In this thesis, CNF-based robust tracking and Disturbance observer for nonlinear systems with input saturation is presented in order to improve transient performance. The tracking control law is set to force the output of the closed-loop system to track the reference with fast response in the presence of these external disturbances. The composite nonlinear feedback technique includes two components: a
linear feedback portion constructed in such a way that it changes the damping ratio so as to speed up the system’s response. Also, a non-linear feedback controller is designed to further increase the damping ratio of the closed-loop system in such a way as to ensure tracking while reducing overshoot caused by the linear part. By using the Lyapunov-Krasovsky function or the Razumikhin function, which is the most common method of analyzing the stability of systems with delays, the stability of nonlinear time-delay systems with input saturation and disturbance is investigated, and the asymptotic stabilization conditions are obtained in the form of linear matrix inequalities and generalized Lyapunov and Riccati equations. Also, an observer-based composite nonlinear feedback control method for robust tracking of nonlinear singular systems with input saturation has been proposed for the first time, which, in addition to improving the transient performance of the system, it will have uniform bounded tracking error in the presence of disturbances and uncertainties. The purpose of this research is to design a robust controller in order to reduce tracking error, improve transient response, high efficiency and speed, and steady state accuracy in limited time, so that the output can track the reference path in the presence of disturbances and input saturation and time-varying system uncertainties. Next, in order to show the effective and robust performance of the proposed control method compared to other methods, various simulation examples have been investigated.