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Solving the challenge of locating countless objects by integrating RFID technology with practical room-level infrastructure, enhancing search efficiency and reducing manual effort.
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Sherlock: Automatically Locating Objects for Humans • Aditya Nemmaluri, Mark D. Corner, Prashant Shenoy • Department of Computer Science • UMass Amherst
Can’t Find Your Keys? • People own uncountable objects (1000s?) • Humans don’t posses DB indexing abilities • Lose, lend, misplace, waste time, rebuy, ... • A grand challenge for pervasive computing
Wouldn’t it be Nice? Index, Search, and Locate Anything!
RFID Changes Everything • Non-computers become computers • For dimes, pennies, or less • no batteries = scalability • Affix tags to every inanimate object • Clothes, books, tools, doors, food, trash...
Challenges • Localization: the finer the better • User interfaces: augmented reality • Search: temporal and physical data • Security and privacy
Sherlock • Infrastructure based, steerable antennas • Combine with PTZ cameras • Localize objects to an small area • Rely on humans to do the rest • Practical demonstration in a realistic setting • Search and display results
RFID Endpoint • RFID reader equipped w/steerable antenna • Can identify each passive tag within view • Can’t localize them directly • Localization depends on (not)seeing tag • Antenna has limited beamwidth/range • Sherlock steers antenna intelligently
Idealized Localization Can locate tag to narrow (10 degree sliver)
Does This Work? • Set up 30 tags in a near-ideal setting • 60-70 degree antenna beam width (spec) • Expect to see 60-70 degree tag beam width • Expect low error rates • tag is actually in that narrow 10 degrees
Realistic Setting • 100 Tags in a one person office • books, doors, coffee mugs, staplers... • metal cabinets, desks, windows, walls...
Reflections/Occlusions Occlusions Reflections
Conservative Correction Add 30-45 degrees depending on measured beamwidth Yields zero error rate 10 degree sliver becomes 70-100 degrees
Multiple Antennas • Fuse 3D area from multiple antennas • Chances are one gets a good view of tag • Use a 3D intersection algorithm
Scan Strategies • Localization takes time (lots of fine steps) • Delays detection of new or stale objects • Coarse, Fine, Localize: see paper for details
Implementation • Mechanically steerable antenna • substitute for electronically steerable • Two antennas (range: ~3m) • ThingMagic Mercury5 Reader • Alien RFID tags 98x12mm 76x76mm • libGTS graphics library for 3D Intersections
Steerable Antenna PTZ Base as stand in for electronic steering
Evaluation • Same office environment as before • Can it localize objects quickly? • Can it localize to a reasonable volume?
Single Antenna Useable localization Half of objects are difficult to localize
Two Antennas Many difficult localizations solved with second antenna
Visualization • For each localization take snap shot of area • Project volume onto 2D photo • Works if camera has view of object
Related Work • RFID Localization (Hähnel et. al) • SLAM robotics problem • Ferret (Liu et. al) • mobile reader • RFID Radar • TTF technology, precise timing
Sherlock • Practical room-level object indexing system • Iterative and robust localization algorithm • Visualization and search system