Transcript Sherlock: Automatically Locating Objects for Humans

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
Sherlock Architecture
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
Localization-Pan
Localization-Zoom
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
Ideal Results
Realistic Setting
• 100 Tags in a one person office
• books, doors, coffee mugs, staplers...
• metal cabinets, desks, windows, walls...
Realistic Results
Reflections/Occlusion
s
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?
Office Environment
Latency
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
Web Interface
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