Accubeacon

1. Accubeacon Andrew Gans, Spencer Curran, Shreyank Amartya, Alex Fouss, John Bullock

2. Avalanche Hazards background • Winter backcountry recreation has become increasingly popular. • Thousands of skiers and sledders put themselves in dangerous avalanche zones each year • 90% are caused by a victim or someone in their party. Personal Account of Avalanche Video Spencer

3. Avalanche Hazards include data on life expectancy Spencer

4. Spencer

5. Avalanche Rescue Methods • Probe line - A technique used with an abundance of searchers • K9 search team - Avalanche dogs are trained to sniff out buried victims • Proper Shoveling - There are several methods for fast and swift extractions • Air Bag - A backpack air bag that can be deployed when victim triggers an avalanche to prevent being buried. Spencer

6. Spence

7. Other Innovations Use of sensors 1. Knowledge about the state of the victim; survival chances, urgency, vital signs. 2. Orientation of victim in snow 3. Depth of buried victim. Multiple Buried victim markers

8. System Overview Accubeacon Avalanche Transceiver

9. Statement of Purpose To design a set of avalanche transceivers that can communicate with each other to allow for more accurate pinpointing of buried victims and multiple burial detection Spencer

10. Requirements-Primary Spencer

11. Requirements-Secondary Spencer

12. Subsystems 1. 457 kHz RF Transmits/receives standard 457kHz frequency signal and processes associated RSSI signal 2. ZigBee Wireless Transmits in the ISM band and uses RSSI or RTOF (round trip time of flight) to get triangulation information 4.User Interface/Data Processing Provides clear and concise information about the location of burial Alex

14. Processing and User Interface Subsystem Accubeacon Avalanche Transceivers

15. Processing and User Interface • Collects data from 457khz and zigbee subsystems • Uses data to run required algorithms for multiple burial detection, localization and trilateration

16. Algorithms • Trilateration • Localization • Multiple Burial Detection

17. Localization • Uses distances between three or more searching beacons to determine relative x,y positions of other searchers • Requires accurate distance measurement between searching beacons • x,y positions of other searchers allows for triangulation using 457khz signal

18. Trilateration Process -Localization determines relative position of other searchers -Trilateration uses localized distance vectors from other searchers to compute buried location -Buried location presented to searcher via user interface Shreyank

19. Trilateration Diagram Shreyank

20. System Setup Alex

21. Multiple Burial Detection • Use 457khz signal strength from multiple antenna and multiple beacons to determine distance from buried victim(s)

25. User Interface and Hardware • Requirements • Processor that can run all required algorithms • User interface that displays results of algorithms

26. Development Board Atmel xmega 256-A3 microcontroller • Power Conversion • Serial Connectors • 4.5V Battery Jack • Test Pads • USB connector • Power and Serial LED's • PDI interface for AVR ISP mkii

27. Microcontroller - ATxmega 256A3U • Past experience with Atmel microcontrollers and AVR Studio • Can easily switch to a different series of Atmel microcontroller • Easily accessible drivers and libraries for different peripherals and modules • Can be easily programmed through PDI using Atmel mkii In System Programmer

28. User Interface • Push Buttons to power on, switch between search and transmit mode • LCD module to display the grid and relative positions of the searchers and victims

29. Zigbee Wireless Subsystem Accubeacon Avalanche Transceivers

30. Tasks and Responsibilities • Sends data between searching beacons • Detects RTOF/RSSI from received signal to calculate distance

31. Display/Processing ZigBee -Received Signal Packer from Other Searchers -Distance correlation (RTOF/RSSi) Transmitted Signal Packet to Other Searchers ZigBee Modem Distance Data to Microcontroller Processing and Display -Triangulates burial location -Displays to screen -Distances between searchers -Distance/Angle to buried victim -Mode information Alex

33. Wireless Distance Measurement RSSI(Received Signal Strength Indicator) -RSSI is the measurement of power present in the received radio signal. RSSI is directly proportional the distance as follows RSSI 10 log (P/Pref) Shreyank

34. Wireless Distance Measurement Time of Arrival - Using synchronized clocks and time stamps to record signal travel time -Travel time can be correlated with distance -More accurate than RSSI but requires precise timing Shreyank

35. Wireless Packet -Currently we are using XBee libraries to transmit packet arrays amongst other searcher. -The packet contains the following data 1. Sender's XBee ID 2. 1st RF distance 3. 2nd Searchers RF distance 4. 3rd Searchers RF distance 5. Distance from 3 to 1 6. Distance from 3 to 2 7. Distance from 2 to 1 -Each individual XBee processes this data and extract all relevant data for their own array.

36. 457 kHz RF Subsystem The backbone of avalanche transceivers

37. The 457 kHz subsystem is the bare minimum needed for a working avalanche beacon • Other marketed beacons only have this system. • Some beacons use digital signal processing and 3 axis antennas to eliminate false readings • No current beacon uses communication with other searchers to correlate information and further eliminate error

38. 457 kHz Receiver 457 kHz Transmitter Transmit on (Oscillators / Filtering) USER INPUT (device power on) Ferrite Rod Antenna (2x, orthogonal) Outputs Radiation Pattern Ferrite Rod Antenna (2x, orthogonal) Determines Orientation Analog Front End (Filtering, Multiplexing, A/D) Directional Information to Microcontroller USER INPUT (device switched to search mode) Alex

39. 457 kHz Transmitter (Level 3) Pulsed 457 kHz 457 kHz Crystal Oscillator RF Filters MUX RF PWR AMP Demux Buffer AMP Gnd Antenna selection Frequency Divider Frequency Divider Counter pulse RF Choke Power

40. 457 kHz Receiver (Level 3) Antenna selection (sync with Tx) Creates a DC voltage relative to received RF signal strength 457 kHz tunning Pulsed 457 kHz Mux Band pass filter Rectifier Signal Conditioning RF AMP Out to CPU buffer 457 kHz tunning RF Choke Power

41. Using cross-searcher data communication reduces guesswork and ambiguity with ultimate goal of eliminating a coarse search • Trilateration (Triangulation) • Quick and precise pinpointing of multiple buried victims (even with unintended signal modulation - overlap)

42. Tasks • Transmit RF signal within margin of error up to current standards (457 kHz ± 80 Hz) • Differentiate signals of multiple buried victims • Relay analog information to microcontroller when in search mode

43. Features Backwards Compatibility • Receive RF signals within a large margin of error (457 kHz ± 200 Hz) • Covers range of frequencies for 1970's era beacons • If all else fails (one searcher, no xbee communication, etc) the transceiver will function as a regular ("digital”) beacon

44. Prototyping & Testing Multiple searcher tests done • Differences in signal waveform (BCA Tracker DTS) give signature characteristics based on buried beacon’s orientation • Use the differences in signal to communicate between beacons and determine instantaneous location of buried victim • This method can be extrapolated for multiple burials

45. Prototyping & Testing Digital signal processing • Differentiate between signal overlap and no signal overlap • Smooth out signal modulation when overlapping

46. Prototyping More information is needed to reduce degrees of freedom • Searcher inputs number of burials • Digital compass used to find magnetic north

48. Antenna 1 Antenna 2 Transmitting Antenna (Buried Person) Receiving Antennas Arrangement (BCA Tracker DTS)

50. Two TransmittersSame Relative Distances