Beyond Time-Triggered Co-simulation of Cyber-Physical Systems for Performance and Accuracy Improvements

Cyber-Physical Systems consist of cyber components controlling physical entities. Their development involves different engineering disciplines, that use different models, written in languages with different semantics. A coupled simulation of these models is of prime importance to rapidly understand the emerging system behavior. The coupling of the simulations is realized by a coordinator that conveys data and ensures time consistency between the different models/simulators. Existing coordinators are usually time triggered. In this paper we show that time-triggered coordinators may introduce poor performance and accuracy (both temporal and functional) when used to co-simulate cyber-physical models. Therefore, we propose a new coordinator mixing time- and event-triggered mechanisms. We validated the approach in the context of the FMI standard for co-simulation. To make possible the writing of the new coordinators, we implemented backward compatible extensions to the FMI API. Also, we implemented a new FMI exporter in an industrial tool.