Previous online reachability algorithms for hybrid automata reduced conservatism in verified Simplex controller architectures, but were restricted to the imprecise real-time paradigm, i.e., their precision increases over time. Yet, many safety-critical cyber-physical systems are hard real-time systems, requiring an upper bound on the worst-case execution time (WCET) of each task to be known. We show that the iteration bound of the reachability loop can be parameterized by a single factor which determines the precision. Consequently, an algorithm could select a fixed precision depending on the time left until its deadline. In this paper we present such a WCET-aware reachability algorithm, based on an existing algorithm for imprecise real-time. Its smallest WCET bound on an Infineon XMC4500 microprocessor is 32.861 milliseconds.
