  In the present paper, we study observer design and we establish some
sufficient conditions for practical exponential stability for a class of
time-delay nonlinear systems written in triangular form. In case of delay, the
exponential convergence of the observer was confirmed. Based on the
Lyapunov-Krasovskii functionals, the practical stability of the proposed
observer is achieved. Finally, a physical model and simulation findings show
the feasibility of the suggested strategy.
