Roadmap for technology development and validation

Transcription

1 Roadmap for technology development and validation Alessandro Neri*, Francesco Rispoli**, Salvatore Sabina**, Veronica Palma*, Cosimo Stallo*, Andrea Coluccia*, Alessia Vennarini*, Pietro Salvatori* *RadioLabs **ANSALDO STS

2 ERTMS/ETCS Train Localization GPS RBC ETCS trainborne position report Balise In ERTMS/ETCS Train location is determined by means of Balises and Odometry The Balises are transponders deployed at georeferenced points The odometer provides the relative positioning w.r.t. the last balise When the Balise Reader energizes a balise, it receives a message with the balise Id The on board computer (EVC) sends a position report to the Radio Block Center

3 ERTMS/ETCS GNSS based Train Localization GPS BEIDOU RBC ETCS trainborne position report Interlocking Virtual Balise The GNSS Location Determination System generates the same signals produced by a Balise Reader detecting a physical Balise, through the same logical and physical interface, then emulating the Balise reader behavior with respect to the train equipment. In this way the On Board ERTMS/ETCS location determination functions do not need to be changed.

4 GNSS-based services for Train Control GNSS based train location determination can be considered a disruptive technology. It will succeed in replacing the current technologies based on balises and track circuits if and only if it will be cost-effective. THR 2X10-9 /h Functionality Current Technology SIS Integrity Monitoring Augmetation Accuracy Train Location Determination Single track Train Location Determination Multiple tracks Based on Balise + Odometry Based on Balise, Track Circuit X X Medium X X High Train Integrity Track Circuit + On Board Circuitry X High

5 ERSAT EAV High Integrity Augmentation Architecture GPS BEIDOU SPACE SEGMENT Radio Block Center QoS EGNOS RS 1 RS 2 RS N LDS OBU TAIM TALS QoS EDAS TAAN - CPF Track Area Augmentation Network CPF TALS RS EDAS LDS OBU Central Processing Facilities Track Area LDS Server Reference Station EGNOS Data Access Service Location Determination System On Board Unit

6 ERSAT EAV 2 nd Tier Reference Stations Sites Location Cagliari Sanluri Vallermosa Guspini Iglesias Serramanna Premises Revenue Agency Revenue Agency Municipality Municipality TBD Train Station

7 ERSAT EAV 2-tier Local Integrity Function implements a Fault Detection and Exclusion algorithm aimed at the detection of o single satellite faults o constellation faults o RIM faults verifies health status of each SIS at RIM level. RIM Faults detection and exclusion from augmentation computation Residual Double Differences

8 RIM FAULT DETECTION AND MITIGATION - LDS Performance VIRTUALIZED TESTBED: SYNTHETIC (FAULTY RIM) + RECORDED DATA (EGNOS, HEALTHY RIMS, OBU) One faulty RIM with simulated fault corresponding to an increase of the measurement noise, σ F = 2.5 m. RIM, cod Fault detection & exclusion OFF Fault detection & exclusion ON

9 GNSS AND ODOMETER FUSION Given the train mileage estimated by the GNSS LDS at time t h the distance travelled by the train during the interval [t h, t k ] the mileage of the train at time t k can be computed as m st ˆ( ; t) = sˆ ( t) + s ( t, t) k h GNSS h OD h k From the statistical independence of GNSS LDS and Odometer estimation errors it follows that the variance of estimate is σ sˆ ( tk; th) = σ s ( t ) m (, ) GNSS h + σ t s h t k OD 2 ( t t ) σ t t ( t ) σ ( ; ) σ ( ) + α sˆ tk th s th + σ β k h V ( k h), tk h GNSS Protection Level (solution Separation Method) PL t t k t t b t s t s t ( n) (0) ( n) ( ; ) =, σ ( ; ) + ( ) + ( ) ( ) sˆ n k h md n ( n ) k h Max h GNSS h GNSS h { } PL( t ; t ) = Max PL ( t ; t ) k h n k h 0 n N F OD

10 GNSS AND ODOMETER FUSION In principle, for a given time instant t k,several estimates can be performed by varying t h in the interval [t k - t, t k ] This redundancy can be exploited to filter out outliers produced by local hazards

11 Experimental results Test campaign in the framework of the ESA ARTES 20 3InSat project PONTREMOLESE line Line length: 120 km Physical Balises: about 500 Track AreaAugmentation Network 3 RIMs equipped with 2 GPS receivers each Trains: 2 Ale.642 tractions equipped with 2 GPS receivers each Track Database based on RTK positioning survey

12 Experimental results Test campaign in the framework of the ESA ARTES 20 3InSat project PONTREMOLESE line Line length: 120 km Physical Balises: about 500 Track AreaAugmentation Network 3 RIMs equipped with 2 GPS receivers each Trains: 2 Ale.642 tractions equipped with 2 GPS receivers each Track Database based on RTK positioning survey Challenging environment w.r.t. multipath Tunnels Sky occlusions

13 Experimental results

14 Integrity Monitoring

15 TRAIN INTEGRITY functionality to determine whether all carriages are still coupled each others, and, in case, to rise a timely alert. Rear position Gap Front position Goal: Baseline Define a Virtual Track Circuit to reduce operational cost and increase the line capacity. Approach: Apply a double difference algorithm to the SISs received by a pair of GNSS receivers and exploit the Track constraint Front position Rear position

16 Gap emulation Mileage between receivers [m] Estimated mileage between receivers Real mileage between receivers Elapsed time from beginning of simulation [s] The train moves at constant speed (80 km/h) Detection Error Tradeoff Curves for MooN Approach 10 0 The train is a rigid block (no dynamic coupling between carriages) One of the carriages decouples from the previous one The front train section continues its 10-8 movement after the decoupling as if nothing Single Detector has been occurred oo3 Approach 2oo4 Approach The tail section stops only by action of rolling 10 resistance 3oo4 Approach 10 Track slope effect has been neglected P md =(1-P D ) P fa

17 Performance Assessment: The Virtualized Testbed Assessing the performance of a Safety of Life system is a rather challenging task due to the fact that very small probabilities are involved. Approach: virtualized testbed, with rich sets of data collected in a real railway environment (e.g., 3InSat & ERSAT EAV Test Bed), historical time series related to rare GNSS SIS fault events (satellite malfunctions and atmosphere anomalous behaviors) simulated faults for the new-coming constellations

18 GSA H2020 RHINOS Project Railway High Integrity Navigation Overlay System RadioLabs Ansaldo STS SOGEI Stanford University Nottingham University Univerzita Pardubice DLR Deutsches Zentrum Fuer Luft - Und Raumfahrt EV Based on international cooperation between EU and USA Objective a positive step beyond the proliferation of GNSS platforms, mainly tailored for regional applications, in favour of a global solution. Work programme investigation of candidate concepts for the provision of the high integrity needed to protect the detected position of the train, as required by the train control system application. Reference Infrastructure GNSS (GPS and GALILEO) plus the SBAS (EGNOS and WAAS) Local augmentation elements, ARAIM techniques and other sensors on the train are the add-on specific assets for mitigating the hazards due to the environmental effects which dominates the rail application. Ambition Fast release of the potential benefits of the EGNSS in the fast growing train signalling market.

19 Conclusions Multi-constellation architectures offer higher degree of flexibility to reach the SIL-4 level (recommended for high demanding accuracy in the railways applications). Nevertheless, the availability of an augmentation network is of paramount importance in reducing the Protection Level. Sharing as much as possible of the supporting (i.e., augmentation) infrastructure and on board processing, including new developments such as Advanced Receiver Autonomous Integrity Monitoring (ARAIM), with the avionics field is a key factor for cost effectiveness. Definition of a standard for the Railway High Integrity Navigation Overlay System is a key success factor for spreading the GNSS application into the rail. Definition of a strategic roadmap for the adoption of an international standard is of primary concern.

20 THANKS FOR YOUR ATTENTION

21 Simulation tool Scenario definition GNSS records DB LAAS Servers DB RIM RU DB Track & Train DB DTM EM Environment DB Analytics Satellite Orbit Generator GNSS Tx Signals Generator Propagation RIM RU RIM RIM RU RU TAAS IP Backbone TALS Server Train Motion OBU Head GNSS Rx GNSS Localization GNSS Train Integrity Train Control Command Generator OBU End GNSS Rx GNSS Localization

22 Multi-constellation Approach Single constellation False Alarm Probability : 1 γ k Pfa, k = erfc 2 σ L 2 k Neyman Pearson criterion γ ( P ) NP 1 k 2σL erfc 2 fa = k 2 erfc( x) = e t x π 2 dt Single constellation detection probability 1 k PDk, [ ] erfc δ δ = γ 2 2 σ L NK k Than an all in view or an M out of N combination can be applied

23 Protection Level Evaluation We can define Protection Level as a statistical over bound of the gap estimation error. In fact Nominal p-th Satellite location β p decoupled Lˆ > < η coupled True p-th satellite location We have to link the train integrity issue with the SIS integrity issue Rx E r p Rx E e p Rx E b Rx H r p Rx H e p Rx H

24 Double Difference approach Sat i SD = r 1 ˆ, ˆ, ˆ e e be i i i i i Rx Rx Rx Rx H H E E b eˆ, eˆ b i Rx H DD = SD SD = ij Rx Rx i j H E Rx E ˆ i e Rx E b eˆ, eˆ b eˆ b i Rx E b 90 ˆ i e Rx H Rx H i i i j j j = r 1 ˆ, ˆ 1 ˆ, ˆ RxH RxH Rx r e e E Rx H erx e H Rx + E i j be, ˆ eˆ. Rx E Rx We adopt a constrained positioning algorithm to map the 3-D estimation problem into a 1-D estimation problem E ( m) ( m) ( m) G = eˆ ˆ b e H be, ˆ ( m) ( m) b h e b h H = H G ( m) ( m) ( m) constr

25 Train Integrity Train Integrity is the ability to determine whether all the carriages are still coupled each others and, in case, to rise a timely alert. Gap Actual Train Length Gap Braking curve