Real-time Ethernet Research Articles

A Distributed Instrument for Performance Analysis of Real-Time Ethernet Networks

Ethernet technology is widely used in real-time industrial automation. Thanks to real-time Ethernet (RTE) protocols, defined in IEC61784-2 standard, new top-performance automation solutions can be created. Such systems may have communication cycle time down to tens of mus and cycle jitter less than 1 mus, making network testing and debugging very critical. Existing network and protocol analyzers can perform detailed local analysis, but characterization of high-performance RTE systems requires measurement of transmission delays and these instruments cannot be adequately synchronized among them to realize a distributed measurement network. This paper introduces a new low-cost distributed measurement instrument to measure timing characteristics of RTE nodes (end-to-end delays, synchronization, etc.). The proposed instrument has multiple FPGA-based probes that allow for simultaneous/synchronized logging on different place of the target RTE network. A PC-based monitor station stores all the data, ready for further elaboration. Architecture details are discussed, a prototype has been realized, and some experimental results are presented. For instance, synchronization accuracy between probes is below 100 ns.

Get on the digital bus to substation automation

This paper presents next-generation measuring systems with a real-time Ethernet process bus. Digital communication has proven its advantages in high voltage substations from bay control and protection up to the telecommunication interface. The enlarged digital area in substations offers wide ranges and easy adjustment of parameters for in improved fitness of the investment for future demands.

Time synchronization of hierarchical real-time networked CNC system based on ethernet/internet

With the development of Ethernet/Internet, using Ethernet/Internet technology to implement the communication of computer numerical control (CNC) system is a new research field of networked CNC system. To support the synchronization control of the CNC system based on Ethernet/Internet, a time synchronization solution for the hierarchical real-time networked CNC system based on Ethernet/Internet is designed in this paper. To evaluate the performance, some experiments were conducted and the results were analyzed. The results show that the field level time synchronization based on the hard real-time Ethernet time synchronization protocol IEEE 1588 meets the requirement of the hard real-time tasks, and the time synchronization between the NC server and the NC core computer based on global positioning system (GPS) and network time protocol (NTP) also meets the requirement of the soft real-time tasks. The results testify that the time synchronization solution based on Ethernet/Internet for the CNC system is realizable.

PERFORMANCE ANALYSIS OF ETHERNET/IP NETWORKS

Real–time Ethernet networks, which are described by both the IEC 61784 and IEC 61158 International Standards, are even more employed in factory automation systems. In this paper we focus on the performance of EtherNet/IP, one of the most popular networks specified by the above standards. In particular, we evaluate two Performance Indicators, namely the Delivery Time and the Throughput RTE for a specific network configuration. For both the indicators, we firstly propose a theoretical analysis and then report the results of an extensive set of tests we carried out in order to measure their actual values for different hardware components. Finally, we provide an adequate explanation of the inevitable differences between the data obtained via the theoretical analysis and the experimental outcomes.

A CONCEPT FOR THE SYSTEM INTEGRATION OF WIRELESS SENSOR NETWORKS TO INDUSTRIAL AUTOMATION SYSTEMS USING PROFINET

Contemporary industrial automation systems are using real-time Ethernet protocols, like PROFINET, for exchanging process and configuration data. In order to make automation systems more flexible and due to many other advantages, wireless technologies are introduced in certain application areas, e.g. the connection of sensors by the use of a wireless sensor network. In this typical scenario the integration of a newly deployed wireless sensor network into an existing system is required and of vital importance. This paper gives a short introduction to different wireless technologies that are being discussed at the moment for wireless sensor networks (WSNs) and to PROFINET IO. It also proposes a feasible integration approach regarding application layer object models and their corresponding mapping.

Hierarchical real-time networked CNC system based on the transparent model of industrial Ethernet

Given the rising importance of industrial Ethernet in the market, a networked CNC (Computer Numerical Control) system based on the transparent model of industrial Ethernet is urgently needed. To this end, a hierarchical real-time network based on Ethernet/Internet, called RNH-CNC, is designed in this paper. To evaluate the performance, some experiments were conducted and the results were analyzed. The results show that the field level communication based on the real-time Ethernet meet the requirement of hard real-time tasks, and the communication between the NC server computer and the NC core computer based on the switched Ethernet also meet the requirement of soft real-time tasks. The results testify that the CNC system based on the transparent model of industrial Ethernet is realizable.

PERFORMANCE ANALYSIS OF INDUSTRIAL ETHERNET NETWORKS BY MEANS OF TIMED MODEL-CHECKING

Ethernet networks are promising for the harmonization of the communication technologies in manufacturing automation but they have not been specifically intended for industrial control applications. Investigations have thus become necessary to evaluate their performance. Most analysis approaches use probabilistic models to validate the system's behavior. However, if the deterministic behavior of a system needs to be ensured exhaustively, formal verification techniques, like model-checking are more appropriate. Unfortunately the state-space explosion problem constitutes a serious obstacle. Considering a real-time Ethernet network as a case-study, this paper describes sophisticated modeling-techniques, which help to alleviate the state-space explosion, for the timed model-checker Uppaal.

Real-Time Ethernet - Industry Prospective

After more than ten years of experience with applications of fieldbus in automation technology, the industry has started to develop and adopt Real-Time Ethernet (RTE) solutions. There already exists now more than ten proposed solutions. International Electrotechnical Commission standards are trying to give a guideline and selection criteria based on recognized indicators for the user.

FIELDBUS INTEGRATION TO THE REALTIME ETHERNET STANDARD PROFINET

For the investment protection of installed plants and machines suitable concepts for the integration of Fieldbus systems to future Realtime Ethernet Networks are very important. In this paper a approach for the integration of the fieldbus system INTERBUS into the Realtime Ethernet standard PROFINET IO will be presented. It shows that it is possible despite very different device models to realize a deep integration.

Standardization of Real-Time Ethernet for Measurement and Control

Standardization of Real-Time Ethernet for Measurement and Control

Achieving real-time Ethernet

In the 25 years or more that have elapsed since its creation, Ethernet has become the classic bus system. Ethernet is steadily permeating the industrial control environment where users are seeing enormous benefits in the ease of integration of industrial control systems with higher level of manufacturing execution systems. As Ethernet continues its drive into the industrial arena, the Ethernet still needs to overcome several challenges to redefine the shape of automation networks. Although Ethernet has a bright future in the industrial environment, many functions and application profiles are not yet available on industrial Ethernet and have still to be implemented.

How to Guarantee Realtime Behavior using Ethernet

Ethernet is now conquering the field level in automation technology. Realtime behavior is a knock-out criterion therefore. This paper deals with the key concepts for guaranteed realtime behavior using Ethernet, based on the requirements of factory automation. A classification of the vendor-driven approaches that are currently under discussion for realtime Ethernet is provided.

The future of industrial communictions technology: Switched Ethernet

Siemens A&D recently released the third version of PROFInet, which extends the network into motion control applications, called real-time or IRT, the new scheme allows jitter accuracy of one millisecond. PROFInet v3 involves some reengineering of standard Ethernet. All stations on a PROFInet v3 network, including the network nodes, must be precisely synchronized. For isochronous real-time Ethernet, the switches are synchronized to the communication cycle with accuracy in the sub-microsecond range. For Seimens and their partners, the key to deploying 'hard' real-time Ethernet is in the special IRT switches.

The race for real-time Ethernet

Ethernet is starting to replace the industrial fieldbuses that were developed in the 1990s. Not only that it's going after the domain reserved for high-speed fibre optic buses like SERCOS. There are now three proposals for real time Ethernet. Two are from German companies, Siemens and Beckhoff, and the third is from B&R Automation, based near Salzburg. We endeavor to give some idea of how these three real-time Ethernet proposals work.

Making real-time Ethernet a reality

Current Ethernet standards promise transfer speeds of 100Megabits and more. This is significantly faster than established most of the field bus systems, and embedded network. Therefore Ethernet also seems to be a good choice for connecting industrial devices with real time requirements. With Ethernet, data communication can be delayed unpredictably. The reason for Ethernet's nondeterminism is its stochastic media access mechanism CSMA/CD (carrier sense multiple access with collision detection). To achieve predictable timing on Ethernet network collision need to be avoided. Moving from shared Ethernet to a switched Ethernet seems to be a promising solution. Time slicing is a better method for predictable data communication via Ethernet with very short cycle times and precise timing.

Distributed prototyping from validated specifications

We present vpl2cxx, a translator that automatically generates efficient, fully distributed C++ code from high-level system models specified in the mathematically well-founded VPL design language. As the Concurrency Workbench of the New Century (CWB-NC) verification tool includes a front-end for VPL, designers may use the full range of automatic verification and simulation checks provided by this tool on their VPL system designs before invoking the translator, thereby generating distributed prototypes from validated specifications. Besides being fully distributed, the code generated by vpl2cxx is highly readable and portable to a host of execution environments and real-time operating systems (RTOSes). This is achieved by encapsulating all generated code dealing with low-level interprocess communication issues in a library for synchronous communication, which in turn is built upon the adaptive communication environment (ACE) client-server network programming interface. Finally, example applications show that the performance of the generated code is very good, especially for prototyping purposes. We discuss two such examples, including the RETHER real-time Ethernet protocol for voice and video applications.

Using application benefit for proactive resource allocation in asynchronous real-time distributed systems

This paper presents two proactive resource allocation algorithms, called RBA* and OBA, for asynchronous real-time distributed systems. The algorithms consider an application model where timeliness requirements are expressed using Jensen's benefit functions and propose adaptation functions to describe anticipated application workload during future time intervals. Furthermore, the algorithms consider an adaptation model, where application processes are dynamically replicated for sharing workload increases and a switched real-time Ethernet network as the underlying system model. Given such models, the objective of the algorithms is to maximize the aggregate application benefit and minimize the aggregate missed deadline ratio. Since determining the optimal allocation is computationally intractable, the algorithms heuristically compute near-optimal resource allocations in polynomial-time. While RBA* analyzes the process response times to determine resource allocation decisions, which is computationally expensive, OBA analyzes processor overloads to compute its decisions in a much faster way. RBA* incurs a quadratic amortized complexity in terms of process arrivals for its most computationally intensive component when DASA is used as the underlying scheduling algorithm, whereas OBA incurs a logarithmic amortized complexity for the corresponding component. Our benchmark-driven experimental studies reveal that RBA* produces a higher aggregate benefit and lower missed deadline ratio than OBA.

A new real-time ethernet MAC protocol for time-critical applications

The authors propose a new persistent transmission-based real-time Ethernet MAC protocol that provides a predictable upper bound for the delivery delay of real-time frames. Moreover, it is compatible with the protocol used by the existing Ethernet controllers for conventional datagram traffic and thus standard Ethernet stations can be used in the system without any modification. The paper describes the protocol in detail and analyses the maximum delivery delay for real-time traffic and the efficiency of the channel.

Parallel and Distributed Real-Time Systems

Parallel and Distributed Real-Time Systems

Switched Real-Time Ethernet with Earliest Deadline First Scheduling—Protocols, Trafic Handling and Simuation Analysis

There is a strong interest of using the cheap and simple Ethernet technology for industrial and embedded systems. This far, however, the lack of real-time services has prevented this change of used network technology. This paper presents enhancements to full-duplex switched Ethernet for the ability of giving throughput and delay guarantees. The switch and the end-nodes controls the real-time tra.c with Earliest Deadline First (EDF) scheduling on the frame level. No modi.cation to the Ethernet standard is needed in the network that supports both real-time and nonreal- time TCP/IP communication. The switch is responsible for admission control where feasibility analysis is made for each link between source and destination. The switch broadcasts Ethernet frames regularly to clock synchronize the end nodes and to implement .ow control for non-real-time tra.c. We have characterized the performance of the network in terms of channel acceptance ratio by simulations with di.erent number of nodes connected to the switch.