Accubeacon
Andrew Gans, Spencer Curran, Shreyank
Amartya, Alex Fouss, John Bullock
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
Avalanche Hazards
include data on life expectancy
Spencer
Spencer
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
Spence
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
System Overview
Accubeacon Avalanche Transceiver
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
Requirements-Primary
Level
Requirement
Dependencies
Primary
P1
Triangulate relative location of buried
S1,S2,S3
Primary
P2
Display victim location in an easy to read format
S4
Primary
P3
Supply enough power for extended use in the backcountry
S5
Primary
P4
Meet all standard specifications and functionality of current
transceivers
S7,S8
Primary
P5
Detect multiple burials
S6
Spencer
Requirements-Secondary
Level
Requirement
Secondary
S1
Calculate distance between user beacon and buried beacon using
457kHz wireless signal
Secondary
S2
Calculate distance between user beacon and other searching
beacons using other wireless protocol
Secondary
S3
Receive distance data from other searching beacons
Secondary
S4
Place relative location of buried victim onto visual display
Secondary
S5
Provide a sufficiently sized battery pack to meet power
requirements
Secondary
S6
Determine the event of multipal burials
Secondary
S7
Transmit at standard 457kHz frequency
Secondary
S8
Incorporate standard signal strength indicator search functionality
Spencer
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
Processing and User
Interface Subsystem
Accubeacon Avalanche Transceivers
Processing and User Interface
• Collects data from 457khz and zigbee
subsystems
• Uses data to run required algorithms for
multiple burial detection, localization
and trilateration
Algorithms
• Trilateration
• Localization
• Multiple Burial Detection
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
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
Trilateration Diagram
Shreyank
System Setup
Alex
Multiple Burial Detection
• Use 457khz signal strength from multiple
antenna and multiple beacons to
determine distance from buried victim(s)
User Interface and Hardware
• Requirements
o Processor that can run all required
algorithms
o User interface that displays results of
algorithms
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
•
•
•
•
•
•
•
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
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
Zigbee Wireless
Subsystem
Accubeacon Avalanche Transceivers
Tasks and Responsibilities
• Sends data between searching beacons
• Detects RTOF/RSSI from received signal
to calculate distance
ZigBee
-Received Signal
Packer from Other
Searchers
ZigBee
Modem
-Distance correlation
(RTOF/RSSi)
Transmitted Signal
Packet to Other
Searchers
Distance Data to
Microcontroller
Display/Processing
-Distances between searchers
-Distance/Angle to buried victim
-Mode information
Processing and Display
-Triangulates burial location
-Displays to screen
Alex
Module
Zigbee Wireless Transceiver Level 2
Input
48 bit packets using TOA (Time of Arrival) or RTT (Round Trip Time)
Output
48 bit packets using TOA (Time of Arrival) or RTT (Round Trip Time)
Functionality
Provide 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.
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
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
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.
457 kHz RF Subsystem
The backbone of avalanche transceivers
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
457 kHz Transmitter
USER INPUT
(device power
on)
Transmit on
(Oscillators /
Filtering)
Ferrite Rod
Antenna (2x,
orthogonal) Outputs
Radiation Pattern
457 kHz Receiver
Ferrite Rod
Antenna (2x,
orthogonal)
Determines
Orientation
USER INPUT
(device
switched to
search mode)
Analog Front
End
(Filtering,
Multiplexing,
A/D)
Directional
Information to
Microcontroller
Alex
457 kHz Transmitter (Level 3)
Crystal
Oscillator
RF
Filters
457
kHz Buffer
MUX
AMP
RF
PWR
AMP
Pulsed
457 kHz
Demu
x
Power
Gnd
RF Choke
Frequency
Divider
Counter
pulse
Frequency
Divider
Module
457 kHz Transmitter Level 3
Input
Power
Output
457 kHz pulsed RF power on either of two antennas
Functionality
Provide adequate radiation to allow for detection when buried ~50m away
Antenna
selection
457 kHz Receiver (Level 3)
Power
457
kHz
tunning
457
kHz
tunning
Antenna selection
(sync with Tx)
Mux
Pulsed
457 kHz
RF
AMP
Creates a DC voltage relative to
received RF signal strength
Band pass
filter
buffer
Rectifier
Signal
Conditioning
RF Choke
Module
457 kHz Receiver Level 3
Input
RF Radiation (tuned to 457 kHz), power
Output
Analog signal to be processed by microcontroller
Functionality
Provide a meaningful analog voltage that represents signal strength for each antenna
orientation
Out to
CPU
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)
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
Features
Backwards Compatibility
• Receive RF signals within a large margin
of error (457 kHz ± 200 Hz)
o 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 & 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
Prototyping & Testing
Digital signal processing
• Differentiate between signal overlap and
no signal overlap
• Smooth out signal modulation when
overlapping
Prototyping
More information is needed to reduce
degrees of freedom
• Searcher inputs number of burials
• Digital compass used to find magnetic
north
Antenna 1
Antenna 2
Transmitting
Antenna
(Buried Person)
Receiving Antennas Arrangement
(BCA Tracker DTS)
Two Transmitters
Same Relative Distances
1 Transmitter Closer to CH. 2
CH. 2
CH. 1
90 Degree Triangle
In H-Plane Closer to CH. 2
In H-Plane Tx, RxCH.1,RxCH.2 Orientation
Same Configuration with RxCH.2 Rotated
90 Degrees
Both CH. 1 and CH. 2 90 Degree Offset
Development 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
Design Approach
Milestones
1. Proof of Theory
2. Rev A. - Proof Of Concept
3. Rev. B
4. Final Rev.
Wheeler
Design So Far
•
•
•
Completed 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 arduino
Wheeler
Current Setup
• Arduino Uno
• Xbee
•
•
Point to Point network
RSSI -Distance Measurement
• BCA Tracker Beacon
• RSSI pulled from 7-Segment Display
• Allows for easy implementation of
algorithms
Revision B
-First PCB Revision
-Atmel Microcontroller on “development
board”
-Multiple Burial Algorithm Implemented
-Lower Level Input from Existing Beacon
-RTOF implementation
Wheeler
Revision C - Final Rev.
-Integration of our own 457kHz Transceiver
-Finalized Zigbee System
-Finalized Multiple Burial Determination
System
-Finalized Processing/Display
Wheeler
Team/Project Management
Wireless
Communication
RF
Communication
Multiple Burial
Determination
User
Interface/Data
Processing
Spencer
X
X
X
Wheeler
X
X
X
John
X
Alex
X
Shreyank
X
X
X
X
X
John
Scheduling Tasks
Along 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.
John
Budget
Estimated Costs
Research
$102
Rev A
$133
Rev B
$294
Rev C
$294
Total
$823
Applied for UROP and using Personal Funds.
John
Risks and Contingencies
1.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 beacons
4. Multiple Burial Determination
John
Conclusion
-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
John
Questions & Comments