12 research outputs found
Modeling, Analysis, and Simulation of Two Connected Intersections Using Discrete and Hybrid Petri Nets
Indiana University-Purdue University Indianapolis (IUPUI)In recent decades, Petri nets (PNs) have been used to model traffic networks for different purposes, such as signal phase control, routing, and traffic flow estimation, etc. Because of the complex nature of traffic networks where both discrete and continuous dynamics come into play, the Hybrid Petri net (HPN) model becomes an important tool for the modeling and analysis of traffic networks. In Chapter 1 a brief historical summery about traffic systems control and then related work is mentioned followed by the major contributions in this research. Chapter 2 provides a theoretical background on Petri nets. In Chapter 3, we develop a HPN model for a single signalized intersection first, then we extend this model to study a simple traffic network that consists of two successive intersections. Time delays between different points of network are also considered in order to make the model suitable for analysis and simulation. In addition to HPN models, we also consider discrete Petri nets where their modeling simplicity enables the characterization of the occurrences of all events in the system. This discrete PN is particularly useful to give a higher-level representation of the traffic network and study its event occurrences and correlations. In Chapter 4, we build a discrete PN model to represent a traffic network with two successive intersections. However, we find that the model leads to unbounded places which cannot accurately reflect the dynamics of the traffic in terms of event occurrences. Hence, we introduce the Modified Binary Petri nets (MBPN) to overcome the limitation and resolve the confliction problem when we design our controllers. This MBPN model is a powerful tool and can be useful for the modeling and analysis of many other applications in traffic networks. Chapter 5 gives a summary for each chapter, provides conclusion and discusses future work for both discrete and hybrid Petri nets
Engenharia de sistemas baseada em modelos: um sistema para o tráfego & ambiente
Doutoramento em Gestão IndustrialThe contemporary world is crowded of large, interdisciplinary, complex systems
made of other systems, personnel, hardware, software, information, processes,
and facilities. The Systems Engineering (SE) field proposes an integrated
holistic approach to tackle these socio-technical systems that is crucial to take
proper account of their multifaceted nature and numerous interrelationships,
providing the means to enable their successful realization. Model-Based
Systems Engineering (MBSE) is an emerging paradigm in the SE field and can
be described as the formalized application of modelling principles, methods,
languages, and tools to the entire lifecycle of those systems, enhancing
communications and knowledge capture, shared understanding, improved
design precision and integrity, better development traceability, and reduced
development risks.
This thesis is devoted to the application of the novel MBSE paradigm to the
Urban Traffic & Environment domain. The proposed system, the GUILTE
(Guiding Urban Intelligent Traffic & Environment), deals with a present-day real
challenging problem “at the agenda” of world leaders, national governors, local
authorities, research agencies, academia, and general public. The main
purposes of the system are to provide an integrated development framework
for the municipalities, and to support the (short-time and real-time) operations
of the urban traffic through Intelligent Transportation Systems, highlighting two
fundamental aspects: the evaluation of the related environmental impacts (in
particular, the air pollution and the noise), and the dissemination of information
to the citizens, endorsing their involvement and participation. These objectives
are related with the high-level complex challenge of developing sustainable
urban transportation networks.
The development process of the GUILTE system is supported by a new
methodology, the LITHE (Agile Systems Modelling Engineering), which aims to
lightening the complexity and burdensome of the existing methodologies by
emphasizing agile principles such as continuous communication, feedback,
stakeholders involvement, short iterations and rapid response. These principles
are accomplished through a universal and intuitive SE process, the SIMILAR
process model (which was redefined at the light of the modern international
standards), a lean MBSE method, and a coherent System Model developed
through the benchmark graphical modeling languages SysML and OPDs/OPL.
The main contributions of the work are, in their essence, models and can be
settled as: a revised process model for the SE field, an agile methodology for
MBSE development environments, a graphical tool to support the proposed
methodology, and a System Model for the GUILTE system. The comprehensive
literature reviews provided for the main scientific field of this research
(SE/MBSE) and for the application domain (Traffic & Environment) can also be
seen as a relevant contribution.O mundo contemporâneo é caracterizado por sistemas de grande dimensão e
de natureza marcadamente complexa, sócio-técnica e interdisciplinar. A
Engenharia de Sistemas (ES) propõe uma abordagem holística e integrada
para desenvolver tais sistemas, tendo em consideração a sua natureza
multifacetada e as numerosas inter-relações que advêm de uma quantidade
significativa de diferentes pontos de vista, competências, responsabilidades e
interesses. A Engenharia de Sistemas Baseada em Modelos (ESBM) é um
paradigma emergente na área da ES e pode ser descrito como a aplicação
formal de princípios, métodos, linguagens e ferramentas de modelação ao ciclo
de vida dos sistemas descritos. Espera-se que, na próxima década, a ESBM
desempenhe um papel fundamental na prática da moderna Engenharia de
Sistemas.
Esta tese é dedicada à aplicação da ESBM a um desafio real que constitui
uma preocupação do mundo actual, estando “na agenda” dos líderes mundiais,
governantes nacionais, autoridades locais, agências de investigação,
universidades e público em geral. O domínio de aplicação, o
Tráfego & Ambiente, caracteriza-se por uma considerável complexidade e
interdisciplinaridade, sendo representativo das áreas de interesse para a ES.
Propõe-se um sistema (GUILTE) que visa dotar os municípios de um quadro
de desenvolvimento integrado para adopção de Sistemas de Transporte
Inteligentes e apoiar as suas operações de tráfego urbano, destacando dois
aspectos fundamentais: a avaliação dos impactos ambientais associados (em
especial, a poluição atmosférica e o ruído) e a divulgação de informação aos
cidadãos, motivando o seu envolvimento e participação. Estes objectivos
relacionam-se com o desafio mais abrangente de desenvolver redes de
transporte urbano sustentáveis.
O processo de desenvolvimento do sistema apoia-se numa nova metodologia
(LITHE), mais ágil, que enfatiza os princípios de comunicação contínua,
feedback, participação e envolvimento dos stakeholders, iterações curtas e
resposta rápida. Estes princípios são concretizados através de um processo de
ES universal e intuitivo (redefinido à luz dos padrões internacionais), de um
método simples e de linguagens gráficas de modelação de referência (SysML
e OPDs/OPL).
As principais contribuições deste trabalho são, na sua essência, modelos: um
modelo revisto para o processo da ES, uma metodologia ágil para ambientes
de desenvolvimento baseados em modelos, uma ferramenta gráfica para
suportar a metodologia proposta e o modelo de um sistema para as operações
de tráfego & ambiente num contexto urbano. Contribui-se ainda com uma
cuidada revisão bibliográfica para a principal área de investigação (ES/ESBM)
e para o domínio de aplicação (Tráfego & Ambiente)
Safety and Reliability - Safe Societies in a Changing World
The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management
- mathematical methods in reliability and safety
- risk assessment
- risk management
- system reliability
- uncertainty analysis
- digitalization and big data
- prognostics and system health management
- occupational safety
- accident and incident modeling
- maintenance modeling and applications
- simulation for safety and reliability analysis
- dynamic risk and barrier management
- organizational factors and safety culture
- human factors and human reliability
- resilience engineering
- structural reliability
- natural hazards
- security
- economic analysis in risk managemen