Real time locating systems employ active RFID tags that periodically broadcast their presence and identity—rather like the “peek” in the child’s game.
Children play the "peek-a-boo" game based on the assumption that "I can't see you so you can't see me." In a warehouse, that may actually be true.
A well-designed warehouse management system (WMS) can help you keep track of products that are stored properly, which assumes that everything does get stored properly. In today's fast-paced logistics environment, some pallets, bins, tubs, and what-have-you are sometimes placed on the floor for easy access because they're being cross-docked, because they're waiting for a storage location to open up, or for a variety of other reasons.
But of course life never runs smoothly. Sometimes these "convenient" storage locations get crowded, the unit doesn't get moved as quickly as anticipated, or logistics get snarled. There are just as many reasons that items don't move, as there are reasons to put them in temporary storage locations. As a result, these items can easily get "lost" because their location may not be entered into the WMS.
On the other hand, there are carts, dollies, lifts, and other mobile assets that are constantly being moved around the facility. Finding one—or the closest one—when you need to can be frustrating. So, how do you keep track of items in your facility that are playing "peek-a-boo"?
Interestingly enough, it's almost the same as the child's game only it's called a " realtime locating system" (RTLS) and it uses radio-frequency identification (RFID). (See "NYK Logistics Automates Yard Management," on page 48.)
RTLS employs active RFID tags that periodically broadcast their presence (and identity)—rather like the "peek" in the child's game. When two or more antennas receive a tag's signal, the difference in the time the signal is received by various antennas is calculated and the relative location of the tag can be determined, generally within several feet. The precision of the location depends on the number of antennas that receive the signal as well as on the system's software.
Some systems are designed to have three or more antennas cover an area to provide greater precision. Others employ only a single antenna to locate a tag in a general area, typically a relatively confined space. Single antenna systems are useful to indicate an item's presence with the assumption that, as long as you know generally where to look, it will be easy enough to find.
Tags are usually permanently attached to fixed assets but they can also be used on a temporary basis on pallets and other items. They are not designed to be "disposable."
The time delay between tag broadcasts can be set from a relatively short period of time (seconds) to relatively long (hours). The delay depends on the velocity of the tagged items within a facility as well as the potential urgency of locating an item. The fact that the tags only broadcast periodically also means that batteries last for years in actual use.
Different types of items can use different delay periods. For example, carts and other mobile carriers might be set to a short period since they're easily moved. Pallets, which might be in transit, might have a shorter delay set.
RTLS can also be used to monitor critical safety equipment. An RTLS tag on a fire extinguisher, portable defibrillator, HazMat kit or other health-or safety-related item could ensure that the item is where it's supposed to be—something that's rather important in an emergency.
Some RTLS systems use a dedicated RF infrastructure. This is particularly useful if many tags and many antennas are installed in a facility. Other RTLS systems use a WiFi infrastructure and can piggyback on existing infrastructure.
Today's logistics and warehouse management challenges aren't all fun and games. But real time locating systems can help turn a frustrating situation into... well... child's play.
Real time locating systems employ active RFID tags that periodically broadcast their presence and identity— rather like the "peek" in the child's game.