Observability and State Estimation for a Class of Nonlinear Systems

We derive sufficient conditions for the solvability of the state estimation problem for a class of nonlinear control time-varying systems, which includes the dynamics that have a triangular structure. The state estimation is exhibited by means of a sequence of functionals approximating the unknown state of the system on a given bounded time interval. More assumptions guarantee solvability of the state estimation problem by means of a hybrid observer.