Realization theory for linear hybrid systems, part II: Reachability, observability and minimality

The paper is the second part of the series of papers started in [1]. The paper deals with observability, reachability and minimality of linear hybrid systems. Linear hybrid systems are continuous-time hybrid systems without guards, whose continuous dynamics is determined by time-invariant linear control systems. We will show that that if a set of input-output maps has a realization by a linear hybrid system, then it has a realization by a minimal linear hybrid system. We will present conditions for observability and span-reachability of linear hybrid systems and we will show that minimality is equivalent to observability and span-reachability. We will sketch algorithms for checking observability and span-reachability and for transforming a linear hybrid system to a minimal one.