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Fieldbus System Fundamentals
Published in Richard Zurawski, Industrial Communication Technology Handbook, 2017
During the last years, a number of industrial solutions appeared that tackled the real-time requirements, mostly on the basis of switched Ethernet. Still, as with fieldbus systems, they were tailored to specific needs. Not even the use of standard Ethernet is really a common denominator, and above the data link layer, the approaches are completely different. Some use standard TCP/UDP/IP mechanisms for transmitting data, maybe enhanced by additional software layers to support both real-time and non-real-time communication, and some use dedicated communication stacks that bypass the entire IP suite. Figure 1.25 sketches the various appearances of the protocol stack. Manifold differences are also possible on the physical layer. Some approaches foresee redundant media (VNET/IP, TCnet), PROFINET-I/O uses dedicated built-in switches to reduce the data transmission jitter [73], and EtherCAT as well as SERCOS III need dedicated controllers [59]. Ethernet Powerlink uses the old shared Ethernet and places a master–slave scheduling system on top of it. Common to many proposed networks is that they employ clock synchronization to support real-time applications. To this end, the standard IEEE 1588 [74], which originally emerged in the instrumentation area, was officially adopted also by IEC. The specific requirements in the automation domain have led to several suggestions for improvement of the standard regarding performance or fault tolerance [75,76] that were taken into account in the subsequent revision.
Ethernet Powerlink
Published in Sunit Kumar Sen, Fieldbus and Networking in Process Automation, 2014
Ethernet Powerlink is an open and standard compliant architecture whose development and standardization are maintained by EPSG. It is one of the fastest real-time Ethernet systems with cycle time around 200 µs and jitter below 1 µs obtained without any special hardware support. EPL devices can straightway talk to each other without a detour through PLC taking the help of either publish/subscribe or client/server relationship. This is particularly suitable in multi-axis drive applications. This cross-traffic communication between devices bypasses the master. It supports any network topology like star, tree, or daisy chain. EPL supports on the fly, i.e., hot plugging is possible. It implies that any node can be plugged in or disconnected without impairing network functionality or else no rebooting is needed. This facility gives Ethernet Powerlink an edge over its peers. Using mixed polling and time slice mechanism in EPL guarantees transfer of time critical data in very short and precise isochronous cycles with configurable timing and less time critical data in reserved asynchronous cycles.
ORHRO: OPEN Robotics Humanoid RObot - from a mechanical retrofit to a new real time industrial controller based walking robot
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
A. Eon, J. Gastebois, P. Laguillaumie, P. Vulliez, P. Seguin, J. P. Gazeau
The heart of the control hardware (Figure 1) is a B&R X20CP1586 unit PLC (ATOM 1.6 GHz processor with 512 MB DDR2 RAM) that communicates over an Ethernet POWERLINK protocol with the drives and I/O cards. The ACOPOSmicro drives provide a small computation unit to support the adjustable low level control loop and a limited number of functions, notably the feed forward controller.
Response time evaluation of industrial-scale distributed control systems by discrete event systems formalisms
Published in International Journal of Control, 2022
Ouail Himrane, Alain Ourghanlian, Saïd Amari
Note that, several industrial Ethernet solutions (Ethernet/IP, Modbus-TCP, Ethernet Powerlink, Pro_net,…) can be selected to implement an NCS. Hence, the purpose of this chapter is to provide some predictability elements for the Ethernet/IP networks utilised in our architecture by both the RIO network and the control network.