Runtime Verification for FMI-Based Co-simulation

Co-simulation allows modelling and simulation of heterogeneous systems: the analysis of a system is achieved through the joint simulation of coupled stand-alone sub-simulators for its individual parts, using a standardized interface (e.g. Functional Mock-up Interface - FMI). Runtime verification can be employed to validate the evolution of cosimulation runs, but currently this is feasible only within the scope of individual simulators that may support very diverse monitoring functionalities. This work introduces a technical approach for the runtime verification of properties for the entire co-simulated system. We present the integration of the DejaVU monitor synthesis tool at the master algorithm level of FMI-based co-simulation, such that predicates and events from all constituents of a simulated system can be monitored. Communication between the master and the individual Functional Mock-Up Units (FMUs) is bidirectional, whereas the FMI master does not need to change for monitoring the property of interest. Since FMUs are synchronized by the master algorithm, runtime monitors can be used also as a means to control the co-simulation run. We provide results from co-simulation experiments to give insight into the runtime overhead.