Trying to make sense of the wireless milieu? Good luck! Here’s my attempt to help with some commentary and links to recent articles on wireless in automation:
First, remember that there is more than one type of “wireless.” I classify three types: RTU, sensor level, and backbone. By RTU, I mean radio connection to Remote Terminal Units typically found in the field like at a water pumping station. It reports status and values via proprietary radios. There is no standardization of the radios although the protocol is frequently Modbus RTU. Backbone defines what PROFINET uses. Because PROFINET is standard IEEE 802.3 wired Ethernet, it is easily connected wirelessly via IEEE802.11 WiFi. This is suitable for bridging difficult-to-wire gaps. Its cost and power requirements make it unsuitable for sensor level wireless. Sensor level wireless has been proprietary in the past but now WirelessHART provides an open standard for this application. ISA is also working on a standard for this space, too. There is some amount of politicking between supporters of the two standards.
Here’s a good article that showcases some of that back and forth between WirelessHART and ISA SP100: “Unplugged: Developing Standards for Wireless Automation” by Maribel Rios in the May issue of Pharmaceutical Technology. After all the point/counter-point comes this conclusion: “The thing to remember is that it doesn’t matter who puts out the standard, it’s what the users adopt that is going to be important.” [While you’re there, click on the sidebar “Which Wireless” for an expansion of the discussion on the kinds of wireless.]
There is one correction to make about how PI will proceed. *** Caro says in the article that PI “appears to be leaning toward founding the wireless version of Profibus on top of the WirelessHART protocol.” We are not going to create a wireless version of PROFIBUS at all. Instead, PI has decided to collaborate with Fieldbus Foundation and HART Communication Foundation in a unified approach to wireless. (See the original announcement from last September and the recent update. I also blogged about this recently.) We are working with FF and HCF to create gateways to FF, PROFIBUS, and PROFINET from WirelessHART. Once the spec for ISA SP100 is done, the collaboration team will determine how to approach it.
For an ISA-oriented view of the situation read the Control magazine article “Which Way Wireless?” by *** Caro. For a strong users’ advocacy perspective, follow Walt Boyes’ blog – he can’t go long without raising the topic. PI has also come down on the side of the users by foregoing a PROFIBUS process wireless sensor network of its own and instead collaborating with FF and HCF.
A more generic overview of wireless is in the Industrial Ethernet Book: “Industrial Wireless: Unplugged Version of the Factory Network.”
For those of you concerned with the security of wireless networks, read “Wireless Security on the Plant Floor”, also in the Industrial Ethernet Book. This article is by ProSoft’s Wally Gastreich.
Come to the PTO General Assembly Meeting in August in Scottsdale for more discussion on these topics including presentations from Wally Gastreich on wireless security, from Ron Helson of HCF on the wireless collaboration effort, and from Tom Burke of OPC Foundation on the EDDL Cooperation Team (ECT). Collaboration and complementary technologies is one of our themes at the GAM this year.