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Wireless Sensor Project
Search Triangulation Aerial
Rescue Team (START)
Search Triangulation Aerial Rescue Team (START)
Sarah Kovach – Introduction/Market Research
Jason Schoenbaechler – System Overview
Kevin Yu – Stargate/DSP
Antonius Ismanto – Microcontroller/Conclusion
Adam Porr – Audio Details
Andrew Gilleon – GPS/Triangulation/User Interface
Our Objective is to improve search and rescue capabilities
with an aerial wireless sensor network
Market Research
Similar Product – Avalanche Beacon
Companies already in the market include Ortovox,
Pieps, and Barryvox
Disadvantages
• Price on average is about $200-$400
(needing at least 2 beacons to be effective)
• Range is very narrow (~20-30 meters)
Advantages to Our Design
• Price could be cut to as low as $242
• Range will cover several square miles
System Overview
• Stargate Node
• Sensors
• User Interface
System Overview
• Stargate Node
• DSP Functions
• Communication
• Power
• Distribution
• Sensors
• GPS
• Audio
• Expansion Port
Digital Signal processing (DSP)
• signals come from the real world - this intimate connection
with the real world leads to many unique needs such as the
need to react in real time and a need to measure signals and
convert them to digital numbers
• signals are discrete - which means the information in between
discrete samples is lost
• digital systems can be reprogrammed for other applications
• digital systems do not depend on strict component tolerances
• digital system responses do not drift with temperature
DSP cont.
Other
Node
Other
Node
Atmel ATtiny26L-8PI Microcontroller
Specification:
• Operating Voltage: 2.7V – 5.5V
• Speed Grades : 8 MHz
• ADC resolution : 10 bits
• ADC speed : 15 kSPS
• ADC Channel : 11
• I/O Pins : 16 (Programmable I/O)
• Functions:
• A/D Converter.
• Storing A/D Conversion result.
• Sending A/D Conversion result along with channel index to Starg
ate.
• A/D Conversion:
• Four channel A/D Conversion.
• 8 bits of resolution to have higher sampling rate.
• Sampling rate at 10kSPS or 10kHz.
Atmel Flowchart & Schematic
Acoustic Beamforming - Overview
Phased array of 4 omnidirectional microphones
Microphones arranged on 4 corners of a square
Works like a directional microphone
Can form a directional “beam” in 3 dimensions
Makes use of constructive and destructive interference:
• Signals within beam are added in-phase
• Signals outside beam are added out-of-phase
• Frequency range limited by microphone spacing
• Better than linear array (no azimuthal ambiguity)
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Acoustic Beamforming – Details
Hardware
• Panasonic WM-61A microphone
• Good sensitivity for receiving weak
signals, inexpensive, small
• Approximately 2 cm spacing needed to
prevent spatial aliasing
Software
• Determine the delays for the signal to travel between each microphone
• Record the signal at each microphone and shift data according to
delays
• Sum the microphone data and calculate the combined signal energy
• Repeat for all possible look-angles
• The angle with the greatest signal energy is the direction of arrival
Acoustic Beamforming – Geometry
GPS Sensor
• Garmin GPS 15L
• Compact
• 1.4”x1.8”x0.3”
• 0.50 oz.
• Accurate
• WAAS enabled
• Position to 3m
• Velocity to 0.1 knot
• Low Power
• 85mA @ 3.3V
• Serial Interface
• NMEA 0183 standard
Triangulation
• Nodes transmit position information
• Longitude and Latitude
• Altitude
• Velocity
• Signal Direction
• Nodes collect position information
• Node performs independent triangulation
• Result can be used for guidance
Triangulation
• Calculation is performed between two nodes
• Based on:
• Positions
• Velocity
• Signal Direction
• Equations
B
• Pythagorean theorem
• Law of Sines
sin A sin B sin C


a
b
c
A
c
b
a
C
User Interface
• Passive System
• User computer can “listen” to nodes
• Graphical interface:
• List of available nodes and status
• Mapping shows:
• Node locations
• Triangulation result
• Can be implemented on portable systems
• Laptops
• Tablet PCs
• PDAs
Conclusion
Flexibility
• Increase number of microphone in the array to get better
direction and triangulation using the same microcontroller.
• Expansion in sensors, such as temperature and wind speed.
• Able to be used in remote area without too much setup.
Potential problems / issues
• Microphones blind spot.
• Memory capacity for storing A/D conversion result.
• Lost of data due to A/D conversion multiplexing.
Questions