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TriopusNet : Automating Wireless Sensor Network Deployment and Replacement in Pipeline Monitoring. 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. Previously….

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triopusnet automating wireless sensor network deployment and replacement in pipeline monitoring

TriopusNet: Automating Wireless Sensor Network Deployment and Replacement in Pipeline Monitoring

IPSN 2012

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

NSLab study group 2012/03/26

Reporter: Yuting

previously
Previously…
  • 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)
the overview of triopusnet
The overview of TriopusNet
  • Sensor network data is wirelessly transmitted to nearby gateway nodes
  • The gateway is a (laptop) computer wired to a Kmote node
outline
Outline
  • Abstract
  • Introduction
  • System Overview, Assumptions and Limitations
  • Hardware Design
  • System Design
  • Experiment
  • Discussion
  • Conclusion
outline1
Outline
  • Abstract
  • Introduction
  • System Overview, Assumptions and Limitations
  • Hardware Design
  • System Design
  • Experiment
  • Discussion
  • Conclusion
abstract
Abstract
  • 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
abstract1
Abstract
  • Evaluated on testbed
  • Advantage:
    • Less sensor nodes to cover a sensing area
    • High data collection rate
    • Recover from the network disconnection
outline2
Outline
  • Abstract
  • Introduction
  • System Overview, Assumptions and Limitations
  • Hardware Design
  • System Design
  • Experiment
  • Discussion
  • Conclusion
motivation
Motivation
  • 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
sensor deployment
Sensor Deployment
  • 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 replacement
Sensor Replacement
  • 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
main contributions
Main Contributions
  • 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
outline3
Outline
  • Abstract
  • Introduction
  • System Overview, Assumptions and Limitations
  • Hardware Design
  • System Design
  • Experiment
  • Discussion
  • Conclusion
system overview
System Overview
  • 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 asthe storage point wheresensor nodes are depositedinto a dispatch queueat the start of deployment
triopusnet node
TriopusNet node
  • 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
four steps
Four Steps
  • Preparation Step
  • Sensor Deployment Step
  • Sensor Latching Step
  • Sensor Replacement Step
1 preparation step
1. Preparation Step
  • 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
2 sensor deployment step
2. Sensor Deployment Step
  • Runs the sensor deployment algorithm prior to releasing
  • Then sends the “release” message including the deployment position, to the head sensor node
3 sensor latching step
3. Sensor Latching Step
  • 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)
4 sensor replacement step
4. Sensor Replacement Step
  • Some sensor node may report low-battery to the system
    • Detach itself, carried out by the water
    • Triopusnet releases fresh one
gateway nodes
Gateway Nodes
  • 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
outline4
Outline
  • Abstract
  • Introduction
  • System Overview, Assumptions and Limitations
  • Hardware Design
  • System Design
  • Experiment
  • Discussion
  • Conclusion
some information not all here
Some Information (Not All Here)
  • 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
outline5
Outline
  • Abstract
  • Introduction
  • System Overview, Assumptions and Limitations
  • Hardware Design
  • System Design
  • Experiment
  • Discussion
  • Conclusion
1 sensor deployment order
1. Sensor Deployment Order
  • 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
2 sensor deployment position
2. Sensor Deployment (Position)
  • 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”
3 sensor movement faucet turn on order
3. Sensor Movement (Faucet Turn-On Order)
  • 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
4 sensor localization
4. Sensor Localization
  • There are both vertical and horizontal pipes
  • Adopts the pipeline localization technique from the PipeProbesystem [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 velocityby traveled time
        • Buoyancy? -> the sensor node was designed with its weight density equal to the water density
5 sensor latching
5. Sensor Latching
  • 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
6 data collection
6. Data Collection
  • Collection tree protocol (CTP) implemented in TinyOS2.1
  • Use anycast (provided by CTP) to multiple sinks(gateway nodes) in order to balance traffic load
7 sensor replacement
7. Sensor Replacement
  • 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!
outline6
Outline
  • Abstract
  • Introduction
  • System Overview, Assumptions and Limitations
  • Hardware Design
  • System Design
  • Experiment
  • Discussion
  • Conclusion
experimental testbed
Experimental Testbed
  • 6 “transparent” pipe tubes (10 cm in diameter)
  • 2 water valves control the volumetric flow rate on each flow path
performance metrics
Performance Metrics
  • And:time to replacementenergy consumption (2 cases)
experimental procedure
Experimental Procedure
  • 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 measuredin scenario #4
    • 20 test runs of node replacement
deployment node locations
Deployment - Node Locations
  • 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 locations1
Deployment - Node Locations
  • The radio range can reach up to 170 cm for nodes placed in different tubes
  • Benefits of using online deployment
deployment data collection rate dcr
Deployment - Data Collection Rate (DCR)
  • 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 positional accuracy
Deployment - Positional Accuracy
  • 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 time to deployment
Deployment - Time to Deployment
  • 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 energy consumption
Deployment - Energy Consumption
  • 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
replacement data collection rate dcr
Replacement – Data Collection Rate(DCR)
  • 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 time to replacement
Replacement - Time to Replacement
  • Depends on the location of the node and the size of the network
outline7
Outline
  • Abstract
  • Introduction
  • System Overview, Assumptions and Limitations
  • Hardware Design
  • System Design
  • Experiment
  • Discussion
  • Conclusion
before practical deployment
Before Practical Deployment
  • 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
an opportunistic node placement scheme
An Opportunistic Node Placement Scheme
  • 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
outline8
Outline
  • Abstract
  • Introduction
  • System Overview, Assumptions and Limitations
  • Hardware Design
  • System Design
  • Experiment
  • Discussion
  • Conclusion
conclusion
Conclusion
  • 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
comments
Comments
  • 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
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