triopusnet : automating wireless sensor network deployment and replacement in pipeline monitoring

1

TriopusNet: Automating Wireless Sensor Network

Deployment and Replacement in Pipeline

MonitoringIPSN 2012

Ted Tsung-Te Lai, Wei-Ju Chen, Kuei-Han Li, Polly Huang, Hao-Hua Chu

NSLab study group 2012/03/26Reporter: Yuting

2

PipeProbe: A Mobile Sensor Droplet for Mapping Hidden Pipeline

Jeffery reported it at study group last year◦ http://nslab.ee.ntu.edu.tw/NetworkSeminar/index.

php?action=schedule&year=2010_Fall&pattern=

http://mll.csie.ntu.edu.tw/papers/PipeProbe_Sensys10.pdf

http://mll.csie.ntu.edu.tw/papers/PipeProbe_Sensys10.pptx (Best Presentation Award)

Previously…

http://nslab.ee.ntu.edu.tw/NetworkSeminar/index.php?action=schedule&year=2010_Fall&pattern=






http://mll.csie.ntu.edu.tw/papers/PipeProbe_Sensys10.pptx



3

Sensor network data is wirelessly transmitted to nearby gateway nodes The gateway is a (laptop) computer wired to a Kmote node

The overview of TriopusNet

4

Abstract Introduction System Overview, Assumptions and

Limitations Hardware Design System Design Experiment Discussion Conclusion

Outline

5



Outline

6

Autonomous sensor deployment◦ For pipeline monitoring

Centralized repository at pipeline’s source◦ Automatically releasing nodes

Placement:◦ Nodes will latch itself in pipeline

Replacement:◦ Source will send new nodes to replace failed one,

ex: low battery level; experiences a fault

Abstract

7

Evaluated on testbed

Advantage:◦ Less sensor nodes to cover a sensing area◦ High data collection rate◦ Recover from the network disconnection

Abstract

8



Outline

9

Flow assurance◦ A major safety concern◦ Ex: clean and uncontaminated water

Traditional method:◦ Manually placing, but it’s hard and waste time

TriopusNet◦ Automated◦ Scalable◦ Human effort strictly needed only at the start to

deposit mobile sensors

Motivation

10

Sensor deployment algorithm depends on:◦ Sensing coverage◦ Network connectivity ◦ Deployment location

Upon arrival at its deployment location, a traveling sensor activates its latching mechanism

Sensor Deployment

11

Upon detection of low battery level (or a fault), the sensor node retracts its mechanical arms to detach itself◦ Flow in the pipes carries it out◦ System releases a fresh sensor node and runs the

sensor replacement algorithm ◦ And adjust the locations of existing ones

Sensor Replacement

12

Automates sensor deployment and replacement by leveraging natural water propulsion to carry sensor nodes throughout pipes

Real prototype and pipeline testbed show that this quality deployment using no more sensor nodes

Successfully replaced a battery-depleted sensor node with a fresh sensor node while recovering data collection rate from the departure of a battery-depleted sensor node

Main Contributions

13



Outline

14

Pipelines interconnect a set of vertical and horizontal pipes, starting with a single water inlet and ending at multiple water outlets

Pipelines form a virtual tree! The inlet also serves as

the storage point wheresensor nodes are depositedinto a dispatch queueat the start of deployment

System Overview

15

A significant size reduction in 2nd type - 6 cm in diameter◦ May still get stuck in some pipes

(a~d): gyro, water pressure sensors, relays, Kmote(TelosB-like w/o USB)◦ In water, sonar and light are better than radio -> they leave the choice in future

One customized motor drives three arms in 2nd type

TriopusNet node

16

Preparation Step Sensor Deployment Step Sensor Latching Step Sensor Replacement Step

Four Steps

17

Pipeline spatial topology must be measured a-priori as an input for automated sensor deployment◦ PipeProbe system (their previous work)

Inlet must be filled with sensor nodes Faucets in the pipeline are turned on

◦ Manually or automatically (by installing a remote-control actuation device)

One-time manual effort

1. Preparation Step

18

Runs the sensor deployment algorithm prior to releasing

Then sends the “release” message including the deployment position, to the head sensor node

2. Sensor Deployment Step

19

Sensor node continuously computes its current location as it travels

When the node approaches its deployment position:◦ Latch itself◦ Report the completion◦ Triopusnet releases the next (repeat step2)

3. Sensor Latching Step

20

Some sensor node may report low-battery to the system◦ Detach itself, carried out by the water◦ Triopusnet releases fresh one

4. Sensor Replacement Step

21

Must be installed prior to any sensor node deployment inside the pipelines

Must have wireless communication with at least one in-pipe sensor node

Must also have a network connection to a computer for:◦ Remote control◦ Data logging◦ Automated sensor deployment and replacement

algorithms

Gateway Nodes

22



Outline

23

Linear actuator controls a mechanical arm◦ Push: SW1&4, pull: SW2&3

Motor calibration was achieved by adding a spiral gear that connects and pushes three separate gears

Some Information (Not All Here)

24



Outline

25

Placing nodes close to the releasing point early may result in blockage◦ Transforms the layout of the pipelines into a tree◦ Subsequently runs a post-order traversal of the tree◦ Deploying nodes in the above sequence will:

assure covering all pipes without blocking others

1. Sensor Deployment Order

26

Before sensor nodes can be released, the sensor deployment algorithm computes first the coarse-grain positions:◦ The pipe segment◦ The approximate latching point

Assume a simple coverage function (but not limited)◦ Circle with radius R◦ “Subtracting 2*R distance from the most recently

deployed sensor node in segment S gives the position of the new one”

◦ “If segment S is not long enough to accommodate the new sensor node, the new sensor node is placed in the next segment”

2. Sensor Deployment (Position)

27

The sensor movement algorithm computes first the flow paths from the inlet to each outlet

Then selects a path intersecting the pipe segment the node is positioned to

3. Sensor Movement (Faucet Turn-On Order)

28

There are both vertical and horizontal pipes Adopts the pipeline localization technique

from the PipeProbe system [4] Sensor node tracks its location by:

◦ Counting the number of turns with: pressure and gyroscope sensors

◦ Segment offset distance from the last run: Vertical: the change in water pressure Horizontal: multiplying velocity by traveled time

Buoyancy? -> the sensor node was designed with its weight density equal to the water density

4. Sensor Localization

29

Turning on radio after latching and measures the packet received rate for the link quality

Upon detecting a low packet received rate, the sensor node moves one increment closer to its downstream sensor node

Until a pre-defined link quality threshold is met, sends a “latching completion” packet◦ May be tricky to ensure the first sensor node of an

intermediate segment is connected to the sensor nodes of all downstream segments May moves into one of the unreachable downstream

segment Repeats until full sensing and network coverage

5. Sensor Latching

30

Collection tree protocol (CTP) implemented in TinyOS 2.1

Use anycast (provided by CTP) to multiple sinks(gateway nodes) in order to balance traffic load

6. Data Collection

31

Battery-depleted node (determined simply by voltage)

◦ Informs the downstream gateway◦ Faucet can be turned on◦ Downstream nodes are also flushed out◦ Fishing net is inserted at the ends of pipelines

Good nodes◦ Each upstream node repeats:

detachment, movement, localization, reattachment◦ Until the uncovered area reaches the root location◦ System then releases fresh nodes

With a smaller prototype in the future, it will be easier and save more energy!

7. Sensor Replacement

32



Outline

33

6 “transparent” pipe tubes (10 cm in diameter)

2 water valves control the volumetric flow rate on each flow path

Experimental Testbed

34

And:time to replacementenergy consumption (2 cases)

Performance Metrics

35

System parameter:◦ PRR threshold = 95%◦ Water flow velocity = 12.5 cm/sec◦ Each node’s sensing range R >= radio range

4 scenarios * 5 runs/scenario = 20 test runs Data was logged during both:

◦ node deployment and data collection Replacement performance is measured

in scenario #4◦ 20 test runs of node replacement

Experimental Procedure

36

Static deployment: a good baseline for performance comparison◦ Nodes are 90 cm apart ( average radio range

between two sensor nodes in a straight pipe )◦ Might have better DCR, but more redundant

nodes(DCR: Dada Collection Rate)

Deployment - Node Locations

37

The radio range can reach up to 170 cm for nodes placed in different tubes

Benefits of using online deployment

Deployment - Node Locations

38

Indicate whether a network is well connected

80% of the sensor nodes show a data collection rate exceeding 99%◦ And all are above 86.5%

Each sensor node sent 1000 data packets to a gateway node

Deployment - Data Collection Rate (DCR)

39

18,20,20,30 location estimates for scenario 1~4, respectively

Overall median: 7.14cm 90% of the errors are less than 20.45 cm Sufficient for most pipeline applications,

ex: pinpointing the location of pipe leakage

Deployment - Positional Accuracy

40

Time to manually turn on/off faucets is not included here

If the flow velocity is set at 12.5 cm/sec, the average time to deploy nodes is less than 2.5 minutes

Deployment - Time to Deployment

41

Primary energy consumer in the sensor node is in the motor and relays that drive the three mechanical arms◦ (Note: energy consumption: motors > radio >

MCU) A single act of latching:

◦ 1.01W * 2 sec < 1% * 600mAh = 2.16J # of latching:

◦ average is: 2.35; 90% of nodes required less than 5

Deployment - Energy Consumption

42

DCR before a node reported low-battery level and after the node was replaced:◦ 0.989 and 0.984 respectively◦ Small difference, effective!◦ [YT] But which node are they use? ( last or 2nd last

) DCR without automated replacement: 0.81

Replacement – Data Collection Rate(DCR)

43

Depends on the location of the node and the size of the network

Replacement - Time to Replacement

44



Outline

45

Several assumptions and limitations require extensions before practical deployment◦ Node is too big to be flushed out independently

[YT] If the size is reduced, there may be extra works on gryo measurement

◦ Node placement requires controlling or obtaining the direction of the water flow in the pipes Automatical method:

attaching a sensor-trigger node to activate/deactivate the infrared sensor in each automatic faucet

Before Practical Deployment

46

Nodes are equipped with a water flow sensor

Can infer the current flow path May Releases new nodes whose

destinations must match the current water flow path

An Opportunistic Node Placement Scheme

47



Outline

48

Pipeline monitoring Autonomous sensor deployment Scales down human effort Real pipeline testbed No more nodes than non-automated static

sensor deployment Restore sensing and network coverage from

the departure of a battery-depleted node

Conclusion

49

Strength◦ Save lots of nodes using online deployment method◦ Successfully replaced a battery-depleted sensor node

with a fresh one Weakness

◦ Not adaptive with varying water flow rate now◦ No automatically water faucet now◦ Will the mechanical arms be reliable under strong

water flow?◦ For high traffic load, the deployment performance may

not be as good as now◦ Evaluation for DCR in replacement is not clearly

enough

Comments

50

Thanks for your listening!

triopusnet : automating wireless sensor network deployment and replacement in pipeline monitoring

Documents