Efficient control representation in Digital Twins: an imperative challenge for declarative languages

Digital twins (DTs) are enablers for the fast optimization processes required in the Industry 4.0 context. Declarative equation-based modeling languages, in turn, enable the creation of large-scale simulation-based DTs, as they relieve the analyst from creating the solution code. However, most industrial assets are cyber-physical systems, the cyber part being their digital controls. With the available technology, a precise representation of modulating and logic controls conflicts with DT simulation performance. The result is a barrier to using DTs for system-level optimization. We analyze the problem, propose a modeling paradigm to solve it, and suggest how to integrate that paradigm into equation-based language compilers. We support our proposal by presenting a Modelica/C++ library, which we release as free software, built according to the said paradigm.