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 – • Speed Grades : 8 MHz • ADC resolution : 10 bits • • ADC speed : 15 kSPS ADC Channel : 11 • 5.5V

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

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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 • • Pythagorean theorem Law of Sines

B c a

sin

a A

 sin

b B

 sin

C c A b C

User Interface

• • • • Passive System User computer can “ listen ” Graphical interface: to nodes • • 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