OUTPUT TRACKING WITH NONHYPERBOLIC AND NEAR NONHYPERBOLIC INTERNAL DYNAMICS - HELICOPTER HOVER CONTROL

A technique to achieve output tracking for nonminimum phase linear sys tems with nonhyperbolic and near nonhyperbolic internal dynamics is pr esented. This approach integrates stable inversion techniques, which a chieve exact tracking, with approximation techniques, which modify the internal dynamics, to achieve desirable performance. such modificatio n of the internal dynamics is used 1) to remove nonhyperbolicity, whic h is an obstruction to applying stable inversion techniques, and 2) to reduce large preactuation times needed to apply stable inversion for near nonhyperbolic cases. The method is applied to an example helicopt er hover control problem with near nonhyperbolic internal dynamics for illustrating the tradeoff between exact tracking and reduction of pre actuation time.