Blaise Conrard

Multilevel Modeling of the Traffic Dynamic

Currently traffic management is becoming more important to achieve the goal of sustainable transport, and a good traffic model can describe the traffic behavior efficiently. The traffic models can be classified based on level of details as submicroscopic-, microscopic-, mesoscopic-, and macroscopic-level models. In this paper, we provide a review of the four types of models (submicro, micro, meso, and macro) and then propose a multilevel model of traffic, which combines submicroscopic, microscopic, and macroscopic levels of traffic model. In this work, we do not consider the mesoscopic-level model. At the submicroscopic level, we develop a bond graph model of a four-wheeled vehicle considering the longitudinal, lateral, yaw, and actuator dynamics. At the microscopic level, we develop a car-following model based on virtual interconnections between the submicroscopic bond graph models of vehicles. Then, at the macroscopic level, we deduce macroscopic variables (average speed, density, and flow) from the submicroscopic and microscopic models. Having a multilevel model of traffic allows combining two properties of modeling simulation, one in real-time mode at microscopic and submicroscopic levels and the other at offline mode at macroscopic level. Thus, the whole supervision of the road traffic can be performed. Finally, the multilevel model of traffic is validated on a real-time simulator of vehicle dynamics, based on experimental measurements acquired from intelligent autonomous vehicles (IAVs). In addition, real experiments on IAVs are performed to validate the model.

Instrumentation for electrical vehicle model on road slope using structural analysis

This paper focuses on the design of instrumentation of the control system for electrical vehicle model. The method is based on a structural model that describes qualitatively the different relations of the physical variables. The motivation for the choice of structural analysis approach is that this analysis uses a poor knowledge of the system; it uses only the relation between constraints and variables. By analyzing this model, we obtain the different ways to control the unknown variables in function of the sensors measurements and thanks to the available actuators. The main contributions of this paper combines the merits of: i) the modified structural analysis model in order to take into account different operating cases slope of the road constant and variable and their specific features; ii) to study reject disturbance using graph techniques; iii) to obtain the optimal instrumentation for the system of electrical vehicle which insure controllability in despite of the disturbance.

From extended integrity monitoring to the safety evaluation of satellite-based localisation system

Global Navigation Satellite Systems (GNSS) such as GPS, already used in aeronautics for safety-related applications, can play a major role in railway safety by allowing a train to locate itself safely. However, in order to implement this positioning solution in any embedded system, its performances must be evaluated according to railway standards. The evaluation of GNSS performances is not based on the same attributes class than RAMS evaluation. Face to these diffculties, we propose to express the integrity attribute, performance of satellite-based localisation. This attribute comes from aeronautical standards and for a hybridised GNSS with inertial system. To achieve this objective, the integrity attribute must be extended to this kind of system and algorithms initially devoted to GNSS integrity monitoring only must be adapted. Thereafter, the formalisation of this integrity attribute permits us to analyse the safety quantitatively through the probabilities of integrity risk and wrong-side failure. In this paper, after an introductory discussion about the use of localisation systems in railway safety context together with integrity issues, a particular integrity monitoring is proposed and described. The detection events of this algorithm permit us to conclude about safety level of satellite-based localisation system.

Multilevel Reconfiguration Strategy for the System of Systems Engineering: Application to Platoon of Vehicles

In the present work, a generic method for multilevel modeling and reconfiguration of the System of Systems Engineering (SoSE) is proposed based on the bond graph modeling approach. The proposed formulation is applied to the road traffic dynamic for a platoon of Intelligent Autonomous Vehicles (IAVs). A bond graph model-based reconfiguration strategy is proposed for the multilevel model of the road traffic dynamic combining three levels namely submicroscopic, microscopic and macroscopic. This multilevel model is simulated for two scenarios of normal and faulty situations in a platoon of four IAVs.

Sensitivity assessment to analyse dependability of a multisensor localisation system based on GNSS

This paper proposes to use sensibility measures to analyse the dependability and safety of railway localisation systems based on GNSS. In such systems, train positions are determined by combining all available sources of localisation information. However, each source of data suffers from specific errors, which are inherent to the nature of the sensors and, which are difficult to manage with common dependability methods. The proposed evaluation method based on a sensitivity analysis aims at showing the influence of the variability of sensor parameters on the RAMS (Reliability, Availability, Maintainability and Safety) attributes. This implies (i) to identify characteristics of the different sensors that compose the system like features, behaviour and error model, and (ii) to make assumptions about the nature of position error on the output system (continuity, differentiability, etc...). This paper proposes a sensitivity computation method and interpretations related to a train positioning system. This can constitute a new approach in dependability analysis in GNSS-based systems with a low or nonexistent feedback.

Design methodology of a reliable control system using a structural analysis approach

This work focuses on developing a design methodology for reliable control system instrumentation. This methodology aims at optimising the instrumentation using a dependability criterion based on reliability and cost. The design methodology is primarily based on three processes: structural analysis of the relations between different variables and physical quantities that govern the system; evaluation of the reliability of the main mission of the control system instrumentation using the structural links, which depends on a graphical tree representation of the system in the design phase; and optimisation, which allows us to determine the best architecture for instrumentation. This methodology is illustrated for the design of an electric vehicle.

Bond graph model-based for fault tolerance level assessment of a wireless communication link in a system of systems concept

The main focus of this paper is on graphical modeling of wireless link of a System of Systems (SoS) for the purpose of Fault Tolerance Level Assessment. Having used hypergraphs previously for modeling the structural organization of SoS, its now important to introduce another graphical tool for modeling the wireless communication channel (WCL) between component systems of SoS, namely Bond Graph, and to evaluate at the same time, the fault tolerance level of each WCL so that we are able to compare various SoS configurations in terms of communication reliability and robustness. We perform an experiment on cooperative behavior of NAO humanoids forming an SoS to exploit model benefits at microscopic level and at macroscopic level, by developing a simulator that demonstrates how we can assess the fault tolerance level of each WCL in SoS.

Fault tolerance level assessment of a wireless communication link in a system of systems concept modeled using bond graph

The main focus of this paper is on graphical modeling of wireless link of a System of Systems (SoS) for the purpose of Fault Tolerance Level Assessment. Having used hypergraphs previously for modeling the structural organization of SoS, its now important to introduce another graphical tool for modeling the wireless communication channel (WCL) between component systems of SoS, namely Bond Graph, and to evaluate at the same time, the fault tolerance level of each WCL so that we are able to compare various SoS configurations in terms of communication reliability and robustness. We perform an experiment on cooperative behavior of NAO humanoids forming an SoS to exploit model benefits at microscopic level and at macroscopic level, by developing a simulator that demonstrates how we can assess the fault tolerance level of each WCL in SoS.