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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)
 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:
                                                       A
       • Positions
       • Velocity
       • Signal Direction                      c
• Equations                                            b
                                     B
   • Pythagorean theorem
   • Law of Sines                                  a


                                                           C
                sin A sin B sin C
                          
                  a     b     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

								
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