Note: Descriptions are shown in the official language in which they were submitted.
~s ~
2 ~ g 2
IlaFRa~:D ~ICI~3 Il)E~TIFICATIO~il SYSTEll
Back~lround of the Invention
This invention relate~ to identification of airport
surface traffic and in particular to an apparatus and method
for detecting and identifying aircraft or other vehizle
movement on airport taxiways, ru~ways and other surface
axea~.
Currently, ground control of aircraft at an airport is
done visually by the air traffic controller in the tower.
10 Low vi3ibili~y conditions ~ometLmes make it Lmpos~ible for
the controller to see all parts of the field. Ground
surface radar can help in providing coverage during low
vi~ibility conditions; it play~ an important part in the
solution of the runway incursion problem but cannot solve
15 the entire problem. A runway incursion i8 defined as "any
occurrence at an airport involving an aircraft, vehicle,
person, or ob~ect on the ground that create a collision
hazard or r~sul~s in loss of separation with an aircraft
taking off, intending to take off landing, or intending to
20 land." The U.S. Fed~ral ~dministration Ag0ncy (FAA) has
e~kimated that it can only ju~tify the cost of ground
surface radar at 29 4f the top lO0 airpor~s in the United
Stat~s. However, ~uch radar only provides location
information; it cannot alert the controller ~o pos~ible
25 conflicks be~ween aircraft.
In the prior art, an airport control and monitorinq
system has been used to sense when an airplane reaches a
certain point on a taxiway and controls switching lights on
and off to indicate to the pilot when he may proceed on to a
runway. 5uch a syskem ~ends microwave ~ensor information ~o
a computer in the control tower. The compu~er comprises
software for con~rolling ~he airport lighting and for
pxoviding fault information on the airport lighting via
display~ or a con~rol panel to an operator. Such a system
is described in sales in~ormation provided on a Bi-
directional Series 7 ~ransceiver (BRITEE) produced by ADB-
ALNACO, Inc., A Siemens Company, of Columbus, Ohio~
However, such a sy~tem does not ~how the location of all
vehicle~ on an airfield and i~ not able to detect and avoid
a pos~ible vehicle incursion.
A well known approach to airport surface traffic
control has been the use of scanning radars operating at
high freguencie~ such as ~-band in order to obtain adequate
definition and re.olution. ~n existing airport ground
tra~fic control equipment of tha~ type is known in the art
a~ Airport Surface Detection ~.quipment (ASDE). How~ver,
5uch equipment provids~ ~urv~illance only, no discrete
identi~ication of aircraft on the ~urface being aYailable,
A150 there i8 a ~eed for a rela~ively high an~enna tower and
a relatively large rotation antenna system thereon.
Another approach to airport ground surveillance is a
system described in U. S. Patent No. 3,872,474, issued March
18, 1374, to Arnold M. Levine and assigned to International
Telephone and Telegraph Corporation, New York, NY, referred
to as LOCAR (Lo~alized Cable Radar) which comprises a ~eries
of small, lower powered, narrow pulses, transmitting radars
ha~ing limi~ed range and time seguenced along opposite sides
of a runway ramp or taxiway. In another U. S. Patent No.
4,197,536, issued on April 8, 1980, to Arnold M. ~evine, an
airpor~c surface identification and control system is
de~cribed for aircraft equipped with ATCRBS (Air Traffic
Control Radio Beacon System) and ILS (Instrument Landing
Sy~tem). However, these approaches are expensi~e, require
sp~cial cabling and for identification pu~poses require
expensive equipmsnt to be in~luded on the aircraft and other
vehicles.
Another approach to vehicle identification such as
types of aircraft by identifying the unique characteristic
of the "footprintl~ presented ~y the configuration of wheels
unique to a particular type of vehicle is des~ribed in U.S.
Patent ~o. 3,872,283, issued Narch 18, 1975, to Gerald ~.
Smith et al. and as~igned to The Cadre Corporation of
A~lanta Georgia.
An automatic system for surveillance, guida~ce and
fire-fighting at airpor~s using i~frared sen~ors is
- ' -
2 ~
described in U. SO ~atent No. 4,845,629, i.ssued July 4, 1989
to Maria Y. Z. Murga. The infrared sensors are arranged
along the flight lanes and their output signals are
processed by a computer ~o provide information concerning
S the aircraft movements along the flight lanes. Position
detectors are provided for detecting the position of
aircraft in the taxiways and parking areas. However, such
system does not teach the use of edge lights along the
runways and taxiways along with their associa~ed wiring and
it is not able to detect and avoid a possible vehicle! -
incursion.
The manner in which ~he invention deals with the
disadvantages of the prior art to provide a low co~t
infrared vehicle identification system will be evident as
the description proceeds.
Sum~ary of the Tn~ention
Accordingly, it is therefore an object of this
in~ention to provide a low cost infrared system that
identifies aircraft or other vehicles on airport taxiways
and runways.
It is also an object of ~his inven~.ion to provide at an
ai~port a low C03t aircraft or vehicle i.den~ification system
using existing edge light as~emblies and associated wiring
along runway~ and taxiways.
I~ is another objec~ of this invention to provide an
infrared vehicle identification system tha~ generates a
graphic display of ~he airport showing the location of all
ground traffic includiny direction and velocity data and
identifie~ ~uch ground traffic.
The objects are further accompli~hed by pro~iding a
vehicle identificatio~ system for identifying aircr~ft and
other vehicles on surface pathways incl~ding runways a~d ~-~
other areas of an airport comprising mean~ dispo ed on the
aircraft and o~her vehicles for transmitting identification
message data, means di~pose~ in each of a plurality ef light
as~mbly means on the airport for recei~ing and decoding the
message data from the transmittiny means, means for
providing power to each of the plurality of light assembly
means, means for processing the decoded identification
message data generated by the receiving a~d decoding means
- ` 2 ~ s~
in each of the plurality of light assembly means, means for
providing data communicat:ion b~tween each of the light
assembly means and ~he processing means, and the processing
mean~ comprise~ means for providing a graphic display of the
airport comprising 5ymbol~3 representing the aircraft and
other vehicles, ~ach of t]he ~ymbols having the
identifica~ion message data di~played. The transmitting
means comprises meanS for creating unique mes~age data which
includes aircraft and flilght identification~ and infrared
mean~ coupled to the me~,age creating means for txansmi~ting
coded stream o~ the me~,3age data. The message data
further includes position information. The receiving and
decoding means comprises ,an infrared sensor. The receiving
and decoding means compri;ses microprocessor means coupled to
the infrared sensor for d,ecoding the message data. The
plurality of light assembly means are arranged in two
parallel row along runways and taxiways of the airport.
The ligh~ assembly means comprises ligh~ means coupled to
the line~ of the power providing means for lighting the
airport, vehicle ~ensing:mean~ or de~ecting aircraft or
other vehicles on the airport~ microproce~or mean~ coupled
to the receiving and decoding means, the ligh~ means~ the
vehicle sensing means and the data co~munication means for
decoding the identificatio~ me~sage data, and the data
communication mean~ being couple~ to the microproce~sor
21~82
means and the lines of ~he power providing means. The
symbols representing aircraft and other v hicles comprise
~, icons having a shape indicating ~ype o~ aircraf~ or vehicle.
The processing means determines a location of the symbols on
the graphic display of the aixport in accordance with data
~ recei~ed from the light assembly means.
¦ The object~ are fur~her accomplished by a vehicle¦ identification system for surveillance and identification of
~ aircraft and other vehicles on an airport compri~ing a¦ 10 plurality of light circuits on the airpor~, each of the
light circui~ comprises a plurality of light as~embly
mean~l means for pro~iding power to each of the plurality of
light circuits and to each of the light ass~mbly means,
means in each of ~he ligh~ a sembly means or sensing ground
traffic on tha airport, means disposed on the aircraft and
other vehicles for tranæmit~ing identification me~sage data
mean~ di~posed in each of the light assembly means for
receiving and decoding the meæsage data from the
tran~mitting means, mean~ for processing ground traffic data
fro~ the sensing mean~ and decoded message data from each of
khe light a~sembly mean~ for pre~entation on a graphic
di~play of the airport, means for providing da~a
co~munication between each of the light asse~bly means and
the processing means, the processing means comprises means
for provi~ing such graphic display of the airport c~mprising
symbols r~presen~ing the ground traffic, each of th~ ~ymbols
having direction, velocity and the identification message
data displayed. Each of the light circuits are located
along the edges of taxiways or runways on the airport. The
S sensing means comprises infrared detectorx. The
transmitting means comprises means fo~ crea~ing unique
me3sage data which includes aircraft and fligh~
identification, and infrared means coupled to the message
creating mean~ for transmit~ing a coded stream of the
me~ age data. ~he message data further comprise~ position
inform~tion. The receiving and decoding means comprises an
infrared sensorq The receiving and decoding means comprise~
microprocessor means coupled to the infrared sensor for
decoding the me~sage data. The plurality of light assembly
means of the light circuits being arranged in two parallel
rows along ru~ways and taxiways of the airport. The light
a~se~hly means comprises light means coupled to the lines of
th~ power providing mei~n~ for ligh~ing ~he airpor~, the
sround traffic sensing m~an for detecting aircraf~ or other
vehicle~ on the airport, microproce~sor means coupled to the
receiving and decoding means, the light means, the ground
traffic sensing means and the data communication means for
decoding the identifica~ion mes~age data and processing a
detection signal from ~he ground traffic sensing means, a~d
-` 211~2
the data communica$ion means being coupled to the
microprocessor means and the line~ of the power providing
means. The ligh~ a~embly means further comprises a
photocell mean~ coupled to the microprocessor means for
detecting the light intensity of the light means. The light
assembly means further c~mprises a strobe light coupled to
the microprocessor means. The processing means comprises
redundant co~puteræ for fault tolerance operation. The
symbols represen~ing the ground traffic comprise icons
having a shape indicating type of aircraft or vehicle. The
proces~ing mean~ detsrmines a location of the symbols on the
graphic display of the ai~por~ in accordance with the data
receive from the light assembly m~ans. The processing means
determines a fu~ure path of the ground traffic based on a
ground clearance command, the future path being shown on the
graphic display. The processing mean~ further comprises
mea~s for predicti~g an airport incursion. The power
providing means comprises constant ourrent power means for
providing a separate line to each of the plurality of light
circuits, and network bridge means co~pled to the constant
current power mean~ for providing a communication channel to
the processi~g mean~ for each line of the con~tant current
power means.
The ob~ect~ are further accomplished by providing a
method of providing a vehicle identification system for
2 1 ~ 2
identifying aircraft and other vehicles on surface pathways
including runways and other areas of an airport comprising
the steps of transmitting identification message data with
means disposed on the aircraf~ and other vehicles, receiving
and decoding the message da~a from the transmitting means
with means disposed in each of a plurality of light assembly
means on the airport, providing power to each of the
plurality of light as~embly means, processing the decoded
identification mes~age data generated by the receiving and
decoding means in each of ~he plurality of light assembly
means, providing data communication between each of the
light assembly means and the proce~sing means, and providing
a graphic display of the airport with the processing means
comprising 8ymbols representing the aircraft an~ other
~ehicles, each of the ~y~bols having the iden~ification
messase da~a displayed. The step of transmitting
identification message data comprises the steps of cxeating
unique message data ~hich includes aircraft and flight
identification, and transmitting a coded stream of the
message data wi~h infrared means coupled to the mes~age
creati~g means. The step of transmitting mes~age data
further includes transmitting position information. The
step of receiving and decoding the message data includes
u~ing an infrared sensor. ~he step of recei~ing and
decoding ~he me~sage data further comprises the step of
~ 21~4~2
coupling microprocessor means to ~he infrared sensor for
decoding the message data. Th~ step of receiving and
decoding the message data with means disposed in the
plurality of light assembly means further comprises the step
of arranging the plurality of lisht assembly means in two
parallel rows along runways and taxiways of the airport.
The step of providing a graphic display comprising symbols
representing aircraft and other vehicles further comprises
the step of providing icons having a shape indica~ing type
of aircraft or Yehicle. q~he step of providing a graphic
di~play comprises the step of deterrnining a location of the
symbols on the graphic display of the airport in accordance
with data rec~ived from the light assembly mearls.
2 1 ~ 2
Brief Description o~ the Drawin~s
Other and further features of the invention will become
apparent in connection with the accompanying drawings
wherein:
FIG. 1 is a block diagram of an airpor~ vehicle
incursion avoidance system;
FIG. 2 i~ a block diagra~ of an edge light assembly
showing a sensor electronics unit coupled to an edge light
o~ an air~ield lighting system;
FIG. 3 is a pictorial diagram of the edge light
assembly showing the edge liyht positioned above the sensor
electronics unit;
FIG. 4 is a diagram of an airfield runway or taxiway
having a plurality of edge light assemblies positioned along
each side of the runway or taxi~ay for detecting variou~
size aircraft as shown;
FIG. 5 is a block diagram of the central co~puter
~ystem ~hown in FIG. l;
FIG. 6 shows el2ven ne~work variables used in
programming the microproce~sor of an edge light assembly to
interface with a sensor, a ligh~ and a strobe light;
FIG. 7 is a block diagram sh~wing an in~erco~nection of
network variables for a plurality of edge light assemblies
located on both sides of a runway, e ch comprising a sensor
olectronics uni~ 10 positioned along a taxiway or runway;
s~ 4 8 2
FIG. 8 ~hows a graphic display o~ a typical
taxiway/runway on a portion of an airport as seen by an
operator in a control tower, the display showing the
location of vehicles as they are detected by the sensors
mounted in the edge light assemblies located along ~a~iways
and runways;
FIG. 9 is a block diagram of the data flow wi~hin the
system shown in FIG. 1 and FIG. 5;
FIG. 10 is a pictorial diagram of an infrared
identification system showing an IR transmitter mounted on
an airplane wheel strut and an I~ recei~er mounted in an
edge light a~sembly of an airport lighting system;
FIG. 11 is a block diagram of an IR transmitter of an
IR vehicle iden~ification ~ystem;
FIGo 12 ~how~ a ~op ~iew of the IR transmitter mounted
on an airplane wheel strut providing a 195 a~ea o coverage
generated by an IR light emit~ing diode array in the IR -:
transmitter;
FIG. 13 shows data fields of a coded data stream
transmitted by the IR transmitter;
FIGJ 14 is a blocX diagram of an IR recei~er of the IR :~
vehicle identification sy~tem;
FIG. 15 i~ a flow chart of an IR message routine which
is a communicati4n protocol continuously pPrformed in an IR
receiver micropxocessor; and
13
2 ~ 2
~ IG. 16 is a flow chart of a vehicle sensor routine
which is con~inuou~ly performed in an IR receiver
microprocessor.
14
~4l~2
DeBcription of the Preferred ~mbodiment
Referring to FIG. 1 a block diagram of an airport
vehicle incursion avoidance system 10 is shown comprising a
plurality of light circuit~ 121n, each of said light
circuits 181 D comprises a plurality of edge light assemblies
201n connected via wiring 211n to a lighting vault 16 which
is connected to a central computer system 12 via a wide area
network 14. Each of the edge light ass~mblies 201n
compri~es an infrared tIR) detector vehicle sensor 50 (FIG.
~)
The edge light assemblies 201n are generally located
along ~ide the runway~ and taxiways of the airport with an
average 100 foot spacing and are interconnected to the
lighting vault 16 by single conductor series edge lis~ht
wiring 211n. Eaeh of the edge light circuits 18lnis
powered via the wiring 211n by a constant current su~ply
241n located in the lighting vault 16.
Referring now to FIG. 1 and FIG. 2, communication
between the edge ligh~ as~emblies 201n a~d the central
computer sy~tem 12 is accomplished wi~h LON Bridges 221n
interconnecting the edge light wiring 211n with the Wide
Area Network 14. Information from a microprocessor 44
located in each edge light a~se~bly 201n i~ coupled to the
edge light wiring 211n via a power line modem 5~. The ~0
bridge~ 221n transfer~ mes~age informa~ion from the edge
.; . . ~ , . , . . , , , ~ . , " , ,
~` 2 ~
light circuits 181n via the wiring 211n to the wide area
network 14. The wide area networ~ 14 provides a
transmission path to the central computer system 12. These
circuit components also provide the return path
communications link from the central computer sys~em 12 to
the microprocessor 44 in each edge light assembly 201n.
Other apparatus and methods, known to one of ordinary skill
in the art, for data communication between the edge light
assemblies 201n and the central compu~er system 12 may be
employed, such as radio techniques, but ~he present
embodiment of providing data communication on the edge light
wiring 211n provides a low cost system for present airports.
The LON Bridge 22 may be embodied by devices manufactured by
Echelon Corporation of Palo Alto, California. The wide area
network 14 may be implemented by one of ordinary ~kill in
the art using standard ~thernet or ~iber Distributed Data
Interface (FDDI) components. The con~tant current ~upply 24
may be embodied by devic~ manufactured by Crouse Hinds of
Winslow, CoDnecticut.
Referring now to ~IG. 2 and FIG. 3, FIG. 3 shows a
pictorial diagr~m of the edge light assembly 201n. The edge
light assembly 201n comprises a bez~l including an
incande~cent lamp 40 and an optional strobe light assembly
48 (FIG. 2) which are mounted above an electronics enclosure
43 comprising a vehicle sensor 50. ~he electronic~
16
~ 2
enclosure 43 si~s on ~he top of a tubular sha~t extending
from a base support 56. The light assembly bezel with lamp
40 and base support 56 may be embodied by devices
manufactured by Crouse-Hinds of Winslow, Connecticut.
A block diagram of the contents of the electronics
enclosure 43 is ~hown in FIG. 2 which c~mprises a coupling ~:
transformer 53 conne~tPd to the edge light wiring 211n. The
coupling transfonmer 53 provides power to both the
incandescent lamp 40 via the lamp ~ontrsl triac 42 and the ~:.
microproceSsor power supply 52; in addition, the coupling
transfo~mer 53 provides a data communication path betwe~n
the power line modem 54 and the LON Bridges 221~ via the
edge light wiring 211n. The microprocessor 44 provides the
computa~ional power to run the internal software pxogram
that controls the edge light assemblies 201n. The
microproces~or 44 is powered by the microprocessor power
supply 52. Also connected ~o the microprocessor 44 is the
lamp control triAc 42, a lamp m~nitoring photo cell 46, ~he
optional strobe light assembly 48, the vehicle sen~or 50,
and the data communications modem 54, The micropxocessor 44
is usPd to control the incand~scen~ edge light 40 int.ensity
and optional strobe light assembly 48. The use of the
microprocessor 44 in each light a~sembly 201n allows
complete addressable control over every light on the field.
The microprocessor 44 may be embodied ~y a Y~SI device
17
manufactured by Ech~lon Corporation of Palo ~lto, California
94304, called the Neuron~ chip.
Still referring to FIG. 2, the sensor 50 in the present
embodiment comprises an infrared (I~3 detector and in other
embodLments may comprise other devices such as proximity
detectors, CCD cameras, microwave motion detectors,
inductance loops, or laser beams. The program in the
microprocessor 44 is responsible for the initial $iltering
of the sensor data received from the sensor 50 and
responsible for the transmission of such da~a to the central
computer system 12. The sensor 50 must perform the
following functions: detect a stationary object, detect a
mo~ing ob~ect, have a range at least half the width of the
runway or taxiway, be low power and be immune to false
alarms. This system design does not rely on ~ust one type
of sensor. Since sen~or fu~ion function are performed
within the central computer -Qystem 12, data inputs from all
different types of sensors are acceptable. Each sensor
relays a different vie~ of what i8 happening on the airfield
and the central computer system 12 combines them. ~here are
a wide range of sensor~ that may be used in thi~ system.
Ag a new sensor type becvmes available, i~ can be integrat~d -~
into this system with a minimum of difficulty. The initial
sensor u~ed is an IR proxLmity detector based around a
piezoelectric s~rip. The~e are the kind of sensors you use
at home to turn on your flood lights when heat and/or
movement is de~ec~ed. When the sensor ou~put provide~ an
analog signal, an analog-to-digital converter readily known
in the art may be us,ed to interface with the microprocessor
44.
Another proximity detector tha~ can be used is based
around a microwave!S;unn diode oscillator. These are
currently in use in such applications as Intrusion Alarms,
Door Openérs, Distanee Measurement, Collision Warning,
Railroad Switching, ~atc. These types of sensors have a
drawback becau~e they are not passive devices and care needs
to be taken to selec:t frequencies that would not interfere
with other airport e~uipment. ~inally, in locations such as
the hold position l~nes on taxiway~, solid state laser and
detector combinatio}ls could be u3ed between adjacent taxiway
ligh~s. The e sensor systems create a beam that when
broken would identi~Ey the location of the fron~ wheel of the
airplane. This tn?e of detector would be used in those
locations where the absolute po~i~ion of a vehicle was
needed. The laser beam would be modulated by the
microprocessor 44 tc\ avoid the detector being fooled by any
other stray radi2tic~n.
Referring to F:lG. 2 and FIGo 4~ a portion of an airport
runway 64 or ta~ ay i~ shown ha~ing a plurality of edge
light as~emblie~ 20~a positioned along each side of the
19
2 ~
runway or taxiway for detecting various size airplan~s or
vehicles 60, 62. The dashed lines represent the coveraye
area of the sensors 50 located in each edge light assembly
201B positioned along each ~ide of the runway 64 or taxiway
~o insure detection of any airplane 60, 52 or other vehicles
traveling on such runway 64 or ~axiway. The edge light
assemblies 201_n comprising the sensor 50 are logically
connected together in such a way that an entire airport is
sensitized to the movement of vehicles. Node to node
communication takes plare to verify and iden~ify the
location of the vehicles. Once thi~ is done a me~sage is
sent to the central computer sy tem 12 reporting the
vehicles location. ~dge light~ assemblies (without a sensor
electronics unit 43) and taxiway power wiring currently
exist along taxiways, runways and open areas of airports, ~:
therefore, the sensor electronics unit 43 i~ readily added
to existing edge lights and existing taxiway power wiring
without the inconvenience and expense of closing down
runways and taxiways while installing new cabling.
Referring now to FIG. 1, FI~. 5, FIG. 8 and FIG. 97 the
central computer system 12 is generally loca~ed at ~ control
tower or terminal area of an airport and is interconnected ~:
to the LON Bridges 221n loca~ed in the ligh~ing vault 16
with a Wide Area ~etwork 14. The cen~ral computer system 12
comprises two redundant compu~ers, compu~er #1 26 and
2~ ~ ~4~2
computer #2 28 for fault tolerance, the display 30, speech
syn~hesis units 29 & 31, alert lights 34, keyboard 27 and a
speech recognition unit 33, all of these elements being
interconnected by the wide area network 14 for the transfer
of information. The two computer~ 26 and 28 communicate
with the microproc~ssors 44 located in the edge li~ht
assemblies 201n. Data received from the edge light assembly
201n microproces~ors 44 are u~ed as *n input to a sensor
fusion software module 101 (FIG. 9~ run on the redundant
computers 26 and 28. The output of the sensor fusion
software module 101 operating in the computers 26, 28 is
used to drive the CRT display 30 which displays the location
of each vehicle on the airpor~ taxiway and runways as shown
i~ FIG. 8. The central computer system 12 may be embodied
by device~ manufacturPd by IB~ Corporation of White Plains,
New ~ork. The Wide Area Network 14 may be embodied by
devicPs manufactured by 3Com Corpor~tion of Santa Clara,
California. Th~ speech synthesis units 29, 31 and the
~peech recognition unit 33 may be embodied by devic~s
manufactured by BBN of Cambridgel Massachusetts.
The speech synthesis unit 29 is coupled to a speaker
32. Limited information is sent to the speech synthesis
unit 29 via the wide area network 14 to provide the
capa~ility to gi~e an air traffic controller a verbal ~lert.
Th~ speech synthesis unit 31 is coupled to a radio 37 having
- ` 2 ~ 2
an antenna 39 to provide the capability to give the pilots a
verbal alert. The voice commands from th~ air traffic
controller to the pilots are captured by microphone 35 and
~ent to the pilots via radio 36 and antenna 38. In the
present embodiment a tap is made and the speech information
is sent to both the radio 36 and the speech recognition unit
33 which i~ programmed to recognize the limited air traffic
control vocabulary used ~y a controller. This includes
airline names, aircraft type, the numbers 0-9, ~he name of
the taxiway~ and run~ays and various short phra~es ~uch a~
"hold short~ 'expedite'' and ~give way to.~ The output of
the speech recognition unit 33 is fed to the computers 26,
28.
Referring again to FIG. 2, the power line modem 54
provides a data communication path over the edge light
wiring 211 ~ for the microproce~sor 44. This two way path is ~--
used for th~ passing of command and control inform~tion
betwee~ the various edge light assemblies 201n and the
central computer system 12. A power line transceiver module
in the power line modem 54 i~ u~ed to provide a data
channel. These modules u~e a carrier current approach to
create the data channel. Power line modems ~hat operate at -~
carrier frequencies in the 100 to 450 ghz band are available
from many manufacturers. These modems provide digital
communication pa~hs at data rates of up to 10,000 bits per
211 4~82
second utilizing direct sequ~nce spread spectrum modulation.
They conform to FCC power line carrier requirements for
conducted Pmissions, and can work with up ~o 55 dB of pow0r
line attenuation. The power line modem 54 may be embodied
by a device manufactured by Echelon Corporation of Palo
Alto, California 94304, called the PLT-10 Power Line
Transceiver Module.
The data channel prsvides a transport layer or lowest
layer of the open system interconnec~ion (OSI) protocol used
in the data network. The Neuron~ chip which Lmplemen~s the
microprocessor 44 contains all of the firmware required to
implement a 7 layer OSI protocol. When interconnected via
an appropriate medi~m the Neuron~ chips automatically
communicate wi~h one another using a robust Collision Sense
Multiple Access (CSMA~ protocol with forward error
corrections, error checking and automatic retransmission of
missed mes~age (ARQ3.
The command and control information is placed in data
packets and sent over the networX in accordance with the 7
Layer OSI protocol. All mes~age~ generated by the
microprocessor 44 and destined for the cen~ral computer
system 12 are received by the network bridge 22 via the
power line~ 211n and routed to the central computer system
12 over the wide area network 14.
23
~.
The Neuron~ chip of the microprocessor 44 comprises
three processors (not shown) and the firmware required to
suppor~ a full 6 layer open systems interconnection ~OSI)
protocol. ~he user is alloca~ed one of the processors for
the ap~lication code. The other two processors give the
application program access to all of the o~her Neuron~ chip~
in the network. This access create~ a Local Operating
Network or LON. A LON can be thought of as a high level
local area network LAN. The use of the Neuron~ chip for the
impleme~tation of this invention, reduces the amount of
custom hardware and software that otherwise would have to be
developed.
Data from the sensor electronic unit 43 of the edge
light assemblies 201n is coupled to the central computer
sy~tem 12 via the existing airport taxiway lighting po~er
wiring 21. U~ing the exi~ting edge light power line to
transfex the sensor da~a into a LO~ network has many
advantages. As previously pointed out, the reu~e of the
e~isting edge lights elLminates the inconvenience and
expense of closing down runways and taxiways while running
new cable and provides for a low cost system.
The Neuron~ chip allows the edge light assemblies 201n
to automatically communicate with each other at the
applications level. This is accomplished ~hrough network
variables which allow individual Neuron0 chip~ to pass data
2~
2 ~ 8 2
between ~hemselves. Each Neuron~ 'C~ program comprises both
local and network variables. The local variables are used
by the Neuron program as a ~cratch pad memory. The network
variables are used by the Neuron~ program in one of two
ways, either as a network output variables or a network
input variables. Both kinds of variables can be
initialized, evaluated and modified locally. The difference
comes into play in that once a network output variable is
modified, network message~ are automatically sent to eaeh
network input variable that is linked ~o tha~ output
variable. This variable linking is done at installation
tLme. As ~oon as a new ~alue of a network input variable is
received by a Neuron~ chip, the code i5 vectored off to take
appropriate action ba~ed upon the value of ~he network input
variable. The ad~antage t9 the progr~m is that this me~sage
pa~sing scheme i~ entirely ~ran~parent since the message
passing code is part of ~he embedded Neuron~ operating
system.
Referring now ~o FIG. 6, eleven network variables have
been identified for a sensor program in each microprocessor
44 of the edge light assemblies 201~. The sensor 50
function has two output variables: prelLm_detect 70 and
confirmed_detect 72. The idea here i~ to have one output
trigger whenever the sensor 50 det~cts movement. The other
output does not trigger unless ~he local 3ensor and the
- - - 2 1 ~ 2
sensor on the edge light a~ro~s the runway both spot
movement. Only when the detection is coninmed will the
signal be fed back to the central computer system 12. Thi~
technique of confirmation helps to reduce false alarms in
1 5 order to Lmplement this techni~ue the adja~ent sensor 50 has
an inpu~ variable called ad~_prelLm_detec~ 78 that is used
to receive the other sensors prelim detect output 70. Other
input variables are upstream detect 74 and downstream_detect
76 which are used when chaining adjacent sen~ors together.
Also needed i~ a detec~or_sensitivity 80 input that is used
by the central computer system 12 to control the detection
ability of the sen~or 50.
The incandescent light 40 require~ two ne~work
¦ variable~, one input and the other an output variable. The
1 15 input variable light_level 84 would be used to control the
ligh~s brigh~ness. The range would be O~F or 0% all the
way to FmLL O~ or 100%, This range from 0% ~o 100% would be
made in 0.5% s~eps. 5ince th edge light assembly 2O1 D al~o
contains the photocell 46, an output variable light failure
84 is created t~ ~ignal that the lamp did no~ obtain the
de~ired brightnes~.
The strobe light 48 requires three input variables.
The ~trobe-mode 86 ~ariable is used to select either the
OFF, SEQUENTIA~, or ALT~RN~TE fla~h mo e~. Since the two
fla~h modes require a distinct pattern to be created, two
26
2 1 ~ 2
input variables active_delay 88 and flash_delay 90 are used
to tLme align the strobe flashes. By setting these
individual delay factors and then addressing ~he Neuron
chips as a group, allows the creation of a field stro~e
pattern with just one command.
Referring now to FIG. 7, a block diagram of an
interconnection of ne~work variables for a plurali~y of edge
light assemblies 201n located on both sides of a runway is
shown, each of the edge light assemblies 201n comprising a
microproce~sor 44. Each ~euroni-~ program in the
microprocessor 44 i5 designed with certain networX input and
output variables. The user writes the code for the Neuroni~
chip~i in the microprocessor 44 a~suming tha~ the inputs are
supplied and that the outputs are used. To create an actual
network the user has to ~wire up~ the network by
interconnecting the individual nodes with a software
linkir. The resulting distributed process is ~est shown in
~chematic foxm, and a portion of the network in~erconnec~
matrix is shown in ~igure 7. The prelim_de~ect 70 output of
a sensor node 441 is connected to the ad; prLmary_detect 92
input of the sensor node 444 across the taxiway. This i~
u~ed as a means to ~erify actual detections and eliminate
falRe reports. The communication~ link between these~two
nodes 441 and 444 i~ part of the distributiPd procei~sing.
~he two nodes communicate iImong them~elvies witho~lt in~olviny
27
g ,, ~ : '~-': ' ., i '" ` ': ,
the central computer system 12. If in the automa~ic mode or
if instructed by the controller, the system will also alert
the pilots via audio and visual indications.
Referring again to FIG. 1 and FIG. 4, the central
computer system 12 tracks the movement of vehicle~ as they
pass from the ssnsor S0 to sensor 50 in each edge light
assembly 201n. Using a varia~ion of a radar automatic track
algorithm, the system can ~rack position, velocity and
heading of all aircraft or vehicles based upon the sensor 50
readings. New vehicles are entered into the system either
upon leaving a boarding gate or landing. Unknown vehicles
are also trac~ed automatically. Since taxiway and runway
lights are normally across from each other on the pavement
~as shown in FIG. 4 and FIG. 7), the microproce~sor 44 in
each ~ge lights assembly 201n is programmed to combine
their sensor 50 i~puts and agree before reporting a contact.
A further refinement is to have the microprocessor 44 ch~ck
with the edge light assemblies 201~ on ei~her side of them
to see if their sensors 50 had detected the vehicle. This
allows a vehicle to be handed off from sensor elsctronic
unit 43 to sensor electronic unit 43 of each edge light
assembly 2 l-n as it travels down the taxiway. This also
as~ures that vehicle position reports remain consistent.
Vehicle veloci~y may also be calculated by using the
2~
~1~4~2
! distance between sensors, the sensor pat~ern and the time
,' between detections.
¦ Referring to FIG. 5 and FI~. 8, the di~play 30 is a
~ color monitor which provides a gr~phical display of the
¦ 5 airport, a portion of which is shown in FIG. 8. This is
accomplished by storing a map of ~he airport in the
redundant computers 26 and 28 in a digital format. The
display 30 show~ the loca~ion of airplanes or vehicles as
they are de~ected by the sensors 50 mounted in th edge
light a~sembli~s 201_~ along each taxiway and runway or other
airport ~urfac~ areas. All aircraft or vehicles on the
airport surface are displayed as icons, wi~h the shape of
the iccns being determined by the vehicle type. Vehicle
position is shown by the loca~ion of the icon on the screen.
Vehicle direction is shown by ei~her the orienta~ion of the
icon or by an arrow e~ana~ing from the icon. Vehicla status
is conveyed by the color of the icon. The future path of
the vehicle a~ provided by the ground clearance command
entered via the controller~ microphone 35 is shown ac; a
~0 colored line on ~he display 3U. The status of all field
lights including each edge light 201n in each edge light
circuit 181n is shown via color on the display 30.
Use of ob~ect orientated software pro~ides the basis
for building a model of an airpor~0 ~he automatic
- 2 ~ 8 ~
inheritance feature allows a data structure to be de~ined
once for each object and then replicated automatically for
each in~tance of that object. Automatic flow down assures
that elements of the data base are not corrupted due to
typing errors. It also assures that the code is regular and
structured. ~ule ~ased object oriented programming makes it
difficult to create unintelligible "spaghetti code.l' Object
oriented programming allows the runways, taxiways, aircraft
and sensors, to be decoded directly as objects. Each of
these objects contains attributes. Some of these a~tributes
are fixed like runway 22R or flight UA347, and some are
variable like vehicle statu~ and position.
In conventional programming we describe the attributes
of an ob~ect in data structures and then describe the
behaviors of the object as procsdures that operate on those
data ~tructures. Obiect oriented programming ~hif~s the
emphasi~ and focuses first on the data ~tructure and only
secondarily on the procedure~. More importantly, object
oriented programming allow~ us to snalyze and design
programs in a natural manner. We can thin~ in term~ of
runways and aircraft in~ead of focusing on ei~her the
behavior or ~he data xtructures of ~he runways and aircraft.
Table 1 shows a list of ob~ect~ with corresponding
attributes. Each physical object that i5 important to the
ru~way incursion problem i~ modeled. The basic airplane or
--" 211~82
vehicle tracking algorithm is shown in Table 2 in a Program
Design Language ~PDL). The algorithm which handles ~ensor
fu~ion, incursion avoidance and safety alerts i9 shown in a
~ ~ingle program even though it i~ Lmplemented as distributed
¦ 5 system using both the central computer sy~tem 12 and the
I sensor microprocessor~ 44.
~aBLE 1
a~CT ATTRIBUTB DBSC~aN
Sensor ~;ocation X s Y coordinates of sensor
0 Clrcuit ~aC wiring circuit n~ns h namber
.. Unique a~dress ~et address or thll3 sensor ~md its m~te
Lamp inten6ity 0~ to 100~ ln 0.59~ steps
S~robe stntus ~link rate/off
-
Strobe-delay Prom start signnl
Sensor status ~st~ct/no d~tect
Sensor typa IEI, laser, proximity, etc.
Runway Name 22R, 27, 33L, etc.
~ocation X & Y coordln~tes of stnrt of center lina
Iength In feet
Width In feet
Diraction In degrees from north
Status ~ot nctive, active ta~soff, ctive lnnding, alar~
Sensors ~MV) 1ist of lightsJsensors nlong this runway
Interssctions (~V) List of intersactions
Vehiclea ~ist of vshiclss on th~ runway
Trlxi~ay Name ~l~e of tnxlway
locutlon h ~ Y coordinat0s of start of centsr lins
Lsngth In f~et
Width In ieet
Dirsction In d~grees fr~m north
Status Not aGtive, active, alarm
Sensors ~!SV) I,i~t of interssctions
llold I,ocntions I,ist oi~ holding loontions
Vehiclss ~IV) I.ist o1' veh~clE~ on the runwny
31
r~ 21 1 4 ~ 8 ~
In~er~eo~ion Name Intersectlon NaDe
Location In~orsectlon of two center lines
St~tus V~ca~t/Occupi~d
So~sors (~V) Liat o~ ~en~ora creatLng lntersection border
Aircra~t AlrlLne Unitad
ModQl 727-200
Tall-number N3274Z
~pty welght 9.5 ton~
I Frulght welght 2.3 to~
¦ 10 Fu~l woight 3.2 tons
¦ T4p ~pe~d 598 mph
Vl ~peed 100 ~ph
V2 spo~d 140 mph
Ae~el~r~tLon 0.23 9'8
D~coleratlon 0.3~ g's
MY - MultL-v~rl~blo or array
Table 2
while (fore~er)
¦ if tedge light show~ a de~2ction)
¦ ¦ i (adjacent light al~o ahow~ a detection sen~or fusion)
¦ ¦ ¦ j* CONFIRMED DETECTION */
¦ ¦ ¦ if (previou~ block ahowed a detection)
¦ ¦ ¦ ¦ /* AC OE PT HANDOFF */
¦ ¦ ¦ ¦ Update aircraft poaition and speed
1 1 1 el~a
¦ ¦ ¦ ¦ ~* ~aY BE AN ANYMAL OR SERVI OE TRUCK ~/
¦ ¦ ¦ ¦ Alert operator to po~ible incursion
¦ ¦ ¦ ¦ /* NaY BE AN AI~CRAFT ENTERI~G T~B SYSTEM */
¦ I I ¦ Start a ~ew track
¦ ¦ el~e
¦ ¦ ¦ Reque~t 0tatu~ ~rom adjacent light
32
¦ ¦ ¦ if (Adjacent light i~ OR)
¦ ¦ ¦ ¦ /* NON CONFIRMED DETECTION */
I I I elr~e
¦ ~ ¦ ¦ Flag ad~acent light for repair
¦ ¦ ¦ endif
¦ ¦ endif
¦ endi~
¦ if (Edge light lo~er~ a detection AND atat-l~ ir~ OK)
¦ ¦ if ~Naxt block sho~ed a detection)
~ P~OPER HANDOFF */
I I elr~
¦ ¦ ¦ i~ (vehicle apsed > - takeQff)
~ andof~ to departuro control
¦ ¦ ¦ el~e
¦ ¦ ¦ ¦ /* MI~SING HaNDOFF *~
Alert operator to po~ible incur ion
endif
I I endif
¦ ~ndif
¦ /* C~ECR FOR POSSIBLE COLLIS~ONS ~/
~or (all trac~ed aircra~t)
I j Plot futur~ positLon
¦ ¦ i (po~ition conrlict)
l l l Alert operator to por~ible incur~ion
¦ ¦ endif
I endif
¦ Update display
endwhile
R~3f erring agaill to ~IG . 1 and FIG . 2; the control of
taxiway lighting lnten31ty i~ u~ually done by plas::ing all
33
8 ~
the lights on the same series circuit and then regulating
the curren~ in that circuit. In the presen~ embodLment the
intensity of the lamp 40 is controlled by ~ending a message
with the light intensity value to the microproc~ssor 44
located within the ligh~ assembly ~l-n . The message allows
for intensity settings in ~he range of 0 to 100% in 0.5%
steps. The use of photocell 46 to chec.k the light output
allows a return message to be 3ent if the bulb does not
respond. This in turn generat~s a maintenance repor$ on the
j 10 ligh~. The strobe light 48 provides an additional optional
capability under program control of the microproce~sor 44.
~ach of the microproces~ors 44 in the edye light assemblies
20 is individually addressable. This means every l~np on
the field is controlled individually by the central computer
system 12.
The system 10 can be programmed to provide an Active
Runway Indicator by using the s~robe lights 48 in those edge
light assemblie~ 201n located on the runway 64 to continue
the approach light ~rabbit~ strobe pattern all the way down
the runway. This ligh~ing pat~ern could be turned-on as a
plane i~ cleared for landing and then turned-off after the
aircraft has touched down. A pilot approaching the runway
along an intersecting ta~iway would be alerted in a clear
and unambiguous way that the runway was ac~i~e and should
not be crossed.
2 ~ g 2
If an incursion was detected the main computers 26, 28
could switch the runway strobe lights 48 from the "rabbit"
pattern to a pattern that altern~*ively flashes either side
of the runway in a wig-wag fashion. A switch to this
pattern would be int~rpreted by ~he pilot of an arriving
aircraf~ a~ a wave off and a signal to go around. The
abrupt switch in ~he pattern of the strobes would be
in~ta~taneously picked up by the air crew in time for th~m
to initiate an aborted landing procedure.
During Category III weather conditions both runway and
taxiway visibility are very low. Currently radio ba~ed
landing systems are used to get the aircraft from final
approach to the ru~way. Once on the runway it is not always
obvious which taxiway~ are to be used to reach the airport
terminalO In system 10 the main computers 26,28 can control
the taxiway lamps 40 as the mean~ fsr guiding aircraft on
the ground during ~AT III conditions. Since the intensity
of the taxiway lamps 40 can be contrvll~d remotely, *he
lamp~ just in fron~ of an aircraft could be intensified or
flashed as a means of guiding it to the terminal.
Alternatively, a short sequence of th~ "rabbit" pattexn
may be programmed into the taxiway strobe~ ~ust in front of
the aircraft. At interseotions 7 either ~he unwant~d p ths
may have their la~p8 *urned off or ~he en~rance *o the
proper section of taxiway may fla~h directing the pilot ~o
2 ~ 2
head in ~hat direction. Of course in a smart system only
those lights directly in front of a plane would be ~:
controlled, all other lamps on ~he field would remain in
their normal mode. .
S Referxing now to FI&. 9, a block diagram is shown of
the data flow within the ~y~tem 10 (as ~hown in FIG. 1 and
FIG. 5). The software modules are shown that are used to
proces the da~a wi~hin the computers 26, 2B of the central
computer system 12. The tracking of aircraft and other
vehicles on the airport operates under the control of
~ensor fu~ion software module 101 which resides in the
computers 26, 28. The sensor fu~ion software module 101
receives data ~rom the plurality of sensors 50, a sensor 50
being located in each edge light assembly 201n which reports
the heat level detected, and this software module 101
combines this information ~hrough the use of rule ba~ed
artificial intelligence to create a complete picture of all
ground traffic at ~he airpor~ on a display 30 of the central
co~puter sy8t8m 12.
The tracking algorithm starts a trac~ upon the first
report of a sen~or 50 detecting a heat leYel that is above
the ambient background level of radiation. This d tection
is then verified by ch~cking ~he heat level reported by the
~ensor directly acro~s the pavement from ~he first reporting
sensor. Thi~ secondary reading is used to confirm the
vehicle de~ected and to elLminate false alarms. After a
vehicle has been con~irmed ~he sensors adjacent to the firs~
reporting sensor are queried for changes in their detected
! heat level. ~s soon as one of the adjacen~ sensors detects
I S a riss in heat level a direction vector for the vehicle can
:¦ be established. This process continues as the vehicle i3
I handed off from sensor to sensor in a bucket brigade fashion
;1 as shown in FIG. 7. Yehicle speed can be roughly determined
by calcul~ting the tLme be~ween vehicle detection by
adjacent sensors. Thi information i8 combined with
: information from a sy~tem data base on the location of each
sensor to calculate ~he veloci~y of the target. Due to hot
e~haust or ~et blast, the sensors behind the vehicle may not
return to a background level Lmmediately. Because of these
condition, the algorithm only uses the first four sensors
(~wo on either side of the taxiway) to calculate the
vehicles position. The vehicle is always ass~med to be on
the centerline of the pavement and betwee~ the first four
reporting sensors.
Vehicle identification can be added to the tra~k either
manually or automatically by an automated source that can
identify a vehicle by its position. An ex~mple would be
prior knowledge of the next aircraft to land on a particular
runway. Tracks are ended when a vehicle leaves the
detection system. This can occur in one of two ways. The
37
first way is ~hat the vehicle leaves ~he area covered by the
sensors 50. This is determined by a vehicle track moving in
the direction of a gateway sensor and ~hen a lack of
detection after the gateway sensor ha~ lost contact. A
second way to leave the detection sy~tem is for a tr~ck to
be lost in the middle of a sensor ~rray. Thi5 can occur
when an aircraft departs or a v~hicle runs onto the grass.
Takeoff scenarios can be de~ermined by calculating the speed
of the vehicl~ just before detection was lo~t. If the
vehicle speed was increasing and above rotation speed then
the aircxaft is assumed to have taken off. If not then the
vehicle is assumed ~o have gone on to the grass and an alarm
i8 sounded.
Referring to FIG. 5 and FIG. 9, the ground clearance
routing function is performed by the ~peech r~cognition unit
33 along with the ground clearance compliance verifier
~oftware module 103 running on the computers 26,28. ~his
software module 103 comprises a vehicle iden~ification
routine, clearance path rou~ing, clearance checking routine
2~ and a path checking routine.
~he vehicle identification routine is u3ed ~o receive
the airline name and flight number (i.e. ~Delta 374") from
the speech recognition uni~ 33 and it highligh~s the i~on of
that aircraft on the graphic display of the airport on
display 30.
38
-` 2 1 ~ 2
The clearance path routine takes the remainder of the
controller~s phrase (i.e. "outer taxiway to echo, hold short
of runway 15 Left~) and provides a graphical display of the
clearance on the display 30 showing the airport.
The clearance checking routine checks the clearance
path for possible conflict with other clearances and
¦ vehicles~ I a conflic~ is found the portion of the path
that would cause an incursion is highligh~ed in a blinking
red and an audible indication is given to the controller ~i~
speaker 32.
Th0 path checking routine checks the actual path of the
vehicle as detected by the sen~ors 50 after the clearance
path has been entered into the computerC 26, 28 and i.t
monitor~ the actual path for any deviation. If this routine
detects that ~ vehicle has strayed from the a~signed course,
the vehicle icon on the graphic display of the airport
flashes and an audible indicator is given to ~he con~roller ~-:
via speaker 32 and optionally the vehicle operator via radio
37.
The airport vehicle incursion avoidance system 10
oparates under the control of safety logic routines which
reside in the collision detection software module 104
running on c~mputers 26, 28. ~he safety logic r~utines
receive data from the sensor fusion software module 101
location program via the tracker software module 102 and
39
2 1 ~ 2
I interpret this information through the use of rule based
I artificial intelligence to predict posæible collisions or
I runway incur~ions. This in~ormation is then used by the
I central computer sys~em 12 to aler~ tower controllers,
aircraft pilots and ~ruck operator~ to the possibility of a
I runway incursion. The tower oontrollers are alerted ~y the
¦ display 30 along with a computer synthesized voice message
via speaker 32. Ground traffic is aler~ed by a combination
of traffic lights, flashing lights, stop bars and other
alert lightis 34, lamp8 40 and 48, and computer generated
voice commands broadcast via radio 36.
Knowledge ba3ed problem~ are also called fuzzy problems
and their solution~ depend upon both program logic and an
interface engine tha~ can dynamically create a decision
tree, selecting which heuristics are most appropriate for
the ~pecific oase being considered. Rule based systems
broaderl the scop~ of possible applications. They allow
designers to incorporate judgement and experience, and to
take a consisten~ solution approach across an entire problem
~0 8et.
The programming of the rule based i~cursion de~ections
software i8 very straight forward. The rules are written in
~nglish allowing th experts, in this case the to~er
personnel and the pilo~s, to review the system at an
under~tandable level. Another feature of the rule based
- ~ 2 ~
system is that the rules stand alone. They can be added,
deleted or modified without affecting the rest of the code.
This is almost impossible to do with code that is created
from scratch. An example of a rule we mi~ht use is.
If (Runway Statu~ = Active)
then ~Stop Bar Lighta = RED).
This is a very ~Lmple and ~traight forward rule. It ~tands
alone requiring no extra knowledge except how Runway_Statu~
is created. So let's make some rules affecting
Runway Statu~.
If ~Departura = APPROVED) or ~Landing = I~INENT),
then (Runway Statu~ = A~TIVE). ~
For incursion detection, another rule is: -
If (Runway_St~tu~ = A~TIVE~ and tInter~ction = OCCUPIED),
th~n (Runway Incur~ion = TRUE).
Next, deteet ~hat an inter~ection o$ a runway and taxiway
are occupied by the rules:
I~ ~Inter~ction_Sen~or~ = DET~CT),
then (I~ter~ectLon = OCC~PI~D). ~:
To predict that an aircraf~ will run a Hold ~osition stop,
the following rule is created:
If (Aircra~t_Stopping_Distance > Di~tance_to_Hold Poaition),
th~n ~Inter~ectLon = OCCUPIED)~
In order to show that rules can be added wi hout
affecting the rese~ o~ the program, assume that af~er a
demons~ration of the sy~ em 10 to tower controllers, they
41
2 ~ 2
, decided that they wanted a ~Panic Button~ in the tower to
- override the rule based software in case they spok a safety
,~ violation on ~he ground. Beside~ installing the button, the
;ll only other change would be to add this extra rule.
If (Par~ button = PRESSED),
th~n (Runway Incursion = TRIJE).
It is readily seen that the central rule based computer
program i8 very straight forward to create, understand and
modify. As types of incursio~s are defined, the system 10
. 10 can be upgraded by adding more rules.
Referxing again to FIG. 9, the block diagxam shows the
data flow between the functional elemen~3 within the system
10 (FIG. 1). Vehicles are detected by the sensor 50 in each
o~ the edge light assemblies 201~. This information is
pas~ed over the local operatiny network (LON) via edge light
wiring 211n to the LON bridge~ 221n. The individual message
¦ packets are then passed to ~he redundant computers 26 and 2B
o~er the wide area ne~work (WAN) 14 to the WAN interEace
108. After arriving at the redundant computer~ 26 and 28,
the message packet is checked and verified by a mes~age
parser software module 100. The contents o~ the message are
then sent to the sensor fusion ~oftware module lOlo The
sensor fusion softwar2 ~odule 101 is used to keep track of
the status of all the sensors 50 on the airport; it ~Eilters
and verifies the data from the airport an stores a
42
21 14~2
representative picture of th~ sensor array in a memory.
This information is used directly by the display 30 to show
which senssrs 50 are responding and used by the tracker
sof~ware module 102. Th~ tracker software module 102 uses
the sensor status information to determine which sensor 50
reports corre3pond to actual vehicles. In addition, as the
sen~or reports and status chanae, the tracker software
module 102 identifies movem~nt of the vehicles and produces
a target location and direction output. Thi~ information is
used by the display 30 in order to display the appropriate
vehicle icon o~ t~e screen.
The location and direction of the vehicle is also used
by the collision detection software module 104. This module
checks all of the vehicles on the ground and plot~ their
expected course. If any two taryets are on inter~ecting
paths, this software mo~ule generates operator alerts by
u3ing the display 30, the alert ligh~s 34, ~he ~peech
synthesis unit 29 coupled to the associated ~peaXer 32, and
the speech 3ynthesi~ uni~ 31 coupled to radio 37 which is
coup}ed to antenna 39.
Still referring to FIG. 9, ano~her user of target
location and position data i8 the ground clsarance
compliance verifier ~oftware module 103. This software
module 103 receives the ground clearance command~ fro~ the
controller~ 3 mîcrophone 35 via ~he speech recogni~ion unit
~3
--` 2 ~ 2
¦ 33. Once the cleared route has been determined, it is
stored in the ground clearance compliance verifier software
module 103 and used for comparison to the actual route taken
by the vehicle. If the information received from the
tracker software module 102 shows that the vehicle has
de~iated fxom it~ assigned course~ this ~Zoftware module 103
generates operator alerts by using the display 30, the alert
lights 34, the speech synthe~is unit 29 coupled to speaker
32, and the ~peech synthesis unit 31 coupled to radio 37
which iZ~ coupled to antenna 39.
The keyboard 27 is connected to a keyboard parser
softwar0 module 109. When a command has been verified by
the keyboard par~Zer software modul~ 109, it is used to
change display 30 option~ and to reconfigure ~he sen~or5 and
network parame~ers. A network configuration data base 1~6
is updated with these reconfiguration commands. This
i~formatioZn is then turned into LON message packets by the
command message generator 107 and seZnt to ~he edge light
assemblies 201n via the WAN interfac~ 108 a~d ~he LON
bridge8 22 l-n ~
Referring now to FIG. 1 and FIG. 10, FIG~ 10 shows a
pictorial diagram of an infrared vehicle identification
sZystem 109 invention comprising an infrared (IR) tran mitter
112 mou~ted on an airplane 110 wheel Ztrut 111 and an IR
reZceiver 128 which comprises a plurality of edge light
44
--` 2 ~ 8 2
assemblies 201n of an airport lighting system also shown in
FIG. 1. The combination of the IR transmi~ter 112 mounted
on aircraft and/or other vehicles and a plurality of IR
' receivers 128 loc~ted along runways and taxiways form the
¦ S infrared vehicle identification system 109 for use at
airports for the safety, guidance and control of surface
vèhicles in order to provide positive dletec~ion and
identification of all aircraft and other vehicles and to
preven~ runway incursions. Runway incursions generally
occur when aircraft or other vehicles get onto a runway and
I conflict with aircraft cleared to land or takeoff on that
¦ same runway. All such incursions are caused by human error.
¦ Referring now to FIG. 11, a block diagram of the IR
~i transmitter 112 is ~hown comprisiny an embedded
microprocessor 118 having DC power 114 inputs ~rom the
~ aircraft host or vehicle on which the IR transmit~er 112 is
¦ moun~ed and an ID switch 116 within the aircraft for
entering vehicle identificatio~ data which is received by
~ the IR transmit~er 112 on a ~erial line. Vehicle po~ition
¦ 20 information is provided to the IR transmit~er 112 from a
vehicle po~ition receiver 117 which may be embodied by a
global positioning system (GP~) receiver readily known in
the art. The output of embedded microproce~sor 118 feeds an
IR emitter comprising a light emitting diode (LED) array
120. When power i~ applied to ~he IR transmitter 112, the
211~482
microproces~or con~inuously outputs a coded data stream 121
IFIG. 13) which i3 transmitted by the IR ~ED array 120. The
embedded microprocessor 118 may be embodied by
microprocessor Model MC 6803 or equivalent manufactured by
Motorola Microprocessor Products of Austin, TPxas. The IR
LED array 120 may be embodied by IR LED Devices manufactured
by Harris Se~iconductor of ~Ielborne, ~lorida.
Referring now to ~IG. 12, a top view of the IR
transmitter 112 comprising the IR LED array 120 mounted on
an airplane wheel strut 111 is shown. The IR ~ED array 120
comprises a plurality of high power hEDs each having a beam
width of 15. By placing thirteen LEDs in an array, a 195
area can be co~ered. The IR LED array 1~0 illuminates edge
light assemblies 20l4 along the edges of the runway 64.
Each of the edge light assemblies 20l4 comprises an IR
receiver 12 8 .
Referring now to FIG. 13, the coded da~a stream emitted
from the IR transmitter 112 compriRes six separats fields.
The first field i~ called ~Lming pat~ern 122 and comprises a
sst of equally spaced pulses. The second field is called
unique word 123 which marks the beginning of a message. The
third field is called character count 124 which specifies :~
the number of character~ in a message. ~he fourth field is
called vehicle identifica~ion number 125. The fif~h field
i8 called ~ehicle posi~ion 126 and provides latitude and
46
- 21 ~4~L~2
longi~ude information~ The sixth field is called message
checks~m 127. The equally spaced pulse~ of the timing
pattern 122 allow the IR receiver 128 to calculate th~ baud
rate of a transmitted message and automatically ad~ust its
internal timing to compen~a~e for either a doppler shi~t or
an offset in clock frequency. The checksum 126 field allows
the IR receiver 128 to find the byte boundary. The
character count 124 field is used to alert the IR receiver
128 in the edge light as~emblies 20l4 as to the leng~h of
the message being received. The IR receiver 128 uses this
field to determine when the message has ended and if the
message was truncated.
The vehicle identification number 125 field comprises
an airline flight number or a tail number of an aircraft or
a license number of other vehicles. The actual number can
be alpha-numeric since each charac~er will be allocated
eight (8) bits. An ASCII code which is known to those of
ordinaxy skill in the ar~ is an example of a code type that
may be used. ~he only constrain~s on the Yehicl ID number
is that it be unique to th~ vehicle and ~ha~ it be entered
in the airport' 8 central computer data base to facilitate
automatic identîfication. The checksum 127 guarantees that
a complete and corre~t message is received. If the message
is interrupted for any reason, such as a blocked beam or a
2S change in vehicle direction, it is in~tantly detected and
47
~ 2
the reception voided. This procedure reduces the number of
false detec~s and guarantees that only perfect vehicle
identifisation m~ssages are passed on to the central
computer system 12 at the airport tower.
~eferring now ~o FIG.1, FI~. 2, FIG. 10 and FIG. 14, a
block diagram of th~ IR receiver 128 i~ sho~m in FI~. 14
which comprises and I~ sensor 130 connected to an edge light
a~sembly 201n shown in FIG. 1, PIG. 2 and FIG. 10, on an
airport. In FIG. 14, only ~he relevan~ portion of FIG. 2
are ~hown, but it should be understood that all of the
elements of the edge li~ht assembly 201n shown in FIG. 2 axe
considered pre~ent in ~IG. 14. The IR receiver 128
comprises the IR sen~or 130 which receives the coded data
stream 121 (FIG. 13) from the transmitter 112. The output
of the IR sensor 130 is fed to the microprocessor 44 for -~
processing by an IR message routine 136 for detecting the
data message. A vehicle sensor rou~ine 138 in
microprocessor 44 processes signals from the vehicle ~ensor
50 for detecting an aircraft or other ~ehicles~ The IR
message routine 136 is implemen~ed with ~oftware within the
microproce~sor 44 a3 shown in the flow chart of FI~. 15.
The vehicle ~en~or routine 138 is also Lmplemented with
~oftware within the microprocessor 44 as shown in the f~ow
chart of FIG. 16. The output~ of the IR mes~age routine 136
and v~hicle sensor routine 138 are processed by the
48
2~
microprocessor 44 which send~ via the power line modem 54
the identified aircraft or vehicle and their position data
over ~he edge light wiring 211n communication line~ to the
central compu~er system 12 shown in FIG. 1 at the airport
S v terminal or con~rol tower. The IR sensor 130 may be
embodied with Model RY5BD01 IR sensor manufac~ured hy Sharp
Electronics, of Paramus, New Jersey. The microprocesssr 44
may be embodied by the VLSI Neuron Chip, manufactured by
Echelon Corporation, of Palo Alto, California~
Referring to ~IG. 15, a flow chart of ~he IR message
routine 136 i8 ~hown which i~ a communication protocol
continuously performed in the microprocessor 44 of the IR
receiver 128. After an IR signal is detected 150 the next
action is tran~mitter acqui~ition or to acquire tLming 152.
The microprocessor 44 looks for the proper ~iming
relationship between the received IR pulse~. If the correc~
on/off ratio exists, the microprocsssor 44 calculates ~he
baud rate from the received tLming and waits to acquire the
unique word 156 ~ig~ifying byte boundary and then checks for
th~ cap~ure of the character co1ln~ 160 field byte. A:Eter
the character count i~ known, the microprocessor 44 then
capture~ each character in the vehicle ID 162 field and
stores th~m away in a buffer. It then captures vehicle
position 163 including lati~ude and longitude data. If the
IR coded dat~ ~tream i8 disrup~ed before all ~he vehicle ID
49
,'~ . ' ' '~" '`','',.'` ' " ' ',` '' ` ` ` ' `
characters are received, the microproces~or 44 aboxts this
recep~ion try and returns to the acquisition or I~ detected
150 sta~ After all characters have been received, the
checksum 164 is calculated. If the checksum matches 166,
then the message is validated and the vehicle ID relayed 168
to the central computer system 12. With this scheme the
microprocessor 44 is implementing both the physical and a
link layer of the OSI protocol by providing an error free
channel.
Referring now to FIG. 16, flow chart is ~hown of the
vehicle sensor rou~ine 138 software running on
microprocessor 44. This software rou~ine 138 runs as a
continuous loop. An internal timer i5 continuously checked
for a time out condition ~timer = zero 170). As soon as the
timer expires the analog value from ~ensor 50 is read ~ead
Sensor ~alue 171) by the microprocessor 44 and ~he timer is
reset to the poll_tLme 172 variable downloaded by the
central co~puter system 12. This sensor value is compared
again~t a predetermined detection threshold 173 and
downloaded by the cen~ral computer system 12. If ~he sensor
value is less than the detaction threshold, the
microprocessor 44 set~ the network variable prelim_detect to
¦ the ~ALSE state 174. If the sensor value i3 greater than
the detec~ion threshold the microprocessor 44 ~ets the
natwork variable prelim dP~ect to the T~UE state 17~. If a
5~
-~ 211~
preliminary detection is declared, the program then checks
to see what reporting mode 176 is in use. If all detections
are required to be sent to the central computer syst~m 12,
then this sensor value 180 is sent. If only those readings
that are different from the previous reading by a
predetermined delta and download by the central computer
~ystem 12, then ~his check is made 177. If the change is
greater than the delta 177, ~he program check~ to se~ if it
should confirm the detection 178 to eliminate any false
alarms. If a confirmation is not required, then this sensor
value 181 is sent. If in the confirmation mode, then the
adjacent sensor~s 179 prelLminary network variable is
checked. If the adjacent sensor has also detected the
ob~ect, then the current sensor value 182 i5 sent.
This concludes the description of the preferred
embodiment. However, many modifications and alterations
will be obvious to one of ordinary skill in the art without
departing from the ~pirit and scope of the inventive
concept~ Thsrefore, it i~ intended ~hat the scop~ of this
invention be limited only by the appended claLms.
