Observers and feedback control for a rotating vortex pair

An observer is developed to estimate and to feedback-regulate the location of the vorticity centroid and the mutual distance of an interacting, same sign vortex pair. The combination of the crude approximation provided by very low-order vortex models, and high nonlinearity, even at that level, seem to make sensitive gain scheduling and high-order vector field derivatives in geometrical observer design methods, ill suited for the system at hand. This paper explores possibilities for dynamic extraction of needed information directly from leading frequencies and phasors of a sensor signal, using an extended Kalman filter. Intended advantages include simplicity, robustness, and the filtering of unmodeled dynamics.