Transaction-level Functional Mockup Units for Cyber-Physical Virtual Platforms

The modelling process of Cyber-physical Systems aggregates semantics and languages tailored to specific domains. The simulation of these complex systems involves different tools and their coupling requires computational effort. In the last few years both Academy and Industry worked toward the definition of standard interfaces able to overcome such issues. The Functional Mockup Interface (FMI) standard emerged as one of the most promising tool to easily export and integrate heterogeneous models. However, the standard still shows some weaknesses, particularly when dealing with Functional Mockup Units (FMUs) describing discrete-event systems. This paper explore the features of the standard to find its shortcomings when dealing with discrete models. Then, it proposes a systematic approach to fully exploit the features of the current standards to overcome such limitations. The solution is based on two concepts: (1) giving to FMUs the capability to simulate unconditionally (2) exposing the internal time of the FMUs. The combination of these two concepts allows to optimize the FMUs coordination algorithms by reducing the number synchronization points. The impact of these optimizations is measured on a set of benchmarks having different balancings between computation and control.