A Multi-sensor Platform for High Integrity Multi-modal Positioning System

Roberto Capua, Ales Filip, Alessandro Neri, Sam Pullen, Francesco Rispoli, Pietro Salvatori, Cosimo Stallo

Abstract:	The GNSS has been selected as one of the main step charge innovation in the land transportation domain. This contribution considers as target users’ railway and automotive applications. As a matter of fact, these two applications share the same electromagnetical environment and both of them are subjected to constrained movement profile. More in details, train signalling, connected cars and UAV for surveillance of roads and railways can take advantage of this technology to realize cost-effective solutions for high integrity and high accuracy positioning systems. One of the objectives is to create a synergic ecosystem among rails and roads sharing digital infrastructures, safety and certification processes to lower energy consumption and pollution. Furthermore, the liaison among these two transportation means is motivated by a market perspective. In fact, the rail stand-alone marketplace for GNSS localizers will never be so large as to motivate volume production while the driverless cars can target to millions of vehicles [1]. The main pillars behind this solution are the implementation of a high-performance Multi-modal Augmentation & Integrity Monitoring Network (AIMN) and a multi-sensor on-board unit (MOBU). The multi-modal AIMN will be design to complement the existing SBAS systems. Furthermore, the number of local stations can be reduced thanks to the synergy between rail and road application. In addition to that, UAVs operations monitoring the roads and railways assets, can take a boost to these applications contributing again to a significant reduction of energy and pollution. Concerning the OBU, a data fusion among several sensors will be used to increase the availability and the accuracy; however, to increase the system integrity, the final solution will be designed by accounting for at least two independent estimation chains. In terms of Key Performance Indicators, land transportation systems require not only high integrity and high accuracy, but also navigation solutions validated and certified according to standardized procedures. The actual trend to fulfil these requirements is to resort to the functional redundancy by exploiting the integration of multiple low-cost Commercial Of The Shelf (COTS) sensors, including GNSS receivers, IMUs, Odometers and speedometers, LIDARs, video cameras, and so on. In terms of performance assessment, at the moment the major role has been spent on the Position domain. Nevertheless, also the Velocity and the Timing will play a central role in the future applications both for rail and for automotive sectors. Particularly, in the railway domain, the Moving Authority (a set of information required for the train to move within the ERTMS system) contains the speed restrictions that the train must follow. The speed information will be crucial in the ERTMS Level3 when the distance among two consecutives convoys will be dynamically allocated under the moving block approach. Concerning the automotive, the velocity estimation (both longitudinal and lateral) are crucial in the overtake procedure (e.g. to estimate if there is enough space to return into the lane after the overtake without colliding with a car occupying the other lane). Having a high integrity and high accuracy velocity estimation will play an important role In all these applications. Beside the speed, the timing is crucial for all the applications related to cooperative navigation like the platooning for example where the synchronization of the PVT solution will be mandatory or when the relative position among vehicles will be used. A major role in the framework of high integrity and high accuracy land transportation positioning systems is played by the requirements definition. Particularly, each application will have a set of specific user requirements expressed both in term of functional and non-functional requirements. This requirement will be retrieved according to the use cases taken from the standards (like ERTMS, SAE and CENELEC norms). The first challenge to realize the multi-modal platform is to provide a harmonized set of requirements. The first aim of this work is to lay the basis for a shared framework among railway and automotive requirements mapping them from the uses cases to the system requirements. In this work different categories of requirements will be considered such as: functional, performance, and interface. Particular emphasis will be given in the safety case study. The apportionment of the requirements from system to the subsystem level will be derived through a fault tree analysis. In the full paper, the full process from the user requirements collection to the system and sub-system level requirements definition will be described. Particularly, the selection of the use cases and operational scenarios from the norms and from the state-of-the-art documentation will be described. The user requirements will be collected and described as well as their harmonization exploiting the synergies among rail and road will be shown. After that, the mapping of user requirements into system requirements will be given and the apportionment of requirements from system to the subsystem level will be shown through the fault tree analysis. Finally, from the obtained set of requirements a candidate architecture solution will be provided. [1] Salvatori, Pietro, Stallo, Cosimo, Coluccia, Andrea, Pullen, Sam, Lo, Sherman, Neri, Alessandro, "An Augmentation and Integrity Monitoring Network for Railway and Automotive Transportation," Proceedings of the 2019 International Technical Meeting of The Institute of Navigation, Reston, Virginia, January 2019, pp. 790-801. https://doi.org/10.33012/2019.16724
Published in:	Proceedings of the 33rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2020) September 21 - 25, 2020
Pages:	362 - 386
Cite this article:	Capua, Roberto, Filip, Ales, Neri, Alessandro, Pullen, Sam, Rispoli, Francesco, Salvatori, Pietro, Stallo, Cosimo, "A Multi-sensor Platform for High Integrity Multi-modal Positioning System," Proceedings of the 33rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2020), September 2020, pp. 362-386. https://doi.org/10.33012/2020.17608
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