Timed control with partial observability

We consider the problem of synthesizing controllers for timed systems modeled using timed automata. The point of departure from earlier work is that we consider controllers that have only a partial observation of the system that it controls. In discrete event systems (where continuous time is not modeled), it is well known how to handle partial observability, and decidability issues do not differ from the complete information setting. We show however that timed control under partial observability is undecidable even for internal specifications (while the analogous problem under complete observability is decidable) and we identify a decidable subclass