Introducing Explicit Causality in Object-oriented Hybrid System Modeling

Along with the rapid development of embedded devices and network technology, the area of Cyber Physical Systems (CPS), has arisen. In terms of modeling and simulation, CPS—like many technical systems—have a hybrid nature, i.e., discrete-event behavior and continuous-time dynamics have to be integrated with each other. Basically, this integration is supported by modern object-oriented modeling paradigms such as Modelica. The equation-based concept resolves the causality between interconnected components, which qualifies this modeling scheme for complex multi-domain systems. However, in hybrid systems, explicit causality is required to correctly manage iterative events. This paper highlights these issues, including algorithmic loops and instantaneous multiple updates, which essentially arise from incompatibilities between the object-oriented concept and specific discrete-event phenomena. We discuss several possible solutions and introduce the concept of re-allocating the objects’ behavioral intelligence.