Otonom Araçların Teknolojik Gelişim Süreci ve Trafik Seyir Özelliklerinin İncelenmesi

Otonom araçlar gelecek ulaştırması ve kentinin en önemli unsurlarından bir tanesini teşkil etmektedir. İçinde bulunduğumuz yüzyılda kentleşme, sürdürülebilirlik ve dijitalleşme en temel unsurlar olacaktır. Bunun merkezinde ise otonom araçlar etkin ve belirleyici bir konuma sahiptir. Otonom araçların trafikte ağırlığı arttıkça ulaştırma ve kentleşme de yeniden şekillenecektir. Bu çalışma kapsamında, öncelikle otonom araç özelliklerinin kent ve ulaşımla ilişkisi ortaya konulmuştur. Ardından ise otonom araçların gelişim süreci detaylı olarak ele alınmıştır. Akabinde otonom araçlarda güvenlik ve emniyet konusu değerlendirilmiş bu olup sonrasında otonom araç teknolojileri çok yönlü olarak paylaşılmıştır. Son olarak da bu kapsamda sonuçlar verilmiştir

Correct-by-Construction Tactical Planners for Automated Cars

One goal of developing automated cars is to completely free people from driving tasks. Automated cars that require no human driver need to handle all traffic situations that a human driver is expected to handle, and possibly more. Although human drivers cause a lot of traffic accidents, they still have a very low accident and failure rate that automated systems must match.Tactical planners are responsible for making discrete decisions during the coming seconds or minute. As with all subsystems in an automated car, these planners need to be supported with a credible and convincing argument of their correctness. The planners\u27 decisions affect the environment and the planners need to interact with other road users in a feedback loop, so the correctness of the planners depend on their behavior in relation to other drivers and the environment over time. One possibility to ascertain their correctness is to deploy the planners in real traffic. To be sufficiently certain that a tactical planner is safe by that methods, it needs to be tested on 255 million miles without having an accident.Formal methods can, in contrast to testing, mathematically prove that the requirements are fulfilled. Hence, they are a promising alternative for making credible arguments of tactical planners\u27 correctness. The topic of this thesis is how formal methods can be used in the automotive industry to design safe tactical planners. What is interesting is both how automotive systems should be modeled in formal frameworks, and how formal methods can be used practically within the automotive development process.The main findings of this thesis are that it is natural to express desired properties of tactical planners in formal languages and use formal methods to prove their correctness. Model Checking, Reactive Synthesis, and Supervisory Control Theory have been used in the design and development process of tactical planners, and all three methods have their benefits, depending on the application.Formal synthesis is an especially interesting class of formal methods because they can automatically generate a planner based on requirements and models. Formal synthesis removes the need to manually develop and implement the planner, so the development efforts can be directed to formalizing good requirements on the planner and good assumptions on the environment. However, formal synthesis has two limitations: the resulting planner is a black box that is difficult to inspect, and it is difficult to find a level of abstraction that allows detailed requirements and generic planners

On Compositional Approaches for Discrete Event Systems Verification and Synthesis

Over the past decades, human dependability on technical devices has rapidly increased.Many activities of such devices can be described by sequences of events,where the occurrence of an event causes the system to go from one state to another.This is elegantly modelled by state machines. Systems that are modelledin this way are referred to as discrete event systems. Usually, these systems arehighly complex, and appear in settings that are safety critical, where small failuresmay result in huge financial and/or human losses. Having a control functionis one way to guarantee system correctness.The work presented in this thesis concerns verification and synthesis of suchsystems using the supervisory control theory proposed by Ramadge and Wonham. Supervisory control theory provides a general framework to automaticallycalculate control functions for discrete event systems. Given a model of thesystem, the plant to be controlled, and a specification of the desired behaviour,it is possible to automatically compute, i.e. synthesise, a supervisor that ensuresthat the specification is satisfied.Usually, systems are modular and consist of several components interactingwith each other. Calculating a supervisor for such a system in the straightforwardway involves constructing the complete model of the considered system, whichmay lead to the inherent complexity problem known as the state-space explosionproblem. This problem occurs as the number of states grows exponentially withthe number of components, which makes it intractable to examine the globalstates of a system due to lack of memory and time.One way to alleviate the state-space explosion problem is to use a compositionalapproach. A compositional approach exploits the modular structure of asystem to reduce the size of the model. This thesis mainly focuses on developingabstraction methods for the compositional approach in a way that the finalverification and synthesis results are the same as it would have been for the nonabstractedsystem. The algorithms have been implemented in the discrete eventsystem software tool Supremica and have been applied to verify and computememory efficient supervisors for several large industrial models

Efficient Symbolic Supervisor Synthesis for Extended Finite Automata

The state-space explosion problem, resulting from the reachability computations in controller synthesis, is one of the main obstacles preventing supervisory control theory from having an industrial breakthrough. To alleviate this problem, a strategy is to symbolically perform the synthesis procedure using binary decision diagrams. Based on this principle, the work presented in this brief develops an efficient symbolic reachability approach for discrete event systems that are modeled as finite automata with variables, referred to as extended finite automata. Using a disjunctive event partitioning technique, the proposed approach first partitions the transition relation of the considered system into a set of partial transition relations. These partial transition relations are then selected systematically to perform the reachability analysis, which is the most fundamental challenge for synthesizing supervisors. It has been shown through solving a set of benchmark supervisory control problems for EFA that the proposed approach significantly improves scalability in comparison with the previously published results

Symbolic Supervisory Control of Resource Allocation Systems

<p>Supervisory control theory (SCT) is a formal model-based methodology for verification and synthesis of supervisors for discrete event systems (DES). The main goal is to guarantee that the closed-loop system fulfills given specifications. SCT has great promise to assist engineers with the generation of reliable control functions. This is, for instance, beneficial to manufacturing systems where both products and production equipment might change frequently.</p> <p>The industrial acceptance of SCT, however, has been limited for at least two reasons: (i) the analysis of DES involves an intrinsic difficulty known as the state-space explosion problem, which makes the explicit enumeration of enormous state-spaces for industrial systems intractable; (ii) the synthesized supervisor, represented as a deterministic finite automaton (FA) or an extended finite automaton (EFA), is not straightforward to implement in an industrial controller.</p> <p>In this thesis, to address the aforementioned issues, we study the modeling, synthesis and supervisor representation of DES using binary decision diagrams (BDDs), a compact data structure for representing DES models symbolically. We propose different kinds of BDD-based algorithms for exploring the symbolically represented state-spaces in an effort to improve the abilities of existing supervisor synthesis approaches to handle large-scale DES and represent the obtained supervisors appropriately.</p> <p>Following this spirit, we bring the efficiencies of BDD into a particular DES application domain -- deadlock avoidance for resource allocation systems (RAS) -- a problem that arises in many technological systems including flexible manufacturing systems and multi-threaded software. We propose a framework for the effective and computationally efficient development of the maximally permissive deadlock avoidance policy (DAP) for various RAS classes. Besides the employment of symbolic computation, special structural properties that are possessed by RAS are utilized by the symbolic algorithms to gain additional efficiencies in the computation of the sought DAP. Furthermore, to bridge the gap between the BDD-based representation of the target DAP and its actual industrial realization, we extend this work by introducing a procedure that generates a set of "guard" predicates to represent the resulting DAP.</p> <p>The work presented in this thesis has been implemented in the SCT tool Supremica. Computational benchmarks have manifested the superiority of the proposed algorithms with respect to the previously published results. Hence, the work holds a strong potential for providing robust, practical and efficient solutions to a broad range of supervisory control and deadlock avoidance problems that are experienced in the considered DES application domain.</p