Null Controllability —Discrete-Time Systems
This chapter studies null controllability of discrete-time linear systems with bounded controls. As in the continuous-time case, when the control input is limited by the actuator saturation, a discrete-time linear controllable system might not be globally null controllable. We are thus led to the characterization of the null controllable regionCthe set of all states that can be steered to the origin by the bounded controls delivered by the actuators
We continue the study of bottom-up unranked tree automata with equality and ::: disequality constraints between direct subtrees. In particular, we show that ::: the emptiness problem for the nondeterministic automata is decidable. In ::: addition, we show that the universality problem, in contrast, is undecidable.