Output controller for uncertain nonlinear systems with structural, parametric, and signal disturbances

We design the output feedback controller for a class of nonlinear systems with a state delay, structural and external disturbances. The external perturbation is bounded. Structural disturbance means the unmodeled and unknown stable dynamics in the control loop. In this paper we consider the problem of exponential stability for disturbed systems which can be represented as a feedback connection of a linear dynamical system with unknown parameters and a uncertain nonlinearity satisfying a sector constraint. Proposed approach is extended for the case of unknown relative degree of the system by modification of the control law.