GPS and RFID

Passive radio frequency tags are relatively inexpensive to manufacture and embed with a small amount of binary information. This allows them to become a “Swiss army knife” solution to a multitude of problems, such as inventory management, pet identification, or personnel tracking. There seems to be few places the tags aren't being put.

The next level of automation will combine RFID and robotics. Robotic devices can perform most of the labor-intensive (or boring) tasks to stock, move, label or query inventory.

So, how can you tell a multi-functional robot where it is?

There has been a lot of research in using a tag reader's Receive Signal Strength Indicator (RSSI) capabilities for positioning. The idea is simple: the closer the tag, the larger the value of the indicator. The further away, the smaller.  With two antennas, it becomes possible to derive coordinates. Or so the thought goes, until tried. Due to the physics of how an antenna works, the effect of bouncing radio waves off surfaces and other factors, positioning based on RSSI alone is error prone.

The answer, this time, comes from the secondary function of the tag. Positioning coordinates can be embedded within the tag, which in turn are placed on walls or floors. As the robot navigates a passage, its reader can use the tag with the strongest RSSI to determine just where it's at. It can use tag identification filtering to limit which tags it uses for positioning.

You can now think of your inventory as a geocache. Instead of the painful process of telling a robotic device how to get there, you tell it where to go. An internal compass for direction, corrected by tag information would be enough. Direct flooring plans are not necessary provided the building is adequately tagged. Again, the expense of this type of system is in the robot, not the tags.

A robot armed with precise GPS coordinates would be a luxury. Fortunately, for the system described here, it isn't necessary. Tactical coordinates, relative to the internals of the building/area, is the minimum data required to operate.

There are several projects and companies investing in this as a kind of hybrid solution. Some solutions are even used in cars, proving rfid can compliment a wide variety of everyday solutions.