Intelligent Transportation Systems ICT for Collision Avoidance in Transportation Prof. Dr. Thomas Strang
Outline
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
ICT based Collision Avoidance for Aircrafts Maritime (Ships) Railways
ATC, TCAS, ADS-B AIS RCAS
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Collision Avoidance for Aircrafts (ATC, TCAS, ADS-B)
Slide 3
Several information and communication technologies (ICT) are used to communicate with, navigate and monitor aircrafts The most relevant ones for this lecture are Air Traffic Control (ATC) Traffic Collision Avoidance System (TCAS) Automatic Dependent Surveillance-Broadcast (ADS-B)
[Moir & Seabridge, 2006]
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
RF Spectrum
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Base: Radio Detection and Ranging (RADAR)
Slide 5
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Air Traffic Control (ATC) A ground-based primary surveillance radar (PSR) detects the presence of an aircraft and indicates its bearing and distance. At the same time a secondary surveillance radar (SSR), synchronized with the PSR, interrogates the aircraft using a series of pulses. The aircraft transponder responds with a different series of pulses containing situational information, typically its aircraft identifier and altitude. The information from the PSR and SSR is then integrated and presented on the ATC console.
Transponder: automatic device that transmits a predetermined message in response to a predefined received signal.
1300 MHz (echo)
Transponder Modes used in ATC
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Mode A (simple system): Aircraft identification (12 bit=4.096 codes, e.g. “7000”, but not call-sign) So called “Squak”, dyn. assigned by ATC
Mode C (more advanced): Mode A + altitude
Mode S (more recently): Mode C + 24 bit address identifier (hardcoded) S = select: discrete addressing to interrogate just one aircraft Provides limited air-air and air-ground communications Can also provides whereabouts of other aircraft in its vicinity Uses digital error-correcting codes for improved reliability EEE381B
Transponder Interrogation & Response
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Interrogation sent from ground on 1.030 MHz Time between P1 and P3 determines mode P2 (omni) is used to detect main lope When directional P1 is not at least 9dB greater than the omnidirectional P2 pulse, no reply will be generated. Airborne transponder mode A/C responds on 1.090 MHz Coded reply in frame with duration of 20,3 microseconds
Reply code is divided into four interleaved pulse groups labeled A, B, C, and D, expressing 3 bits each, i.e. 12 bits alltogether Slide 8
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Altitude Encoding 12 bit Gillham Code (special Gray Code) Hamming Distance = 1 for two adjacent altitudes Difference to Standard Pressure Altitude 1013 hPa Usualla not equal to „real“ altitude as this depends on current pressure at current position in the atmosphere
e.g. FL100 (10.000 ft above 1013 hPa level) Difference +10.000 ft Gilham Code = 000011101010
1013 hPA level (at mean sea level / 0 ft altitude in standard atmosphere)
Slide 9
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Traffic Collision Avoidance System (TCAS) Introduced to reduce the risk of midair collisions between aircraft. Interrogates other aircrafts in its vicinity and listens for the transponder replies. TCAS builds on airborne ATC equipment, in particular .. requires that all possible conflict aircraft are equipped with an SSR transponder. Mandated above 10,000 ft Altitude and identification is obtained from modes C or S of an airborne ATC transponder (only bearing from mode A). Distance is obtained by calculating the response delay. Directional antennas obtain the bearing of the responding aircraft.
different TCAS cockpit displays
TCAS types
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
TCAS I Indicates distance and bearing Issues traffic advisories (TA) : 'TRAFFIC, TRAFFIC’
TCAS II Negotiates and indicates deconfliction strategies Issues resolution advisories (RA): ‘Climb Climb Climb’, ‘Descend Descend Descend’, ‘Maintain vertical speed … ’, ...
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
3D Threat Surveillance
[Williams, 2004] Slide 12
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Automatic Dependent Surveillance Broadcast (ADS-B) • Automatic – Periodically transmits information with no pilot or operator input required, nor common or specific interrogation
•
Dependent – Position and velocity vector are derived from the Global Positioning System (GPS)
•
Surveillance – A method of determining the position of aircrafts, vehicles, or other assets
•
Broadcast – Transmitted information available to anyone with the appropriate receiving equipment
ADS-B
(Transponder in „Squitter“ Mode)
Hi, I´m Aircraft AXX, and my position is X3,Y3, Z3
Hi, I'm Aircraft A7E579 and my position is X2, Y2, Z2
[Rico-Garcia, 2007]
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Hi, I'm Aircraft 3C4283 and my position is X1, Y1, Z1
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
No system is perfect: Überlingen, July 1, 2002 Boeing & Tupolew crossing Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
B757-200
TU154M
!
21:33:03 Alarm from Collision Avoidance System (TCAS)
21:34:49 Human controller command
[Frehse, 2005]
No system is perfect: Überlingen, July 1, 2002 Boeing & Tupolew crossing Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
B757-200
TU154M
!
21:33:03 Alarm from Collision Avoidance System (TCAS)
21:34:49 Human controller command
21:34:56 TCAS recommendation
[Frehse, 2005]
No system is perfect: Überlingen, July 1, 2002 Boeing & Tupolew crossing Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
B757-200
TU154M
!
21:33:03 Alarm from Collision Avoidance System (TCAS)
21:34:49 Human controller command
21:34:56 TCAS recommendation
21:35:32 Collision [Frehse, 2005]
No system is perfect: Überlingen, July 1, 2002 Boeing & Tupolew crossing Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
B757-200
TU154M
!
21:33:03
Alarm from Collision Official Recommendation: Avoidance System (TCAS)
21:34:49 “pilots are to obey and Human controller command follow TCAS advisories, regardless of whether21:34:56 contrary instruction is given” TCAS recommendation
21:35:32 Collision [Frehse, 2005]
[Schanne/FAA, 2006]
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Not every „aircraft“ is equipped with transponders
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Literature
http://www.amazon.de/Avionik-Flugsicherungstechnik-Einf%C3%BChrung-Kommunikationstechnik-Surveillance/dp/3642016111
Slide 21
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Collision Avoidance for Ships (AIS)
Slide 22
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Maritime Automatic Identification System (AIS) The Automatic Identification System (AIS) is designed for improving safety and efficiency of navigation in the open sea and coastal waters through the automatic exchange of navigational, statistic and voyage information between the ships and coastal stations.
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Establishing “Maritime Awareness” through AIS Automatic Identification System (AIS) Mandated on all vessels over 300 gross tons (IMO) Two types of shipboard AIS: CLASS A: 300+ gross tons subject to SOLAS 12.5W VHF Antenna GNSS Receiver link Maritime electronic data interface VHF receivers CLASS B: Smaller vessels 2W VHF Antenna w/ GPS receiver GNSS Position normally derived from ship position receiver Timing from integrated GPS receiver
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Automatic Identification System (AIS) Dynamic information transmitted (every ~2-10 seconds): Course over Ground (COG) Maritime Mobile Service Identity (MMSI) Number Latitude & Longitude (position as determined by GNSS) Navigation Status, in particular position accuracy Differential GPS Indication if Receiver Autonomous Integrity Monitoring (RAIM) processing is being used (Class B only) True Heading and Time Stamp
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Automatic Identification System (AIS) Static information transmitted (every 6 minutes): Destination (20 characters) Dimensions of vessel to nearest meter Draught of vessel ETA at Destination (In UTC) Name Radio call sign: International call sign Type of ship & cargo (i.e. Tanker, petroleum) Type of positioning fixing device
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
AIS. Automatic Identification System All the ships interchange over the system continuously their data. Static Information: 6 min. Dynamic Information
AIS uses GNSS to calculate its own position and timing.
MAC Layer: SOTDMA Physical layer: VHF [Rico-Garcia, 2007]
Speed
Dynamic Report Rate
< 14 knots
10 sec.
< 14 knots and changing course
3.3 sec.
14 > < 23 knots
6 sec.
14 > < 23 knots and changing course
2 sec.
> 23 knots
2 sec.
> 23 knots and changing course
2 sec.
At Anchor or moored > 3 Knots
30 sec.
At Anchor or moored < 3 Knots
3 minutes
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Comparison Frequency
AIS
ADS-B
TCAS
AIS1: 161.975 MHz
1090 MHz
Interrogation: 1030MHz
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
AIS2: 162.025 MHz
Answer: 1090 MHz
Bandwidth
12.5 or 25 MHz
10 MHz
10 MHz
Modulation
GMSK FM
Pulse position
Binary Modulation
Power
12.5 W
250 W
250 W
Message Length
256 bits
112 bits
56 or 112 bits
Data Rate
9.6 kbps
1 Mbps
1 Mbps
Message Rate
2 sec. – 3 min.
0.4-0.6 sec.
1 sec. for threats
Users
Around 400 ships.
MAC Layer
SOTDMA
Aloha
30 aircrafts Interference limiting. Passive detection. Directional Antenna. Aloha.
Data Link Layer
HDLC
Address Check Code
Parity Check Code in Address
Range
28-55 km
370 km
56 km [Rico-Garcia, 2007]
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Collision Avoidance for Railways (RCAS)
Motivation
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Accidents in Rail Traffic in Germany 14 12 10 8 6 4 2 0
(Source: Freenet-Lexicon, 06.09.2005)
Collisions
Others Collisions
1971- 1976- 1981- 1986- 1991- 1996- 20011975 1980 1985 1990 1995 2000 2005 DB: "251 collisions on German railroad crossings in 2004" Others, e.g. derailment
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Equivalence to Air and Sea Transport
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Collision Avoidance using GNSS and local broadcast („RCAS“) Railway specific technical and operational requirements Know-How Traffic Alert and Collision Avoidance System (TCAS, ADS)
Know-How Maritime Automatic Identification System (AIS)
Railway Collision Avoidance System (RCAS) using ad-hoc train-to-train communications
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Alert!
EBULA
Railway specific conditions
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Movement trajectory of Trains are highly predictable (~ 1D) Movement vectors pointing to each other sometimes indicate a dangerous situation, but are also sometimes desired as in Joining of two trains Overtaking while running Only reduced reactions possible in the case of a detected conflict: Braking or acceleration by the train driver Set and interlock of routes by the signaller Railway tracks are normally above ground, but some effects influence satellite reception: Tunnels (Shadowing) Station roofs (Shadowing) Buildings beside the track (Reflection and Multipath)
Basic recognisable scenarios Train 2
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Train 1
Track 1 Track 2
No Collision Train 2
Train 1
Track 1
Head-on collision erkannt Track 1 Train 1
Train 2
Track 2
Rear-end collision Train 2
Weiche 1
Track 1 Track 2
Train 1
Collision detected on the basis of a digital map (flanking) Weiche 1 Train 1
Weiche 2
Collision can not be ruled out
Train 2
Track 1 Track 2
GNSS in Railway Environment
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Integrity Local Elements Position Direction Speed Railway Environment with: shadowing, reflection and multipath effects Topological Route Map – Today partially available in the train – Safe and track selective map matching using safety of life (SoL) service
RCAS transmission procedures
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
[Bilder: http://www.skydsp.com/publications/4thyrthesis]
concurrent access on shared medium „frequency“ requires reliable medium access procedure, e.g.
FDMA
TDMA
alignment to road-based C2C/C2I frequencies at 5.9 GHz (e.g. addressing the "daily" railroad crossing collision in Germany)
CDMA
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Example Structure of RCAS Telegram Parameter
Meaning
Possible values / examples
RCAS-ID
Unique identification of the RCAS unit
Time stamp
Absolute time
UTC
Type of object
Classification of the RCAS Unit
Train mission Out-of-gauge transport construction site, …
Position in train
Position of the RCAS unit in the train
Head Tail
Out-of-gauge class
Class of out-of-gauge load transport
None, A, B, C, D
LX status
Result of danger zone supervision
Secured, cleared Secured, temporarily occupied Secured, static occupied Unsecured Unknown
Train length
Total length of train
in m
Topol. position
Track element ID
Track vector
List of next track elements
Geogr. position
WGS84 Position information
Lat, Lon, Alt
Speed
Absolute speed of train
in km/h
Dangerous goods ID
Classifier according to the EU standards
UN No.
Railway specific data to be transmitted
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Out-of-Gauge class ("LÜ") 4 classes: N
A
B
C
D
acceptable situations on parallel tracks: A
N
B
N C
N
N
A
B
B
B
D C
A
A
B
N
A
A
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Railway specific extensions critical goods surveillance
Railway specific extensions
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Sensor information propagated by trains in the vicinity GPS/ GALILEO „Friction Value 0.08 (Ice)“
Temperature Sensor
Where GNSS may also help for RCAS…
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Interferences caused by high vehicle density in a geographic region assigning region-specific Multiple Access slots via GNSS
Securing trackway workers today
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Alarm Bell
Train
Kable Trackway Contact
Physical Balise
Workers
Collision Avoidance between Trains and Humans Alarm Bell Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Position Train
GNSS
Virtual Balise
Physical Balise
Workers
Collision Avoidance between Trains and Humans
GNSS Alarm Bell
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Position SAR Distress Train
GSM-R o. RCAS Virtual Balise
Physical Balise
Workers
Lecture Intelligent Transport Systems, Prof. Dr. Thomas Strang, SS 2010
Conclusions Several ICT based collision avoidance systems are used already in different transport systems, including Aircrafts, Ships, and Railways Systems are designed to the particular needs and constraints of the particular mode of transport In the future similar system also available for cars?
