Abstract
Communication protocols are evolving continuously as the interfacing and interoperability requirements are the foundation of Industry 4.0 and Industrial Internet of Things (IIoT), and the Open Platform Communication Unified Architecture (OPC UA) protocol is a major enabling technology. OPC UA was adopted by the industry, and research is continuously carried out to extend and to improve its capabilities, to fulfil the growing requirements of specific industries and hierarchical levels. Consistent issues that have to be approached are related to the latest specifications and the real-time context that could extend the applicability of the protocol and bring significant benefits in terms of speed, data volumes, footprint, security. The real-time context is essential in the automotive sector and it is highly developed within some specific protocols. The current work approaches first the conceptual analysis to improve the OPC UA interfacing using the Publish-Subscribe mechanism, focusing on real-time constraints and role distribution between entities, and considering some well-founded interfacing strategies from the automotive sector. The conceptual analysis is materialized into a solution that takes OPC UA Publish-Subscribe over User Datagram Protocol (UDP) mechanism to the next level by developing a synchronization algorithm and a multithreading broker application to obtain real time responsiveness and increased efficiency by lowering the publisher and the subscriber footprint and computational effort, reducing the difficulty of sending larger volumes of data for various subscribers and the charge on the network and services in terms of polling and filtering. The proof of concept is evaluated and the results prove the efficiency of the approach and the solution.
Highlights
Industry 4.0 and Industrial Internet of Things (IIoT) principles are guiding productivity, quality, efficiency, and safety, and at the same time are improving openness and competitiveness [1,2]
Open Platform Communication Unified Architecture (OPC UA) was first implemented on the Supervisory Control and Data Acquisition (SCADA) level in SCADA software environments and OPC UA centralizing servers, but the tendency was to use the advantages of the protocol and use it on other levels
The authors are proposing the analysis of a multithreading broker application in the context of OPC UA Publish-Subscribe paradigm targeting User Datagram Protocol (UDP) as transport protocol, with focus on real time constraints and role distribution among involved entities
Summary
Industry 4.0 and Industrial Internet of Things (IIoT) principles are guiding productivity, quality, efficiency, and safety, and at the same time are improving openness and competitiveness [1,2]. Structures, methods, objectives, and constraints are targeted to achieve improvements, and the outcome may be almost immediate as systems are able to communicate and understand each other [3,4], or may come after collecting data, identifying dependencies and patterns, defining and testing recipes, and reacting over the functioning systems [5,6]. All improvements are relying on interfacing, and a major enabling technology is the Open Platform Communication Unified Architecture (OPC UA) protocol [7,8]. The technology entered using the Client-Server concept on the PLC level and companies slowly extended its functions to include as Sensors 2020, 20, 5591; doi:10.3390/s20195591 www.mdpi.com/journal/sensors.
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