Nonlinear Velocity Observers

Rolf Johansson, Department of Automatic Control, Lund University-Sweden

The decomposition of nonlinear output feedback control into an observer and a state feedback control is an open problem. A solution for dynamic positioning of ships has been proposed in Fossen and Grovlen (CDC '96), where an observer-based backstepping method is used.

Although the the observer suggested is of general interest for control of nonlinear mechanical systems, the algorithm does not apply in the case of unstable open-loop dynamics.

We propose a method to extend the result for non-Hurwitzian open-loop dynamics for cases where an additional detectability condition can be fulfilled.