Abstraction-Based Guided Search for Hybrid Systems

Abstract

Abstract. Hybrid systems represent an important and powerful formalism for modeling real-world applications such as embedded systems. A verification tool like SpaceEx is based on the exploration of a symbolic search space (the region space). As a verification tool, it is typically optimized towards proving the absence of errors. In some settings, e.g., when the verification tool is employed in a feedback-directed design cycle, one would like to have the option to call a version that is optimized towards finding an error path in the region space. A recent approach in this direction is based on guided search. Guided search relies on a cost function that indicates which states are promising to be explored, and preferably explores more promising states first. In this paper, we introduce an abstraction-based cost function based on pattern databases for guiding the reachability analysis. For this purpose, we introduce a suitable abstraction technique that exploits the flexible granularity of modern reachability analysis algorithms. Our cost function is an effective extension of pattern database approaches that have been successfully applied in other areas. We have implemented our approach in the SpaceEx model checker. Our evaluation shows its practical potential.

Scalable Static Hybridization Methods for Analysis of Nonlinear Systems

“…This algorithm is implemented in the Hyst [12] model transformation tool, which allows it to quickly be applied to new systems and with new simulation parameters. Finally, we validate our claims that the method is more scalable than existing static approaches by evaluating it on nonlinear models, including a six-dimensional water tank model, and then using an unmodified version of SpaceEx [13,15,24], which does not natively support nonlinear dynamics, to compute the set of reachable states.…”

Falsification of safety properties for closed loop control systems

“…A black-box assumption for the plant allows our technique to operate on highly non-linear hybrid systems designed inside environments such as Simulink TM /Stateflow TM 1 . Furthermore, our approach can be integrated into state-space search techniques like RRT [1,7], systematic simulation [4,6], property guided search [2]. If the model of the plant is provided as a hybrid automaton, then symbolic execution using flowpipe computation [3,5] can also be used.…”

A CEGAR approach for the reachability analysis of PLC-controlled chemical plants

“…Important for us is also the recently published PHAVER scenario [21] that supports urgent transitions and non-convex invariants. Furthermore, in [6] an extension of SPACEEX for hybrid automata is presented where the search is guided by a cost function. This enables a more flexible way of searching the state space compared to a breath-or depth-first-search.…”