Flat systems, equivalence and trajectory generation
Phillipe Martin, Richard Murray, Pierre Rouchon
CDS Technical Report
Flat systems, an important subclass of nonlinear control systems introduced via differential-algebraic methods, are deﬁned in a differential geometric framework. We utilize the inﬁnite dimensional geometry developed by Vinogradov and coworkers: a control system is a diffiety, or more precisely, an ordinary diffiety, i.e. a smooth inﬁnite-dimensional manifold equipped with a privileged vector ﬁeld. After recalling the deﬁnition of a Lie-Backlund mapping, we say that two systems are equivalent if they are related by a Lie-Backlund isomorphism. Flat systems are those systems which are equivalent to a controllable linear one. The interest of such an abstract setting relies mainly on the fact that the above system equivalence is interpreted in terms of endogenous dynamic feedback. The presentation is as elementary as possible and illustrated by the VTOL aircraft.