Discrete Events Systems

There are various theoretical perspectives developed to explain how events impact on individual, team, and firm outcomes. The most recent of the theoretical advancements in this area is the Event System Theory (EST). This theory identifies three main traits reflecting the strength of the event that enable the event to be impactful. These are; the extent to which the event is novel referred to as the unique trait, the extent to which the event is disruptive, referred to as the change trait, and the extent to which the event is critical, referred to as the impact trait.

Innovation, the subject of discussion of this chapter, has been variously described in literature. We are however limiting our views in this study to innovation as process and product improvements. As a process, it involves turning of ideas into reality, and adding or giving value as a result. However, as a product, innovation is something novel, original or new that 'breaks into' the market or into the society. Based on the above descriptions, this chapter is an attempt to trace the transformation of Fuji music to the innovative foundations laid by its proponents.

The aim of this paper is to report a new concept of safe controllability using prognosis to deal with problems of fault tolerant control in the framework of discrete event systems modeled as automata. To achieve this goal, a necessary and sufficient condition for a DES to be safe controllable by prognosis is introduced and an algorithm to obtain the prognosis as early as possible is presented. We describe how the problem can be solved using a special kind of diagnoser called prognosing controller, which is used to prognose the faults and switch between the nominal supervisor and one degraded supervisor in a bank of reconfigured supervisors. This approach allows the system be more proactive by prognosing occurrences of faults events and anticipating the control actions.

A bstract: Thi s contribution addresses the modular synthL'S is of supervisory controllers for a class of hybrid systems called event-drive n hybrid systems. The obj ective is to synthesize nonblocking supervisors, each to enforce specific tasks given in terms of sequence of threshold eve nts , in such a way t.hat the joint action of these supervisors is 1I0nblocking and optimal. The problenl is fannulated within the framework o f condition /eve nt sy st e ms and it is convert.ed into a modular supervisor synthesis problem for discret.e-event systems. A condition under which the proposed approach can be applied is given and a n example is presented.

This paper presents a methodology for modeling and controlling autonomous mobile robots and illustrates this approach using a sumo robot problem. The free behavior of the robot and its control specifications are modeled by finite state machines, and the supervisory control theory of discrete event systems is used to obtain the logical behavior of the robot in closed-loop. We also present a proposal for implementing the control structure obtained by the presented approach.

Esse trabalho propõe a aplicação de modelos de simulação computacional para a avaliação da melhoria da qualidade de software por meio de implantação e políticas e práticas de processos de desenvolvimento de software e realizando a medição da
evolução da qualidade por meio da metodologia Seis Sigma. Com o intuito de fornecer aos tomadores de decisão de melhoria de processos foi proposto um modelo de simulação por dinâmica de sistemas. Para uma análise operacional do processo visando possibilitar um olhar detalhado da execução do processo, foi proposto um modelo de simulação por eventos discretos. A validação dos modelos foi realizada por
meio dos dados coletados de vários projetos desenvolvidos em uma empresa de
tecnologia da informação sediada em Belo Horizonte - MG. Os modelos elaborados e aqui apresentados nesta dissertação fornecem aos tomadores de decisão de melhoria de processos um arcabouço ferramental capaz de realizar predições, previsões,
análise de cenários no modelo “what if”. Como resultado deste trabalho temos um modelo de simulação por dinâmica de sistemas e por simulação por eventos discretos capaz de realizar a avaliação da qualidade de software em Nível Sigma. Também é apresentado a comparação e análise de dados reais de projetos de desenvolvimento
de software com os dados de simulação dos modelos apresentados. Foram feitas
mudanças no processo de desenvolvimento onde as referências para as mudanças
foram retiradas dos modelos de simulação aqui apresentados. Os ganhos com a nova
versão do processo superam em mais de 50% o aumento, em Nível Sigma, da
qualidade do software desenvolvido e redução em mais de 55% do tempo de
desenvolvimento do projeto

The use of MES (Manufacturing Execution System) is an alternative to link the ERP (Enterprise Resource Planning) to the activities at the shop floor. Due to the difference between the transactional feature of the ERP systems and the real-time features of the operations of the shop floor, MES becomes an important tool. SCADA (Supervisory Control And Data Acquisition) are responsible for monitoring the behaviour of shop floor and can interfere or alert in case of failures. The SCT (Supervisory Control Theory) is a formal methodology for modelling and control synthesis of DES (Discrete Event Systems). SCT appears to be an appropriate tool for this task, ensuring an optimal control logic that is minimally restrictive and non-blocking. The simultaneous use of MES, SCADA, ERP and controllers synthesized by SCT requires the creation of an interface between them. This creation requires development time, delays the project, being inflexible to change and is subject to failure. One of the formal models for the synthesis of DES controllers in the SCT is the DFA (Deterministic Finite Automaton). DFA is one of the computational models within the theory of automata. This paper shows the use of the DFA models to build the DES controller to interface SCADA and MES to save development time and to deal with flexibility and failure-tolerant issues.

The use of MES (Manufacturing Execution System) is an alternative to link the ERP (Enterprise Resource Planning) to the activities at the shop floor. Due to the difference between the transactional feature of the ERP systems and the real-time features of the operations of the shop floor, MES becomes an important tool. SCADA (Supervisory Control And Data Acquisition) are responsible for monitoring the behaviour of shop floor and can interfere or alert in case of failures. The SCT (Supervisory Control Theory) is a formal methodology for modelling and control synthesis of DES (Discrete Event Systems). SCT appears to be an appropriate tool for this task, ensuring an optimal control logic that is minimally restrictive and non-blocking. The simultaneous use of MES, SCADA, ERP and controllers synthesized by SCT requires the creation of an interface between them. This creation requires development time, delays the project, being inflexible to change and is subject to failure. One of the formal models for the synthesis of DES controllers in the SCT is the DFA (Deterministic Finite Automaton). DFA is one of the computational models within the theory of automata. This paper shows the use of the DFA models to build the DES controller to interface SCADA and MES to save development time and to deal with flexibility and failure-tolerant issues.

In this paper, we have proposed a new approach to evaluate the response time of Networked Control Systems (NCS) working under client/server protocol. For this, we have used two tools of discrete event systems: Timed Automata with Guards (TAGs) and (max,+) algebra. A preliminary result is to define a formal representation to describe the behaviour for TAGs with multiple clocks in (max,+) algebra and to deduce some performance indicators of these asynchronous models. The second contribution consists of modelling the NCS with TAGs and determining the upper bounds of the response time by an analytical formula. Finally, we have shown the agreement between experimental measures of the response time found in the literature and the theoretical predictions of our formulas.

Supervisory control of discrete event systems using limited lookahead has been studied by Chung-Lafortune-Lin, where control is computed by truncating the plant behavior up to the limited lookahead window. We present a modification of this approach in which the control is computed by extending the plant behavior by arbitrary traces beyond the limited lookahead window. The proposed supervisor avoids the notion of pending traces. Consequently the need for considering either a conservative or an optimistic attitude regarding pending traces (as in the work of Chung-Lafortune-Lin) does not arise. It was shown that an optimistic attitude may result in violation of the desired specifications. We demonstrate here that a conservative attitude may result in a restrictive control policy by showing that in general the proposed supervisor is less restrictive than the conservative attitude based supervisor. Moreover, the proposed approach uses the notion of relative closure to construct the supervisor so that it is non-blocking even when the desired behavior is not relative closed (Chung-Lafortune-Lin assume relative closure). Finally, the proposed supervisor possesses all the desirable properties that a conservative attitude based supervisor of Chung-Lafortune-Lin possesses. We illustrate our approach by applying it to concurrency control in database management systems.

Free left-turn lanes are common at major signalized intersections of Delhi to create additional capacity, and to facilitate continuous flow to left-turning traffic. The present study aims at examining the pedestrians' risk and road crossing behavior at free left-turns. Two most used binary probabilistic models, namely Logistic and Probit, were fitted to the data-set. Pedestrians cross the free left-turn when gaps are available within the traffic flow. Analysis of the data suggests that pedestrians' waiting time prior to the crossing of free left-turn is very less. Gap size is a significant parameter. Pedestrians' characteristics and type of conflicting vehicle do not influence their crossing behavior. Most of the pedestrians cross the free left turns with the gap size less than the adequate gap size. Both the univariate binary response Logistic and Probit regression models have been found to give similar results for the selected case.

Nowadays, tasks of detection and location of faults must be included in the systems to increase their reliability because they are increasingly large and complex. This work focus on Discrete Event Systems because they are the most used in the industry, some examples are manufacturing systems, urban traffic, communication protocols, among others. If a component breaks or stops functioning as it should (a fault occurs) and this malfunctioning is not detected in time, it can cause an explosion, for example, and this compromises the safety of the operators as well as causing great economic losses. The objective is to avoid these situations, especially for systems that, due to their structure and design, it is not possible to detect and locate faults in a specific time because they are not diagnosable. A new Intelligent Regulation Circuit is proposed that makes a system be diagnosable, it is a type of controller modeled with Petri nets that contains a Decision-Making System that monitors the events that happen, and after K events determines if a fault has occurred. Faults detection is made through the reduction of a parameter called relative distance. What is relevant is that this reduction does not change the way the system operates, as other diagnosers do. In this work is presented its definition and its operation while its application is shown in an access control system to a parking lot. The result shows the advantages of its use with respect to another Regulation Circuit.

Revolving doors are a means to provide access to a building, while maintaining the interior climate. To study pedestrian behavior in and around automated revolving doors, Delft University of Technology has performed laboratory experiments. In the experimental scenarios, we varied the door rotation speed, the population, the presence of a guiding device and the walking pattern. This paper shows new insights into this behavior with respect to travel times, delays, queue characteristics, free speed distributions and the capacity of a revolving door (Tournex with diameter 3.60 m). From our investigations, it turns out that the free travel times are nearly equal for all scenarios, although lower door rotation speeds lead to slightly higher travel times. Commuters appear to form bulk queues upstream of the entrance, leading to frequent activations of the safety sensors, and thus to numerous breakdowns and longer waiting times. A fence in front of the revolving door has a positive effect on the behavior of these hasty commuters. In the experiments, considerable differences between the walking operations of different types of pedestrians were observed. For both commuter and shopping population, an increase in door rotation speed results in a higher mean capacity (up to 19%). Opposite flows cause a reduction in the capacity (~ 15%). When the door is loaded with commuters, the door capacity is 10.1%-26.2% higher than with a shopping population. This is mainly due to the larger space requirements and the lack of urgency to completely fill a segment.

Due to urbanization, increased automobile growth, and lack of attention by drivers as well as pedestrians to the traffic regulations, traffic collisions affecting pedestrians, which have now become a serious safety issue in many developed nations such as India. The established road design does not have sufficient pedestrian facilities and thus there is a constant dispute between automobiles and pedestrians over sharing the limited space on a road. This often contributes to a dangerous situation and overcrowded traffic conditions for the slow speed vehicles and pedestrians. Although adequate control systems including signals are given at unregulated crossings, but still most of the pedestrians do not use the signals and tend to avoid pedestrian crossing areas that adversely impact the characteristics of the flow of traffic and the movement of road users. The objective of this research is to bring out the factors related to pedestrian accidents, characteristics of pedestrian behaviors...

A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), to generate a document that supports the development of future research, compiling the various studies focused on the analysis of the pedestrian-vehicle interaction at unsignalized crosswalks. Firstly, 381 studies were identified by applying the search protocol in the database sources; however, only nine studies were included in this review because most of the studies are not focused on this type of crosswalks or have not considered the micro-simulation perspective. For each study, an analysis of the used methodology for data collection was carried out, in addition to what type of model it was applied, including the variables that represent the PVI (Pedestrian-Vehicle Interaction). The outcomes obtained by this systematic review show that although the video camera observation technique is the most used, it is possible to complement them with other tools to add...

Atualmente, as empresas de manufatura precisam de mais flexibilidade para permanecer competitivas no mercado. Novas técnicas para projetar e implementar sistemas de manufatura flexível em menos tempo são pontos cruciais para aumentar a produtividade em tais indústrias. O objetivo deste artigo é apresentar uma abordagem sistemática por meio do uso de diversas técnicas formais, a fim de automatizar processos de fabricação de forma rápida, evitando a migração de erros entre as fases do projeto. A chave para alcançar esse desempenho é usar formalismo equivalente em todas as fases do projeto, incluindo verificação e implementação. A abordagem foi aplicada à automação de uma célula de manufatura robotizada didática, tipo de sistema de manufatura flexível, e os resultados mostram que ela pode ser útil em aplicações reais da indústria, reduzindo o custo e diminuindo o tempo de desenvolvimento no processo de projeto.

Currently, manufacturing automation has assumed an increasingly important role within the industry and the problems of automated control systems have become increasingly complex. Thus, the traditional use of empirical methods heavily base on the experience of the programmer can lead to inappropriate or ineffective solutions. In this case, the Supervisory Control Theory (SCT) of Ramadge and Wonham (1989) cam be a suitable tool because it ensures the achievement of optimal control logic (minimally restrictive and nonblocking) and also that meets the specifications of control. This paper presents a methodology for implementation of SCT in Programmable Logic Controllers (PLCs). The modeling of the plant and the specification of control is done by automata and languages, and in order to exploit the modular nature of the plant and the specifications we use the local modular approach (QUEIROZ and CURY, 2000) for the synthesis of supervisors. The use of a formal methodology for implementing control system also allows to standardize in the development, testing and structure of the PLC code and obtain a free of errors solution and crashes, discarding the empirical methods. The methods of implementation of the TCS in PLC existing literature have the feature to limit the evolution of the system, often dealing with one event per PLC scan cycle. Also presented is a series of problems that can occur in the implementation of supervisors in control elements such as PLCs (FABIAN and HELLGREN, 1998). However, not all of these problems have solutions and for some of them are presented some properties that the modeling of the system must ensure in order to avoid such problems. This method treats all the uncontrollable events produced by the plant in just one PLC scan cycle. The also promotes the control of the plant at the end of cycle. The development of this methodology takes into account the possible problems when using the theory into practice. Thus providing solutions to the problems. In this case the solutions, "Choice", stands out. It promotes the random generation of controllable events. One it is give priority to a particular event over another, it can cause the system to lock or be inoperative (MALIK, 2002). To facilitate the implementation of supervisory control structure in PLC, was created a computational tool for the automatic generation of control logic, based on the proposed methodology that converts the list generated by the software Discrete Event System (DES) in LADDER code. The validation of the results obtained with the tool generation was done through simulations for different problems of supervisory control.

Resumo-Neste trabalho utiliza-se a Teoria de Controle Supervisório de Sistemas a Eventos Discretos para sintetizar um supervisor para um sistema industrial de transporte pneumático de matérias-primas em pó. Apresenta-se uma sistemática de tradução do autômato do supervisor para uma lógica de controle em linguagem Ladder a ser implementada em CLP. Apresenta-se ainda uma ferramenta desenvolvida para realizar esta tradução de forma automática, bem como um ambiente virtual criado para a realização de testes de validação. A lógica de controle foi então gerada pela ferramenta e validada no ambiente virtual.

* O autor recebeu apoio financeiro da Chamada Pública FAPESC/CNPq n. 004/2007-Infra-estrutura de CT&I para Jovens Pesquisadores Resumo-Neste trabalho estuda-se a técnica de implementação do controle modular local para uma célula flexível de manufatura didática a ser utilizada para pesquisa de técnicas de controle supervisório. Pretendese, desta forma, contribuir para disseminar o uso da teoria de controle supervisório junto às indústrias.

This paper presents a study about the performance of programs implemented in microcontrollers according to the control logic obtained through the monolithic Supervisory Control Theory (SCT) and its extension called local modular approach. To study the performance, following monolithic approach and the modular approach, was proposed two implementation structures in controllers. Intending to identify factors that may restrict the use of microcontrollers, such as memory and runtime implementation cycle, were compared performance for each approach implementation. As a case of study was chosen a successive expansion of a small factory. The results for small systems shows that the monolithic approach had a better performance, but the addition of subsystems cause the memory occupation increase exponentially, until the program be bigger than the microcontroller's memory, fact that with the local modular approach is less problematic, once that an increase of subsystems increases the memory occupation linearly.

Resumo-Este artigo trata do desenvolvimento de controles eletrônicos para eletrodomésticos e apresenta uma proposta de projeto baseada na teoria de controle supervisório de sistemas a eventos discretos. Utiliza-se a abordagem modular local para a síntese de supervisores e propõe-se uma metodologia para a implementação destes supervisores. A aplicação da metodologia é ilustrada via um estudo de caso intitulado Refrigerador Autônomo.

This paper presents an application of the supervisory control theory in the development of control logics for refrigerators. A structure containing a Peltier Mini-Refrigerator controlled by an electronic circuit was developed, aiming to create and validate different control strategies that will be implemented in household and commercial refrigerators. The local modular control approach is applied in the supervisor synthesis, bypassing computational restrictions found in the monolithic approach. An implementation framework is proposed and some experimental results are obtained. Keywords⎯ Discrete-event systems, locally modular supervisory control, Peltier effect, embedded systems. Resumo⎯ Este artigo apresenta uma aplicação da teoria de controle supervisório no desenvolvimento de lógicas de controle para refrigeradores. Uma estrutura contendo um Mini-Refrigerador Peltier controlado por um circuito eletrônico foi desenvolvida, visando criar e validar diferentes estratégias de controle, que serão implementadas em refrigeradores domésticos e comerciais. A abordagem de controle modular local é aplicada na síntese dos supervisores, contornando dificuldades computacionais encontradas na abordagem monolítica. Uma estrutura de implementação é proposta e alguns resultados experimentais são obtidos. Palavras-chave⎯ Sistemas a eventos discretos, controle supervisório modular local, efeito Peltier, sistemas embarcados.

This paper presents the implementation of a controller that automatizes the ice cubed production in a domestic refrigerator, known as Ice Maker, using the Discrete Event System Supervisory Control Theory through the monolithic approach and compares it with an implementation based on state machine. The work explores the system and specifications modeling and synthesizes a supervisor that attends the specifications. The supervisor was implemented in a microcontroller using ANSI-C language and embedded to control a real system. Keywords Discret event system, supervisory control, monolithic supervisor, microcontroller, ice maker Resumo Este artigo apresenta a implementação de um controlador para um dispositivo que automatiza a produção de gelos em cubos em um refrigerador doméstico, conhecido como Ice Maker, utilizando a Teoria de Controle Supervisório a Sistemas de Eventos Discretos através da abordagem monolítica e mostra uma comparação com a técnica de implementação baseada em máquina de estados. O trabalho explora a modelagem do sistema e das especificações de controle e síntetiza um supervisor que atende as especificações. O supervisor foi implementado em um microcontrolador utilizando linguagem ANSI-C e embarcado para controlar um dispositivo real.

This paper presents the implementation of a controller that automatizes the ice cubed production in a domestic refrigerator, known as Ice Maker, using the Discrete Event System Supervisory Control Theory through the monolithic approach and compares it with an implementation based on state machine. The work explores the system and specifications modeling and synthesizes a supervisor that attends the specifications. The supervisor was implemented in a microcontroller using ANSI-C language and embedded to control a real system. Keywords Discret event system, supervisory control, monolithic supervisor, microcontroller, ice maker Resumo Este artigo apresenta a implementação de um controlador para um dispositivo que automatiza a produção de gelos em cubos em um refrigerador doméstico, conhecido como Ice Maker, utilizando a Teoria de Controle Supervisório a Sistemas de Eventos Discretos através da abordagem monolítica e mostra uma comparação com a técnica de implementação baseada em máquina de estados. O trabalho explora a modelagem do sistema e das especificações de controle e síntetiza um supervisor que atende as especificações. O supervisor foi implementado em um microcontrolador utilizando linguagem ANSI-C e embarcado para controlar um dispositivo real.

* O autor recebeu apoio financeiro da Chamada Pública FAPESC/CNPq n. 004/2007-Infra-estrutura de CT&I para Jovens Pesquisadores Resumo-Neste trabalho estuda-se a técnica de implementação do controle modular local para uma célula flexível de manufatura didática a ser utilizada para pesquisa de técnicas de controle supervisório. Pretendese, desta forma, contribuir para disseminar o uso da teoria de controle supervisório junto às indústrias.

Resumo-Neste trabalho utiliza-se a Teoria de Controle Supervisório de Sistemas a Eventos Discretos para sintetizar um supervisor para um sistema industrial de transporte pneumático de matérias-primas em pó. Apresenta-se uma sistemática de tradução do autômato do supervisor para uma lógica de controle em linguagem Ladder a ser implementada em CLP. Apresenta-se ainda uma ferramenta desenvolvida para realizar esta tradução de forma automática, bem como um ambiente virtual criado para a realização de testes de validação. A lógica de controle foi então gerada pela ferramenta e validada no ambiente virtual.

In this paper, we apply the Supervisory Control Theory of Discrete Event Systems to model an industrial system of transportation of powder raw material. We use the monolithic approach for the synthesis of a nonblocking and minimally restrictive supervisor for this system to restrict its closed-loop behavior to meet the control specifications. The automaton obtained for the supervisor is translated to a programming language suitable for use on a Programmable Logic Controller. The logic implemented is then tested on a test platform, yielding a closed loop behavior in accordance with the control specifications. Keywords    Supervisory Control Theory, Discrete Event Systems, PLC, industrial system of transportation, powder raw material. Resumo    Neste trabalho aplica-se a Teoria de Controle Supervisório de Sistemas a Eventos Discretos para modelar um sistema industrial de transporte de matérias-primas em pó. Utiliza-se a abordagem monolítica para a síntese de um supervisor não bloqueante e minimamente restritivo para este sistema a fim de restringir o seu comportamento de malha fechada de forma que atenda às especificações de controle. O autômato obtido para o supervisor é traduzido num programa em linguagem Ladder e implementado num Controlador Lógico Programável. A lógica implementada é então testada sobre uma plataforma de testes, obtendo-se o comportamento de malha fechada em consonância com as especificações de controle. Palavras-chave    Teoria de Controle Supervisório, Sistemas a Eventos Discretos, CLP, sistema industrial de transporte, matérias-primas em pó.

This paper introduces a methodology for the implementation of the supervisory control structure in programmable logic controllers. The implementation's strategy includes a solution for the choice problem between several controllable events and uses the concept of control cells, furthermore makes possible the treatment of many events in the same PLC scan cycle. A hypothetical industrial transfer line is used as an example to illustrate the application of the proposed methodology and control logic in ladder language. Keywords Discrete event systems, Supervisory control, Programmable logic controllers. Resumo Este artigo apresenta uma metodologia para a implementação da estrutura de controle supervisório em controladores lógicos programáveis. A estratégia de implementação contempla uma solução para o problema da escolha entre diversos eventos controláveis e utiliza o conceito de células de controle, além disso, possibilita o tratamento de diversos eventos num mesmo ciclo de scan do CLP. Uma linha de transferência industrial hipotética é proposta como exemplo para ilustrar a aplicação da metodologia e da lógica de controle em linguagem ladder. Palavras-chave Sistemas a eventos discretos, Controle supervisório, Controladores lógicos programáveis.

In this paper is used the technique of implementation of the modular local control to a didactic flexible manufacturing cell developed to search for techniques of supervisory control techniques. The control of the cell is made by a Programmable Logic Controller (PLC), which coordinates the operation of equipment. The supervisors were implemented in the PLC in LADDER language and the programming has been structured in blocks, better organization of the program. Whit this work, we intend to contribute towards the dissemination of the Supervisory Control theory in the industries. Keywords    Flexible Manufacturing Cell, Supervisory Control, Discrete Event Systems. Resumo    Neste trabalho utiliza-se a técnica de implementação do controle modular local para uma célula flexível de manufatura didática desenvolvida para pesquisa de técnicas de controle supervisório. O controle da célula é feito por um Controlador Lógico Programável (CLP), o qual coordena o funcionamento dos equipamentos. Os supervisores foram implementados no CLP em linguagem LADDER e a programação foi estruturada em blocos, visando uma melhor organização do programa. Com este trabalho pretende-se contribuir para disseminar o uso da teoria de controle supervisório junto às indústrias. Palavras-chave    Célula Flexível de Manufatura, Controle Supervisório, Sistemas a Eventos Discretos.

This paper presents a study about the performance of programs implemented in microcontrollers according to the control logic obtained through the monolithic Supervisory Control Theory (SCT) and its extension called local modular approach. To study the performance, following monolithic approach and the modular approach, was proposed two implementation structures in controllers. Intending to identify factors that may restrict the use of microcontrollers, such as memory and runtime implementation cycle, were compared performance for each approach implementation. As a case of study was chosen a successive expansion of a small factory. The results for small systems shows that the monolithic approach had a better performance, but the addition of subsystems cause the memory occupation increase exponentially, until the program be bigger than the microcontroller's memory, fact that with the local modular approach is less problematic, once that an increase of subsystems increases the memory occupation linearly.

This paper presents an application of the supervisory control theory in the development of control logics for refrigerators. A structure containing a Peltier Mini-Refrigerator controlled by an electronic circuit was developed, aiming to create and validate different control strategies that will be implemented in household and commercial refrigerators. The local modular control approach is applied in the supervisor synthesis, bypassing computational restrictions found in the monolithic approach. An implementation framework is proposed and some experimental results are obtained. Keywords⎯ Discrete-event systems, locally modular supervisory control, Peltier effect, embedded systems. Resumo⎯ Este artigo apresenta uma aplicação da teoria de controle supervisório no desenvolvimento de lógicas de controle para refrigeradores. Uma estrutura contendo um Mini-Refrigerador Peltier controlado por um circuito eletrônico foi desenvolvida, visando criar e validar diferentes estratégias de controle, que serão implementadas em refrigeradores domésticos e comerciais. A abordagem de controle modular local é aplicada na síntese dos supervisores, contornando dificuldades computacionais encontradas na abordagem monolítica. Uma estrutura de implementação é proposta e alguns resultados experimentais são obtidos. Palavras-chave⎯ Sistemas a eventos discretos, controle supervisório modular local, efeito Peltier, sistemas embarcados.

This research explores factors associated with driver yielding behavior at unsignalized pedestrian crossings and develops predictive models for yielding using logistic regression. It considers the effect of variables describing driver attributes, pedestrian characteristics and concurrent conditions at the crosswalk on the yield response. Special consideration is given to 'vehicle dynamics constraints' that form a threshold for the potential to yield. Similarities are identified to driver reaction in response to the 'amber' indication at a signalized intersection. The logit models were developed from data collected at two unsignalized mid-block crosswalks in North Carolina. The data include 'before' and 'after' observations of two pedestrian safety treatments, an in-street pedestrian crossing sign and pedestrian-actuated in-roadway warning lights. The analysis suggests that drivers are more likely to yield to assertive pedestrians who walk briskly in their approach to the crosswalk. In turn, the yield probability is reduced with higher speeds, deceleration rates and if vehicles are traveling in platoons. The treatment effects proved to be significant and increased the propensity of drivers to yield, but their effectiveness may be dependent on whether the pedestrian activates the treatment. The results of this research provide new insights on the complex interaction of pedestrians and vehicles at unsignalized intersections and have implications for future work towards predictive models for driver yielding behavior. The developed logit models can provide the basis for representing driver yielding behavior in a microsimulation modeling environment.

Gap acceptance behavior of pedestrian is significant to Safety and crash of pedestrian. The issue of gap acceptance
by pedestrians is relevant for road safety. It is novel to analyze the gap acceptance behavior and the effects of
selected factors based on observation survey. Many studies examined the mid-block crossing behavior of
pedestrians in the developed country. In contrast, this study is one of the first to analyze and model the crossing
choice behaviors of pedestrians within an entire Malaysia. However, the main aim of this paper is to investigate
and model non-compliant pedestrians’ traffic gap acceptance at unsignalised pedestrian mid-block crossings in
Malaysia. For this purpose, a field survey was carried out using videotaped data. Gaps size accepted, number and
size of the rejected gaps are examined against pedestrians’ and traffic attributes, using statistical analysis (
SPSS.22) and modeling approach (Multiple linear Regression and Binary logit regression). In addition, Critical
gap were determined using Raff’s method. The results reveled that seven factors that influence the pedestrian
crosing behaviour in terms of accepted gap size in seconds. Results showed traffic speed, pedestrian waiting time,
vehicle size, pedestrian gender, crossing distance, age group, and pedestrian number are the significant factors
for accepted gap size of pedestrian in Batu Pahat. Pedestrian waiting time was found to have negative impact on
gap size acceptance while the remaining factors showed positive influence on the gap size acceptance. In the
development of crossing choice model in Batu Pahat, traffic speed, driver yield, pedestrian number and pedestrian
age group are the significant influencer for pedestrian choice. Raff’s method result shows the critical gap size
value is approximately 12.5 seconds, which is quite similar to reported in previous studies. These outcomes would
be recommended to use in the evaluation of unprotected mid-block crosswalks and designing of new crosswalk
facility in Malaysia..

Road crossings are considered as an unavoidable part of walking in which the desirable route of pedestrians interacts with vehicles. These interactions may expose the pedestrians to risks or delays. In Malaysia, road accident statistics show that pedestrian casualties are fairly high. Inappropriate gap acceptance when pedestrians cross roads is a main contributing element to this situation. In this context, the purpose of this study was to develop realistic models for pedestrian road crossing behaviour using the regression technique for mid-block street crossing. A choice model was produced to capture the decision making process of pedestrians whereas rejected or accepted vehicular gaps was based on the discrete choice theory. Gap acceptance data under real mix traffic conditions was collected using video camera on a typical unsignalised two lane one way urban street section in the city center of Kuala Lumpur, Malaysia. The lognormal regression model developed for the crossing behaviour model shows that traffic speed, pedestrian waiting time, gender, crossing distance, age group, frequency of attempts and pedestrian number are the significant factors which are able to predict 77.0% of variance or changes in accepted gap size at 0.05 significance level. Higher traffic speed, lower waiting time, being a male, wider crossing distance, older age group, lower frequency of attempts and higher number of pedestrian were found to influence pedestrians to accept a bigger gap size. The binary logistic regression developed for the crossing choice model was found to be influenced by traffic speed, driver yield, pedestrian number and age group. Furthermore, lower traffic speed, willingness of drivers to slow down, more pedestrian crossings at the same time and a younger age group lead to a higher chance or probability of crossing roads. The model was validated again using 100 isolated samples and an accuracy of 98% was obtained compared to the calibrated model which yielded an accuracy of 98.9%.

Pedestrian is one of the most important components in transportation system which behaves vulnerable at unprotected mid-block locations under mixed traffic conditions. At mid-block crossing some vehicles yield to pedestrian who are already at crosswalk but some pedestrian use forced gap to cross the road. This action of pedestrian affects the vehicular flow characteristics. As compared to crossing road and sidewalk, sidewalk do not show direct effect on vehicular flow characteristics. The present study discuss about effect of pedestrian walking at mid-block un-signalized road section on traffic LOS (Level of Service). This paper studies the effect of pedestrian movement on traffic LOS. The study result indicated that observed LOS for traffic was 'D' with average vehicle speed as 22.268 kmph. Gap acceptance was determined by use of Multi linear regression model. Regression was done using Microsoft excel.

In this paper, we discuss the different types of faults for discrete event systems that lead to a system malfunction, afterwards we illustrate the principle of control of discrete event systems, and at the end we present an algorithm that controls the start and the end of each action intending to ensure that each step runs are in their permitted time range, this algorithm is easy and effective to perform the proper functioning of discrete event systems.

Pedestrian flow is an important component in the design and analysis of transportation facilities and in urban transportation planning. The need to assess the level of service of pedestrian walkways motivates much of the work on modeling pedestrian flows. Statistically derived flow models, expressing the fundamental relationships between density, flow, and speed, are used to generate level of service criteria. The methodology of assessing level of service for pedestrian walkways is similar to that for vehicle roadways.

Os requisitos de eficiência dos sistemas produtivos requerem que os sistemas de manufatura sejam cada vez mais facilmente reconfigurados, tanto na disposição física quanto no sequenciamento das atividades. E, este sequenciamento deve ser feito de forma a tornar todo o arranjo efetivo e funcional para um novo produto de forma rápida e eficaz. Isso tudo fica ainda mais complexo à medida que se consideram equipamentos flexíveis na célula como os robôs. Com estas dificuldades, é cada vez maior a pressão para produzir uma programação de controle correta e da primeira vez. Um sistema que possa simular graficamente e em 3D toda a sequencialização de eventos da célula auxilia nestas restrições, e evita que se paralise a linha de produção a fim de criar e testar uma nova sequência.

This paper presents behavioral-based models for describing pedestrian gap acceptance at unsignalized crosswalks in a mixed-priority environment, where some drivers yield and some pedestrians cross in gaps. Logistic regression models are developed to predict the probability of pedestrian crossings as a function of vehicle dynamics, pedestrian assertiveness, and other factors. In combination with prior work on probabilistic yielding models, the results can be incorporated in a simulation environment, where they can more fully describe the interaction of these two modes. The approach is intended to supplement HCM analytical procedure for locations where significant interaction occurs between drivers and pedestrians, including modern roundabouts.

This research explores factors associated with driver yielding behavior at unsignalized pedestrian crossings and develops predictive models for yielding using logistic regression. It considers the effect of variables describing driver attributes, pedestrian characteristics and concurrent conditions at the crosswalk on the yield response. Special consideration is given to 'vehicle dynamics constraints' that form a threshold for the potential to yield. Similarities are identified to driver reaction in response to the 'amber' indication at a signalized intersection. The logit models were developed from data collected at two unsignalized mid-block crosswalks in North Carolina. The data include 'before' and 'after' observations of two pedestrian safety treatments, an in-street pedestrian crossing sign and pedestrian-actuated in-roadway warning lights.

This research explores factors associated with driver yielding behavior at unsignalized pedestrian crossings and develops predictive models for yielding using logistic regression. It considers the effect of variables describing driver attributes, pedestrian characteristics and concurrent conditions at the crosswalk on the yield response. Special consideration is given to 'vehicle dynamics constraints' that form a threshold for the potential to yield. Similarities are identified to driver reaction in response to the 'amber' indication at a signalized intersection. The logit models were developed from data collected at two unsignalized mid-block crosswalks in North Carolina. The data include 'before' and 'after' observations of two pedestrian safety treatments, an in-street pedestrian crossing sign and pedestrian-actuated in-roadway warning lights.

Recent developments in several other emerging fields enable us to think of the fields of prototype design, development and automation in new ways and to consider new applications. This paper presents trends of prototyping design and automation with an emphasis on the following two sub-topics: 1) a review on prototyping discrete event and hybrid systems; and 2) the trends on prototyping real-time machine vision system design