Stabilizability of uncontrollable systems via generalized delayed feedback control

In this paper, the stabilizability problem via a generalized delayed feedback control (GDFC) for uncontrollable discrete systems is addressed. For single-input uncontrollable systems, a necessary and sufficient condition of stabilizability via the GDFC is obtained, which completely describes the limitation of the GDFC. For multi-input systems, a new necessary condition is derived, which reveals the limitation of the GDFC more exactly than the odd number limitation. Moreover, for a class of nonlinear systems with uncertain parameters, a nonlinear robust GDFC is designed for the first time to stabilize the unknown fixed points associated with the uncertain parameters.