Time-varying observers for a class of nonlinear systems

For a class of time-varying nonlinear systems, including those whose dynamics have triangular structure, the global observer design problem is investigated. First, a general result is presented providing sufficient conditions for the existence of both causal and noncausal Luenberger time-varying observers for a class of time-varying nonlinear systems with no inputs. This result together with a forwarding induction procedure is used to derive sufficient conditions for the solvability of the observer design problem for a wide class of triangular time-varying systems. The corresponding methodology extends some ideas of earlier author’s works on same subject.