Towards the Complexity of Controls for Timed Automata with a Small Number of Clocks

Control of timed systems has become a very active research area. In this paper, we revisit the complexity of safety and reachability control problems for timed automata. Generally, these problems turn out to be exptime-complete and we aim at finding tractable subclasses which admit efficient control. To this purpose, we consider the control for timed automata with a small number of clocks. We first show that for three clock TAs, the complexity has climbed up to exptime-complete; We then propose efficient algorithms to control one-clock TAs and show that inthis setting, the control problems become P-complete, both in the known and unknown switch condition assumptions; In the end, we prove the pspace-hardness of control for two-clock TAs.