output of the disturbance observer, the robust control scheme is proposed for the uncertain system. By utilizing the Lyapunov analysis method and combining it with linear matrix inequality technique, the robust stability of the closed-loop system is proved. Finally, a numerical example is given to illustrate the proposed robust control scheme for uncertain systems.