Universal solution for plant networks
01 February 2008
Industrial Ethernet is the fastest growing industrial network choice, but what exactly is it, how does its implementation differ from that of a traditional fieldbus, and does it really offer the single universal solution that is so often talked about? We put these questions to the experts in the field
Industrial Ethernet is the fastest growing industrial network choice
Against a background where there is increasing pressure on manufacturers in all sectors of industry to improve processes, reduce costs and boost productivity, Ethernet technology is being hailed as the key to achieving all these goals, and so boosting companies’ competitiveness on increasingly aggressive global markets.
The move to industrial Ethernet has been fast paced across all sectors of industry, and is a step change from the standardisation on the various open and proprietary fieldbus protocols that we saw though the 1990s. But what exactly is industrial Ethernet? Steve Jones of CLPA (CC-Link Partners Association) explains: “Industrial Ethernet, in essence, is the use of Ethernet as the data link layer protocol in the OSI seven layer model, with a fieldbus protocol as the application layer. This is conceptually similar to the various fieldbus options that are actually the use of RS232/485 as the data link layer, with the fieldbus protocol itself at the application layer.
There are many advantages to moving to industrial Ethernet, not least of which is a vast increase in speed, up from the sub-10kbps typical with RS232 to the gigabit and beyond potential of Ethernet. Overall performance is also increased, and costs are significantly reduced, since industrial Ethernet offers the ability to use standard access points, routers, switches, hubs and cables which are far cheaper than equivalent serial port devices. Other advantages include the use of peer-to-peer architectures to replace master-slave architectures.
“From the user’s point of view, however, the biggest advantage aside from cost is the significantly greater interoperability between devices offered by industrial Ethernet,” says Jones. “In particular, there is the potential for a seamless flow of data from field devices all the way up to higher level business systems, and back, delivering huge gains in flexibility for manufacturers looking to boost their productivity to the max. And for users who take their use of industrial Ethernet to its ultimate potential, there is the possibility of using a single, standard network for information, configuration, control, safety, synchronisation and even real-time distributed motion – the most demanding of applications.”
The key to this performance is the speed of industrial Ethernet, with the latest development delivering a ten-fold increase in communications rates to 1Gbps(gigabit per second), This has come with the release of a new open communication standard by the CLPA. Called CC-Link IE (Control and Communication Link Industrial Ethernet), it is the first completely integrated gigabit Ethernet network for industrial automation. “It really does define the new threshold for open standards for Industrial Ethernet,” says Jones.
It is the evolution of Ethernet technology from a 10Mbps bus/tree topology to a gigabit, switch-based topology that has really paved the way for using Ethernet to support such time-critical applications in industrial networks. This switch-based topology makes the implementation of an industrial Ethernet network very different from implementing a device-level network.
The infrastructure of Layer 2 and Layer 3 switches is the core of the industrial Ethernet network, providing the determinism and throughput required for control applications. The switch’s ability to eliminate collisions is the most important mechanism to provide real-time capability for Ethernet-based control systems. Switches can be added to split the data load between segments, resulting in higher performance. In addition, managed switches can prioritise traffic, allowing the preferential handling of real-time traffic over supervisory traffic.
The Ethernet switch also makes it possible to build into the industrial Ethernet network something which was very difficult and/or expensive to do with standard fieldbus networks: and that is redundancy. Dave Cook of GarrettCom Europe comments: “At field device level, dual connectivity is the standard approach for providing redundancy, but the lack of PLCs and field devices with dual connectivity built in for sensor and controller applications has made this almost impossible to achieve cost effectively. Modern Ethernet switches provide a solution to the problem, with the advent of dual homing technology built into even the smallest of switch products. Offering convenient plug-and-play dual connectivity in a physically small package, these products provide high reliability to enable redundancy for nodes at the edge of the network at a low cost.”
Further, Ethernet has the unique characteristic of being a network with an active infrastructure. Therefore, unlike typical device or control level networks-which generally have a passive infrastructure that limits the number of devices that can be connected and the way they can be connected, the industrial Ethernet network infrastructure can accommodate a virtually unlimited number of point-to-point nodes, providing users with unsurpassed flexibility in designing networks that accommodate their current requirements while enabling easy, cost-effective expansion in the future.
In addition, recent hardware developments have removed the communications distance limitations that have been a recognised issue with the move to gigabit Ethernet, giving users a simple upgrade path to the increased performance afforded by this high-speed technology. The new CSG14 converter switches from GarrettCom Eruope allow industrial installations with multi-mode fibre to achieve 2000m gigabit connectivity that has previously only been available when using single-mode fibre cable.
“While transmission distances of 2000m over multi-mode fibre are standard for 10/100Mb Ethernet, any upgrade to gigabit speeds has always been a problem because the distance has been limited to just 550m,” explains Cook. “Users looking to upgrade have been forced to rework their network installations around shorter transmission distances and/or single-mode topologies, implying significant time and expense. With the introduction of the CSG14 converter switches, GarrettCom Europe has overcome these problems, and made the upgrade path simple and cost-effective.”
With its performance benefits, then, industrial Ethernet is a good fit for applications where the required volume and speed of data exchange among plant floor controllers and between controllers and information systems is exploding. In addition, being based on standard Ethernet, the network addresses the increasing need to reduce total cost of ownership of production processes across development, commissioning, operation, and maintenance.
Stefan Knauf of Mitsubishi Electric says: “As industrial Ethernet extends its reach to even the most lowly field devices, so the various controllers, PLCs and ERP systems are able to access any sensor connected to the control and device network. The result is better information on manufacturing processes, with process operators able to monitor and fine tune system performance, access plant information and communicate directly with their production line managers.”
But along with enterprise wide connectivity, industrial Ethernet brings with it the possibility for connectivity to the plant over the internet. Knauf continues: “This allows plant performance to be viewed remotely, production planning to be centralised across manufacturing sites that could be continents apart, and faults to be diagnosed remotely and in real-time in plants that could potentially be thousands of miles away.”
Perhaps most importantly, and in contrast to the fieldbus options of the past, industrial Ethernet frees up the user to a far greater extent from the danger of being locked into a single solution, enabling the system integrator to focus on installing the network without having to worry about the protocol that will eventually be used over it, whether that be CC-Link IE, EtherNet/IP, Profinet or one of the others. “An industrial Ethernet infrastructure will happily accommodate multiple application protocols in use at the same time, with the switch network routing the data packets appropriately,” says Knauf. “This means users can make a decision on an industrial Ethernet protocol based on today’s requirements, confident that the investment will not have been wasted should tomorrow’s requirements in a different area of the plant dictate the use of a different protocol.”
There is no doubt that the real value proposition for industrial Ethernet to manufacturers lies in the enabling of a single network architecture to meet the needs of all enterprise levels. Instead of using architectures composed of multiple separate networks, Industrial Ethernet can unite a company’s administrative, control-level, and device-level networks to run over a single network infrastructure.
Further, anyone looking to make a new investment in networking technology should look at the huge performance benefits over fieldbus in a given application, in terms of its real-time performance, its speed, and its capacity. Your industrial Ethernet network won’t simply do the job you intend it to do today and no more: it will offer the ability to evolve and grow with your application over time in a way no fieldbus will ever be able to do.
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