Lukasz Wisniewski

Using OPC-UA for the autoconfiguration of real-time Ethernet systems

In the future, production systems will consist of modular and flexible production components, being able to adapt to completely new manufacturing processes. This requirement arises from market turbulences caused by customer demands, i. e. highly customized goods in smaller production batches, or phenomenon like commercial crisis. In order to achieve adaptable production systems, one of the major challenges is to develop suitable autoconfiguration mechanisms for industrial automation systems. This paper presents a two-step architecture for the autoconfiguration of real-time Ethernet (RTE) systems. As a first step, an RTE-independent device discovery mechanism is introduced. Afterwards, it is shown how the parameters of an RTE can be configured automatically using Profinet IO as an exemplary RTE system. In contrast to the existing approaches, the proposed discovery mechanism is based on the OPC Unified Architecture (OPC-UA). In addition, a procedure to autoconfigure modular IO-Devices is introduced.

Towards autoconfiguration of industrial automation systems: A case study using Profinet IO

Nowadays the deployment and commissioning of complex production processes or Internet-enabled applications interacting with production systems requires a time consuming and error-prone manual system configuration process. This is due to the need to maintain a high level of determinism, safety, and security of the production process itself and avoiding both safety-critical failures and costly production interruptions. The project “IoT@Work - Internet of Things at Work” aims at delivering tools and runtime mechanisms to significantly simplify commissioning, operating, and maintaining complex production processes, thus enabling Plug-and-Produce for automation systems. This paper presents a novel approach for the autoconfiguration of real-time Ethernet systems, and all relevant mechanisms. A case study, based on Profinet IO, evaluates the approach and shows its feasibility.

Fast and simple scheduling algorithm for PROFINET IRT networks

Scheduling of the communication in industrial networks takes time. Since it has to be carried out every time a new network is brought to work, the time necessary to perform scheduling becomes a prominent factor. The approach presented in this paper, simplifies the scheduling problem of PROFINET IRT by resolving communication conflicts by utilization of the dynamic frame packing (DFP) mechanism.

A flexible approach for real-time wireless communications in adaptable industrial automation systems

Due to several advantages, such as flexibility, increased mobility, and lower costs, the deployment of wireless technologies in factory automation systems is rapidly growing. However, current wireless technologies, e. g., IEEE802.11 Wireless Local Area Networks (WLANs), are not able to satisfy the requirements of industrial applications in terms of real-time communication. In this paper medium access control mechanisms in IEEE 802.11 are investigated and a new isochronous MAC is proposed. In combination with a traffic scheduler specifically designed for it, typical constraints of soft real-time flows found on the factory floor can be satisfied. A preliminary analysis shows the effectiveness of the proposed combination.

A Survey of Ethernet Redundancy Methods for Real-Time Ethernet Networks and its Possible Improvements

Abstract Industrial Ethernet switches, form the network backbone in automotive production, substation automation systems, intelligent transport systems, and other major industrial automation projects. In the operation of industrial switches, the recovery time of a switch is vital for its applicability. In the last few years, a large number of solutions have emerged among the switch manufacturers which have been accompanied by standardisation activities in IEC. This paper gives a brief introduction of the industrial requirements for network redundancy and discusses details of existing solutions with a special focus on the ring topology. A possible optimisation of existing Ethernet based industrial switches is also discussed.

Effective and fast approach to schedule communication in PROFINET IRT networks

Todays market demands products with a high variety of configurations from the manufacturers. This causes the necessity of production line reconfiguration, allowing to add necessary equipment. Since, in some cases the whole communication has to be planned in advance, the communication planning needs to be performed again, whenever a network structure has been changed. In this paper a simple and fast approach of communication planning for the PROFINET IRT protocol is proposed. The proposed approach is able to calculate communication schedule for a 500 network devices in a time less than 0.2s. This is a significant step in direction of flexible PROFINET IRT systems.

Location-based handover in cellular IEEE 802.11 networks for Factory Automation

The use of wireless technologies in Factory Automation is attractive due to several advantages (mobility, cost, etc.); however, to satisfy the requirements of industrial applications, they have to be improved in terms of real-time performance. Handover is a particular weakness in cellular wireless systems, e. g., in IEEE 802.11, since it may introduce delay beyond acceptable bounds. The project “flexWARE - Flexible Wireless Automation in Real-Time Environments” aims at implementing such an infrastructure based on IEEE 802.11. To enhance overall system performance, it offers a localisation service. In this paper we present the flexWARE handover mechanism which exploits localisation to reduce the discovery phase. A performance evaluation, based on simulation and empirical measurements, shows that the mechanism results in a seamless handover for a class of industrial applications.

Node to node synchronization accuracy requirements of Dynamic Frame Packing

The evolution of industrial communication inexorably moves towards Ethernet based networks. One important reason for using Ethernet at the shop floor is to participate on the continuous advancements of standard Ethernet. In contradistinction to the star topology, used commonly in home and office networks, in the industrial automation most common network structure is line. It is due to the fact that it simply follows the architecture of plants (production line). Depending on the size of an automation facility the size of such a network structure may contain up to 100 nodes. Thus, the node to node synchronization jitter, with its cumulative behavior, becomes a relevant performance factor for high demanding applications such as motion control. This paper examines influence of the synchronization jitter on the industrial Ethernet networks by taking the example of PROFINET IO, a common representative of an industrial Ethernet based protocol. It uses a Time Division Multiple Access (TDMA) procedure together with the communication scheduling to fulfill hard real-time requirements. Additionally the protocol uses Dynamic Frame Packing (DFP) in order to optimize bandwidth utilization. The efficiency of both mechanisms strongly depends on the node to node synchronization accuracy.

Investigation in automatic determination of time synchronization accuracy of PTP networks with the objective of Plug-and-Work

Todays information technology applies Plug-and-Play / Plug-and-Work mechanisms allowing automatic configuration of network components or computer peripheries (USB or IP address assignment by DHCP). PTP also defines Plug-and-Work mechanisms, such as Grand Master selection with the BMCA. For realization of PTP based applications, like motion control or phasor measurements in energy grids (PMU) with high accuracy demands, determination of the synchronization accuracy is a basic requirement. Today, synchronization accuracy often is determined using measurement equipment like scopes or system modelling and simulation approaches. But these approaches require manual tasks and on this reason they are not capable for Plug-and-Work. Other approaches are device qualification and defined system limitations or the calculation of worst cases inaccuracies by the protocol itself. This paper gives an overview of synchronization accuracy determination methods and evaluates advantages and disadvantages using a case study. Further on more adaptable approaches are introduced, with the goal to achieve a more precise inaccuracy calculation in Plug-and-Work scenarios. This automatic synchronization performance adaptability can help to increase system performance and robustness.

Link-layer retransmissions in IEEE 802.11g based industrial networks

Characterization of the behaviour of link-layer retransmissions is helpful when designing MAC protocols and scheduling algorithms for Factory Automation WLANs. In this paper, we measure retransmission rates and consecutive retransmission occurrences of IEEE 802.11g communication links in an industrial indoor environment. The employed wireless channel at 2.4 GHz is characterized. Experimental results show that the distribution of consecutive retransmission occurrences tends to concentrate around just one retry when devices operate within their transmission range. It is also shown that smaller frames result in fewer retransmissions.