nicole oring pic

Measurement & Characterization of Hurricane Wind Loads on Structures
Using a Wireless Sensing Networking System
Lead P.I. Jean-Paul Pinelli Co-P.I.'s: Chelakara Subramanian, Ivica Kostanic
Team Members: Gabriel Lapilli, Jiten Chandiramani, Connor Poske
Software
Embedded Firmware
System Overview
A third generation of wireless sensors was developed to study
wind-borne pressure variations in low-rise buildings during
hurricanes. The system has the capability of measuring
pressure and temperature along a roof, collecting data and
sending it to a server to process and publish on the web in
nearly real-time. Also wind speed and direction are measured
by the system with the use of an anemometer.
Sensors are placed inside individual custom-made plastic
weatherproof cases. Small size of all components allows an
aerodynamic shape, reducing the shape effect of the sensor on
the flow. Low power consumption combined with Li-ion
batteries provide several days of continuous data collection.
The platform created allows using almost any type of sensor
via a planned expansion port.
Laptop + base unit
Cellular data
network
cellular tower
wireless
card
Remote sensor
units
Public Internet
Public Internet
Central server
wireless
Laptop + base unit card
There are two versions of the firmware running in the PIC processors for this system: one to collect
data from the pressure and temperature transducers, and another to collect the data from the
anemometers. They use 3 operating states that can be commanded by the control client software:
· Sleep Mode: Processor is put into a low power state.
· Idle Mode: A heartbeat message indicating remaining battery life will be sent to the base once
every 5 seconds.
· Data Mode: The logic behind both versions of the firmware implements a synchronized data
pipeline between the external sensors and the Xbee transceiver module. The sensor data is sampled
via a configurable hardware interrupt mechanism. A synchronized, shared buffer is written with
the samples taken. Once a data packet is assembled, another routine that is constantly running (not
interrupt based) reads the buffer and passes the sensor
data along with other status information in the form of a
pre-defined frame to the Xbee, which handles the
transmission to the base unit.
cellular tower
Control Client Application
Communication network
The Control Client application is used to monitor status,
control individual or groups of endpoints, display sensor
data in real-time, and generate logs of sensor data. The
design is a user-friendly Graphical User Interface that is
written in C# and utilizes Windows Forms, the
ZedGraph framework for real-time graphing, and
custom built GUI components for Xbee network status
and endpoint status display.
House installation
Remote sensor
units
House Installation
Set of remote sensor units (up to 30 pressure sensors and two anemometers) that are installed on the roof of the house of interest, plus
an associated base unit
Sensors
Results - Tests
Up to 30 sensors can be deployed with each system.
They collect pressure and temperature data with a
sample rate of up to 36 samples/second. Their
range varies depending on the surroundings from
20 to 100 meters
Sensors
Router
Repeated static pressure tests at +50 mbar relative
pressure show that the sensor output follows a Gaussian
distribution with a standard deviation of:
mbar
mbar
Therefore, considering ± 3σ we can infer with a 99.73% of
reliability that the data measured is between ± 0.867 mbar.
Routers
Base Unit
Are used to extend the range of the sensors, acting as bridges between
the base and sensors. Routers have high-gain omnidirectional antennas
built into them to increase their range. Since they are optional, sensors
can connect either directly to a base unit or through a router.
MLB Airport
Sensors
Laptop
Processor
Transceiver
Pressure
Transducer
Frequency
Data Rate
Operating
Channels
Sensor-base
communication
Clock speed
A/D Converter
Resolution
Maximum
reliable sample
rate (full system)
Battery type
Battery life
Base Unit
Anemometer
Consists of three separate
Xbee units in USB to serial
bridge boards connected to a
USB concentrator and
assembled in a weatherproof
plastic box.
An expansion card is used to connect an RM
Young's anemometer to a sensor board. Wind
speed sampling rate is one-half the pressure
sampling rate, and direction is one quarter. This is
done to reduce the bandwidth usage of the
network.
Previous System
(2nd Generation)
Current System
(3rd Generation)
PIC 16F876
Radiometrix
BiM3A-914-64
914.50 MHz
64kbps
PIC 18LF2553
Digi
XBee XB24-Z7
Freestream
MP3H6115A
2.4 GHz
256kbps
1
16
Cyclic – Manual
organization
20MHz
Individual – Auto
Negotiation
48 MHz
10 bit
12 bit
Motorola MPX-4115
~22 samples/sec
Lead-Acid 6V 3.4Ah
4 days
~36 samples/sec
Sensor unit
Weathertight connector:
On-Off switch and charging
plug
A comparison with Melbourne International
Airport's (MLB) weather station was conducted
for 50 hours to evaluate the accuracy of the system.
Considering the fact that both measurements
were taken at a distance of about two miles, the
agreement is very good, in the order of ±1mbar.
Tropical Storm Nicole
Plastic case
sealed with standard O’Ring
Pressure plug
Hose
Aluminum
Stiffening
Ring
Sensor board
Future Tests - Deployments
Li-Ion 3.7V 6000mAh battery allows a lifetime of >5
days of continuous data collection. Fully charged in 6
hours at 900mAh (charger circuitry is onboard)
Plastic base plate
Screw tightened
Li-Ion 3.7V 6Ah
>5 days
Direct USB firmware updates
Custom-made surface mount board, built using liquid
solder, stencil and baked in infrared oven
Expansion port: possibility to mount almost any
sensor with voltage output
Xbee XB24-Z7CIT-004
Throughput: 256kbps
PIC18LF2553
Running at 48 MHZ
Temperature transducer:
MCP9700AT-E/TT from
Microchip Technologies
Pressure transducer:
Freestream Electronics
MP3H6115A
The system was deployed on a Satellite Beach house, in Florida during Tropical Storm Nicole in
September 28th, 2010. This storm was predicted to move along Florida's east coast, although it
dissipated before reaching the land. Although no high speed winds were captured (1-minute
averages always below 5 m/s), measurements taken during this storm are useful to analyze the
static behavior of the sensors over a relatively long period of time. The differences between sensors
are never over 1mbar. The areas where the divergence is higher coincide with the higher velocity.
These variations are due to the interaction between structure and wind at higher velocities, which is
not uniform due to the geometry of the roof and wind gusts of different size. It is interesting to see
also the increase in atmospheric
pressure as the tropical depression
dissipated.
The plastic cases were designed to be
weatherproof and aerodynamic. The new
transceivers have built-in antennas which
allow for a more aerodynamic dome shape
without external protrusions that disturb air
flow.
Full scale tests will be performed
(spring 2011) in the wind tunnel of
the state-of-the-art, multi-risk
applied research and training
facility of the Institute of Business
and Home Safety. This wind
tunnel has an exceptionally large
chamber: 145’ wide by 145’ long,
with a clear interior height of 60’, and it is has the capability to create proper aerodynamic flows to
recreate realistic Category 1, 2, and 3 hurricanes. Following these tests, the research team will be
ready to deploy 3 instrumentation sets in the field during the 2011 hurricane season.
NSF GRANT # 0625124 - NSF PROGRAM NAME: Structural Systems and Hazard Mitigation of Structures - Civil and Mechanical Systems