IPSN 2012
Ted Tsung-Te Lai, Wei-Ju Chen, Kuei-Han Li, Polly Huang, Hao-Hua Chu
NSLab study group 2012/03/26
Reporter: Yuting
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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=
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http://mll.csie.ntu.edu.tw/papers/PipeProbe_
Sensys10.pdf
http://mll.csie.ntu.edu.tw/papers/PipeProbe_
Sensys10.pptx (Best Presentation Award)
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Sensor network data is wirelessly transmitted to nearby gateway nodes
The gateway is a (laptop) computer wired to a Kmote node
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Abstract
Introduction
System Overview, Assumptions and
Limitations
Hardware Design
System Design
Experiment
Discussion
Conclusion
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Abstract
Introduction
System Overview, Assumptions and
Limitations
Hardware Design
System Design
Experiment
Discussion
Conclusion
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Autonomous sensor deployment
◦ For pipeline monitoring
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Centralized repository at pipeline’s source
◦ Automatically releasing nodes
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Placement:
◦ Nodes will latch itself in pipeline
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Replacement:
◦ Source will send new nodes to replace failed one,
ex: low battery level; experiences a fault
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Evaluated on testbed
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Advantage:
◦ Less sensor nodes to cover a sensing area
◦ High data collection rate
◦ Recover from the network disconnection
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Abstract
Introduction
System Overview, Assumptions and
Limitations
Hardware Design
System Design
Experiment
Discussion
Conclusion
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Flow assurance
◦ A major safety concern
◦ Ex: clean and uncontaminated water
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Traditional method:
◦ Manually placing, but it’s hard and waste time
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TriopusNet
◦ Automated
◦ Scalable
◦ Human effort strictly needed only at the start to
deposit mobile sensors
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Sensor deployment algorithm depends on:
◦ Sensing coverage
◦ Network connectivity
◦ Deployment location
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Upon arrival at its deployment location, a
traveling sensor activates its latching
mechanism
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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
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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
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Abstract
Introduction
System Overview, Assumptions and
Limitations
Hardware Design
System Design
Experiment
Discussion
Conclusion
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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 where
sensor nodes are deposited
into a dispatch queue
at the start of deployment
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A significant size reduction in 2nd type - 6 cm in diameter
◦ May still get stuck in some pipes
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(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
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One customized motor drives three arms in 2nd type
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Preparation Step
Sensor Deployment Step
Sensor Latching Step
Sensor Replacement Step
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Pipeline spatial topology must be measured
a-priori as an input for automated sensor
deployment
◦ PipeProbe system (their previous work)
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Inlet must be filled with sensor nodes
Faucets in the pipeline are turned on
◦ Manually or automatically (by installing a remotecontrol actuation device)
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One-time manual effort
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Runs the sensor deployment algorithm prior
to releasing
Then sends the “release” message including
the deployment position, to the head sensor
node
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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)
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Some sensor node may report low-battery to
the system
◦ Detach itself, carried out by the water
◦ Triopusnet releases fresh one
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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
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
Abstract
Introduction
System Overview, Assumptions and
Limitations
Hardware Design
System Design
Experiment
Discussion
Conclusion
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Linear actuator controls a mechanical arm
◦ Push: SW1&4, pull: SW2&3
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Motor calibration was achieved by adding a
spiral gear that connects and pushes three
separate gears
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Abstract
Introduction
System Overview, Assumptions and
Limitations
Hardware Design
System Design
Experiment
Discussion
Conclusion
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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
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Before sensor nodes can be released, the sensor
deployment algorithm computes first the coarsegrain positions:
◦ The pipe segment
◦ The approximate latching point
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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”
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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
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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
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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
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Repeats until full sensing and network coverage
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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
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Battery-depleted node
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(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
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With a smaller prototype in the future, it will
be easier and save more energy!
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
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



Abstract
Introduction
System Overview, Assumptions and
Limitations
Hardware Design
System Design
Experiment
Discussion
Conclusion
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6 “transparent” pipe tubes (10 cm in diameter)
2 water valves control the volumetric flow
rate on each flow path
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And:
time to replacement
energy consumption (2 cases)
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System parameter:
◦ PRR threshold = 95%
◦ Water flow velocity = 12.5 cm/sec
◦ Each node’s sensing range R >= radio range
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4 scenarios * 5 runs/scenario = 20 test runs
Data was logged during both:
◦ node deployment and data collection
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Replacement performance is measured
in scenario #4
◦ 20 test runs of node replacement
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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)
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The radio range can reach up to 170 cm for
nodes placed in different tubes
Benefits of using online deployment
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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%
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Each sensor node sent 1000 data packets to a
gateway node
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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
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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
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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)
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A single act of latching:
◦ 1.01W * 2 sec < 1% * 600mAh = 2.16J
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# of latching:
◦ average is: 2.35; 90% of nodes required less than 5
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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 )
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DCR without automated replacement: 0.81
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Depends on the location of the node and the
size of the network
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

Abstract
Introduction
System Overview, Assumptions and
Limitations
Hardware Design
System Design
Experiment
Discussion
Conclusion
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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
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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
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



Abstract
Introduction
System Overview, Assumptions and
Limitations
Hardware Design
System Design
Experiment
Discussion
Conclusion
47
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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
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Strength
◦ Save lots of nodes using online deployment method
◦ Successfully replaced a battery-depleted sensor node
with a fresh one
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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
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Thanks for your listening!
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