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MIT figured out a better way for drones to use RFID technology

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With a clever hack

RFID drones Image courtesy of MIT

A research team at MIT has created a clever new way for drones to use RFID technology in warehouses for stock-keeping purposes. It lets companies use much smaller, safer drones to find stuff in giant buildings than was possible before.

When RFID tags started replacing bar codes in warehouses, they were supposed to help automate and improve the accuracy of inventory management. The small tags, which are briefly activated by the radio frequency of a reader, have been adopted and used everywhere from pet microchips to optional implantable chips for company employees.

To understand why MIT’s drone hack is useful, you need to know a little about how RFID works and is commonly used. Unlike bar codes, RFID tags don’t need line of sight to be read and the information contained on a tag can be more extensive and more easily altered. They can also be pretty cheap, although lower-end tags have a smaller scan range. Despite RFID’s benefits, it has limitations: there’s no set RFID standard for tracking goods and “tag collision” can prevent readers from picking up signals from multiple tags at the same time. The way RFID tags are scanned also presents awkward problems within large warehouses. Fixed RFID readers and reader antennas can only scan tags that pass through set thresholds, and hand-held readers require people on the floor to go out and manually scan items.

Several companies have addressed the tech’s problems with RFID-reading drones. The drones, which are equipped with RFID readers, can take the place of inventory-taking humans, and complete the job with less hassle and time. High boxes that a person would need a ladder or lift to access can be easily reached by a drone, drones can be programmed to independently navigate spaces, and they’re better at executing large-scale repetitive tasks — like taking inventory — than humans.

While current RFID drones on the market technically solve many of the inelegant problems with RFID, they require bulky readers to be attached to the drone’s body. This means they have to be large enough to support the size and weight of the additional hardware, making them potentially hazardous if they crashed into a human, and relegating them to wide spaces. A large RFID drone also might not be able to navigate to see inventory stacked behind other inventory if weaker tags are used.

MIT’s new solution, called Rfly, allows a drone to read RFID tags without strapping a giant reader to it. Instead, the drone is equipped with a tiny relay, which acts like a Wi-Fi repeater. The drone receives the signal sent from a remote RFID reader and then forwards it to read tags nearby. Since relays are small, this means more compact drones with plastic parts can be used — ones that can fit in narrower spaces and don’t pose a danger of injuring people.

Rfly-outfitted drones make up for not having a physical RFID reader by taking several readings of each tag as they fly by. But, that isn’t enough to determine the tag’s exact location. The drone’s constant movement creates a signal delay, so the reader can’t accurately determine the drone’s location relative to the tag its scanning. MIT solved that by also affixing the drone with its own RFID tag, which is about the size of a grain of rice. The drone alternates between relaying the reader’s signal and pinging back information from its own RFID tag. This allows the system to triangulate the drone’s position, and then locate the tag being scanned to within a few inches.

MIT’s Rfly system is essentially a clever hack for an existing technology. It not only eliminates the need for additional RFID readers, but since it’s a much lighter solution, allows for tiny drones to do the same job as larger ones. The research team is currently testing out the system with a retailer in Massachusetts. As of now, Rfly drones need humans to operate them, but they could eventually be autonomous, freeing humans up to do more important work while they take on our repetitive tasks.