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Mon Bri Bri Mon : A Sensor Network System for Railway Bri dge Mon itoring Kameswari Chebrolu (IIT-Bombay) Bhaskaran Raman ( IIT-Bombay ) Nilesh Mishra (USC) Phani Kumar Valiveti (Cisco Systems) Raj Kumar (Indian Army)

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bri mon a sensor network system for railway bri dge mon itoring

Mon

Bri

BriMon: A Sensor Network System for Railway Bridge Monitoring

Kameswari Chebrolu(IIT-Bombay)

Bhaskaran Raman(IIT-Bombay)

NileshMishra(USC)

Phani Kumar Valiveti(Cisco Systems)

Raj Kumar(Indian Army)

Acknowledgment: Prof. C.V.R. Murty, Dr. K. K. Bajpai (Structural Engineering Lab, IIT-Kanpur)

http://www.cse.iitb.ac.in/silmaril/br/doku.php?id=proj:brimon

motivation
Motivation
  • Aging civil infrastructure
  • Indian Railways consists of 120,000 bridges spread over a large geographical area
    • Many in weak and distressed conditions
    • 57% are over 80 years old
  • 26.7% of 577,000 US bridges rated deficient
  • An automated system to track bridge's health is of utmost importance.
    • Short term monitoring
    • Long term monitoring

Motivation

Design

Architecture

Evaluation

Conclusion

problem statement
Problem Statement
  • Develop an easy to deploy, low maintenanceandlong-term structural health monitoring system for Railway bridges

Easy to deploy:Cost effective and faster deployment

Low maintenance: Technical expertise is difficult to get

Long-term: Useful to monitor a structure's health over time

Motivation

Design

Architecture

Evaluation

Conclusion

application requirements
Application Requirements
  • What to measure? Acceleration in 3-axis of motion
    • Frequency components of interest 0.25-20Hz
  • How long to measure?
    • 40 sec of total vibration during and after train’s passage
  • Time Synchronization
    • Need accuracy of 5ms

30-125m

3-axis accelerometers

Motivation

Design

Architecture

Evaluation

Conclusion

implications of requirements
Implications of Requirements
  • 2km bridge can have as many as 200 sensors
    • 6 nodes per span; 60m span

Motivation

Design

Architecture

Evaluation

Conclusion

existing techniques
Existing Techniques
  • Visual inspection
  • Mostly wired solutions
    • Equipment is bulky and very expensive
    • Large setup time (few days) for short-term monitoring
  • Few wireless solutions
    • Proprietary non scalable solutions
    • Wisden (USC)
    • Golden-gate bridge (UCB)

Image source: www.brimos.com

Motivation

Design

Architecture

Evaluation

Conclusion

solution approach
Solution Approach
  • Battery operated wireless sensor motes
    • Cheap alternative
    • Easy to deploy and maintain
      • Eliminates hassle of laying cable to route data/power
    • No solar panels
      • Expensive and prone to theft
      • Sensors maybe placed under deck in shade

Tmote-sky/Telosb motes

Dual axis ADXL 203 Accelerometer

Motivation

Design

Architecture

Evaluation

Conclusion

solution approach10
Solution Approach
  • Battery operated wireless sensor motes
    • Cheap alternative
    • Easy to deploy and maintain
      • Eliminates hassle of laying cable to route data/power
    • No solar panels
      • Expensive and prone to theft
      • Sensors maybe placed under deck in shade

Key Goal: Minimize energy consumption

Tmote-sky/Telosb motes

Dual axis ADXL 203 Accelerometer

Motivation

Design

Architecture

Evaluation

Conclusion

challenges
Challenges
  • Event Detection
    • Cannot predict train arrival
    • To conserve power, sensor nodes have to duty-cycle (sleep + wake cycle)
  • Remote Access
    • Bridges may not have network coverage to transfer data to central server
  • Scalability
    • Can have as many as 200 sensors per bridge
    • Architecture needs to be scalable

Motivation

Design

Architecture

Evaluation

Conclusion

slide12

Mon

Bri

C 3

C 5

C 7

C 9

Head Node

3

4

5

1

2

Accelerometer

6

Mote

slide13

Mon

Bri

Event Detection(for data collection)

Multi Channel Data Transfer(to moving train)

C 3

C 5

C 7

C 9

Head Node

Interaction amongst functionalities(time synch, routing, event detection and data transfer)

3

4

5

1

2

6

slide14

Motivation

Design

Architecture

Evaluation

Conclusion

slide15

Topology Formation

3

6

1

2

3

4

5

6

1

2

Channel 3

4

5

Channel 5

Motivation

Design

Architecture

Evaluation

Conclusion

slide16

Time Synchronization

3

6

1

2

3

4

5

6

1

2

Channel 3

4

5

Channel 5

Motivation

Design

Architecture

Evaluation

Conclusion

slide17

Sleep-Wakeup

3

6

1

2

3

4

5

6

1

2

Channel 3

4

5

Channel 1

Channel 5

Motivation

Design

Architecture

Evaluation

Conclusion

slide18

Command Control: Wakeup

Train Arrival Detection

3

6

1

2

3

4

5

6

1

2

4

5

Motivation

Design

Architecture

Evaluation

Conclusion

slide19

VibrationSensing

3

6

1

2

3

4

5

6

1

2

4

5

Motivation

Design

Architecture

Evaluation

Conclusion

slide20

Data Gathering by

individual cluster heads

3

6

1

2

3

4

5

6

1

2

Channel 3

4

5

Channel 5

Motivation

Design

Architecture

Evaluation

Conclusion

slide21

Sleep-Wakeup

3

6

1

2

3

4

5

6

1

2

Channel 3

4

5

Channel 1

Channel 5

Motivation

Design

Architecture

Evaluation

Conclusion

slide22

Data Uploading

Train Detection

3

6

1

2

3

4

5

6

1

2

4

5

Motivation

Design

Architecture

Evaluation

Conclusion

slide23

Sleep-Wakeup

3

6

1

2

3

4

5

6

1

2

4

5

Motivation

Design

Architecture

Evaluation

Conclusion

slide24

Data Analysis Centre

Send Data to Repository

Motivation

Design

Architecture

Evaluation

Conclusion

brimon architecture event detection
BriMon Architecture: Event Detection

Span

P

Head node

Motivation

Design

Architecture

Evaluation

Conclusion

brimon architecture event detection26
BriMon Architecture: Event Detection

Span

P

Head node

  • Tdc = max time available between detection of oncoming train and data collection

Motivation

Design

Architecture

Evaluation

Conclusion

radio range measurements
Radio Range Measurements
  • Tdc = Dd/V
  • Dd is found to be about 400m with 8dBi omni-antenna for various speeds

Omni antenna

Motivation

Design

Architecture

Evaluation

Conclusion

error rate vs distance between sender and receiver
Error rate vs. distance between sender and receiver

Motivation

Design

Architecture

Evaluation

Conclusion

radio range measurements29
Radio Range Measurements
  • Tdc = Dd/V
  • Dd is found to be about 400m with 8dBi omni-antenna for various speeds
  • At 80kmph, Tdc = 36s
  • Use of 802.11 extends

range to 800m*

  • Frontier Nodes

Omni antenna

* WWW’06

Motivation

Design

Architecture

Evaluation

Conclusion

event detection
Event Detection
  • Tsl = sleep time
  • Tw = wake-up time

Tdc = Tsl + 2Tw

Tdc

Tdc

Tdc

Tsl

Tw

Tw

Motivation

Design

Architecture

Evaluation

Conclusion

brimon architecture event detection31
BriMon Architecture: Event Detection

Span

Head node

  • Wake-up time (head) = Beacon detection time + clock drift time + command propagation time
  • Wake-up time (non - head) = 2 * clock drift time + command propagation time

Motivation

Design

Architecture

Evaluation

Conclusion

event detection analysis
Event Detection: Analysis

Motivation

Design

Architecture

Evaluation

Conclusion

event detection analysis33
Event Detection: Analysis

Motivation

Design

Architecture

Evaluation

Conclusion

event detection analysis34
Event Detection: Analysis

Motivation

Design

Architecture

Evaluation

Conclusion

event detection analysis35
Event Detection: Analysis

Motivation

Design

Architecture

Evaluation

Conclusion

time synchronization
Time Synchronization
  • Time synchronization required only within a span
    • Each span is an independent data-span
  • We use same protocol for synchronization as well as command issue
    • Flooding with multiple (3) retransmissions on each wake up cycle.
    • Error in synchronization is 0.18ms
      • 1-2 clock ticks per hop

Motivation

Design

Architecture

Evaluation

Conclusion

data transfer
Data Transfer
  • Long distance wide area wireless links infeasible
    • Many bridges in remote locations
  • Transfer over single hop for 10-20 hops complete bridge data presents scalability problems
    • Bridge with 200 sensors generate 1.5MB data
  • 1.5 MB data transferred on single hop 802.15.4 radio with 80 Kbps takes 2.5 minutes.
    • Contact duration only 72 sec (1.2 min) at 80 Kmph

Motivation

Design

Architecture

Evaluation

Conclusion

data transfer our approach
Data Transfer: Our Approach
  • Use multiple channels; one for each data span
    • Data across spans independent
    • At most 12 nodes per span; very scalable
    • Adjacent channels are 7 spans apart with 16 available channels11, 13, 15, 17, 19, 21, 23, 25, 12
  • Gather data of the span motes to the head mote
  • Transfer data from head mote to train

7 spans

Motivation

Design

Architecture

Evaluation

Conclusion

slide39

Mon

Bri

C 3

C 5

C 7

C 9

Head Node

3

4

5

1

2

6

Motivation

Design

Architecture

Evaluation

Conclusion

data transfer within span routing issues
Data Transfer within Span: Routing Issues
  • Outdoor 802.15.4 links can be made to operate in stable settings *
  • Any simple protocol can be used
    • Centralized 2 Phase routing
      • Neighbour-discovery phase
      • Tree construction phase
    • Average duration of routing tree formation for 6 nodes : 567ms
    • Routing runs infrequently once in few hours or on node failure/join

*Reference: “Implications of Link Range and (In)Stability on Sensor Network Architecture”, WINTECH 2006

Motivation

Design

Architecture

Evaluation

Conclusion

mobile data transfer
Mobile Data Transfer
  • Achievable data transfer rate using block transfer transport protocol on hardware is 46Kbps (tested on field)
  • Max data per data span is 693Kbits (12 nodes)
  • Contact duration required is 15sec

Motivation

Design

Architecture

Evaluation

Conclusion

throughput considerations
Throughput Considerations

Contact Range required = contact duration * speed of train

  • Contact range required for data transfer (in 15 sec) is
    • 330m at train speed of 80kmph
    • 250m at train speed of 60kmph
  • Our measurements give a contact range of 400m (one-side)

Contact Range = D

Head node

Motivation

Design

Architecture

Evaluation

Conclusion

throughput considerations43
Throughput Considerations
  • Transfer is possible with enough leeway.
  • Throughput can be further increased via
    • Compression
    • Multiple receivers at head and rear of train
    • Better Hardware
      • Simultaneous operation of flash and radio
      • Bluetooth Radio (1Mbps)

Motivation

Design

Architecture

Evaluation

Conclusion

lifetime estimate
Lifetime Estimate
  • Assuming one data collection operation per day BriMon can achieve 1.5 years of operation using 2500mAH batteries

36s

15s

131s

33s

Motivation

Design

Architecture

Evaluation

Conclusion

measurements on a road bridge
Measurements on a Road Bridge

Omni antenna

Motivation

Design

Architecture

Evaluation

Conclusion

measurements on a road bridge46
Measurements on a Road Bridge

Sink Mote

Motivation

Design

Architecture

Evaluation

Conclusion

measurements on a road bridge47
Measurements on a Road Bridge
  • Dominant free vibration frequency of 5.5Hz
  • Amplitude of vibration as high as 100 milli g (30 milli g for healthy bridges)

Motivation

Design

Architecture

Evaluation

Conclusion

future work
Future Work
  • Deployment on a Railway bridge
  • Extending BriMon to other bridge architectures
    • Current approach focuses on span bridges

Motivation

Design

Architecture

Evaluation

Conclusion

conclusions
Conclusions
  • Application specific design
    • Extensive measurement study
  • Novelty of our contributions
    • Event detection mechanism
    • Mobile data transfer
    • Integration with time-synchronization/routing
  • Estimates indicate network can operate without intervention for 1.5 years

http://www.cse.iitb.ac.in/silmaril/br/doku.php?id=proj:brimon

Motivation

Design

Architecture

Evaluation

Conclusion