A Mobile Sensor Droplet for Mapping Hidden Pipeline

PipeProbeA Mobile Sensor Droplet for Mapping Hidden Pipeline

Tsung-te (Ted) Lai Yu-han (Tiffany) Chen

Polly Huang Hao-hua Chu

National Taiwan University

1. Motivation2. Layout mapping algorithm3. Design iterations4. Testbed and evaluation5. Limitations6. Related work7. Future work

Outline

Water scarcity

Series10.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%Toilet

Clothes Washer

ShowerFaucet

Leakage

Other Domestic Bath

Dish Washer

Source: Residential End Uses of Water, AWWA Research Foundation

35 liters/person/day

Residential water usage

ShowerFaucet

x18

Residential water usage

Motivation

hidden pipes

Pipes are often hidden behind walls or underneath floors

Motivationleaking

leaking

Leakage often occurs at the joints of tubes

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

1. Drop PipeProbe into the main water inlet2. Open a water outlet3. Collect sensor readings from the pressure and gyro sensors4. Analyze the pressure and rotation angle readings

Mapped topology

Open another water outlet to map out the fork path

Gyroscope graph Pressure graph


Outline

Problem formulation

Horizontal layer

Vertical tube

Starting position

Ending position

Problem formulation

Assumptions

1. Diameter of pipes is uniform2. Turns are 90-degree

Assumptions

1. Diameter of pipes are uniform2. Turns are 90-degree

Layout mapping algorithm

(2) Conquer

(1) DivideVertical tube

(3)MergeHorizontal

layer

(3)Merge

(2) Conquer



(3)Merge Horizontal

layer

(3)Merge

Time

Divide phasepartition pipes into vertical tubes and horizontal layers of tubesuse pressure graph to detect vertical-to-horizontal or horizontal-to-vertical turns.

(2) Conquer



(3)MergeHorizontal

layer

(3)Merge

∆height

940

960

980

1000

1020

1040

1060

1080

1100

1120

Time

Pre

ssur

e(m

bar)

∆P =

Conquer phase Estimate vertical tube length Based on pressure principle to estimate vertical tube length

(2) Conquer


(3)MergeHorizontal

layer

(3)Merge


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 = ∆t * v

Time

t2t1∆t = t2 –t1

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

(2) Conquer



(3)MergeHorizontal

layer

(3)Merge

θ

360 degrees of freedom

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

Starting position

Ending position

Merge phase How to determine θ?


Outline

1Prototype PressureSensor

Mote

Design: pressure sensor + Eco mote in a round and flat capsule Problem: unstable flow velocity

2Prototype

Design: spherical capsulecapsule flow velocity ≈ water velocity added weight such that PipeProbe’s density ≈ water density

Problem: arbitrary rotation caused unreliable sensor reading

3 PressureSensor

Gyro

Bottom

Prototype

Design: heavy bottom halfpressure sensor on the top, gyro sensor flat on bottom

Problem: arbitrary horizontal spinning caused high noisy gyro reading

Design: tail-like fin aligns capsule’s heading to the water flow direction

4 Final Prototype

Tail-like Fin

1. Pressure sensor on top and gyro sensor vertical to ground2. Flow velocity ≈ water velocity 3. Flow straight

Gyro graph Pressure graph


Outline

Evaluation metric #1: length error

Actual length: L1

Estimated length:L2

Length error = actual pipe length – estimated pipe length = L1 – L2

Evaluation metric #2: positional error

estimated position (x2, y2, z2) error

actual position(x1, y1, z1)

Positional error (of the pipe turning point) = Euclidean distance between the actual and estimated positions

41Experimental testbed

42Water pipeline testbed

43Control valves to produce different flow paths

44Create a flow path

45

inlet

outlet outlet

Testbed spatial layout (unit: cm)

1 2 3 4 5

6 7 8 9 10

11 12

flow path

Experimental Procedure (12 test scenarios)

pipe probe (2010)Test 11 (flow path in red)

Test 11 (actual flow path)

flow path

Test 11 (1st mapping trip)

flow pathestimates

Test 11 (2nd mapping trip)

flow pathestimates

flow pathestimates

Test 11 (3rd mapping trip)

flow pathestimates

Test 11 (4th mapping trip)

flow pathestimates


55

6 mapping trips per test scenarioDataset stats: - 516 length estimates - 588 positional estimates - avg pipe length: 76cm - avg flow distance: 335cm

Mapping trip results (12 test scenarios)

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 pipe length errors

57

CDF of positional errorsMedian error < 7cm; 90 percentile error < 16cm

58

accumulation effect

Positional errors vs. flow distance

1. Introduction2. Layout mapping algorithm3. Design iterations4. Testbed and evaluation5. Limitations6. Related work7. Future work

Outline

60Limitation: uniform pipe diameter

Limitation: capsule size


Outline

NAWMS (SenSys’08)

Detect and localize leakage by pressure and ultrasonic sensors

PipeNet (IPSN’07)

toilet

kitchen sink

shower

HydroSense (Ubicomp’09)Single-point pressure-based sensor of water usage

Multi-pointSensing

Single -pointSensing

Mobile Sensing

NAWMS HydroSense PipeProbe

PipeNet

Comparison to relate work


Outline

68

Petrochemical plant

Thank reviewers & shepherd for valuable comments

Questions & Answers

PipeProbe: A Mobile Sensor Droplet for Mapping Hidden Pipeline

Tsung-te (Ted) Lai, Yu-han (Tiffany) ChenPolly Huang, Hao-hua Chu

Ubicomp labhttp://mll.csie.ntu.edu.tw

National Taiwan University

A Mobile Sensor Droplet for Mapping Hidden Pipeline

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