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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: • 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
