Transcript Wireless Sensor Networks for Structural Health Monitoring Sukun Kim*, Shamim Pakzad+, David Culler*, James Demmel*, Gregory Fenves+, Steve Glaser+, Martin Turon# *

Wireless Sensor Networks for Structural Health Monitoring
Sukun Kim*, Shamim Pakzad+, David Culler*, James Demmel*, Gregory Fenves+, Steve Glaser+, Martin Turon#
* EECS, UC Berkeley +CEE, UC Berkeley #Crossbow
Overview
Vibration Data from the Footbridge
• Ambient vibrations of the structure
are monitored and used to determine
the health status of the structure.
• With a Wireless Sensor Network,
low cost monitoring is possible
without interfering with the operation
of the structure.
Frequency plot, vertical sensors at L1-L5
Time plot, vertical sensors at L1-L5
8
V2
V4
V13
V7
V9
4
4
10
abs(FFT(.))
Acceleration (mg)
6
V2
V4
V13
V7
V9
2
0
2
10
-2
0
10
-4
-6
-2
10
-8
0
1
2
3
4
5
6
7
8
9
0
10
2
4
6
8
• High Fidelity Data
• High Frequency Sampling with Low Jitter
• Time Synchronized Sampling [FTSP]
• Large-scale Multi-hop Network [Mint]
• Reliable Command Dissemination [Broadcast]
• Reliable Data Collection [Straw]
Accelerometer Board
12
14
16
18
20
Frequency (Hz)
Time (sec)
Challenges
10
First
Vertical
Mode of
Vibration
1.00
0.74
-0.73
0.19
-0.99
Vertical
Frequency (Hz)
Damping Ratio
Frequency (Hz)
Damping Ratio
Horizontal
1st mode
1.35
0.055
2.37
0.26
2nd mode
1.79
0.02
7.87
0.16
3rd mode
11.47
0.043
11.91
0.123
Estimated results match with a FE model of the bridge (SAP)
ADXL
202E
-2G ~ 2G
200(μG/√Hz)
Range
System
ADXL 202E noise floor
Silicon Designs 1221L Price
$10
Silicon Designs
221L
-0.1G ~ 0.1G
30(μG/√Hz)
Deployment at the
Golden Gate Bridge
SF
(south)
Sausalito
(north)
500 ft
$150
• Two measurement axis each with two accelerometers
• Thermometer, 16bit ADC, Low-pass filter
• On-board Digital Signal processing
• Calibration for manufacturing variation and temperature
Software Architecture
Sentri (Application Layer)
1125 ft
4200 ft
246 ft
56 nodes
8 nodes
• Nodes on the main span and the south tower
• Distance between nodes on the west span is either 100ft
or 50ft
• Exposed to strong and salty wind and fog
Straw
FTSP
MintRoute
Best-effort Single-hop Communication
Low-level FLASH
Deployment at the Footbridge
Node, Battery, Antenna
Rusting of C-clamp
300
Time (sec)
400
500
600
5
0
-5
45
2
2
50
55
Time (sec)
60
65
1
0
0
5
10
15
20
25
30
frequency (HZ)
35
40
45
50
1
0
0
0.5
1
1.5
2
2.5
Accel (mg)
200
Accel (mg)
100
0
-50
0
100
200
300
Time (sec)
400
500
0
-10
45
4
4
50
55
Time (sec)
60
65
2
0
0
5
10
15
20
25
30
frequency (HZ)
35
40
0
0
0.5
1
(a) Vertical, Quarter span
North of the South Tower
260ft
9
Berkeley
7
11 12
14
10
8
5
1
2
16ft
SF Bay
13
4
3
Bandwidth (B/s)
mid-span
1.5
2
Base Station
2.5
(b) Vertical, Quarter span
South of the North Tower
Bandwidth versus Hop Count
1000
800
600
400
200
0
0
50
frequency (HZ)
1200
quarter-span
45
2
frequency (HZ)
1400
600
10
PSD (mg/Hz)
0
50
PSD (mg/Hz)
-20
Base station in Tower
Time and Frequency plots, Vertical sensors, s284n45
0
Accel (mg)
Accel (mg)
Time and Frequency plots, Vertical sensors, s284n62
20
PSD (mg/Hz)
• When sampling, only necessary components are turned
on to reduce jitter
• Straw provides reliable data collection
• Selective-NACK is used – complexity is drawn from
the sender (mote) to the receiver (PC)
• Rate-based control
• Pipelining increases channel utilization
PSD (mg/Hz)
Broadcast
BufferedLog
10
20
30
Hop Count
40
50