Mobile Phone Based Drifting Lagrangian Flow Sensors J. Beard, K. Weekly, C. Oroza, A. Tinka, A. Bayen University of California Berkeley Departments of Mechanical, Electrical, Computer Science, Civil, and Environmental Engineering
Motivation Eulerian sensor stations Eulerian fixed position Expensive Insufficient data Lagrangian floating sensors Lagrangian flow thru environment Aka drifters Mobile sensing in a cyber-physical infrastructure Cyber electronic communication network Physical governed by physical laws Mobile phone technology Communication Computation Sensing 13 December 2012 University of California Berkeley 2
Sacramento-San Joaquin River Delta 2/3 of California s fresh water passes thru the Delta Provides fresh water to 22M+ people $10B+ in agriculture Aging infrastructure E.g. levee collapse Challenges to sensing Debris, shores, boats, &c. Begin by monitoring flow Eventually monitor quality 13 December 2012 University of California Berkeley 3
Water cyber infrastructure In situ sensors embedded in the environment Field team for support Wireless network for realtime sensor data communication State estimation: modeling flow dynamics with partial differential equations 13 December 2012 University of California Berkeley 4
Floating sensor generations Generation 1 & 2 3 4 (Android) Image Cost $1200 $2500 $490 Assembly time 60 h 10 h 2 h Mission time 24 h 24 h 48 h Actuation None Twin propellers None Height 39 cm 47 cm 29 cm 13 December 2012 University of California Berkeley 5
Gen. 4 (Android) floating sensor 11 parts Software Android OS Floating sensor app 48-hour battery w/o conserving power Residence time of a water particle in the Delta Compact storage in lab and on vessels Center of mass is much lower than the center of buoyancy 13 December 2012 University of California Berkeley 6
Design Design drivers Size Utility vs. battery capacity Shape (symmetry) Tracking fidelity vs. actuation Waterline Wind exposure vs. RF reception Reliability, usability, and cost Ease of use in harsh environments Eliminate need for user interaction Off the shelf materials Why not shorter than previous generations? Ideal water particle Large drag profile Software GPS location collection Valid flag calculation Tilt sensing via accelerometer Data transmission and logging Cellular data communication to remote servers Mechanical Single water-proof seal Limited machining Wrenched seal Electrical No custom electronics 13 December 2012 University of California Berkeley 7
Applications How they are used? Deployment and retrieval scenario What do they provide? Time series of their position Estimation of the velocity of the water which they travel thru 13 December 2012 University of California Berkeley 8
Real-time sensing What are the goals of realtime sensing and how do the Android floating sensors help? Flow observations Obstacle detection Boundary conditions provided by Satellite imagery Fixed sensor stations 13 December 2012 University of California Berkeley 9
May 9 th experiment Successful operation 70 Android floating sensors 8 hours 5.5+ km span of river 13 December 2012 University of California Berkeley 10
Conclusion & future directions Numerous successful operations No leaks / only 2 lost drifters (1 returned) Continued usage by Stanford University and UC Davis Interest from the California Department of Water Resources (DWR) Active / cheaper Android floating sensor Further software development Power management Fleet control 13 December 2012 University of California Berkeley 11
Contact & thanks For more information, contact Project website float.berkeley.edu Prof. Alexandre M. Bayen bayen@berkeley.edu Jonathan Beard beard.jonathan@gmail.com Thanks to CITRIS citris.berkeley.edu NSF Grants: CBS-0615299, CNS-0915010 Award: CNS-0845076 San Francisco State University Personnel & vessel support 13 December 2012 University of California Berkeley 12