Wireless Sensor Project

Search Triangulation Aerial

Rescue Team (START)

Search Triangulation Aerial Rescue Team (START)

Sarah Kovach – Introduction/Market ResearchJason Schoenbaechler – System OverviewKevin Yu – Stargate/DSPAntonius Ismanto – Microcontroller/ConclusionAdam Porr – Audio DetailsAndrew 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 BeaconCompanies 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.

OtherNode

OtherNode

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

Stargate.• 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 aliasingSoftware

• 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• Pythagorean theorem• Law of Sines

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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