Ready ... Aim ...WIREless

Nov. 1, 2004
When it comes to controlling warehouses and DCs, RFID technology is having a wide impact, from wiring to controls.

Finding better ways to automatically collect data and send them to controls that will automatically take an action is still a challenge for material handlers. The latest quest for 100 percent data accuracy in collection and transmission, in the form of a mandate to implement RFID technology, is pushing attention to the peripheral equipment needed to make the mandate happen. Part of that equipment is the cabling that may, or in the case of wireless may not, be used to connect and power automation components. Another part involves automation controllers and the quest for a new simplicity that is resulting in a reduction of the number of programs and intermediate components needed to implement an integrated system.

Among controls and mandates and new technology, there's a lot of wiring going on in material handling applications. Wires and cables, in general, have several drawbacks: they are expensive, they require maintenance, and they inhibit a warehouse manager's ability to quickly and easily accommodate facility layout changes. Despite some concern on the part of IT departments regarding security, wireless technology offers the best solution today for these problems.

A lot of warehouses have or will grow their wireless installations. According to a Dell'Oro Group report, sales of wireless LAN products will grow 20 percent in 2004 to $2.1 billion, and enterprise-class access point shipments should increase by 75 percent in 2004, growing at an average annual rate of 47 percent through 2008. "With the improvements in management, encryption and user authentication," says Greg Collins, senior director of wireless LAN research at Dell'Oro Group, "wireless LANs will grow because the technology allows users to connect to the network from anywhere."

Another research firm, Venture Development Corp., concurs that wireless will be the communication method of choice for those users looking for more efficient ways to move information between back office systems and other areas in their four-wall operations.

Notes Dan Williams, marketing manager, Avery Dennison, "We've seen efforts to get wiring out of the warehouse. People are going to Ethernet and wireless setups to get around wiring and to have the ability to put things anywhere they want in the warehouse that they can find power, especially when they put in new systems."

Improving access
Wireless applications do not mean that there are never any wires for communications. The infrastructure of wireless systems requires use of some type of cabling that typically can handle Ethernet protocols. The components that must transmit to a wireless system are the parts that are frequently untethered. A wireless system's access points, which are often mounted in ceilings, tend to be connected by Ethernet cabling that provides communication. Providing power to those points has required another set of cabling, until now.

Rather than string an additional set of cables to provide power to these access points, some companies are looking into a newer technology that leverages the Category 5 cable often used in Ethernet installations.

This technology is called Power over Ethernet (PoE). "PoE takes advantage of technology and the lessons learned over the wireless LAN space," says Mike Liard, senior AIDC/RFID analyst, Venture Development Corp. PoE is seen as the next step in wireless technology.

PoE is a way to supply power to small devices using existing Ethernet cabling. If you already use 10, 100 or 1000Mb Ethernet that runs over Category 5 cable, you can implement PoE. It is compatible with existing Ethernet devices. A caution, though, if your system still uses Category 3 cable or connections, there could be compatibility problems.

Manufacturing applications have been using this concept for years, but an official standard has just emerged. It is IEEE 802.3af. Now, engineers are looking into it for building access systems, retail point-of-information systems and applications that involve "smart" signs.

The Category 5 cable consists of four twisted pairs of wire. In PoE, two of those pairs are used to run current to a connected device. PoE power sourcing equipment detects the presence of an access point or other device connected to the cable and injects current into the two twisted pairs of wire. The connected access point can operate solely from the power it receives through the cable.

"There are fail-safes in place so that a system doesn't confuse data with power," adds Liard. "It keeps them separate."

The amount of power supplied is 12.95 watts (at 48 volts). That's not enough power for many types of automation equipment. However, that amount is sufficient for smaller devices, such as sensors, on-off switches, and some bar code scanners. "You won't be able to power a printer or a motor, though," explains Williams.

"You're looking at equipment that is DC powered and low consumption," concurs Gene Vena, Center of Excellence manager, Avery Dennison.

"In our case it goes to our wireless access ports or points in the ceiling," says Gil Bautista, senior director, Warehouse Mobility Solutions Group. Symbol Technologies. "The electrical cost associated with populating a facility with these devices is far less."

PoE and RFID?
Several companies are exploring the use of PoE with RFID equipment, particularly because of the mandate to install RFID systems. "Some RFID equipment may be able to use PoE," adds Vena, "but it depends on the application because of the way you power the antenna, how the antenna excites the RFID chip, and how you extract data from the chip. The transmitter/receiver is the crucial part that needs the power."

"Wal-Mart said [in a November 2003 meeting] that it would like to see PoE-enabled RFID readers as part of the mandate," adds Liard. "But there are lots of performance issues on the transponder side of RFID. The core focus of RFID suppliers has been around dealing with that; then, they will look at the reader portion of the market and try to reduce costs there. It's a long-term consideration for sure."

Liard doesn't see the power limitation as much of a problem yet. "Some regulations in Europe have limits on power output. About 2008 you'll see more PoE in warehousing applications."

"A lot needs to be done in the RFID world first," adds Rick Barnard, electronic components and advanced material practice director, Venture Development Corp. "There is still a lot of questions about RFID technology, standards and read accuracy."

"Our PoE approach has been in support of the wireless infrastructure," adds Bautista. "Wireless from an accessport or access-point perspective, for example, in a ceiling setup that enables your mobile computing devices to communicate through 802.11b. The access points are the point at which communication to the host systems occur."

"There are still challenges with any wireless system," continues Bautista. "Physical elements within a facility, such as the racks, foil packaging, water, anything that can deflect signals."

"Don't forget about competing technologies like 900 MHz phones, radiant signals and a microwave tower next door," adds Williams. "But everyone wants to reduce wiring. The best technologies now are local area networks that are encrypted and the components are all from the same manufacturer. Don't use a mix of best-of-breed items in networking."

PoE is not a panacea for wireless implementations. But it will likely come to the warehouse in a limited form because IT likes it and is currently using it in Voice over IP applications and Telephony.

Simpler control
A reduction or even elimination of cabling promises simpler systems, and simpler systems are keenly desired by material handlers, especially as RFID technology suggests it will add to automation complexity. RFID has created challenges for many PC and PLC suppliers because it can require additional equipment in the form of intermediate hardware and software to enable the control to communicate with RF tag readers to record product shipping information.

"A lot of people are setting up a PC right next to the RFID unit," says Williams. "They want to record information and an Ethernet setup allows them to do that. Fewer connections have to be made. And you're not running a parallel cord back and forth, just one piece of cable."

"There are a lot of devices out there like RFID that have just simple ASCII protocols," says Robb Dussault, product manager, Schneider Electric. "A problem has been that you needed something between your PLC and ASCII device, such as an RFID station, to translate that into a data format the PLC can understand." One solution that is emerging is software code in the form of a function block that enables a PLC to communicate easily with any third-party TCP device, including RF tag readers, printers, bar code readers and other PLCs. Schneider Electric offers such a feature in its Modicon Premium Controller. The code creates an object in an objectoriented programming environment. The object automatically opens an Ethernet communication channel to an RF tag reader, records the data and then closes the channel.

Wireless applications do not mean that there are never any wires for communications. The infrastructure of wireless systems requires use of some type of cabling that typically can handle Ethernet protocols.

"This code handles the overhead associated with TCP/IP over Ethernet," adds Dussault, "so now you can build your own protocol within the application code of your PLC and talk directly to these devices without an intermediate gateway.

"One of our customers, Wels Dairy, has taken an Ethernet IP function block library and created a way to talk directly to its RFID scanners," continues Dussault. "It originally had a computer in between with some software that would perform this translation. Now it's a direct connection of the PLC to the RFID equipment."

And there are other changes coming to control equipment. "Features such as networking, connectivity and programming for traceability require standards, influencing the development of controls that are more standards based," notes Tom Wolff, business development manager, Rockwell Automation. "Many of the features that you have in automation controllers now help handle the tasks that you don't have people for," continues Wolff, "such as monitoring power levels, monitoring and handling network data collection situations, and enabling you to audit, manage and direct everything on a system, including the electromechanical physical health of that network, from actual IP addresses."

In other developments, several makes of controllers have simplified the database stuffing function. Rather than have a piece of software poll a PLC on the data and stuff that data into a database, then have the database forward that information to some decisionmaking software, the controller can write information directly to the decision-making software.

This is an example of a trend to remove layers of software and reduce the cost of integration. Because software integration is turning into an expensive part of an installation process, users have been known to purchase additional hardware if it will make a system simpler.

"What's desired is for data to go to one place where users can then press a button and all that data and information blow all over the plant," says Dussault, "and subroutines figure out where they're supposed to go. The limitation is not in the hardware, it's in this mega piece of software."

You can also expect to see layers of controls disappear, particularly the intermediate layers known as cell controllers and mid-range PLCs. Gateways to bridge data will disappear as well.

For material handlers, the end result, when all of these changes occur in the next few years, will be simpler systems that automate warehouse and DC functions.

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