While Industrial Ethernet has become the kingpin and standard for automation control networks, some devices such as smart sensors and actuators are relying on a simpler, point-to-point communications protocol to save on the cost, size, and complexity that an Ethernet solution requires.
One increasing popular alternative is IO-Link technology because it can provide a fieldbus-neutral means of bringing information from intelligent sensors and actuators onto Industrial Ethernet networks. The technology creates an effective strategy, especially for configuring intelligent devices on the network, simplifying setup, reporting of diagnostic information, streamlining product changeovers, and also provides an ability to proactively collect maintenance data.
The technology is supported worldwide by a consortium of automation control suppliers such as Siemens, Rockwell Automation, Beckhoff, Schneider Electric, plus a large number of sensor, actuator, and other component suppliers. It is particularly popular in Europe, although it is also gaining acceptance worldwide.
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Types of distributed modular I/O slave devices that have implemented IO-Link communications include specialty sensors for measurement, position and color detection, valve manifold control, and industrial RFID processors and heads. (Source: Balluff Inc.)
The key to IO-Link is that it offers a point-to-point communication topology (it’s not a fieldbus), which allows users to configure a sensor, perform diagnostics, and receive process data. Users can retrieve distance information, for example, such as the distance from a sensor to an object for positioning purposes or to measure the dimensions of a carton, pallet, or box.
Because the technology is fieldbus-neutral, there are masters available to connect IO-Link to all of the major fieldbuses and industrial Ethernet networks. In low-cost systems, the problem with using Ethernet to connect directly with smart sensors or actuators can be the amount of overhead required. Plus, cost can certainly be a major issue because IO-Link communication is much simpler and less expensive to implement. But even if Ethernet is cheap enough, putting an RJ45 connector on a proximity switch and an Ethernet controller inside can be impractical from both a physical footprint standpoint and also the overhead standpoint.
IO-Link is beneficial for use in smart sensors because it eliminates the cost issue while every Ethernet drop, IP address, and the total number of connections adds expense.
One benefit is the ability to use IO-Link as a kind of expansion technology, which enables customers to basically do more with their Ethernet drops. Whether it’s EtherNet/IP, Profinet, or other popular fieldbuses, adding IO-Link ports on the drop allows a system to branch off and provide easy expandability.
If you are interested in learning more about how smart sensors are using this technology as a solution for network communications, automated parameter setting, and more robust diagnostics, view the Design News Webcast that covers this topic.
Chuck, I am not sure about the development history of IO-Link. Clearly it was motivated by the need for an inexpensive way to easily set dconfiguration parameters, monitor systems and do troubleshooting of inexpensive devices linked to a fieldbus network. Automation suppliers have widely embraced it for all of those reasons. The overhead and expense of adding Ethernet to these simpler devices, such as sensors, plus the openness of the technology has also played a key role in its gaining support.
Chuck, I think the idea was to have a standard type of communication topoology regardless of the bus structure. Basically, it's due to the many different types of bus out there.
Interesting article, Al. What's the history of IO-Link? Did this grow up in response to Industrial Ethernet, or did it exist in some other form previously?
apresher, the important thing is that Ethernet brings a lot of advantages to the industrial environment, while having a different structure than networking protocols that were designed for that environment. The idea of a two tier approach, with another protocol handling the shorter distance, lower speed aspects of the last foot, is almost inevitable. With the availability of standardized modules that interface these other bus technologies with Ethernet, a system can be created that easily handles modules with different protocols in the same system. As long as the programmer can treat these as I/O points on the Ethernet network, then various suppliers can be used without unduly restricting the design. This is the essence of the systems approach.
Helge, Excellent discussion and analysis. The point is that these technologies can extend networking functionality at low cost the last foot, and provide a way to increase the intelligence of these devices without costs especially for setting parameters, configuration and diagnostics. Thanks.
It is important to clearly separate IO-Link and whatever Ethernet based protocol a user might select. While IO-Link adds functionality and diagnostics capability to an "end device" it is still, as was pointed out, a parallel wiring technology and does therefor not simplify installations using Ethernet. As was pointed out the overhead associated with Ethernet is significant. This makes it necessary for Ethernet field I/O to have a relatively high I/O count; perhaps 16 or 32 I/O points per module. IO-Link is not going to change that fact. Considering applications in material handling or storage and retrieval such a high I/O count results in setting up an Ethernet network PLUS a significant parallel (i.e. hardwired) cabling to the sensors and actuators. IO-Link or not, the extra material (cordsets, wiring duct ...) needed is still considerable. In those cases a highly decentralized solutions like AS-Interface offers better functionality, faster installation, reduced material and ultimately lover cost. And since AS-Interface makes use of a proven installation piercing technology adding low density I/O wherever necessary is possible. It should also be mentioned that AS-Interface does not replace Ethernet. On the contrary, users selecting any Ethernet solution will simply add the appropriate gateway and then collect field I/O through low density/ low cost I/O modules (some are as little as a book of matches.) From the PLC's point of view a gateway is simply an Ethernet I/O module with hundreds of I/O points.
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