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  • Disputas: 2018-12-12 10:15 Wigforssalen, Hus J (Visionen), Halmstad University, Halmstad
    Aramrattana, Maytheewat
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES). The Swedish National Road and Transport Research Institute (VTI), Göteborg, Sweden.
    A Simulation-Based Safety Analysis of CACC-Enabled Highway Platooning2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Cooperative Intelligent Transport Systems (C-ITS) enable actors in the transport systems to interact and collaborate by exchanging information via wireless communication networks. There are several challenges to overcome before they can be implemented and deployed on public roads. Among the most important challenges are testing and evaluation in order to ensure the safety of C-ITS applications.

    This thesis focuses on testing and evaluation of C-ITS applications with regard to their safety using simulation. The main focus is on one C-ITS application, namely platooning, that is enabled by the Cooperative Adaptive Cruise Control (CACC) function. Therefore, this thesis considers two main topics: i) what should be modelled and simulated for testing and evaluation of C-ITS applications? and ii) how should CACC functions be evaluated in order to ensure safety?

    When C-ITS applications are deployed, we can expect traffic situations which consist of vehicles with different capabilities, in terms of automation and connectivity. We propose that involving human drivers in testing and evaluation is important in such mixed traffic situations. Considering important aspects of C-ITS including human drivers, we propose a simulation framework, which combines driving-, network-, and traffic simulators. The simulation framework has been validated by demonstrating several use cases in the scope of platooning. In particular, it is used to demonstrate and analyse the safety of platooning applications in cut-in situations, where a vehicle driven by a human driver cuts in between vehicles in platoon. To assess the situations, time-to-collision (TTC) and its extensions are used as safety indicators in the analyses.

    The simulation framework permits future C-ITS research in other fields such as human factors by involving human drivers in a C-ITS context. Results from the safety analyses show that cut-in situations are not always hazardous, and two factors that are the most highly correlated to the collisions are relative speed and distance between vehicles at the moment of cutting in. Moreover, we suggest that to solely rely on CACC functions is not sufficient to handle cut-in situations. Therefore, guidelines and standards are required to address these situations properly.

  • Disputas: 2018-12-19 13:15 Wigforssalen, Halmstad
    Vedder, Benjamin
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). RISE Research Institutes of Sweden, Gothenburg, Sweden.
    On the Design and Testing of Dependable Autonomous Systems2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Designing software-intensive embedded systems for dependable autonomous applications is challenging. In addition to fulfilling complex functional requirements, the system must be safe under all operating conditions, even in the presence of faults. The key to achieving this is by simulating and testing the system enough, including possible faults that can be expected, to be confident that it reaches an acceptable level of performance with preserved safety. However, as the complexity of an autonomous system and its application grows, it becomes exponentially more difficult to perform exhaustive testing and explore the full state space, which makes the task a significant challenge.

    Property-Based Testing (PBT) is a software testing technique where tests and input stimuli for a system are automatically generated based on specified properties of the system, and it is normally used for testing software libraries. PBT is not a formal proof that the system fulfills the specified properties, but an effective way to find deviations from them. Safety-critical systems that must be able to deal with hardware faults are often tested using Fault Injection (FI) at several abstraction levels. The purpose of FI is to inject faults into a system in order to exercise and evaluate fault handling mechanisms. In this thesis, we utilize techniques from PBT and FI, for automatically testing functional and safety requirements of autonomous system simultaneously. We have done this on both simulations of hardware, and on real-time hardware for autonomous systems. This has been done in the process of developing a quadcopter system with collision avoidance, as well as when developing a self-driving model car. With this work we explore how tests can be auto-generated with techniques from PBT and FI, and how this approach can be used at several abstraction levels during the development of these systems. We also explore which details and design choices have to be considered while developing our simulators and embedded software, to ease testing with our proposed methods.