Falsification of safety properties for closed loop control systems

We present a search technique to falsify safety properties of hybrid systems that model a software system controlling a physical plant. Our approach takes as input (a) the controller code and (b) a plant model given as a black-box system that can be simulated for given inputs over finite time horizons. Our approach combines the symbolic execution of the controller software with an abstraction of the plant, which is discovered on-the-fly using simulations. This process is used to find abstract counterexamples to the safety properties of interest. The plant abstraction is then refined iteratively using the abstract counterexamples until a concrete violation is discovered. Empirical evaluation of our approach shows its promise in treating controller software, whose semantics are well-understood using formal techniques while using numerical simulations to produce abstractions of the underlying plant model, which is often an approximation of the actual plant.