On the state observation and output feedback problems for nonlinear uncertain dynamic systems

The authors examine the problems of state observation and state trajectory control by output feedback for the class of nonlinear systems described by Y.H. Chen (1990) and A. Steinberg and M. Corless (1985). They formulate a nonlinear nonvariable structure type observer that guarantees that the observation error is globally exponentially stable (GES). A nonlinear, nonvariable structure type output feedback controller is then formulated. It forces the state to the origin in the GES sense. Specific time-varying bounds on the observation error and the state trajectory are also developed: revealing how the corresponding observer or control parameters can be adjusted to improve the system performance