Location and Communication Systems for Safety Workers

1

• Location and Communication Systems for Safety
  Workers
• Dr. Neil Goldsman, Dr. Gilmer Blankenship and
• Dr. Carole Teolis
• TechnoSciences Inc.
• TRX Systems

2
The Fire-Safe Locator System

• Determines location of safety workers.
• Communicates vital signs to base
• Determines the presence of environmental factors
  hazardous to safety personnel
• Operates both indoors and outside

3
Hardware Components of the Fire-Safe Locator

• The Fire-Safe Locator System Components
• One central portable base station that is carried
  or worn by command firefighter or placed in
  truck.
• Four substations placed at key locations at
  emergency site.
• Personal transceivers that are worn by individual
  safety personnel.

4
System Illustration
Satellite Transceiver
Satellite Transceiver
Satellite Transceiver
Central Transceiver
Gone Too Far!!!
5
What the Fire-Safe Locator Does

• Demonstrate by Example
• Fire alarm rings. Commander takes personal
  transceivers and the central unit to emergency
  site.
• Each firefighter wears a personal transceiver
  that transmits a unique code.
• The central unit knows which firefighter has
  which code.
• The central unit communicates with each
  firefighter sequentially.
• During the communication sequence, the location,
  the vital signs, and any environmental hazard are
  transmitted to the base station.
• An alarm sounds if a safety worker is in trouble.

6
How it WorksTechnical Summary

• Each transceiver and central unit are designed
  using state-of-the-art CMOS electronics
• Each transceiver and the central unit is
  preprogrammed with a unique code.
• Each transceiver in the system is numbered.
• The user (fire-chief, etc.) tells the central
  unit the name of the firefighter that has each
  transceiver. (Each firefighter is associated with
  a specific transceiver.)

7
How it WorksTechnical Summary

• Using a digital modulation scheme, the central
  unit and the transceiver communicate with each
  other at regular intervals. (Approximately once a
  second.)
• Using a set of state-of-the art location
  algorithms involving hardware and software, the
  central unit determines the location of the
  personal transceiver and hence the firefighter.
• We have designated our state-of-the-art location
  algorithms as Integrated Positioning

8
How Integrated Positioning Works

• Integrated Positioning combines five different
  technologies
• Global Positioning System (GPS)
• Accelerometers and Numerical Integration
• Active Radar
• Received Signal Strength Indication (RSSI)
• Orthogonal Signal Phase Delay Positioning (OSPDP)

9
How Integrated Positioning Works

• Technology I GPS
• Each personal transceiver, base station and
  substation will be equipped with a GPS receiver.
• The GPS location of each personal transmitter
  will be transmitted to the base and substations.
• Upon going indoors the GPS operation will likely
  terminate.
• The final location and time before GPS terminates
  will be recorded by the network providing a
  coordinate origin for the particular safety
  worker.

10
How Integrated Positioning Works

• Technology II Accelerometers and Numerical
  Integration
• Equip firefighter with 3 dimensional
  accelerometer board (size 3cm) and
  microprocessor
• Accelerometer provides instantaneous acceleration
  (a(t))
• Use microprocessor to numerically integrate two
  times to obtain instantaneous position of
  firefighter. (x(t) ?? a(t) dt2 xo)
• Communicate instantaneous position to base
  station.

11
How Integrated Positioning Works

• Technology III Active Radar
• Determines distance using GHz clocks, RF pulses
  and the speed of light.
• Substation sends RF pulse and starts GHz clock
  (super high speed) at same time.
• Firefighters transceiver receives and returns RF
  pulse to substation.
• Substation receives back RF pulse and stops its
  clock.
• Distance from Firefighter to substation
  calculated Distance (speed of
  light) x (elapsed clock time)
• Elapsed clock time is on order of nanoseconds
  realized by high speed CMOS electronics
• Use 3 substations to triangulate and get precise
  coordinates

12
How Integrated Positioning Works

• Technology IV Received Signal Strength Indicator
  (RSSI)
• The base station, substations and personal
  transceivers will all be equipped with an RSSI
  circuit that indicates the power of the signal
  that the firefighter is transmitting to the base
  station, substations (and other figherfighters).
• From the signal strength we will obtain
  information as to how far away a specific
  firefighter is from a base or substation.
• To aid in this process, local RSSIs can be
  placed at known locations indoors at emergency
  site to monitor signal strengths of safety
  workers as well.
• RSSI information will then be transmitted to base
  station.

13
How Integrated Positioning Works

• Technology V Orthogonal Signal Phase Delay
  Positioning (OSPDP)
• OSPDP uses synchronization of continuous
  pseudo-random signals to determine position.
• Suppose at time T0, two clocks are synchronized
  and they both start generating a the same
  continuous signal.
• One clock is at the substation, and another is
  on the personal transmitter.
• The firefighter then moves away from the
  substation and both continue to generate the same
  continuous signal.
• Now the substation will receive the firefighters
  signal, but there will be a delay because now the
  firefighters signal must travel a finite
  distance to reach the substation.
• By comparing the phase difference between the two
  signals using inner product formulation, the
  distance between the substation and the fireman
  will be determined.
• This will be achieved with three independent
  substations to triangulate the precise
  coordinates of the firefighter.

14
Computer Modeling of Radio Frequency (RF) Indoor
Location Signals
15
Computer Modeling of Indoor RF Signals

• Much of indoor location is based on propagation
  of radio frequency (RF) electromagnetic waves.
• We have developed a unique algorithm for
  emulating the propagation of indoor RF.
• This capability provides a unique advantage to
  our Integrated Positioning Technology
• The method has been published in academic
  journals and received enthusiastic response.
• The technique is called the Finite Difference
  Time Domain Alternating Direction Implicit Method
  for Solving Maxwells Equations (FDTD-ADI).
• Maxwells Equations are a complicated set of
  partial differential vector equations that
  describe RF waves.
• The following slides show results of these
  calculations indicating how RF waves propagate
  inside buildings.

16
Back
Simulation Geometry
Source
room 1
With Metal Stud
Right
room 2
Left
Hall Way
Front
Wood Wall
17
Simulation Configuration

• Simulation Geometry
• Two Rooms 4mx4.5m each
• Wall
• conductivity 0.0005 S/m
• Permittivity 10 ?o
• Thickness 12 cm for inner wall 20 cm for outer
  wall.
• Wood Door
• Conductivity 0 S/m
• Permittivity 42 ?o
• Cross-section 90cmx6cm.
• Metal Stud
• Conductivity 107 S/m
• Permittivity ?o
• Cross-section 5cmx8cm
• Stud spacing 30 cm

• Simulation Facts
• Grid resolution 1.0 cm 1100x750 grids are used
  in XY plane.
• Time step 6.0e-11 sec. Radiation source is placed
  at the center of the right room.
• Scenario 1
• Sinusoidal current source with f 433 MHz.
• Jz ? Sin(2?ft) for sec
• Then, switch to 0 for the rest time.
• Both with and without metal wall studs are
  simulated
• Scenario 2
• Sinusoidal current source with f 433 MHz.
• Jz ? Sin(2?ft) for sec
• Then, switch to 0 for the rest time.
• Both with and without metal wall studs are
  simulated

18
Average Power Map of RF Signal (Sum and average)
433MHz Wood Wall
433MHz With metal Stud
19
Average Power Map
2.4GHz Wood Wall
Metal Studs cause interference pattern. Leaking
power is generally less for wall with metal
studs. Leaking power for 2.4Ghz excitation is
larger.
2.4 GHz With metal Stud
20
Detecting Emitted Signal and Estimating Distance
Detect First Dip
Delay for signal to subside
21
Wood Wall f 433 MHz
Wall with Studs f 433 MHz
Monitoring Points We place monitoring points on
4 sides outside the wall 0.5m to the wall, 1.0m
apart. We record the arrival time of the first
dip in the received signal at the monitoring
point. Plots The delay time dt is used to
estimate the distance between the transmitter and
receiver by using c x dt. In the above plots We
plot estimated distance vs. actual distance with
color-coded symbols. The color represents the
monitoring points on different sides as indicated
in the legend. The blue line show the scenario if
the estimated distance equals actual distance.
22
Wood Wall f 2.4 GHz
Wall with Studs f 2.4 GHz
Estimation error is different for monitoring at
different sides. Estimation Errors due to
multi-path propagation delay F 433 MHz Wood
Wall Maximum Error0.4m for distance7.6m.
Wall with metal studs Maximum Error0.9m for
distance8.3m. F2.4 GHz Wood Wall Maximum
Error1.0m for distance8.3m. Wall with
metal studs Maximum Error1.4m for
distance8.3m. Error can be minimized by
monitoring from optimized location and use
magnitude info. (Stronger signal means closer to
the source near side is with less error.)
23
Active RadarSome Technology Details
24
Active Radar Summary

• System Design
• Transmission
• Timing
• Components
• Transmission Theory
• Timing Theory
• Circuit Design
• Current Status

25
System Design
26
System Design

• Transmission
• Transmitter/receiver combination
• built-in en/decoding
• Transmission forms a loop
• Allows devices to query simultaneously

27
System Design

• Timing
• 5 MHz propagation delay counter
• Clock drives counter and Microcontroller
• 800 MHz range finding counter (.35 m resolution)
• Separate clock driver
• Enable controlled by D flip-flop which sets on
  request and resets when a response is received

28
Components

• Microcontroller PIC16F628
• Transmitter Linx TXE-433-KH
• Reciever Linx RXD-433-KH
• Counter ON semicondutor MC100E137FN
• RF Power Amp Linx BBA-519
• Antenna SPLATCH PCB antenna

29
Transmission Theory

• Linx Transmit Encode, Receive Decode pairs
• TXE-433-KH
• RXD-433-KH
• Linx Power amp
• BBA-519 (higher power, less precision)

30
Timing Theory

• Low speed delay counter
• Delay determined by Microcontroller
• Transmit/receive cycle counted with low speed
  counter
• Several counts removed for range finding leaving
  precision to the high speed count
• High speed distance counter
• Distance Velocity time

31
Circuit Design

• Transmission Block

32
Circuit Design

• Transmission Block Board

33
Circuit Design

• Timing Block

34
Current Status

• Transmission board is complete
• Timing schematic needs revision
• High speed counters need to be ordered
• Microcontroller delay and operation code

35
Design Highlights
Antenna
Power Amp
Modulator
Carrier
Code Generator
Firefighter-Name Input
Transmitter Blocks of Central Unit
36
Design Highlights
Antenna
Power Amp
Modulator
Carrier
1001
Personal Digital ID Code
Transmitter Blocks of Satellite Unit
37
Integrated Positioning Summary

1. We are developing a system for indoor and outdoor
   position detection by integrating five different
   technologies
2. Each technology will independently provide values
   for the specific location of a safety worker
3. These independent values will be transmitted to
   the central base station.
4. Using a voting algorithm that we are developing,
   the central base station will use the data from
   the five independent technologies to decide the
   most likely location of the safety personnel.
5. Vital signs and environmental factors will also
   be transmitted to base station. An alarm will
   sound if the safety worker is experiencing too
   high a danger factor.