# A.A. Agrachev, I. Zelenko, On feedback classification of generic control-affine systems with one- and two-dimensional inputs

Title: On feedback classification of generic control-affine systems with one- and two-dimensional inputs
Authors: A.A. Agrachev, I. Zelenko
Journal title: Control and Optimization
Year: 2007
Volume: 48
Pages: 1431-1460
Abstract:

The paper is devoted to the local classification of generic control-affine systems on an $n$-dimensional manifold with scalar input for any $n \ge 4\$ or with two inputs for $n = 4\$ and $\ n = 5$, up to state-feedback transformations, preserving the affine structure (in $C^\infty$ category for $\ n = 4\$  and $C^\omega$ category for $n \ge 5$). First using the Poincare series of moduli numbers we introduce the intrinsic numbers of functional moduli of each prescribed number of variables on which a classification problem depends. In order to classify affine systems with scalar input we associate with such a system the canonical frame by normalizing some structural functions in a commutative relation of the vector fields, which define our control system. Then, using this canonical frame, we introduce the canonical coordinates and find
a complete system of state-feedback invariants of the system. It also gives automatically the micro-local (i.e. local in state-input space) classification of the generic non-affine ndimensional control system with scalar input for $n \ge 3$ (in $C^\infty$ category for $n = 3$ and in $C^\omega$ category for $n \ge 4$). Further we show how the problem of feedback-equivalence of affine systems with two-dimensional input in state space of dimensions 4 and 5 can be reduced to the same problem for affine systems with scalar input. In order to make this reduction we distinguish the subsystem of our control system, consisting of the directions of all extremals in dimension 4 and all abnormal extremals in dimension 5 of the time optimal problem, defined by the original control system. In each classification problem under consideration
we find the intrinsic numbers of functional moduli of each prescribed number of variables according to its Poincare series.