Scalable and efficient digital twins for model-based design of cyber-physical systems

ABSTRACT

The optimised design, operation and management of complex, large-size Cyber Physical Systems (CPSs) – like modern manufacturing and logistic assets – calls for Digital Twins (DTs) in which dynamic modelling and simulation play a relevant role. In such simulation-based DTs computational efficiency is crucial. According to the present state of the art, the said efficiency is hindered by the way the Cyber part of a CPS is represented, which in the manufacturing case practically corresponds to representing digital controls. This paper proposes a modelling framework for an efficient and scalable representation of the Cyber part in a DT of a CPS. The presented solution is based on Object-Oriented Modelling (OOM) and IEC industrial standards. Motivating and explanatory examples are provided, and a proof-of-concept case study is discussed to support the framework potential and industrial viability.

KEYWORDS:

• Digital twins
• cyber-physical systems
• object-oriented modelling
• control system modelling
• simulation performance
• scalability

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Notes

1. The reader may object that, to describe the P part, there are alternatives to DAEs. True, but in such alternative formalisms – such as discrete-time black-box models, queuing networks, and so forth – parameters hardly ever admit a physical interpretation, as is required when a decision taken with the aid of models needs then realising into material equipment. This paper does not further address the matter.

2. Incidentally, this partition of a control block into a time-driven dynamic system – e g., a transfer function – and an automaton is well consistent with the definition of ‘function block’ as per the IEC 61,499 standard.

3. Strictly speaking, programming languages are dealt with in Section 3 (IEC 61,131–3) of the standard; however, since some of the following considerations also pertain to how the host hardware/software architectures work to run controls, this paper refers to the standard as a whole.

4. Should the paper be accepted, all the used models will be made available as free software, which is not possible now owing to the blind review process. As these models can run with the free Modelica translator OpenModelica, the reader will be able to reproduce all the shown results, and to investigate further if interested.

5. Needless to say, the SFC syntax and semantics are far more articulated than this example shows; the interested reader can refer to the IEC 61,131 standard, part 3.