Florian Palm

RESTful Industrial Communication With OPC UA

Representational state transfer (REST) is a wide-spread architecture style for decentralized applications. REST proposes the use of a fixed set of service interfaces to transfer heterogeneous resource representations instead of defining custom interfaces for individual applications. This paper explores the advantages of RESTful architectures, i.e., service-oriented software architectures comprised RESTful services, in industrial settings. These include communication advantages such as reduced communication overhead and the possibility to introduce caching layers, and system design advantages including stable service interfaces across applications and the use of resource-oriented information models in cyber-physical systems. Additionally, a RESTful extension to the open platform communications (OPC) unified architecture (OPC UA) binary protocol is proposed in order to leverage these advantages. It requires only minimal modifications to the existing OPC UA stacks and is fully backward compatible with the standard protocol. Performance benchmarks on industrial hardware show a throughput increase up to a factor of eight for short-lived interactions. This reduction of overhead is especially relevant for the use of OPC UA in the emerging Industrial Internet of Things.

Open source as enabler for OPC UA in industrial automation

As a standardized communication protocol, OPC UA is the main focal point with regard to information exchange in the ongoing initiative Industrie 4.0. But there are also considerations to use it within the Internet of Things. The fact that currently no open reference implementation can be used in research for free represents a major problem in this context. The authors have the opinion that open source software can stabilize the ongoing theoretical work. Recent efforts to develop an open implementation for OPC UA were not able to meet the requirements of practical and industrial automation technology. This issue is addressed by the open62541 project which is presented in this article including an overview of its application fields and main research issues.

A RESTful extension of OPC UA

RESTful interfaces are a wide-spread architecture style for webservice implementations and are built upon the resource-oriented approach to decentralized architectures (ROA). REST postulates a set of requirements that are not covered by the OPC Unified Architecture (OPC UA) communication protocol per se. We propose a set of simple extensions to the OPC UA binary protocol that enable RESTful communication. The evaluation shows an order of magnitude improvement in the use of communication resources for sporadic service requests. Additionally, RESTful OPC UA allows applications to profit from the advantages of the resource-oriented architecture style, such as caching and loose application coupling.

Model based synthesis of automation functionality

Abstract The article demonstrates the advantages of meta-model-based solutions for multi-aspect automation tasks. Multi-aspect tasks require solutions that consider information of multiple system aspects simultaneously. In todays practice, these aspects are maintained in different tools which make implicitly use of tool-driven system models. In contrast, we propose to prioritize the models in order to facilitate the handling of multi-aspect automation tasks. The article exemplifies this idea by introducing typical automation and engineering models and illustrates their utility in a use-case example.

Modelltransformation als Softwareadapter für OPC Unified Architecture

Die klassische Automatisierungspyramide entwickelt sich immer mehr zu dezentralen Netzwerken mit direkter Maschine zu Maschine Kommunikation. Um den damit verbundenen Anforderungen gerecht zu werden, bietet sich OPC Unified Architecture (OPC-UA) als Kommunikationsstandard an. Dabei ist oft keine komplette Migration bestehender und bewahrter Softwaresysteme gewunscht.

Fundamentals for the next generation of automation solutions of the fourth industrial revolution

Due to rising engineering expenses, increasing cost pressure and additional flexibility requirements new methods of software development have to be adapted in the automation domain. The key challenge is the development of reusable, maintainable and adaptable automation solutions. These software qualities are directly influenced by the software architecture. Therefore the authors present a software architecture for the next generation automation solution and a process that ensures the proper implementation of the architecture. Afterward, an example for such an automation solutions is given.

Using Properties as a Semantic Base for Interoperability

Information exchange requires a common semantic understanding of the meaning of the exchanged data by the involved communication partners. Properties with a predefined and standardized meaning are one pillar of such an information exchange. Another pillar is the exchange of information about relationships between semantic entities by an appropriate system description metamodel. In this paper, we focus on the information exchange of property value expressions. Within the last years, domain-specific lists of properties have been standardized. The development was driven by the need to exchange information of industrial products electronically. The standardized lists allow an unambiguous characterization of products. Results of this comprehensive work done by the standardization committees within the last years are, for example, the international standard series IEC 61360CDD, IEC 61987, and the property library eCl@ss. In these standards, thousands of properties of technical assets are semantically defined. An intuitive and general concept to use these standardized properties for information exchange is crucial for the future system design. One recent approach is the so-called property value statement model. In this paper, the basic concepts of this approach are presented. Additionally, methods to reason about property information in a general way are discussed. The presented concepts fit to the standardized property definition models and build a platform for a metadata-based information handling in the digital factory.

Full integration of MATLAB/Simulink with control application development using OPC unified architecture

Integrating control development phases requires a consolidated communication architecture. Currently, different communication protocols are used at the different development stages preventing a fully integrated solution to exist. We propose an approach using a unified communication protocol to jointly integrate the control development stages. MATLAB and Simulink were connected to a programmable logic controller successfully resulting in a fully integrated control development chain and opening the doors for further development in other potential areas.

Hybrid OPC UA and DDS: Combining architectural styles for the industrial internet

OPC UA and DDS are communication protocols for the Industrial Internet. However, they make use of contrasting communication patterns and represent different architectural styles. We discuss these differences and their impact in an Industrial Internet and Internet of Things context. Further, we show up the possibilities for hybrid implementations leveraging the features of both OPC UA and DDS. For this, we provide a) a mapping of the OPC UA data types into DDS and b) a set of DDS quality of service policies that match the guarantees made by the standard OPC UA binary protocol.