Intelligent Transportation Systems. ICT for Collision Avoidance in Transportation. Prof. Dr. Thomas Strang

Intelligent Transportation Systems ICT for Collision Avoidance in Transportation Prof. Dr. Thomas Strang Outline Lecture Intelligent Transport Syst...
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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?

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