Accubeacon

AccubeaconAndrew Gans, Spencer Curran, Shreyank Amartya, Alex Fouss, John BullockWinter backcountry recreation has become increasingly popular.Thousands of skiers and sledders put themselves in dangerous avalanche zones each year90% are caused by a victim or someone in their party.

Personal Account of Avalanche Video

Avalanche Hazards backgroundSpencerinclude data on life expectancyAvalanche HazardsSpencerSpencerProbe line - A technique used with an abundance of searchersK9 search team - Avalanche dogs are trained to sniff out buried victimsProper Shoveling - There are several methods for fast and swift extractionsAir Bag - A backpack air bag that can be deployed when victim triggers an avalanche to prevent being buried.Avalanche Rescue MethodsSpencerSpenceUse of sensors1. Knowledge about the state of the victim; survival chances, urgency, vital signs.2. Orientation of victim in snow3. Depth of buried victim.Multiple Buried victim markersOther InnovationsAccubeacon Avalanche TransceiverSystem Overview

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 detectionStatement of PurposeSpencerRequirements-PrimaryLevelRequirementDependenciesPrimaryP1Triangulate relative location of buried S1,S2,S3PrimaryP2Display victim location in an easy to read formatS4PrimaryP3Supply enough power for extended use in the backcountryS5PrimaryP4Meet all standard specifications and functionality of current transceiversS7,S8PrimaryP5Detect multiple burialsS6SpencerLevelRequirementSecondaryS1Calculate distance between user beacon and buried beacon using 457kHz wireless signalSecondaryS2Calculate distance between user beacon and other searching beacons using other wireless protocolSecondaryS3Receive distance data from other searching beaconsSecondaryS4Place relative location of buried victim onto visual displaySecondaryS5Provide a sufficiently sized battery pack to meet power requirementsSecondaryS6Determine the event of multipal burialsSecondaryS7Transmit at standard 457kHz frequencySecondaryS8Incorporate standard signal strength indicator search functionalityRequirements-SecondarySpencer1. 457 kHz RF Transmits/receives standard 457kHz frequency signal and processes associated RSSI signal

2. ZigBee WirelessTransmits in the ISM band and uses RSSI or RTOF (round trip time of flight) to get triangulation information

4.User Interface/Data ProcessingProvides clear and concise information about the location of burial SubsystemsAlexProcessing and User Interface SubsystemAccubeacon Avalanche TransceiversCollects data from 457khz and zigbee subsystems

Uses data to run required algorithms for multiple burial detection, localization and trilaterationProcessing and User InterfaceTrilateration

Localization

Multiple Burial DetectionAlgorithmsUses 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 signalLocalization-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 interfaceTrilateration ProcessShreyankTrilateration DiagramShreyankSystem SetupAlexUse 457khz signal strength from multiple antenna and multiple beacons to determine distance from buried victim(s)Multiple Burial DetectionRequirementsProcessor that can run all required algorithms

User interface that displays results of algorithms

User Interface and HardwareAtmel xmega 256-A3 microcontrollerPower ConversionSerial Connectors4.5V Battery JackTest PadsUSB connectorPower and Serial LED'sPDI interface for AVR ISP mkii

Development BoardPast experience with Atmel microcontrollers and AVR StudioCan easily switch to a different series of Atmel microcontrollerEasily accessible drivers and libraries for different peripherals and modulesCan be easily programmed through PDI using Atmel mkii In System Programmer

Microcontroller - ATxmega 256A3UPush Buttons to power on, switch between search and transmit mode

LCD module to display the grid and relative positions of the searchers and victims

User InterfaceZigbee Wireless SubsystemAccubeacon Avalanche TransceiversSends data between searching beacons

Detects RTOF/RSSI from received signal to calculate distance

Tasks and ResponsibilitiesZigBee-Received Signal Packer from Other Searchers

-Distance correlation (RTOF/RSSi)ZigBee ModemDistance Data to MicrocontrollerTransmitted Signal Packet to Other SearchersDisplay/ProcessingProcessing and Display-Triangulates burial location-Displays to screen-Distances between searchers-Distance/Angle to buried victim-Mode informationAlexModuleZigbee Wireless Transceiver Level 2Input48 bit packets using TOA (Time of Arrival) or RTT (Round Trip Time)Output48 bit packets using TOA (Time of Arrival) or RTT (Round Trip Time)FunctionalityProvide adequate signal to determine distance from other searchers and transmit own 457 kHz signal to aid in trilateration. As well as receive the distance of other searchers in order to locate them compared to own reference location. Determine their 457 signal of the buried victim to aid in trilateration.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)Wireless Distance MeasurementShreyankTime 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 Wireless Distance MeasurementShreyank-Currently we are using XBee libraries to transmit packet arrays amongst other searcher.-The packet contains the following data1. Sender's XBee ID2. 1st RF distance3. 2nd Searchers RF distance4. 3rd Searchers RF distance5. Distance from 3 to 16. Distance from 3 to 27. Distance from 2 to 1-Each individual XBee processes this data and extract all relevant data for their own array. Wireless Packet457 kHz RF SubsystemThe backbone of avalanche transceiversThe 457 kHz subsystem is the bare minimum needed for a working avalanche beaconOther 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

457 kHz TransmitterTransmit on(Oscillators / Filtering)USER INPUT(device power on)Analog Front End(Filtering, Multiplexing, A/D)Directional Information to Microcontroller457 kHz ReceiverUSER INPUT(device switched to search mode)Ferrite Rod Antenna (2x, orthogonal) Outputs Radiation PatternFerrite Rod Antenna (2x, orthogonal) Determines OrientationAlex457 kHz Transmitter (Level 3)Module457 kHz Transmitter Level 3InputPowerOutput457 kHz pulsed RF power on either of two antennasFunctionalityProvide adequate radiation to allow for detection when buried ~50m awayCrystalOscillatorRFFiltersBufferAMPMUXRFPWRAMPDemuxCounterFrequencyDividerFrequency DividerRF ChokePower457 kHzpulseGnd

Pulsed 457 kHzAntenna selection457 kHz Receiver (Level 3)Module457 kHz Receiver Level 3InputRF Radiation (tuned to 457 kHz), powerOutputAnalog signal to be processed by microcontrollerFunctionalityProvide a meaningful analog voltage that represents signal strength for each antenna orientationPower457 kHz tunning457 kHz tunningMuxRF ChokeRFAMPBand pass filterbufferRectifierSignalConditioningOut to CPUPulsed 457 kHzAntenna selection(sync with Tx) Creates a DC voltage relative to received RF signal strengthUsing cross-searcher data communication reduces guesswork and ambiguity with ultimate goal of eliminating a coarse searchTrilateration (Triangulation)

Quick and precise pinpointing of multiple buried victims (even with unintended signal modulation - overlap)

TasksTransmit 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

FeaturesBackwards 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

Prototyping & TestingMultiple searcher tests done

Differences in signal waveform (BCA Tracker DTS) give signature characteristics based on buried beacons 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

Prototyping & TestingDigital signal processing

Differentiate between signal overlap and no signal overlap

Smooth out signal modulation when overlapping

PrototypingMore information is needed to reduce degrees of freedom

Searcher inputs number of burials

Digital compass used to find magnetic north

Transmitting Antenna(Buried Person)Receiving Antennas Arrangement(BCA Tracker DTS)

Antenna 1Antenna 2Two TransmittersSame Relative Distances1 Transmitter Closer to CH. 2CH. 2CH. 190 Degree TriangleIn H-Plane Closer to CH. 2In H-Plane Tx, RxCH.1,RxCH.2 OrientationSame Configuration with RxCH.2 Rotated 90 DegreesBoth CH. 1 and CH. 2 90 Degree OffsetDevelopment Plan (Multiple Burials)Input data into microcontroller

Analog voltages converted to sampled digital signal

Signal processed using differential algorithms

Vectors assigned to signals and output to high-res matrix display

Milestones1. Proof of Theory

2. Rev A. - Proof Of Concept 3. Rev. B

4. Final Rev.Design Approach WheelerCompleted required background research to show that the concept is feasible - Used existing beacon as test platform

Incorporated Zigbee wireless: -data transmission-distance measurement Algorith Implementation on arduinoDesign So FarWheelerArduino UnoXbeePoint to Point networkRSSI -Distance MeasurementBCA Tracker Beacon RSSI pulled from 7-Segment DisplayAllows for easy implementation of algorithms

Current Setup

-First PCB Revision

-Atmel Microcontroller on development board

-Multiple Burial Algorithm Implemented

-Lower Level Input from Existing Beacon

-RTOF implementationRevision BWheeler-Integration of our own 457kHz Transceiver

-Finalized Zigbee System

-Finalized Multiple Burial Determination System

-Finalized Processing/Display

Revision C - Final Rev.WheelerTeam/Project ManagementWireless CommunicationRF CommunicationMultiple Burial DeterminationUser Interface/Data ProcessingSpencerXXXWheelerXXXJohnXXAlexXXXShreyankXXJohnAlong with our bi-weekly scheduled lab time, we have weekly "scrums" to discuss progress and updates on Monday nights.

We do our best to set up 2 week sprints, in which we set goals and task to accomplish in order to stay on track with our milestone goals.Scheduling TasksJohnBudgetEstimated CostsResearch$102Rev A$133Rev B$294Rev C$294Total$823JohnApplied for UROP and using Personal Funds.RSSI accuracy has not been proven, RTOF should prove to be more accurate, but we have been unsuccessful implementing

2. RF 457 kHz implementation

3. Expandability to function with N searching beacons4. Multiple Burial DeterminationRisks and ContingenciesJohn-Current beacon technology is decades old-Accuracy is going to be our biggest concern and goal-Through 2-way communication we project to minimize search time to save lives and hopefully carve out a spot in the market not yet realized

ConclusionJohn Questions & Comments