Classification and coverage-based falsification for embedded control systems

Abstract

Many industrial cyber-physical system (CPS) designs are too complex to formally verify system-level properties. A practical approach for testing and debugging these system designs is falsification, wherein the user provides a temporal logic specification of correct system behaviors, and some technique for selecting test cases is used to identify behaviors that demonstrate that the specification does not hold for the system. While coverage metrics are often used to measure the exhaustiveness of this kind of testing approach for software systems, existing falsification approaches for CPS designs do not consider coverage for the signal variables. We present a new coverage measure for continuous signals and a new falsification technique that leverages the measure to efficiently identify falsifying traces. This falsification algorithm combines global and local search methods and uses a classification technique based on support vector machines to identify regions of the search space on which to focus effort. We use an industrial example from an automotive fuel cell application and other benchmark models to compare the new approach against existing falsification tools.