Search

For the development of OPC UA servers for machine tools the complex architecture of numeric controls and programmable logic controllers is often depicted in a structure focused on data. The information models provide access to a wide set of available data points but lack intuitive functions, such as handling of NC programs and controlling auxiliary systems, which would be used by machine operators in manual mode. The information model presented in this paper shows a possible solution to combine data and functionality of machine tools in an intuitive structure in order to simplify navigation for clients and users.

With more OPC UA Companion Specifications emerging there is huge potential for the standardization manufacturing devices and their semantic interoperability. Nevertheless, in automation it currently comes with the disadvantage of machinery having to strictly conform to those standards and neglecting vendor- or machine-specific features. The approach presented in this paper aims to enable automation of diverse machinery in a plug- and produce manner through providing descriptions of the interdependencies of atomic skills using state charts in OPC UA. Thereby, device and cell capabilities can be recognized, executed and necessary state changes derived by an independent cell controller.

Worst-case execution time (WCET) analysis is a prevalent way to ensure the timely execution of programs in time-critical systems. With the advent of new technologies such as fog computing and time-sensitive networking (TSN), the interest in timing analysis has increased in industrial communication. This paper highlights experiences made while adjusting the publisher of the open62541 OPC UA stack to enable WCET analysis, following a simple process combined with the open-source platform T-CREST. The main challenges are the required knowledge about the code and the specific communication software characteristics like variable message sizes. Other findings indicate the need for other types of annotation for indirect recursion or callback functions. The paper provides the foundation for further research on adjusting the implementation of existing industrial communication protocols for WCET analysis.

Industrial automation is changing towards higher integration and seamless communication. A stepping stone is end-to-end real-time machine-to-machine communication, now becoming feasible with technologies such as time-sensitive networking (TSN) and OPC Unified Architecture (OPC UA) publish-subscribe. While TSN takes care of communication, the OPC UA stack’s execution time behavior remains unknown. This paper highlights experiences made while adjusting the OPC UA subscriber of the open62541 stack for worst-case execution time (WCET) analysis. Two directly connected time-predictable T-CREST platforms hosting the publisher and subscriber delivered end-to-end timing measures validating the WCET estimates. The paper concludes by outlining further research with several time-predictable publishers and subscribers.

Transmitting time-critical data like safety applications over the traditionally not real-time capable Ethernet standard (IEEE 802.1) requires modifications. Compared to devices, individually connected by signal wires, "network-attached" safety components offer more flexibility in their usage by making their data available to all factory entities instead of just one counter partner.openSAFETY – open-source standard for safety-related applications – enables functional safety, that can be integrated in any network with deterministic behavior. Time-Sensitive Networking (TSN) – a set of IEEE standards that can be applied to IEEE 802 networks – offers the possibility to run Ethernet traffic with real-time requirements without the traditional problems of Ethernet like frame dropping or timing issues.This paper proofs the concept of these two technologies being a suitable combination to transmit time-critical safety data and non-priority traffic within a single Ethernet-based network. Several tests were made to show how TSN can host an openSAFETY-application in different scenarios including background traffic. The results show adequate performance of this system in terms of reliability under worst possible conditions like external broadcast traffic blocking the entire bandwidth.

Smart manufacturing is realizing the idea and potential of Industry 4.0 in reality. An essential part of smart manufacturing are production facilities that dynamically adapt to changing production needs. This brings completely new challenges to functional safety systems, which are mandatory for the protection of man, machine, and environment. Currently, functional safety systems are designed and certified in a static way. The safety design and the configuration are derived from the risk assessment which is performed during the design of a machine. Once the system is put into operation, the safety configuration is not changed anymore. This approach constitutes an impediment to flexibility which smart manufacturing production facilities require nowadays.This paper proposes the design of a self-organizing safety system with the objective to assist an engineer who operates a smart manufacturing facility by discovering all safety-related devices and generating automatically a suitable safety configuration. This configuration will be deployed to the system automatically after adaptation and validation by the safety engineer. The proposed self-organizing safety system, simplifies the safety configuration in a dynamically changing environment. Consequently, it would reduce engineering efforts and decrease machine downtime which improves profitability.

High-mix / low-volume production environments require advanced planning systems to optimize their outputs along conflicting targets such as cost, time and quality. However, given the constant change in those environments, it is becoming increasingly complex to provide a planning system with accurate input information. This work presents an approach to create a closed-loop information system to automatically update selected planning parameters based on historical product and process information. By using available shop-floor data directly from the machines, the information quality level in high-mix / low-volume production environments can be significantly increased.

Due to its modeling capabilities, platform independence, and extendability, Open Platform Communications Unified Architecture (OPC UA) is considered to be the main candidate for a so-called “enabling technology for industry 4.0”. However, the engineering effort for OPC UA applications, in particular the server, is very high as the process of information modeling and linking the resulting model to real-world data is complex and time-consuming. This significantly limits the spread of OPC UA in manufacturing and other domains.This paper presents an approach towards extending OPC UA in a way such that information necessary for the OPC UA server application to access the underlying system can be specified in the information model. This is achieved by defining communication interfaces for all nodes of the information model that represent readable or writable data. The handling of the interfaces needs to be implemented in code only once and from then on they can be modeled, rather than implemented for each node individually. Thus, the implementation effort of OPC UA servers is reduced. Different modeling approaches for communication interfaces are presented and compared.

Cyber Physical Production Systems have a need of sharing and interlinking information and knowledge over different domains. In the area of industrial automation, OPC Unified Architecture (OPC UA) is a widely used and established standard for communication and information modeling. We propose an ontology-based OPC UA data access method utilizing custom property functions, which enables interlinking between OPC UA information and other factory data. To avoid duplicated data and to reduce the communication overhead in the proposed method, the OPC UA run-time data are loaded on-demand and are not persistently stored in the triplestore. To enable fast and easy ontology-based access and interlinking of the OPC UA information, the needed ontology is automatically generated from the OPC UA information model. A proof of concept demonstrates the application of our approach for a laboratory use-case of a Packed-Bed Regenerator.

Heterogeneous production lines as a keystone of smart factories, comprised of machines from various manufacturers, are placing a new range of demands on communication and interoperability. Connectivity is the key element for seamless data communication in Cyber-Physical Systems (CPS). This includes standardized protocols and interfaces as well as vendor neutral technologies. An important aspect of a production line, is functional safety and its technical implementation. Up to now, safety-relevant connections between devices of different manufacturers have been implemented using dedicated cables and line monitoring. The aim of this paper is to design an integrated safety architecture based upon existing technologies. The method proposed in this paper aims at achieving functional safety connectivity, along with non-safe data traffic, based on the vendor-neutral technologies Ethernet, Time-Sensitive Networking (TSN), and OPC Unified Architecture (OPC UA).

Applications within the Internet of Things (IoT) increasingly build upon Semantic Web technologies to ensure interoperability of devices and applications. Hereby, a central aspect is knowledge representation, and in particular how devices can store and exchange semantic data. This paper defines and discusses a methodology for creating application-specific ontologies for the IoT. The two main objectives are to reuse existing knowledge on one hand and to derive reusable ontologies on the other hand. Thereby, a multi-agent system for switching optimization in the smart energy domain serves as a motivating example.

Current trends in manufacturing focus on the use of Information and Communication Technologies (ICT). The physical world and its virtual representation are increasingly converging, which leads to Cyber-Physical Production Systems (CPPS) in the manufacturing environment. CPPS synergize conventional production technology as well as ICT, allowing machines and products to exchange information, trigger actions and control other components autonomously. Therefore, seamless communication between physical objects of the shop floor and various computer systems is required. The Reference Architecture Model Industrie 4.0 (RAMI4.0) provided by the Plattform Industrie 4.0 specifies requirements for CPPS consisting of Industrie 4.0-components. In such systems, a major goal is to enable communication of I4.0 components among each other via industrial networks. For this purpose, RAMI4.0 suggests that each component has a virtual representation and uses Service-Oriented Architecture (SOA) based communication with I4.0-semantics. This paper describes a systematic approach to OPC Unified Architecture (OPC UA) information model for representing the static and dynamic behavior of manufacturing systems. Moreover, the approach is generic in the sense that it can be used to define information models for multiple target technologies, such as OPC UA, MTConnect and others. It even allows to reuse large parts of the generated models for similar manufacturing utilities and various target technologies. Therefore, we first present a concept for system analysis and design by using the Unified Modeling Language (UML), which is widely accepted for interdisciplinary work. The information gathered is then transformed to OPC UA information models which serves as target technology in this paper. The purpose of this approach is to simplify the process of defining virtual representations of manufacturing systems. Applying the presented concept allows transformation of classic manufacturing systems into CPPS with SOA-based communication and semantically rich virtual representations of individual components. It is therefore well suited to meet the requirements specified by RAMI4.0.

Information and communication technology plays a crucial role in increasing reliability and efficiency of our critical infrastructure. This paper presents a distributed multi-agent system for switching optimization in low-voltage power grids. As opposed to centralized approaches, the overall optimization procedure is not implemented in a single node but emerges from the behavior and interaction of the participating agents. Thereby, the communication strictly follows a predefined interaction protocol. Losses are reduced by balancing loads among all available transformers. Based on a small distribution network, an exemplary optimization run is discussed in detail. Furthermore, FNCS, a state-of-the-art co-simulation framework, is used to evaluate the actual potential for energy saving.

The number of devices connected to the Internet of Things (IoT) has steadily been increasing over the last years and so has the variety of applications. There is no sign for this trend to weaken. A broad subset of them imposes requirements on attributes, such as availability, reliability, safety and many more. These attributes are commonly subsumed under the term dependability. In this paper we first give a brief introduction to dependability. Three application scenarios typical for the IoT are presented and their demands for each dependability attribute are discussed. Furthermore, an overview of the current state of the art is presented. Last, a summary of required technologies and future research topics to enable dependability in the IoT is given.

The requirements, functionality, and consequently also the complexity of software used in the automotive industry has continuously been increasing over the last decades. To cope with this development, main car manufacturing companies and automotive suppliers established the AUTOSAR partnership back in 2003. Its main objective is to reduce development costs and to enhance cooperation between different companies by creating standards and specifications for automotive software applications. With the increasing number of ECUs and vision-based advanced driver assistance systems higher communication speeds than provided by nowadays state-of-the-art bus systems like CAN and FlexRay are desired. The tremendous success story of standard Ethernet has led to various enhancements for different industries to make its benefits also available for safety-critical and real-time applications. One of these enhancements is TTEthernet. In this paper we demonstrate and evaluate the integration of TTEthernet in AUTOSAR. We suggest how the AUTOSAR Ethernet stack can be partitioned to support mixed-criticality traffic and how different traffic types can be integrated on a single physical interface. Furthermore, we give an efficient implementation of the TTEthernet clock synchronization algorithm by utilizing state-of-the-art Ethernet hardware controller features. Finally, the TTEthernet implementation is compared to a standard Ethernet implementation as specified by AUTOSAR, with respect to computational and memory overhead.