A Mobile Sensor Droplet for Mapping Hidden Pipeline
Tsung-te (Ted) Lai
Yu-han (Tiffany) Chen
Polly Huang
Hao-hua Chu
National Taiwan University
Outline
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7.
Motivation
Layout mapping algorithm
Design iterations
Testbed and evaluation
Limitations
Related work
Future work
Water scarcity
Residential water usage
30.00%
Toilet
25.00%
35 liters/person/day
Clothes
Washer
20.00%
Shower
15.00%
Faucet
Leakage
10.00%
5.00%
Other
Domestic
0.00%
Source: Residential End Uses of Water, AWWA Research Foundation
Bath
Dish
Washer
Residential water usage
Shower
Faucet
x18
Pipes are often hidden behind walls or underneath floors
hidden pipes
Motivation
Leakage often occurs at the joints of tubes
leaking
leaking
Motivation
PipeProbe system
‧Map 3D spatial topology of water pipelines
‧Mobile sensing approach
‧Leverage natural water flow for mobility
ECo wireless sensor mote (Pai Chou, UC Irvine)
‧ Low-power
‧ 13mm(L) x 11mm(W) x 7mm(H), 3 grams
‧ Radio
‧ 3-axis accelerometer
Pressure sensor
‧0 – 14 bars, resolution: mbar
‧< 5uA operating current
Gyroscope
‧yaw (z) axis rotation angle
‧ ±300 deg/second
Mapped topology
1. Drop PipeProbe into the main water inlet
2. Open a water outlet
3. Collect sensor readings from the pressure and gyro sensors
4. Analyze the pressure and rotation angle readings
Open another water outlet to map out the fork path
Gyroscope graph
Pressure graph
Outline
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4.
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7.
Motivation
Layout mapping algorithm
Design iterations
Testbed and evaluation
Limitations
Related work
Future work
Vertical tube
Horizontal layer
Problem formulation
Starting position
Ending position
Problem formulation
Starting position
Ending position
Problem formulation
Assumptions
1.
2.
Diameter of pipes is uniform
Turns are 90-degree
Assumptions
1.
2.
Diameter of pipes are uniform
Turns are 90-degree
Layout mapping algorithm
Vertical tube
(1) Divide
Horizontal
layer
(2) Conquer
(3)Merge
(3)Merge
Layout mapping algorithm
Vertical tube
(1) Divide
Horizontal
layer
(2) Conquer
(3)Merge
Divide phase
partition pipes into vertical tubes and horizontal layers of tubes
use pressure graph to detect vertical-to-horizontal or horizontal-tovertical turns.
Time
Layout mapping algorithm
Vertical tube
(1) Divide
Horizontal
layer
(2) Conquer
(3)Merge
(3)Merge
Conquer phase
Estimate vertical tube length
Based on pressure principle to estimate vertical tube length
1120
Pressure(mbar)
1100
1080
∆P = ∆height
1060
1040
1020
1000
980
960
940
Time
Layout mapping algorithm
Vertical tube
(1) Divide
Horizontal
layer
(2) Conquer
(3)Merge
(3)Merge
Conquer phase
Map horizontal pipe layout
(1) Detect horizontal turns linking horizontal pipes
based on a change in rotation angles
(2) Estimate horizontal tube length
Time
Conquer phase
Map horizontal pipe layout
(1) Detect horizontal turns linking horizontal pipes
based on a change in rotation angles
(2) Estimate horizontal tube length
- ∆ length = time * water flow velocity
- water flow velocity (constant)
= volume of water outflow / pipe cross-section area
~ capsule moving velocity
∆ length = ∆t * v
∆t = t2 –t1
t1
t2
Time
Layout mapping algorithm
Vertical tube
(1) Divide
Horizontal
layer
(2) Conquer
(3)Merge
(3)Merge
Merge phase
Link vertical pipes to start/end points of each horizontal pipe layout
Problem: Vertical-to-horizontal turn angle (θ) is non-deterministic
θ
360 degrees of freedom
Merge phase
How to determine θ?
Starting position
Θ
Ending position
Outline
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Motivation
Layout mapping algorithm
Design iterations
Testbed and evaluation
Limitations
Related work
Future work
Prototype
Pressure
Sensor
Mote
Design: pressure sensor + Eco mote in a round and flat capsule
Problem: unstable flow velocity
Prototype
Design:
spherical capsule
capsule flow velocity ≈ water velocity
added weight such that PipeProbe’s density ≈ water density
Problem: arbitrary rotation caused unreliable sensor reading
Prototype
Pressure
Sensor
Gyro
Bottom
Design:
heavy bottom half
pressure sensor on the top, gyro sensor flat on bottom
Problem: arbitrary horizontal spinning caused high noisy gyro reading
Final
Prototype
Tail-like Fin
Design: tail-like fin aligns capsule’s heading to the water flow direction
Gyro graph Pressure graph
1. Pressure sensor on top and gyro sensor vertical to ground
2. Flow velocity ≈ water velocity 3. Flow straight
Outline
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6.
7.
Motivation
Layout mapping algorithm
Design iterations
Testbed and evaluation
Limitations
Related work
Future work
Evaluation metric #1: length error
Length error = actual pipe length – estimated pipe length
= L1 – L2
Actual length: L1
Estimated length:L2
Evaluation metric #2: positional error
Positional error (of the pipe turning point)
= Euclidean distance between the actual and estimated
positions
estimated position
(x2, y2, z2)
(x1, y1, z1)
actual position
Experimental testbed
41
Water pipeline testbed
42
Control valves to produce different flow paths
43
Create a flow path
44
Testbed spatial layout (unit: cm)
inlet
outlet
outlet
45
Experimental Procedure (12 test scenarios)
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2
3
4
5
6
7
8
9
10
11
12
flow path
pipe probe (2010)
Test 11 (flow path in red)
Test 11 (actual flow path)
flow path
Test 11 (1st mapping trip)
flow path
estimates
Test 11 (2nd mapping trip)
flow path
estimates
Test 11 (3rd mapping trip)
flow path
estimates
Test 11 (4th mapping trip)
flow path
estimates
Test 11 (5th mapping trip)
flow path
estimates
Test 11 (6th mapping trip)
flow path
estimates
Mapping trip results (12 test scenarios)
6 mapping trips per test scenario
Dataset stats:
- 516 length estimates
- 588 positional estimates
- avg pipe length: 76cm
- avg flow distance: 335cm
55
CDF of pipe length errors
Horizontal length error > vertical length error
- Estimation method is different
Overall median error < 2cm; 90 percentile error < 7cm
- Precise enough to locate hidden pipes
56
CDF of positional errors
Median error < 7cm; 90 percentile error < 16cm
57
Positional errors vs. flow distance
accumulation effect
58
Outline
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Introduction
Layout mapping algorithm
Design iterations
Testbed and evaluation
Limitations
Related work
Future work
Limitation: uniform pipe diameter
60
Limitation: capsule size
Outline
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6.
7.
Motivation
Layout mapping algorithm
Design iterations
Testbed and evaluation
Limitations
Related work
Future work
NAWMS (SenSys’08)
PipeNet (IPSN’07)
Detect and localize leakage by pressure and ultrasonic sensors
HydroSense (Ubicomp’09)
Single-point pressure-based sensor of water usage
toilet
kitchen sink
shower
Comparison to relate work
Multi-point
Sensing
Single -point
Sensing
NAWMS
HydroSense
PipeNet
Mobile
Sensing
PipeProbe
Outline
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2.
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5.
6.
7.
Motivation
Layout mapping algorithm
Design iterations
Testbed and evaluation
Limitations
Related work
Future work
Petrochemical plant
68
Thank reviewers & shepherd for valuable
comments
Questions & Answers
PipeProbe:
A Mobile Sensor Droplet for Mapping Hidden Pipeline
Tsung-te (Ted) Lai, Yu-han (Tiffany) Chen
Polly Huang, Hao-hua Chu
Ubicomp lab
http://mll.csie.ntu.edu.tw
National Taiwan University