Cyber-Physical Microservice

The key construct for modeling Cyber-Physical Systems

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K. Thramboulidis, D. C. Vachtsevanou, I. Kontou, “CPuS-IoT : A Cyber-Physical Microservice and IoT-based Framework for Manufacturing Assembly Systems”, Annual Reviews in Control, March 2019.

K. Thramboulidis, D. Vachtsevanou, A. Solanos,Cyber-Physical Microservices:An IoT-based Framework for Manufacturing Systems", 1st IEEE International Conference on Industrial Cyber-Physical Systems (ICPS 2018), Saint Petersburg, Russia, May 15-18, 2018.

Microservices

Microservices is a new architectural term defined "to describe a particular way of designing software applications as suites of independently deployable services. While there is no precise definition of this architectural style, there are certain common characteristics around organization around business capability, automated deployment, intelligence in the endpoints, and decentralized control of languages and data." [1]

Cyber-Physical Microservices

The Cyber-Physical microservice (CPuS) is defined as a key construct for modelling and development of cyber-physical system (CPSs) [2]. A Cyber-Physical system can be considered as a composition of collaborating CPuSs.

A CPuS implements its functionality by a close integration of physical and cyber artefacts. It offers a specific and narrowly defined physical functionality, such as heat and mix, enriched by cyber artifacts and is deployed on the plant platform as an independent service but within the context defined by the constraints imposed by its mechanical part. CPuSs interact with their environment through well-defined ports that are characterized by their provided and required interfaces [2].

We discriminate Cyber-Physical microservices to primitive and composite ones.

A primitive Cyber-Physical microservice (p-CPuS) is composed of tightly integrated mechanics, electronics and software to provide at the cyber-physical layer a specific functionality. A primitive CPuS encapsulates a physical artefact by adding intelligence on it and transforming it to a smart entity that is able to either process, or transport, or store energy, material, parts, sub-products and products [2]. A p-CPuS encapsulate sensors, actuators and the low-level coordination logic required to offer more advanced functionality compared to the ones offered by the mechanical unit .

Typical examples of p-CPuSs are the smart silo and smart pipe of the Liqueur Plant case study [3] and the three Robot arms and the two workbenches of the Gregor chair case study [4].

A composite CPuS (c-CPuS) is the CPuS that offers its functionality by utilizing (directly or indirectly) the functionality of at least one primitive CPuS. c-CPuSs implement functionality for either processing, and/or transporting, and/or storing material, parts, sub-products and products. The operation of composite CPuSs depends on the availability of the utilized primitive CPuSs with which it is coupled in time, that is another differentiation from software microservices [2].

Typical example of c-CPuSs are plant processes as for example the liqueur generation processes of the Liqueur Plant case study [5].

The UML4IoT profile facilitates the integration of CPuSs using IoT technologies.

CPuS-IoT framework

The CPuS and IoT-based (CPuS-IoT) framework presented in [6] exploits the benefits of the microservice architectural style and the IoT technologies, but also utilizes the existing in this domain huge investment based on traditional technologies, to support the life cycle of evolvable ASs in the age of Industry 4.0.

It provides a solid basis to capture domain knowledge that is used by a model-driven engineering (MDE) approach to semi-automate the development, evolution and operation of ASs, as well as, to establish a common vocabulary for assembly system experts and IoT ones.

The CPuS-IoT approach and framework effectively combines MDE with IoT and the microservice architectural paradigm and supports a goal-driven service composition approach for cyber-physical system of systems (CPSoS).

References

[1] Microservices. https://martinfowler.com/articles/microservices.html

[2] K. Thramboulidis, D. Vachtsevanou, A. Solanos, “Cyber-Physical Microservices:An IoT-based Framework for Manufacturing Systems", 1st IEEE International Conference on Industrial Cyber-Physical Systems (ICPS 2018), Saint Petersburg, Russia, May 15-18, 2018.

[3] K. Thramboulidis, F. Christoulakis, “UML4IoT—A UML-based approach to exploit IoT in cyber-physical manufacturing systems”, Computers In Industry, Volume 82, October 2016, Pages 259–272.

[4] K. Thramboulidis, I. Kontou, D. Vachtsevanou, “Towards an IoT-based Framework for Evolvable Assembly Systems", 16th IFAC Symposium on Information Control Problems in Manufacturing (INCOM 2018), 11-13 June, 2018, Bergamo, Italy.

[5] K. Thramboulidis, P. Bochalis, J. Bouloumpasis, “A framework for MDE of IoT-BasedManufacturing Cyber-Physical Systems”, The 7th International Conference on the Internet of Things (IoT 2017), October 22–25, 2017, Linz, Austria.

[6] K. Thramboulidis, D. C. Vachtsevanou, I. Kontou, “CPuS-IoT : A Cyber-Physical Microservice and IoT-based Framework for Manufacturing Assembly Systems”, July 2018, (under review)