Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 99-104). Also available via the Internet.

The growing widespread use of data communication networks has led to increased reliance on the availability of network resources. The network itself is a critical resource which must be managed in a timely and effective manner. In order to manage the network effectively, the network manager must have powerful tools that present network information in a fast and logical way. The work presented here is the design and development of a network management tool for Sytek broadband networks. The Sytek Network Management Package (SNMP) incorporates a commercial database management system, Rbase System V, and menu oriented management functions for the University of Arizona Sytek broadband networks. The SNMP is written in C and executes on a PC connected to the Sytek network. The SNMP allows a network manager to manage both the Sytek LocalNet 20 and System 2000 networks.

No description available.

Computer Numerically Controlled (CNC) machines are common pieces of equipment in manufacturing plants. In recent years, CNC-user interfaces have been evolving from CNC command languages to menu based and direct manipulation interfaces. However, there have been few efforts to evaluate CNC-user interfaces and to identify those interface features that have major effects on the usability of CNC machines. Thus, an objective assessment of the improvement achieved from different user interface technologies is needed. Two experiments compared the effectiveness of two types of CNC-user interfaces: command-language and direct manipulation interfaces. Two command language interfaces and one object oriented interface were designed and evaluated in terms of human performance and preferences. Experiment 1 compared two command-language interfaces: Layout 1 was a simulation of the original control panel of a CNC-Dyna machine, and Layout 2 was a modified user interface based on the analysis of the Dyna control language. Four factors were manipulated: (1) users’ level of expertise, (2) layouts, (3) tasks, and (4) trials. It was found that both groups of subjects completed the tasks faster using Layout 2 than Layout 1. Modification tasks were performed faster than copy tasks. Subjects’ responses to a questionnaire indicated that Layout 2 was preferred over Layout 1 in several categories. In Experiment 2 subjects used a command-language interface and a direct-manipulation interface. Four factors were manipulated: (1) experimental sessions (two sessions with a one-week interval between them), (2) users’ level of expertise, (3) tasks, and (4) trials. The interval between sessions had a significant effect on task completion time when the command-language interface was used, but there was not a significant effect of this factor when the direct-manipulation interface was used. Subjects’ subjective responses indicated a stable preference for the direct-manipulation interface in several categories of usability. / Ph. D.

Emulation is defined as an intermediate stage of simulation where the model represents the "as specified" mechanical plant and equipment, but not the control logic required to drive it. This thesis investigates the utility of providing a computer representation of the functional elements to be controlled by system control programs. These representations or "emulators" mimic the behavior of the system, or factory being controlled. The advantages of such a scheme are that developers of control software, are able to test out new control methodologies without actually connecting to the hardware system under control. This thesis investigates system control for automated manufacturing systems and identifies how emulation can be used as a valid tool in reducing the implementation time of such systems. The functions and characteristics of system control are identified as well as the problems associated with their implementation. The problems are then categorized to identify where emulation is a valid tool for problem resolution. This thesis is concluded by a description of a software demonstration which validated the concept of using emulation to solve system control problems. / Master of Science

The next generation of intelligent vehicles will evolve from being able to drive autonomously to ones that communicate with other vehicles and execute joint behaviors. Before allowing these vehicles on public roads, we must guarantee that they will not cause accidents. We will apply formal methods to ensure the degree of safety that cannot be assured with simulation or closed-track testing. However, there are challenges that need to be addressed when applying formal verification techniques to cooperative driving systems. This thesis focuses on the techniques that address the following challenges: 1. Automotive applications interact with the physical world in different ways; 2. Cooperative driving systems are time-critical; 3. The problem of state explosion when we apply formal verification to systems with more participants. First, we describe the multiple stack architecture. It combines several stacks, each of which addresses a particular way of interaction with the physical world. The layered structure in each stack makes it possible for engineers to implement cooperative driving applications without being bogged down by the details of low-level devices. Having functions arranged in a layered fashion helps us divide the verification of the whole system into smaller subproblems of independent module verification. Secondly, we present a framework for modeling the protocol systems that uses GPS clocks for synchronization. We introduce the timing stack, which separates a process into two parts: the part modeled as an finite-state machine that controls state transitions and messages exchanges, and the part that determines the exact moment that a timed event should occur. The availability of accurate clocks at different locations allows processes to execute actions simultaneously, reducing interleaving that often arises in systems that use multiple timers to control timed events. With accurate clocks, we create a lock protocol that resolves conflicting merge requests for driver-assisted merging. Thirdly, we introduce stratified probabilistic verification that mitigates state explosion. It greatly improves the probability bound obtained in the original probabilistic verification algorithm. Unlike most techniques that aim at reducing state space, it is a directed state traversal, prioritizing the states that are more likely to be encountered during system execution. When state traversal stops upon depleting the memory, the unexplored states are the ones that are less likely to be reached. We construct a linear program whose solution is the upper bound for the probability of reaching those unexplored states. The stratified algorithm is particularly useful when considering a protocol system that depends on several imperfect components that may fail with small but hard-to-quantify probabilities. In that case, we adopt a compositional approach to verify a collection of components, assuming that the components have inexact probability guarantees. Finally, we present our design of driver-assisted merging. Its design is reasonably simplified by using the multiple stack architecture and GPS clocks. We use a stratified algorithm to show that merging system fails less than once every 5 × 10¹³ merge attempts.

Orientadores: Flávio Vasconcelos da Silva, Luís Cláudio Oliveira Lopes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-24T13:32:43Z (GMT). No. of bitstreams: 1 Costa_ThiagoVazda_D.pdf: 18980163 bytes, checksum: 01508b929c51cbd2ad88d0be37d75084 (MD5) Previous issue date: 2014 / Resumo: A consideração sistemática relacionada ao tratamento de falhas na estrutura de controle é essencial para se atingir as metas de um processo ao mesmo tempo seguro e produtivo. Nesse sentido, este trabalho propõe o estudo e a implementação de técnicas baseadas no controle reconfigurável com aplicações em processos químicos. Essa técnica está relacionada à etapa que lida com a falha no sistema em malha fechada, por meio de sua reconfiguração, evitando a evolução dos seus efeitos na estrutura de controle. Nesse estudo, a atenção é voltada ao rastreamento do comportamento nominal do sistema considerando as técnicas baseadas nos atuadores virtuais. O método considera o desvio da planta em relação ao seu comportamento nominal na presença de falhas em seus atuadores. Deste modo, se o distanciamento em relação ao comportamento nominal pode ser estabilizado por meio das redundâncias físicas e analíticas presentes no processo, o comportamento da planta sujeita à falha também pode ser estabilizado. Neste sentido, uma consideração sobre esse desvio no futuro é proposta, permitindo que técnicas baseadas no controle ótimo e preditivo sejam utilizadas. São consideradas especificamente falhas que comprometam o desempenho do processo quando existe a perda total ou parcial de suas variáveis de entrada. Com os componentes comprometidos devidamente localizados, a redistribuição dos sinais de controle da planta é encaminhada para que a estabilidade e desempenho do processo sejam assegurados. A concepção do atuador virtual com horizonte móvel possibilita o uso de técnicas de otimização, permitindo que as informações referentes às características físicas das redundâncias do processo sejam incluídas, evitando a saturação dos componentes utilizados durante o tratamento da falha. A validação da técnica proposta é avaliada experimentalmente em um processo de neutralização, no qual ferramentas de injeção de falhas são capazes de simular os efeitos de falha dos atuadores no processo real. As estratégias estudadas foram implementadas em um software em código aberto e foram testadas experimentalmente a partir do uso de comunicação OPC (Object Linking and Embedding for Process Control). Cenários com diferentes falhas afetando os atuadores do processo foram concebidos e avaliados. Em todos os estudos, observou-se a capacidade da ferramenta em efetuar a reconfiguração do sistema em malha fechada para mitigar os efeitos indesejáveis da falha. Com base nos resultados, conclui-se que a utilização das técnicas em cenários industriais é viável e pode garantir a operação estável do processo mesmo quando surjam falhas em seus componentes, consideradas as condições de controlabilidade e estabilizabilidade do sistema / Abstract: A systematic approach to fault handling in control loops is important to achieve safe and productive process goals. Therefore, the present work proposes the study and implementation of reconfigurable control methods with applications in chemical processes. This technique is related to the fault handling stage in the closed loop system by means of reconfiguration, preventing the progression of fault effects in the control structure. In this study, particular focus is given to virtual actuator based techniques for tracking nominal system behavior. The method considers the deviation of the plant in relation to its nominal behavior when there are faults in its actuators. Therefore, if the nonconformity from the nominal response can be stabilized using the process physical and analytical redundancies, the faulty plant behavior can also be stabilized. Hence, it is proposed the use of the deviation from the nominal system response in the future, enabling the use of optimal and predictive control techniques. Faults affecting process performance due to total or partial loss of input variables are particularly considered. Once the faulty components are located, input signal redistribution is determined in order to ensure process performance and stability. The moving horizon virtual actuator proposal provides the use of optimization techniques allowing information about physical characteristics of the process redundancies to be included, avoiding component saturation during the fault handling approach. The validation of the technique is performed experimentally in a neutralization process, in which fault injection tools are able to simulate the effects of actuators faults in the real process. The studied strategies were implemented using open-source software and tested experimentally by means of an OPC (Object Linking and Embedding for Process Control) communication. Several fault scenarios considering actuator faults were planned and fulfilled for evaluation. The experimental tests showed that the proposed framework is capable of performing closed loop system reconfiguration to mitigate undesirable fault effects. Based on the results, it is concluded that using such a technique in industrial scenarios is feasible and can guarantee stable process operation even when there are faults in its components, considering system controllability and stabilizability conditions / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química