Nonlinear observers for two classesof perturbed systems

In this paper, we study two important classes of nonlinear systems with perturbation, namely, perturbation with output injection and perturbation of pure feedback systems. With sufficiently good initial error estimates and sufficiently restricted external inputs and perturbation parameter, nonlinear observers for each class of perturbed systems are designed so that the error between the exact states and the estimated states goes to zero. Our simulation results illustrate the applicability of our technique in building nonlinear observers for these two classes of perturbed systems.