Case sharing of the use of RF Localization Techniques Dr. Frank Tong LSCM R&D Centre LSCM Summit 2015
Outline A. LBS tracking and monitoring 1) Case of anti-wandering-off tracking vest system in elderly care B. Location information and navigation 2) Case of walking cane and baggage buggy navigation 3) Case of shopping cart navigation 4) Case of RF robotic navigation for autonomous inventory check 5) Case of D-GPS enhanced geo-positioning in fleet management C. Summary
Case 1 : Anti-wandering-off tracking vest system in elderly care
RFID + GPS Tracker Embedded Vest Demented patients tend to have a behavior of wandering TWGHs Wong Cho Tong Social Service Centre is trial deploying RFID + GPS to prevent their elder service users from wandering lost A system that can locate the lost elder person, if any, quickly and conveniently, which is low in cost and easy to use GPS Tracker - 68x41x21mm - 60g ** For reference only Wander-off Alert System Washable RFID Tag
Solution Overview RFID Reader at door GPS Internet Geo Data Back Office Monitoring Elderly People Mobile Tracking
Case 2 : Walking Cane Navigation for the Blind
RFID as Low-Cost LBS Infrastructure LBS navigation guide to visually impaired people Low cost infrastructure of maintenance-free passive RFID tags embedded in the guiding tiles Affordable RFID reader embedded in the walking sticks of the blind The system has been installed in the Rehabilitation Center under the Hong Kong Society for the Blind Further deployment in public area is under way.
3.1mm Path of Development of LSCM Reader Chip From Reader Chip to Reader Module 3.1mm Examples of Passive RFID tags in guiding tiles and metal-base guiding strip
Smart Guiding Stick for Visually Impaired People Turn Right To Gate No.38 RFID Reader Antenna Other Extended Use of Stick RFID Reader
Case 3 : Shopping Cart Navigation
PDOA vs RSSI RSSI Received Signal Strength Indication Simple to set up. Triangulation in software with backscattering signal strength severely affected by propagation environment Unstable, require tuning all the time PDOA Phase Difference of Arrival Not sensitive to propagation environment, tagged object properties, tag and reader antenna orientation, etc. Backscattering phase does not vary with the incident power on the tag Mostly, problems of PDOA can be approximated with free space or similar distance-dependent model PDOA has better precision and stability than RSSI for passive tag localization
Phase Calculation in PDOA Model The relationship between the RSSI and inphase (I) / quadrature (Q) components of the demodulated tag signal is as follows: (x,y) (x1,y1) d1 d2 (x2,y2) Triangulation with the measured distances
Basic FDOA system block diagram Antenna 1 Antenna 2 Antenna 3 Antenna 4 RF Switche s Leakage Carrier Cancellation RF & Analog Front End MCU FPGA LCC Board Location reader Board Digital Base Band Board Leakage-carriercancellation board Location reader front-end Board
Case of Passive RFID Navigation in Supermarket
Case 4 : RF robotic navigation for autonomous inventory check
What is Ultra-Wideband (UWB) A wireless technology utilizes large bandwidth (BW) for better performance. IEEE 402.15.4-2011 UWB Impulse-Radio (IR-UWB): physical layer for positioning. 15 channels in total; Bandwidth: 500 MHz to 1400 MHz Precise ranging: < 50 cm error Short pulse, robust to multipath interference: Good for indoor applications
Range calculated by signal s Time-of- Flight (ToF): T p = T 1 T 2 2 d = c T p Ranging Technique Localization: Center frequency = 4 GHz Signal BW = 500 MHz.
Case of robot navigation for warehouse automation Smart warehouse Off-shift autonomous robot operations, e.g. taking stock on shelves Planned path around warehouse, UWB guided navigation Robot is tagged Path tracked by 3 anchors Error 20 cm
Case 5 : D-GPS enhanced Geo-positioning in logistic fleet management
Differential GPS (D-GPS) Measured distance between the receiver and the satellite P R = d + c t r + n P R is pseudorange by receiver d is actual distance from satellite t r is satellite signal delay (e.g. ionospheric delay) Ionospheric delay gradient model With known geo-position of reference stations, we can evaluate I 1 I1 I1 grad ( I1) (, ) x y U B C I 1 x U, y U = I 1 x A, y A + A grad I1 ds Thus, satellite s distance can be corrected, user s GPS location can be enhanced in accordance I (, ) 1 xa ya A I (, ) 1 xu yu User
Base-station of the SatRef system
DGPS Data Correction Service SatRef System Data Center in Lands Department DGPS Correction Server Support multiple GNSS systems BeiDou Navigation Satellite System (BDS) Global Positioning System (GPS) GLObal NAvigation Satellite System (GLONASS) Improve Accuracy and Availability Smart Phone OBU LBS applications
DGPS Test at Airport Island Fixed the GPS device (Smartphone) on the top of the survey car. Fixed the RTK device (industrial grade) on the survey car as benchmark
Mobile Accuracy Mean (m) RMS (m) 4.1 4.5 RTK Accuracy Survey Grade Equipment Centimeter level accuracy Benchmark purpose DGPS Accuracy Mean (m) RMS (m) 0.4 1.8
DGPS Test with Lands Dept DGPS RAW GPS 21% 2% 77% 47% 6% 47% within 2m 2m ~ 5m > 5m within 2m 2m ~ 5m > 5m
DGPS Test with Autotoll OBU GPS After DGPS Correction ** OBU takes position for every 30 seconds
Summary D-GPS Vest Outdoor Accuracy BB Tag Premises Low Infra cost Low user cost UWB Robustness Cart 10m Cane 1m
~ Thank You ~