Theory of reliable systems

An attempt was made to refine the current notion of system reliability by identifying and investigating attributes of a system which are important to reliability considerations. Techniques which facilitate analysis of system reliability are included. Special attention was given to fault tolerance, diagnosability, and reconfigurability characteristics of systems

Reconfigurability level assessment in Portuguese companies

O conceito de sistemas de produção reconfiguráveis (SPRs) surgiu como uma estratégia para alcançar sistemas de produção mais ágeis, capazes de ajustar a funcionalidade e capacidade quando necessário. Este tópico é um problema atual para empresas porque a viabilidade de SPRs foi alcançada recentemente devido às novas tecnologias promovidas pela Indústria 4.0. Em SPRs, a reconfigurabilidade é a capacidade que permite a mudança de um produto para outro, a adição ou remoção de recursos, com mínimo esforço e sem demora. Por esta razão, a avaliação do nível de reconfigurabilidade é de extrema importância para as indústrias. O objetivo desta pesquisa é descrever o desenvolvimento de um índice de reconfigu rabilidade (RI) que pode ser utilizado por empresas para definir o quão reconfiguráveis são seus sistemas de manufatura. Especificamente, este estudo pretende determinar em que medida cada característica fundamental contribui para a composição da reconfi gurabilidade e o nível atual de reconfigurabilidade presente nas empresas portuguesas. Adicionalmente, este trabalho tenta estabelecer uma relação entre as características es senciais e o desempenho operacional dos sistemas de manufatura, e a extensão em que cada característica básica é implementada em diferentes setores industriais. Para construir o IR, uma pesquisa por questionário foi usada para selecionar as va riáveis e uma análise de componentes principais (ACP) foi aplicada aos resultados da pesquisa para determinar as contribuições das características centrais. O IR foi usado para estabelecer um ranking dos setores industriais das empresas respondentes e para discutir o nível de implementação das características centrais de reconfigurabilidade. Os resultados mostram que cada característica central contribui com uma quantidade diferente para a composição da reconfigurabilidade. A adaptabilidade e a diagnostica bilidade são as que mais contribuem, com 25% cada. As empresas portuguesas têm um nível moderado de reconfigurabilidade implementado. Em relação ao desempenho ope racional, a modularidade parece contribuir para a qualidade e entrega; integrabilidade para entrega e flexibilidade; adaptabilidade para custo e qualidade e capacidade de di agnóstico para qualidade e entrega. Entre os setores industriais, a reconfigurabilidade varia de níveis baixos a moderados. A implementação das características centrais variam significativamente, mas o RI parece estar relacionado aos níveis de flutuações do mercado

A diagnostics architecture for component-based system engineering

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004.Includes bibliographical references (leaves 58-60).This work presents an approach to diagnosis to meet the challenging demands of modern engineering systems. The proposed approach is an architecture that is both hierarchical and hybrid. The hierarchical dimension of the proposed architecture serves to mitigate the complexity challenges of contemporary engineering systems. The hybrid facet of the architecture tackles the increasing heterogeneity of modern engineering systems. The architecture is presented and realized using a bus representation where various modeling and diagnosis approaches can coexist. The proposed architecture is realized in a simulation environment, the Specification Toolkit and Requirements Methodology (SpecTRM). This research also provides important background information concerning approaches to diagnosis. Approaches to diagnosis are presented, analyzed, and summarized according to their strengths and domains of applicability. Important characteristics that must be considered when developing a diagnostics infrastructure are also presented alongside design guidelines and design implications. Finally, the research presents important topics for further research.by Martin Ouimet.S.M

Reconfigurable manufacturing systems characteristics in digital twin context

The concept of a reconfigurable manufacturing system (RMS) has been introduced to enable production systems to continuously evolve and respond rapidly to unpredicted and fluctuating market environments. To achieve this goal, RMS needs to exhibit six core characteristics: modularity, integrability, scalability, diagnosability, convertibility and customisation. These characteristics are required to ensure manufacturing systems’ resilience while maintaining productivity and quality. Assessing these characteristics at both the design and operating phase can be aided by the digital twinning (DT) of physical systems. To this end, the DT-RMS concept is introduced in this paper as a dynamic cyber-replica of the physical production environment, enabling a high-level of transparency about data, performance, and relevant reconfiguration decisions. As a result, DT-RMS responds to the need to integrate requirements and performance targets for the RMS characteristics at design and operating-tim

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 343)

This bibliography lists 125 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during January, 1989. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance

A Hybrid Approach to Fault Diagnosis in Teams of Autonomous Systems

Discrete event systems (DES) are dynamical systems equipped with a discrete state set and an event driven state transition structure. An event in a DES occurs instantaneously causing transition from one state to another. DES models have emerged to provide a formal treatment of many man-made systems such as automated manufacturing systems, computer systems, communication networks and air traffic control systems. In this thesis, we study fault diagnosis in teams of autonomous systems. In particular, one consider a team of two spacecraft in deep space. The spacecraft cooperate with each other in leader-follower formation flying. Formation flying demonstrates the capability of spacecraft to react to each other in order to maintain a desired relative distance autonomously without human intervention. In the system considered here, instruments (actuators and sensors) may fail and cause error. Because of the communication delays in deep space, each entity should be able to diagnose the failure and decide how to reconfigure itself. Basically, fault diagnosis in such systems requires information exchange between the autonomous elements of the team. The exchanged information for example may include position and velocity data. Our goal in the thesis is to propose a method for fault diagnosis with reduced information exchange. One solution is to transmit only discrete event information between autonomous systems. Transmission of discrete event data occurs less frequently than the transmission of continuous streams of data. The discrete event data may include high level supervisory commands issued every now and then and discretized values of continuous data that are transmitted only when a continuous-variable data (such as angle or acceleration) crosses the threshold. The fault diagnosis scheme proposed in this thesis is an adaptation of hybrid fault diagnosis for distributed autonomous systems. This system is simulated using MATLAB/SIMULINK Software and DECK Toolbox. We examined different maneuvers for spacecraft and investigated the effect of faults on the overall system and the performance of our designed fault diagnoser

The challenge of advanced model-based fdir techniques for aerospace systems: the 2011 situation

For aerospace systems, advanced model-based Fault Detection, Identification, and Recovery (FDIR) challenges range from predesign and design stages for upcoming and new programs up to the improvement of the performance of in-service flying systems. However, today, their application to real aerospace world has remained extremely limited. The paper underlines the reasons for a widening gap between the advanced scientific FDIR methods being developed by the academic community and technological solutions demanded by the aerospace industry