Dissertations / Theses on the topic 'Complex engineering systems'
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1
Venkatesh, Saligrama Ramaswamy. "System-identification for complex-systems." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10440.
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Magee, Christopher, and Weck Olivier de. "Complex System Classification." International Council On Systems Engineering (INCOSE), 2004. http://hdl.handle.net/1721.1/6753.
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The use of terms such as “Engineering Systems”, “System of systems” and others have been coming into greater use over the past decade to denote systems of importance but with implied higher complexity than for the term systems alone. This paper searches for a useful taxonomy or classification scheme for complex Systems. There are two aspects to this problem: 1) distinguishing between Engineering Systems (the term we use) and other Systems, and 2) differentiating among Engineering Systems. Engineering Systems are found to be differentiated from other complex systems by being human-designed and having both significant human complexity as well as significant technical complexity. As far as differentiating among various engineering systems, it is suggested that functional type is the most useful attribute for classification differentiation. Information, energy, value and mass acted upon by various processes are the foundation concepts underlying the technical types.Engineering Systems Division and Mechanical Engineering, Center for Innovation in Product Development
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Case, Denise Marie. "Engineering complex systems with multigroup agents." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/19045.
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Doctor of PhilosophyComputing and Information Sciences
Scott A. DeLoach
As sensor prices drop and computing devices continue to become more compact and powerful, computing capabilities are being embedded throughout our physical environment. Connecting these devices in cyber-physical systems (CPS) enables applications with significant societal impact and economic benefit. However, engineering CPS poses modeling, architecture, and engineering challenges and, to fully realize the desired benefits, many outstanding challenges must be addressed. For the cyber parts of CPS, two decades of work in the design of autonomous agents and multiagent systems (MAS) offers design principles for distributed intelligent systems and formalizations for agent-oriented software engineering (AOSE). MAS foundations offer a natural fit for enabling distributed interacting devices. In some cases, complex control structures such as holarchies can be advantageous. These can motivate complex organizational strategies when implementing such systems with a MAS, and some designs may require agents to act in multiple groups simultaneously. Such agents must be able to manage their multiple associations and assignments in a consistent and unambiguous way. This thesis shows how designing agents as systems of intelligent subagents offers a reusable and practical approach to designing complex systems. It presents a set of flexible, reusable components developed for OBAA++, an organization-based architecture for single-group MAS, and shows how these components were used to develop the Adaptive Architecture for Systems of Intelligent Systems (AASIS) to enable multigroup agents suitable for complex, multigroup MAS. This work illustrates the reusability and flexibility of the approach by using AASIS to simulate a CPS for an intelligent power distribution system (IPDS) operating two multigroup MAS concurrently: one providing continuous voltage control and a second conducting discrete power auctions near sources of distributed generation.
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Devereaux, Jaime E. (Jaime Erin). "Obsolescence : a systems engineering and management approach for complex systems." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59233.
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Thesis (S.M. in System Design and Management)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 79-81).
Obsolescence mitigation is an increasingly important aspect of large systems development & maintenance that has often only been considered once obsolescence is imminent. For long lifecycle systems, this has become a major concern as the lifecycles of the components that are encompassed within these systems are often far shorter - up to ten times shorter - than the overall system lifecycle. Many defense systems can be characterized in this manner and therefore require obsolescence mitigation approaches to ensure the continuing ability for the system to perform and evolve. Current system-level obsolescence mitigation practices make recommendations for designing new systems to slow the onset of obsolescence and make the system more flexible when change for obsolescence is required. However, currently fielded systems were often not designed with this in mind. Other obsolescence mitigation techniques focus only on the approach to mitigating component-level obsolescence locally without examining the impact of the change on the system as a whole. This thesis combines the recommended approaches for obsolescence mitigation, the experience and lessons learned for obsolescence mitigation on a real-world case study system gained from interviews with key subject matter experts, along with systems engineering techniques for dealing with engineering change in systems to develop a robust systems engineering and management approach for obsolescence in large complex systems. The thesis provides the reader with a flow chart and a clustered DSM of the tasks along with a checklist that could be used with this obsolescence engineering and management approach.
by Jaime E. Devereaux.
S.M.in System Design and Management
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Mwanga, Alifas Yeko. "Reliability modelling of complex systems." Thesis, Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-12142006-121528.
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Holbrook, A. E. K. "Design assistance for complex engineering assemblies." Thesis, Cranfield University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303118.
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Abdullah, Rudwan Ali Abolgasim. "Intelligent methods for complex systems control engineering." Thesis, University of Stirling, 2007. http://hdl.handle.net/1893/257.
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This thesis proposes an intelligent multiple-controller framework for complex systems that incorporates a fuzzy logic based switching and tuning supervisor along with a neural network based generalized learning model (GLM). The framework is designed for adaptive control of both Single-Input Single-Output (SISO) and Multi-Input Multi-Output (MIMO) complex systems. The proposed methodology provides the designer with an automated choice of using either: a conventional Proportional-Integral-Derivative (PID) controller, or a PID structure based (simultaneous) Pole and Zero Placement controller. The switching decisions between the two nonlinear fixed structure controllers is made on the basis of the required performance measure using the fuzzy logic based supervisor operating at the highest level of the system. The fuzzy supervisor is also employed to tune the parameters of the multiple-controller online in order to achieve the desired system performance. The GLM for modelling complex systems assumes that the plant is represented by an equivalent model consisting of a linear time-varying sub-model plus a learning nonlinear sub-model based on Radial Basis Function (RBF) neural network. The proposed control design brings together the dominant advantages of PID controllers (such as simplicity in structure and implementation) and the desirable attributes of Pole and Zero Placement controllers (such as stable set-point tracking and ease of parameters’ tuning). Simulation experiments using real-world nonlinear SISO and MIMO plant models, including realistic nonlinear vehicle models, demonstrate the effectiveness of the intelligent multiple-controller with respect to tracking set-point changes, achieve desired speed of response, prevent system output overshooting and maintain minimum variance input and output signals, whilst penalising excessive control actions.
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Wang, Cheng 1971. "Parametric uncertainty analysis for complex engineering systems." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9507.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999.Includes bibliographical references (p. 259-275).
With the rapid advancement of computational science, modeling and simulation have become standard methods to study the behavior of complex systems. As scientists and engineers try to capture more detail, the models become more complex. Given that there are inevitable uncertainties entering at every stage of a model's life cycle, the challenge is to identify those components that contribute most to uncertainties in the predictions. This thesis presents new methodologies for allowing direct incorporation of uncertainty into the model formulation and for identifying the relative importance of different parameters. The basis of these methods is the deterministic equivalent modeling method (DEMM), which applies polynomial chaos expansions and the probabilistic collocation approach to transform the stochastic model into a deterministic equivalent model. By transforming the model the task of determining the probability density function of the model response surface is greatly simplified. In order to advance the representation method of parametric uncertainty. a theoretical study of polynomial chaos representation of uncertain parameters has been performed and an Adomian polynomial expansion for functions of random variables has been developed. While DEMM is applied to various engineering systems to study the propagation of uncertainty in complex models, a systematic framework is introduced to quantitatively assess the effect of uncertain parameters in stochastic optimization problems for chemical product and process design. Furthermore, parametric uncertainty analysis techniques for discrete and correlated random variables have been developed such that the deterministic equivalent modeling method can be applied to a broader range of engineering problems. As a result of these developments, uncertainty analysis can now be performed 2 to 3 orders faster than conventional methods such as Monte Carlo. Examples of models in various engineering systems suggest both the accuracy and the practicality of the new framework for parametric uncertainty analysis established in this thesis.
by Cheng Wang.
Ph.D.
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Zils, Jude. "A Systems Engineering Approach to Complex Tool Realization." Digital Commons at Loyola Marymount University and Loyola Law School, 2010. https://digitalcommons.lmu.edu/etd/448.
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Tooling is defined as the work performed by a tool. In the context of industrial production tooling takes many forms from a simple drill bar to highly complex assembly jigs. In all cases the tooling exists to assist in the accurate and precise performance of work on engineering products. The engineering product therefore defines and constrains the form and function of the associated tooling. The process of defining, fabricating, and verifying tooling is often subject to individual, business, or government perspectives and processes. Relying on individual experience and inadequate processes often results in frequent rework, product design interface issues, and a lack of historical perspective and traceability on the tooling design. The Systems Engineering process, which is already valued as a necessary component of complex system definition, will be beneficial when adapted and applied to the process of defining, fabricating, and verifying tooling. The methodical processes and tools associated with Systems Engineering will embed the tooling process in the product requirement and design process and encourage increased interaction and concurrent engineering practices. A tooling process, based on System Engineering principles combined with best industry practices, that is ingrained in the product life cycle and which thoroughly documents associated technical and producibility requirements will reduce the issues currently prevalent in complex tooling realization.
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Cheng, Fook-Chun. "Object-oriented data structures in complex engineering systems." Thesis, London South Bank University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280785.
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Atkinson, Simon Reay. "Engineering design adaptation fitness in complex adaptive systems." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648674.
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Loureiro, Geilson. "A systems engineering and concurrent engineering framework for the integrated development of complex products." Thesis, Loughborough University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250969.
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Bates, Ronald Anthony. "The robust design of complex systems." Thesis, City, University of London, 1995. http://openaccess.city.ac.uk/17421/.
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Robust Engineering Design has evolved as an important methodology for the integration of quality with the process of design. The methodology encompasses the disciplines of experimental design, model building and optimization. First an experiment is conducted on a system (or a simulation of the system), second a model is built to emulate the system and finally the emulation model is used to optimize the system design. Applying these methods to large problems can be difficult and time-consuming because of the complexity of most design problems. It is the goal of this thesis to introduce methods which reduce problem complexity and so make the application of Robust Engineering Design (RED) methodology easier for large design problems. By drawing from methods used in systems theory and circuit optimization several techniques are presented with the aim of reducing the complexity of performing experiments for Robust Engineering Design. A common framework for experimentation is created by combining a commercial circuit simulator with established methods for experimental design and model building. This provides the basis for experimentation in subsequent chapters. A method of design optimization with respect to quality is presented to complete the model-based Robust Engineering Design cycle. Three approaches to reducing problem complexity are adopted. First a method of system decomposition is applied directly to an electronic circuit to reduce the size of experiment required for RED. Second a method of modelling system response functions is described which integrates the action of the circuit simulator with the model building process. Third information about system topology is used in the design of experiments to enhance the model-building process. Conclusions are drawn about the effectiveness of the approaches described with respect to the impact on problem complexity.
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Reily, Todd R. (Todd Richard). "User experience design of complex systems." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77063.
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Thesis (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 104-105).
Over recent years, the global marketplace and its consumers have developed a mutual recognition for the rising prominence of design that delivers high quality user experience. For the provider of products and services, such design has emerged as a critical differentiator that creates new opportunities for revenue and drives customer loyalty. For the consumer, design can often surpass commoditized technical specifications as a basis for making purchase decisions. Nevertheless, despite their best intentions, many organizations still fail to successfully integrate design strategies into their existing processes and culture. This research examines the critical factors that enable successful implementation of design strategies under current market conditions in a way that produces sustained customer loyalty and revenue. Methods utilized in this research include one-on-one interviews, online surveys, and comparative case studies to ensure proper balance and perspective. The interviews were conducted with design leaders at organizations such as Philips and Frog Design. They covered the role that design plays at organizations, including the conditions necessary for successful design strategies and the barriers that they generally face. Surveys conducted for this research examined the personal experiences of 120 managers, engineers, and designers on the development of consumer-facing products, services, and systems. The result of these methods was a series of findings that supports the notion that a holistic "systems-based" approach offers competitive advantages to organizations looking to successfully implement a design-oriented strategy. It is this perspective that allows organizations to realize solutions that balance business objectives, technical capabilities, and design principles to meet customer intentions. It is proposed by this thesis that a systems-based approach has become necessary due to the ever-converging nature of today's networked products and services, particularly in the consumer marketplace. This thesis concludes with a framework of methods and principles for conceiving and designing user experiences for a complex market of convergent products and services. The framework borrows methods from Systems Thinking, Design Thinking, and User Experience Design to create a singular process that provides the clarity and simplicity necessary for a user experience amidst the complexity of a system design process.
by Todd R. Reily.
S.M.in Engineering and Management
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Scudieri, Paul Anthony. "Information in Complex Product Systems." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236698805.
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Lemmens, Yves Claude Jean. "Modelling and analysis of engineering changes in complex systems." Thesis, Cranfield University, 2007. http://dspace.lib.cranfield.ac.uk/handle/1826/5071.
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Complex products are comprised of a large number of tightly integrated components, assemblies and systems resulting in extensive logical and physical interdependences between the constituent parts. Thus a change to one item of a system is highly likely to lead to a change to another item, which in turn can propagate further. The aim of this research therefore is to investigate dependency models that can be used to identify the impact and trace thepropagation of changes in different information domains, such as requirements, physical product architecture or organisation. Cont/d.
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Marburger, André [Verfasser]. "Reverse Engineering of Complex Legacy Telecommunication Systems / André Marburger." Aachen : Shaker, 2005. http://d-nb.info/1186580232/34.
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Olechowski, Alison L. (Alison Louise). "Essays on decision-making in complex engineering systems development." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111942.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 123-130).
This thesis presents three essays on the topic of tools for assessment and decisionmaking in complex engineering systems development. The first essay presents an extension to the design structure matrix, used to present and analyze the suite of tests a system undergoes at multiple levels of the architecture. This method decomposes the multilevel integration test suite - progressing from component to subsystem to system - and visually represents the test coverage. We demonstrate the new method on a subsea system at BP. The second essay presents a study of the current state of use of the technology readiness level method. We discovered, described and prioritized 15 challenges associated with assessing and using the technology readiness levels. We further discuss existing and potential solutions to these challenges. This paper is based on input from interviews at seven different organizations, and a survey of over 100 system engineers. System complexity related challenges were found to be particularly critical and currently without adequate solution. The final essay presents an expansion of our current understanding of the options available at a phase-gate review. Beyond the typical Go and Kill options, we describe the Waiver (with and without review), Delay and switch to a Back-up plan options. We show how it is feasible to extend a simple decision tree model to analyze the expected value of this broader set of options. We demonstrate this method with four case applications from industry.
by Alison Olechowski.
Ph. D.
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Oliver, John M. "Multi-objective optimisation methods applied to complex engineering systems." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/11707.
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This research proposes, implements and analyses a novel framework for multiobjective
optimisation through evolutionary computing aimed at, but not restricted
to, real-world problems in the engineering design domain.
Evolutionary algorithms have been used to tackle a variety of non-linear multiobjective
optimisation problems successfully, but their success is governed by key
parameters which have been shown to be sensitive to the nature of the particular
problem, incorporating concerns such as the number of objectives and variables,
and the size and topology of the search space, making it hard to determine the best
settings in advance. This work describes a real-encoded multi-objective optimising
evolutionary algorithm framework, incorporating a genetic algorithm, that uses
self-adaptive mutation and crossover in an attempt to avoid such problems, and
which has been benchmarked against both standard optimisation test problems in
the literature and a real-world airfoil optimisation case.
For this last case, the minimisation of drag and maximisation of lift coefficients
of a well documented standard airfoil, the framework is integrated with a freeform
deformation tool to manage the changes to the section geometry, and XFoil,
a tool which evaluates the airfoil in terms of its aerodynamic efficiency. The
performance of the framework on this problem is compared with those of two
other heuristic MOO algorithms known to perform well, the Multi-Objective Tabu
Search (MOTS) and NSGA-II, showing that this framework achieves better or at
least no worse convergence. The framework of this research is then considered as a candidate for smart
(electricity) grid optimisation. Power networks can be improved in both technical
and economical terms by the inclusion of distributed generation which may
include renewable energy sources. The essential problem in national power networks
is that of power
flow and in particular, optimal power
flow calculations of
alternating (or possibly, direct) current. The aims of this work are to propose and
investigate a method to assist in the determination of the composition of optimal
or high-performing power networks in terms of the type, number and location of
the distributed generators, and to analyse the multi-dimensional results of the
evolutionary computation component in order to reveal relationships between the
network design vector elements and to identify possible further methods of improving
models in future work. The results indicate that the method used is a
feasible one for the achievement of these goals, and also for determining optimal
flow capacities of transmission lines connecting the bus bars in the network.
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Sun, Yong. "Reliability prediction of complex repairable systems : an engineering approach." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16273/1/Yong_Sun_Thesis.pdf.
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This research has developed several models and methodologies with the aim of improving the accuracy and applicability of reliability predictions for complex repairable systems. A repairable system is usually defined as one that will be repaired to recover its functions after each failure. Physical assets such as machines, buildings, vehicles are often repairable. Optimal maintenance strategies require the prediction of the reliability of complex repairable systems accurately. Numerous models and methods have been developed for predicting system reliability. After an extensive literature review, several limitations in the existing research and needs for future research have been identified. These include the follows: the need for an effective method to predict the reliability of an asset with multiple preventive maintenance intervals during its entire life span; the need for considering interactions among failures of components in a system; and the need for an effective method for predicting reliability with sparse or zero failure data. In this research, the Split System Approach (SSA), an Analytical Model for Interactive Failures (AMIF), the Extended SSA (ESSA) and the Proportional Covariate Model (PCM), were developed by the candidate to meet the needs identified previously, in an effective manner. These new methodologies/models are expected to rectify the identified limitations of current models and significantly improve the accuracy of the reliability prediction of existing models for repairable systems. The characteristics of the reliability of a system will alter after regular preventive maintenance. This alternation makes prediction of the reliability of complex repairable systems difficult, especially when the prediction covers a number of imperfect preventive maintenance actions over multiple intervals during the asset's lifetime. The SSA uses a new concept to address this issue effectively and splits a system into repaired and unrepaired parts virtually. SSA has been used to analyse system reliability at the component level and to address different states of a repairable system after single or multiple preventive maintenance activities over multiple intervals. The results obtained from this investigation demonstrate that SSA has an excellent ability to support the making of optimal asset preventive maintenance decisions over its whole life. It is noted that SSA, like most existing models, is based on the assumption that failures are independent of each other. This assumption is often unrealistic in industrial circumstances and may lead to unacceptable prediction errors. To ensure the accuracy of reliability prediction, interactive failures were considered. The concept of interactive failure presented in this thesis is a new variant of the definition of failure. The candidate has made several original contributions such as introducing and defining related concepts and terminologies, developing a model to analyse interactive failures quantitatively and revealing that interactive failure can be either stable or unstable. The research results effectively assist in avoiding unstable interactive relationship in machinery during its design phase. This research on interactive failures pioneers a new area of reliability prediction and enables the estimation of failure probabilities more precisely. ESSA was developed through an integration of SSA and AMIF. ESSA is the first effective method to address the reliability prediction of systems with interactive failures and with multiple preventive maintenance actions over multiple intervals. It enhances the capability of SSA and AMIF. PCM was developed to further enhance the capability of the above methodologies/models. It addresses the issue of reliability prediction using both failure data and condition data. The philosophy and procedure of PCM are different from existing models such as the Proportional Hazard Model (PHM). PCM has been used successfully to investigate the hazard of gearboxes and truck engines. The candidate demonstrated that PCM had several unique features: 1) it automatically tracks the changing characteristics of the hazard of a system using symptom indicators; 2) it estimates the hazard of a system using symptom indicators without historical failure data; 3) it reduces the influence of fluctuations in condition monitoring data on hazard estimation. These newly developed methodologies/models have been verified using simulations, industrial case studies and laboratory experiments. The research outcomes of this research are expected to enrich the body of knowledge in reliability prediction through effectively addressing some limitations of existing models and exploring the area of interactive failures.
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Sun, Yong. "Reliability prediction of complex repairable systems : an engineering approach." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16273/.
Full textAbstract:
This research has developed several models and methodologies with the aim of improving the accuracy and applicability of reliability predictions for complex repairable systems. A repairable system is usually defined as one that will be repaired to recover its functions after each failure. Physical assets such as machines, buildings, vehicles are often repairable. Optimal maintenance strategies require the prediction of the reliability of complex repairable systems accurately. Numerous models and methods have been developed for predicting system reliability. After an extensive literature review, several limitations in the existing research and needs for future research have been identified. These include the follows: the need for an effective method to predict the reliability of an asset with multiple preventive maintenance intervals during its entire life span; the need for considering interactions among failures of components in a system; and the need for an effective method for predicting reliability with sparse or zero failure data. In this research, the Split System Approach (SSA), an Analytical Model for Interactive Failures (AMIF), the Extended SSA (ESSA) and the Proportional Covariate Model (PCM), were developed by the candidate to meet the needs identified previously, in an effective manner. These new methodologies/models are expected to rectify the identified limitations of current models and significantly improve the accuracy of the reliability prediction of existing models for repairable systems. The characteristics of the reliability of a system will alter after regular preventive maintenance. This alternation makes prediction of the reliability of complex repairable systems difficult, especially when the prediction covers a number of imperfect preventive maintenance actions over multiple intervals during the asset's lifetime. The SSA uses a new concept to address this issue effectively and splits a system into repaired and unrepaired parts virtually. SSA has been used to analyse system reliability at the component level and to address different states of a repairable system after single or multiple preventive maintenance activities over multiple intervals. The results obtained from this investigation demonstrate that SSA has an excellent ability to support the making of optimal asset preventive maintenance decisions over its whole life. It is noted that SSA, like most existing models, is based on the assumption that failures are independent of each other. This assumption is often unrealistic in industrial circumstances and may lead to unacceptable prediction errors. To ensure the accuracy of reliability prediction, interactive failures were considered. The concept of interactive failure presented in this thesis is a new variant of the definition of failure. The candidate has made several original contributions such as introducing and defining related concepts and terminologies, developing a model to analyse interactive failures quantitatively and revealing that interactive failure can be either stable or unstable. The research results effectively assist in avoiding unstable interactive relationship in machinery during its design phase. This research on interactive failures pioneers a new area of reliability prediction and enables the estimation of failure probabilities more precisely. ESSA was developed through an integration of SSA and AMIF. ESSA is the first effective method to address the reliability prediction of systems with interactive failures and with multiple preventive maintenance actions over multiple intervals. It enhances the capability of SSA and AMIF. PCM was developed to further enhance the capability of the above methodologies/models. It addresses the issue of reliability prediction using both failure data and condition data. The philosophy and procedure of PCM are different from existing models such as the Proportional Hazard Model (PHM). PCM has been used successfully to investigate the hazard of gearboxes and truck engines. The candidate demonstrated that PCM had several unique features: 1) it automatically tracks the changing characteristics of the hazard of a system using symptom indicators; 2) it estimates the hazard of a system using symptom indicators without historical failure data; 3) it reduces the influence of fluctuations in condition monitoring data on hazard estimation. These newly developed methodologies/models have been verified using simulations, industrial case studies and laboratory experiments. The research outcomes of this research are expected to enrich the body of knowledge in reliability prediction through effectively addressing some limitations of existing models and exploring the area of interactive failures.
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Skinner, Stephen C. "A systems engineering methodology for the integration of subsystems into complex systems." Ann Arbor, Mich. : ProQuest, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3288738.
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Thesis (Ph.D. in Applied Science)--S.M.U., 2007.Title from PDF title page (viewed Nov. 19, 2009). Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7641. Advisers: Jerrell T. Stracener; Khaled Abdelghany. Includes bibliographical references.
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Tan, Sofia. "Enhanced functional analysis system technique for managing complex engineering projects." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/Tan_09007dcc803c4e70.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 27, 2007) Includes bibliographical references (p. 27-29).
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Kendall, John Michael Patrick. "Software tools for the automatic configuration of complex engineering systems." Thesis, London South Bank University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357125.
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Due to the ever increasing complexity of modem engineering systems, there exists a need for a new generation of software tools to cope with all aspects of system lifecycles. One of the stages of the lifecycle is configuration, which is the representation of the system for operational purposes. The thesis describes work done to create a methodology for the automatic configuration of engineering systems by the use of intelligent graphical interfaces. One of the main tenets being that all information is entered into the system by using graphics as the 'front end'. This is in contrast to many current methods where the graphical representation is used only as documentation for the systems. Many systems are too complex to be represented on a single screen, so techniques have therefore been created to construct hierarchical models using Object Oriented technology and relation theory. The principles developed can be considered as generic for many applications areas, but were applied to three case studies in differing engineering fields. These are: the configuration of the controlling processors in building management systems, the configuration of the structure of knowledge based systems and the configuration of databases for use in data exchange systems. The former was achieved by the depiction of the engineering system being configured using a symbol set representing hardware items. The physical and logical connections can be represented on the graphical interface, and the hardware is configured when this diagram is compiled into a form interpretable by the controlling processor. The two latter case studies were implemented using a graphical schema language NIAM (Nijssen Information Analysis Method) to represent information structure. The data transfer system compiles the NIAM diagram into Express, the text based schema language of the ISO 10303 STEP (STandard for the Exchange of Product model data) initiative, which can then be translated into database structure formats. In the case of the expert system, the structure is supported by empirical rules, and deductions are obtained using fuzzy set principles.
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Valenzuela, Vega Rene Cristian. "Compact reliability and maintenance modeling of complex repairable systems." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51850.
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Maintenance models are critical for evaluation of the alternative maintenance
policies for modern engineering systems. A poorly selected policy can result in excessive
life-cycle costs as well as unnecessary risks for catastrophic failures of the system. Economic dependence refers to the difference between the cost of combining the maintenance of a number of components and the cost of performing the same maintenance actions individually. Maintenance that takes advantage of this difference is often called opportunistic.
Large number of components and economic inter-dependence are two pervasive characteristics of modern engineering systems that make the modeling of their maintenance processes particularly challenging. Simulation is able to handle both of these characteristics computationally, but the complexity, especially from the model verification perspective, becomes overwhelming as the number of components increases. This research introduces a new procedure for maintenance models of multi-unit repairable systems with economic dependence among its components and under opportunistic maintenance policies. The procedure is based on the stochastic Petri net with aging tokens modeling framework and it makes use of a component-level model approach to overcome the state explosion of the model combined with a novel order-reduction scheme that effectively combines the impact of other components into a single distribution. The justification for
the used scheme is provided, the accuracy is assessed, and applications for the systems of realistic complexity are considered.
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Kandjani, Hadi Esmaeilzadeh. "Engineering Self-designing Enterprises as Complex Systems Using Enterprise Architecture Cybernetics." Thesis, Griffith University, 2013. http://hdl.handle.net/10072/367332.
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Various disciplines have contributed to Complexity Science by experiencing the problem of how to design, build and control more and more complex systems (i.e., to ‘beat the complexity barrier’) and tried to suggest some solutions. However, apart from the description of this problem, very few concrete proposals exist to solve it. The observation of this Conceptual Analytical dissertation is that while improved design methodologies, modelling languages and analysis tools can certainly lessen the designer’s problem, they only extend the complexity barrier that a designer (or group of designers) can
deal with, but they do not remove that barrier. The hypothesis of this dissertation is that perhaps the system (or system of systems) and the designer (group of designers) should not be separated and systems should design themselves, out of component systems that have the same self-designing property.
Therefore the informal research questions are:
1. Is it possible to remove this problem from the design of complex systems?
2. If yes how (or to what extent)?
Many disciplines attempted to attack the question of complexity management, and as will be seen, an interdisciplinary approach seems necessary to be able to give useful answers. Enterprise Architecture as a discipline, which evolved in the past 20 to 30 years (initially called 'enterprise integration'), has defined as its mission to bring together all that knowledge which is necessary to maintain enterprises through life (ISO 15704, 2000). Therefore, this thesis will attempt to look at the problem through the eyes of an interdisciplinary EA researcher.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Information and Communication Technology
Science, Environment, Engineering and Technology
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Hovorka, Ondrej Friedman Gary. "Hysteresis behavior patterns in complex systems /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1791.
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Hemann, Justin M. (Justin Matthew). "Improving complex enterprises with system models." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/35615.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, 2005.Includes bibliographical references (leaves 96-98).
Air Force sustainment operations are the focus of an intensive internal effort to improve performance and reduce costs. Past improvement initiatives have often failed to produce the intended results, and have caused performance to decline in some cases. Exploratory research was conducted at an Air Logistics Center to study how improvements are executed. Two conclusions are drawn from this research. The first is that changing sustainment operations is a problem of high dynamic and behavioral complexity. The second conclusion is that system models are well suited to coordinating change at the ALC because they provide insight into how a complicated system can be managed and improved. Three key findings support these conclusions. First, there is significant correlation between categories of unavailable F-16 aircraft such that reductions in one category are associated with increases in another. Second, an analysis of change efforts in two parts of the ALC shows that systemic influences, such as the inability to reinvest in improvements, are hindering change initiatives in one part of the ALC.
(cont.) The third finding is that a model of sustainment operations suggests that independent improvement initiatives are outperformed by coordinated efforts driven with an understanding of systemic interactions. Leaders throughout the sustainment community have expressed their desire to understand how sustainment operations function as a system. A hybrid approach to change is offered as a method for understanding and improving sustainment operations. System models are used to quantify and model system interactions; then policies and recommendations are drawn from the models. Recommendations may include process-level improvements utilizing change methods already in use at the ALC.
by Justin M. Hemann.
S.M.
29
Louie, Raymond (Raymond T. ). 1976. "Hybrid intelligent systems integration into complex multi-source information systems." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86533.
Full textAbstract:
Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (leaves 98-100).
by Raymond Louie.
S.B.and M.Eng.
30
Henneman, Richard Lewis. "Human problem solving in complex hierarchical large scale systems." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/25432.
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Du, Dawei. "Biogeography-based optimization for combinatorial problems and complex systems." Cleveland State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=csu1400504249.
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Sonntag, Christian [Verfasser]. "Model Transformations for the Engineering of Complex Automated Systems / Christian Sonntag." Aachen : Shaker, 2018. http://d-nb.info/1188550268/34.
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Glaser, Philipp [Verfasser], and Vincent [Akademischer Betreuer] Heuveline. "Uncertainty Quantification for Complex Engineering Systems / Philipp Glaser ; Betreuer: Vincent Heuveline." Heidelberg : Universitätsbibliothek Heidelberg, 2021. http://d-nb.info/1233289292/34.
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Shukla, Vikas. "Comprehensive méthodology for the complex systems' requirements engineering & decision making." Thesis, Toulouse, INSA, 2014. http://www.theses.fr/2014ISAT0019/document.
Full textAbstract:
L’objectif principal de l’ingénierie des systèmes est la création d’un ensemblede produits et des services de haute qualité qui permettent l’accomplissement de tâchespour répondre aux besoins des clients. Un projet typique d’ingénierie des systèmes peutêtre divisé en trois phases : la définition, le développement et le déploiement. La phasede définition comprend les activités de capture des exigences et de leur raffinement. Àla fin de la phase de définition du système, nous avons toutes les exigences fonctionnelleset non-fonctionnelles du système. L’un des résultats de la phase de développement est lemodèle de travail initiale du système. La phase de déploiement se compose des activitésliées à (1) l’évaluation opérationnelle du système, à (2) l’utilisation du système et à (3) sonentretien. Dans un cycle de vie du projet, il y a de nombreuses questions qui doivent êtretraitées au cours des différentes phases pour finalement livrer un produit.Nous avons proposé une solution aux problèmes liés à l’ingénierie des exigences et auxtechniques de la détection, de la gestion et de la résolution des conflits entre les partiesprenantes. Cette thèse est basée sur les dernières avancées dans les pratiques industrielleset de recherche dans le domaine de l’ingénierie de conception du système.L’objectif de ce travail de thèse est de proposer une méthodologie de conception novatriceet globale en tenant compte de l’environnement multidisciplinaire et de multiplesintervenants. Nous avons proposé un langage de modélisation des exigences basé sur lestechniques GORE. Nous avons proposé quelques outils pour réduire l’ambiguïté des exigencestels l’utilisation de phrases négatives et de tests á l’aide de négation lorsqu’il s’agitde traiter certaines exigences difficiles à comprendre avec les techniques classiques. Nousavons également proposé des techniques de gestion des exigences pour mieux assurer leurtraçabilité. Concernant la résolution des conflits, nous avons proposé des techniques depondération des critères au cours des différentes étapes du cycle de vie. En utilisant lamême technique de pondération de critères, une méthode de décision multicritères et multiparticipants est proposée pour divers problèmes de décision survenant pendant le cycle devie du projet d’ingénierie systèmes.Enfin, une approche globale de l’ingénierie des systèmes est proposée pour intégrertoutes les contributions faites précédemment et est illustrée sur une étude de cas concernantun projet réel avec la présentation dŠun outil SysEngLab que nous avons développé pourmettre en oeuvre la majorité des méthodes et des techniques proposées au cours de thèseThe primary goal of the systems engineering is the creation of a setof high quality products and services that enable the accomplishment of desiredtasks and needs of the clients or user groups. A typical systems engineering projectcan be divided in to three phases: definition, development, and deployment. Thedefinition phase involves the activities of requirement elicitation and refinement.By the end of system definition phase, we have all the system functional and nonfunctionalrequirements. One of the results of development phase is initial workingmodel of the system. The deployment phase consists of activities of operationalimplementation, operational testing and evaluation, and operational functioning andmaintenance. In a project life cycle there are numerous issues to be sorted out duringthe various phases to finally deliver a successful product. We proposed solution tothe problems of requirements engineering & management, design conflict detection,and stakeholders conflict resolution. This thesis is based on the recent advances inindustrial practices and research in the field of system design engineering.The objective of this thesis work is to propose an innovative and holistic conceptionmethodology taking into account the multidisciplinary environment and multiplestakeholders. We have proposed a requirements modeling language based on theGORE techniques. We have proposed a few of tools for reducing the ambiguity ofrequirements such as: using negation and test cases using negation for contractingdifficult requirements. Requirement management techniques are proposed to providebetter requirements traceability and aid for other systems engineering activities.Few guidelines have been designed to guide the design of traceability policies. Criteriaweighting technique has been designed to better carry out the conflict resolutions,during the various life cycle stages. Using the same criteria weighting technique aflexible multi criteria multi participant decision methodology is proposed for variousdecision problems arising during the life cycle of systems engineering project.Finally, a comprehensive prescriptive systems engineering approach is proposedusing all the previously made contributions and an illustrative case study of a realongoing project is presented developed using the supporting tool SysEngLab, whichimplements majority of the methods and techniques proposed during thesis
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Molesini, Ambra <1980>. "Meta-models, environment and layers: agent-oriented engineering of complex systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/930/1/Tesi_Molesini_Ambra.pdf.
Full textAbstract:
Traditional software engineering approaches and metaphors fall short when applied to
areas of growing relevance such as electronic commerce, enterprise resource planning,
and mobile computing: such areas, in fact, generally call for open architectures that
may evolve dynamically over time so as to accommodate new components and meet new
requirements. This is probably one of the main reasons that the agent metaphor and the
agent-oriented paradigm are gaining momentum in these areas.
This thesis deals with the engineering of complex software systems in terms of the
agent paradigm. This paradigm is based on the notions of agent and systems of interacting agents as fundamental abstractions for designing, developing and managing at
runtime typically distributed software systems. However, today the engineer often works
with technologies that do not support the abstractions used in the design of the systems.
For this reason the research on methodologies becomes the basic point in the scientific
activity. Currently most agent-oriented methodologies are supported by small teams of
academic researchers, and as a result, most of them are in an early stage and still in the
first context of mostly \academic" approaches for agent-oriented systems development.
Moreover, such methodologies are not well documented and very often defined and presented only by focusing on specific aspects of the methodology. The role played by meta-
models becomes fundamental for comparing and evaluating the methodologies. In fact a
meta-model specifies the concepts, rules and relationships used to define methodologies.
Although it is possible to describe a methodology without an explicit meta-model, formalising the underpinning ideas of the methodology in question is valuable when checking its
consistency or planning extensions or modifications. A good meta-model must address all
the different aspects of a methodology, i.e. the process to be followed, the work products
to be generated and those responsible for making all this happen. In turn, specifying
the work products that must be developed implies dening the basic modelling building
blocks from which they are built.
As a building block, the agent abstraction alone is not enough to fully model all the
aspects related to multi-agent systems in a natural way. In particular, different perspectives exist on the role that environment plays within agent systems: however, it is
clear at least that all non-agent elements of a multi-agent system are typically considered to be part of the multi-agent system environment. The key role of environment
as a first-class abstraction in the engineering of multi-agent system is today generally
acknowledged in the multi-agent system community, so environment should be explicitly
accounted for in the engineering of multi-agent system, working as a new design dimension
for agent-oriented methodologies. At least two main ingredients shape the environment:
environment abstractions - entities of the environment encapsulating some functions -,
and topology abstractions - entities of environment that represent the (either logical or
physical) spatial structure. In addition, the engineering of non-trivial multi-agent systems requires principles and mechanisms for supporting the management of the system representation complexity. These principles lead to the adoption of a multi-layered description, which could be used by designers to provide different levels of abstraction over
multi-agent systems.
The research in these fields has lead to the formulation of a new version of the SODA
methodology where environment abstractions and layering principles are exploited for en-
gineering multi-agent systems.
36
Molesini, Ambra <1980>. "Meta-models, environment and layers: agent-oriented engineering of complex systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/930/.
Full textAbstract:
Traditional software engineering approaches and metaphors fall short when applied to
areas of growing relevance such as electronic commerce, enterprise resource planning,
and mobile computing: such areas, in fact, generally call for open architectures that
may evolve dynamically over time so as to accommodate new components and meet new
requirements. This is probably one of the main reasons that the agent metaphor and the
agent-oriented paradigm are gaining momentum in these areas.
This thesis deals with the engineering of complex software systems in terms of the
agent paradigm. This paradigm is based on the notions of agent and systems of interacting agents as fundamental abstractions for designing, developing and managing at
runtime typically distributed software systems. However, today the engineer often works
with technologies that do not support the abstractions used in the design of the systems.
For this reason the research on methodologies becomes the basic point in the scientific
activity. Currently most agent-oriented methodologies are supported by small teams of
academic researchers, and as a result, most of them are in an early stage and still in the
first context of mostly \academic" approaches for agent-oriented systems development.
Moreover, such methodologies are not well documented and very often defined and presented only by focusing on specific aspects of the methodology. The role played by meta-
models becomes fundamental for comparing and evaluating the methodologies. In fact a
meta-model specifies the concepts, rules and relationships used to define methodologies.
Although it is possible to describe a methodology without an explicit meta-model, formalising the underpinning ideas of the methodology in question is valuable when checking its
consistency or planning extensions or modifications. A good meta-model must address all
the different aspects of a methodology, i.e. the process to be followed, the work products
to be generated and those responsible for making all this happen. In turn, specifying
the work products that must be developed implies dening the basic modelling building
blocks from which they are built.
As a building block, the agent abstraction alone is not enough to fully model all the
aspects related to multi-agent systems in a natural way. In particular, different perspectives exist on the role that environment plays within agent systems: however, it is
clear at least that all non-agent elements of a multi-agent system are typically considered to be part of the multi-agent system environment. The key role of environment
as a first-class abstraction in the engineering of multi-agent system is today generally
acknowledged in the multi-agent system community, so environment should be explicitly
accounted for in the engineering of multi-agent system, working as a new design dimension
for agent-oriented methodologies. At least two main ingredients shape the environment:
environment abstractions - entities of the environment encapsulating some functions -,
and topology abstractions - entities of environment that represent the (either logical or
physical) spatial structure. In addition, the engineering of non-trivial multi-agent systems requires principles and mechanisms for supporting the management of the system representation complexity. These principles lead to the adoption of a multi-layered description, which could be used by designers to provide different levels of abstraction over
multi-agent systems.
The research in these fields has lead to the formulation of a new version of the SODA
methodology where environment abstractions and layering principles are exploited for en-
gineering multi-agent systems.
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Amin, Md Shahnoor. "Developing a Recall Mitigation Framework for Complex Systems." Thesis, The George Washington University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10689922.
Full textAbstract:
A product is recalled when it is deemed to pose a public safety hazard. As systems become more complex, identifying what factors influence recalls becomes increasingly important for engineering managers and systems engineers. With this in mind, this research endeavor highlights a novel safety framework that assists engineering teams in identifying recall risk factors early in the systems engineering process. The framework is applicable to complex systems, which usually have several stakeholders with requirements, and their needs are to be satisficed. Existing system engineering tools such as Failure Mode and Effects Analysis and Fault-tree Analysis are incorporated to identify risks. Five sequential activity phases are integral to the framework: Stakeholder Identification, Data Acquisition, Statistical Analysis, Safety Analysis, and Risk Review. The framework is especially useful in identifying and evaluating factors that could be associated with recalls prior to the next system design revision. For example, the framework can be applied by the engineering team during the redesign phase of a vehicle model (e.g. 2018 Toyota Camry), using historical data from the previous generation (e.g. 2011 Toyota Camry). Validation of the recall mitigation framework is highlighted through a case study involving the engineering of a new vehicle model in the automotive industry. Original Equipment Manufacturers (OEMs) of complex systems like cars issue recalls whenever the vehicle is perceived to have defects impacting public safety, whether due to airbag issues or excessive emissions. For over four years (2010–2013), the influence of recall factors for each automaker was analyzed. An additional, more qualitative, case study was performed of Lithium-Ion battery recalls, based on learnings from Sony’s woes in 2006. These case studies further validate the framework. Utilizing the framework within a new project environment can greatly assist engineering managers and their teams in identifying recall risk factors early in the systems engineering lifecycle.
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Hu, Kenneth T. "Bayesian design of experiments for complex chemical systems." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65760.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 317-322).
Engineering design work relies on the ability to predict system performance. A great deal of effort is spent producing models that incorporate knowledge of the underlying physics and chemistry in order to understand the relationship between system inputs and responses. Although models can provide great insight into the behavior of the system, actual design decisions cannot be made based on predictions alone. In order to make properly informed decisions, it is critical to understand uncertainty. Otherwise, there cannot be a quantitative assessment of which predictions are reliable and which inputs are most significant. To address this issue, a new design method is required that can quantify the complex sources of uncertainty that influence model predictions and the corresponding engineering decisions. Design of experiments is traditionally defined as a structured procedure to gather information. This thesis reframes design of experiments as a problem of quantifying and managing uncertainties. The process of designing experimental studies is treated as a statistical decision problem using Bayesian methods. This perspective follows from the realization that the primary role of engineering experiments is not only to gain knowledge but to gather the necessary information to make future design decisions. To do this, experiments must be designed to reduce the uncertainties relevant to the future decision. The necessary components are: a model of the system, a model of the observations taken from the system, and an understanding of the sources of uncertainty that impact the system. While the Bayesian approach has previously been attempted in various fields including Chemical Engineering the true benefit has been obscured by the use of linear system models, simplified descriptions of uncertainty, and the lack of emphasis on the decision theory framework. With the recent development of techniques for Bayesian statistics and uncertainty quantification, including Markov Chain Monte Carlo, Polynomial Chaos Expansions, and a prior sampling formulation for computing utility functions, such simplifications are no longer necessary. In this work, these methods have been integrated into the decision theory framework to allow the application of Bayesian Designs to more complex systems. The benefits of the Bayesian approach to design of experiments are demonstrated on three systems: an air mill classifier, a network of chemical reactions, and a process simulation based on unit operations. These case studies quantify the impact of rigorous modeling of uncertainty in terms of reduced number of experiments as compared to the currently used Classical Design methods. Fewer experiments translate to less time and resources spent, while reducing the important uncertainties relevant to decision makers. In an industrial setting, this represents real world benefits for large research projects in reducing development costs and time-to-market. Besides identifying the best experiments, the Bayesian approach also allows a prediction of the value of experimental data which is crucial in the decision making process. Finally, this work demonstrates the flexibility of the decision theory framework and the feasibility of Bayesian Design of Experiments for the complex process models commonly found in the field of Chemical Engineering.
by Kenneth T. Hu.
Ph.D.
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Yildirim, Unal. "Function Modelling of Complex Multidisciplinary Systems. Development of a System State Flow Diagram Methodology for Function Decomposition of Complex Multidisciplinary Systems." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14385.
Full textAbstract:
The complexity of technical systems has increased significantly in order to address evolving customer needs and environmental concerns. From a product development process viewpoint, the pervasive nature of multi-disciplinary systems (i.e. mechanical, electrical, electronic, control, software) has brought some important integration challenges to overcome conventional disciplinary boundaries imposed by discipline specific approaches. This research focuses on functional reasoning, aiming to develop a structured framework based on the System State Flow Diagram (SSFD) for function modelling of complex multidisciplinary systems on a practical and straightforward basis. The framework is developed at two stages. 1) The development of a prototype for the SSFD framework. The proposed SSFD framework are tested and validated through application to selected desktop case studies. 2) Further development and extension of the SSFD framework for the analysis of complex multidisciplinary systems with multiple operation modes and functional requirements. The developed framework is validated on real world case studies collaborated with industrial partners. The main conclusion of this research is that the SSFD framework offers a rigorous and coherent function modelling methodology for the analysis of complex multidisciplinary systems. Further advantages of the SSFD framework is that 1) the effectiveness of the Failure Mode Avoidance (FMA) process can be enhanced by integrating the SSFD framework with relevant tools of the FMA process, and 2) the integration of the SSFD with the SysML systems engineering diagrams is doable, which can promote the take-up of the approach in industry.
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Agrawal, Janak. "Distributed parameter estimation for complex energy systems." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129082.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, September, 2020Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 81-83).
With multiple energy sources, diverse energy demands, and heterogeneous socioeconomic factors, energy systems are becoming increasingly complex. Multifaceted components have non-linear dynamics and are interacting with each other as well as the environment. In this thesis, we model components in terms of their own internal dynamics and output variables at the interfaces with the neighboring components. We then propose to use a distributed estimation method for obtaining the parameters of the the component's internal model based on the measurements at its interfaces. We check whether theoretical conditions for distributed estimation approach are met and validate the results obtained. The estimated parameters of the system can then be used for advanced control purposes in the HVAC system. We also use the measurements at the terminals to model and verify the components in the energy-space which is a novel approach proposed by our group. The energy space approach reflects conservation of power and rate of change of reactive power. Both power and rate of change of generalized reactive power are obtained from measurements at the input and output ports of the components by measuring flows and efforts associated with their ports. A pair of flow and efforts is measured for electrical and gas ports, as well as for fluids. We show that the energy space model agrees with the conventional state space model with a high accuracy and that standard measurements available in a commercial HVAC can be used for calculating the interaction variables in the energy space model. A novel finding is that unless measurements of both flow and effort variables is used, the sub-model representing rate of change of reactive power can not be validated. This implies that commonly used models in engineering which assume constant effort variables may not be sufficiently accurate to support most efficient control of complex interconnected systems comprising multiple energy conversion processes.
by Janak Agrawal.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Malada, Awelani. "Stochastic reliability modelling for complex systems." Thesis, Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-10182006-170927.
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Laracy, Joseph R. (Joseph Raymond). "A systems-theoretic security model for large scale, complex systems applied to the US air transportation system." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39256.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 129-132).
Classical risk-based or game-theoretic security models rely on assumptions from reliability theory and rational expectations economics that are not applicable to security threats. Additionally, these models suffer from serious deficiencies when they are applied to software-intensive, socio-technical systems. Recent work by Leveson in the area of system safety engineering has led to the development of a new accident model for system safety that acknowledges the dynamic complexity of accidents. Systems-Theoretic Accident Models and Processes (STAMP) applies principles from control theory to enforce constraints on hazards and thereby prevent accidents. Appreciating the similarities between safety and security while still acknowledging the differences, this thesis extends STAMP to security problems. In particular, it is applied to identify and mitigate the threats that could emerge in critical infrastructures such as the Air Transportation System. Furthermore, recommendations are provided to assist systems engineers and policy makers in securely transitioning to the Next Generation Air Transportation System (NGATS).
by Joseph R. Laracy.
S.M.
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Clements, N. Scott. "Fault tolerance control of complex dynamical systems." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/15515.
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Attebo, Edvin. "Safe learning and control in complex systems." Thesis, Umeå universitet, Institutionen för fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-178164.
Full textAbstract:
When autonomously controlling physical objects, a deviation from a trajectorycan lead to unwanted impacts, which can be very expensive or even dangerous. Thedeviation may be due to uncertainties, either from disturbance or model mismatch.One way to deal with these types of uncertainties is to design a robust control sys-tem, which creates margins for errors in the system. These margins make the systemsafe but also lowers the performance, hence it is desirable to have the margins assmall as possible and still make the system safe. One way to reduce the margins isto add a learning strategy to the control system, which improves the model repre-sentation using previous data. In this thesis, we investigate a robust control systemcalled tube-based model predictive control and then combine it with an adaptivegain scheduling method as the learning strategy. The adaptive feature in the gainscheduling method reduces the model mismatch between the model representationand the true dynamics by tuning the control parameters in the gain schedule usinga data-driven framework. To test this design, a dot is controlled to follow a pathin a constrained environment, around an obstacle. The dot should complete thetrack repeatedly without violating any constraints or crash into the obstacle whilereducing the model mismatch. Our results show that the error from the modelmismatch decreases with time without the dot touching the obstacle or moving out-side the constraints. As the error decreases, the margins in the controller becomesmaller, which makes it possible to control the system in a more efficient way andstill guarantee that the system remain safe.
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Long, David Scott Andrew. "A systems architecture-based approach to assess candidate upgrades to complex systems." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/79501.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2012."September 2012." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 163-167).
The Compatibility Assessment Method (CAM), a new structured process for assessing compatibility between parent systems and child subsystems is proposed and applied to several cases where subsystems are being replaced in legacy systems. CAM is a screening process intended to be used by project managers who need to replace components of complex systems. The functional model-based process uses an extension of the Integrated Definition Modeling Language of IDEFO. The IDEFO method is used for defining compatibility measures based on each of the four constituent arrows that show inputs, controls, outputs, and mechanisms (ICOM). In this extension, the control constituents are replaced with constraints. Each of the ICOM constituents is expanded with parameters which include metrics and values. The ICOMs with their parameters and metrics are then used to characterize two or more subsystems in a matrix format. The differences between these matrices are entered into the sparse "Delta Matrix" which shows analysts the differences between the systems. These differences can be assigned to the appropriate levels of technical expertise to be analyzed and to determine feasibility of the child subsystem in the parent system. The process is compared to current practices in government unmanned aircraft system program offices to determine the usefulness of adopting this compatibility assessment process. This dissertation outlines the need for and development of the method for application by practitioners responsible for replacing subsystems on legacy systems. The development includes evaluations of the method and an experiment with cohorts of student system engineers to compare the output of the Compatibility Assessment Method to less-structured methods. This research contributes additional insight into system architecting theory and proposes a structured method for practitioners to use to improve the processes to perform part replacement in legacy systems. While others have offered methods to measure aspects of system architecture, this proposed method moves beyond the extant literature with tools for practitioners.
by David Scott Andrew Long.
Ph.D.
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GHATTAS, HELEN. "Managing complex product development projects : An analytical framework for complex product development." Thesis, KTH, Industriell Management, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-191093.
Full textAbstract:
Under de senaste åren har produkterna blivit mer invecklade beträffande anslutningen, prestanda och funktionalitet. Därför är syftet av denna studie att undersöka hur komplexa system utvecklas och leds genom att genomföra fallstudie på olika svenska företag som utvecklar mekatroniska och cyber-fysiska system. Resultatet av denna studie har lett till identifieringen av många utmaningar som de undersökta företagen har och som i sin tur har lett till framställningen av ett analytiskt ramverk som diskuterar hur och vad man bör göra för att utveckla komplexa produkter på ett effektivt sätt, så att onödig komplexitet i produktutvecklingen kan reduceras.In recent years, products have become more complex in terms of connectivity, performance and functionality. Therefore, this study aims at studying how complex products are developed and managed through conducting multiple case studies at different Swedish companies that develop mechatronic or cyberphysical systems. The results of this study is the identification of many challenges that the investigated companies have, which have led to a presentation of an analytical framework that discusses how complex product development projects can and should be managed in order to be efficient, in order to reduce unnecessary complexity in the way companies develop these complex products.
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Siddique, Shahnewaz. "Failure mechanisms of complex systems." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51831.
Full textAbstract:
Understanding the behavior of complex, large-scale, interconnected systems in a rigorous and structured manner is one of the most pressing scientific and technological challenges of current times. These systems include, among many others, transportation and communications systems, smart grids and power grids, financial markets etc. Failures of these systems have potentially enormous social, environmental and financial costs. In this work, we investigate the failure mechanisms of load-sharing complex systems. The systems are composed of multiple nodes or components whose failures are determined based on the interaction of their respective strengths and loads (or capacity and demand respectively) as well as the ability of a component to share its load with its neighbors when needed. Each component possesses a specific strength (capacity) and can be in one of three states: failed, damaged or functioning normally. The states are determined based on the load (demand) on the component.
We focus on two distinct mechanisms to model the interaction between components strengths and loads. The first, a Loss of Strength (LOS) model and the second, a Customer Service (CS) model. We implement both models on lattice and scale-free graph network topologies. The failure mechanisms of these two models demonstrate temporal scaling phenomena, phase transitions and multiple distinct failure modes excited by extremal dynamics. We find that the resiliency of these models is sensitive to the underlying network topology. For critical ranges of parameters the models demonstrate power law and exponential failure patterns. We find that the failure mechanisms of these models have parallels to failure mechanisms of critical infrastructure systems such as congestion in transportation networks, cascading failure in electrical power grids, creep-rupture in composite structures, and draw-downs in financial markets. Based on the different variants of failure, strategies for mitigating and postponing failure in these critical infrastructure systems can be formulated.
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Shaukat, Tariq M. (Tariq Masud). "Aligning technical and organizational aspects of complex manufacturing systems." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/45473.
Full text
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Austin-Breneman, Jesse. "Aligning stakeholder interests : from complex systems to emerging markets." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93867.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 87-94).
Design often requires balancing competing objectives from a variety of stakeholders. From the design of large-scale complex engineering systems to the design of end-user products for emerging markets, managing the trade-offs between different objectives from a systems-level perspective is a key challenge for design teams. This thesis investigates differences between how formal strategies can be used to balance trade-offs and how practitioners currently perform this task. Through the use of interviews, case studies, and field and laboratory experiments, this thesis seeks to examine how real-world designers approach these problems. The work investigates practitioner strategies and analyzes them to gain a better understanding of how human design teams operate. These insights are then used to inform proposed guidelines for performing design tasks in these contexts. First, observations of practitioners in space system design lead to a new way of modeling interactions between sub-systems. Then, interviews with designers working on products for emerging markets are used to formulate a new methodology, Design for Micro-Enterprise, that focuses on the needs of small-scale entrepreneurs. Results from the analysis suggest that focusing on a micro-entrepreneur's business strategy may be a successful approach to balancing both the end-user and supply chain requirements in these markets.
by Jesse Austin-Breneman.
Ph. D.
50
Hughes, Michael John. "Optimisation of complex distillation colomn systems using rigorous models." Doctoral thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/5317.
Full textAbstract:
Since distillation is still the most widely used separation technique used in the petrochemical industry, optimisation of these unit operations are important to minimise costs and maximise production. This thesis focuses on the development of a tool using rigorous non-equilibrium distillation models to optimise complex columns. Non-equilibrium distillation models are usually avoided in optimisation studies due to the time required to solve them, but this has been overcome by using a technique called orthogonal collocation in which the profiles in the columns are represented by polynomials of a lower order than would be required normally. This significantly reduces the process times and makes the use of non-equilibrium models a possibility in optimisation studies. The orthogonal collocation technique was applied to a packed distillation column model and shown to be effective in modelling the system. A system consisting of a distillation column with integrated external side reactors was chosen as a case study to investigate the use of the methods. These systems have been shown to be effective in certain circumstances in literature, when comparing them to other forms of process intensification, such as reactive distillation. The toluene disproportionation reaction was considered as a potential use for the technology and the optimisation tool was used to find optimum system configurations for achieving maximum toluene conversions and minimum costs. Nonlinear programming techniques were used initially to optimise these systems, but due to the discontinuities associated with multiple side streams, they were replaced by a genetic algorithm. Various system configurations were identified as achieving maximum conversions and minimum costs. These results were used in a comparison with results obtained from a literature study and the results showed significant promise. Unfortunately, the two studies did not have enough in common to truly produce a comprehensive result. This iv lead to further comparisons with another system using the same information. The results obtained in the toluene disproportionation case study showed that there was some possible benefits for using the side reactor systems, but the conventional system was still 30 and 60% cheaper in terms of capital and utility costs respectively. Another case study was investigated that looked at the synthesis of methyl acetate from acetic acid and methanol. The packed collocation model was used as a comparison with another investigation performed in literature (using equilibrium distillation models). Both showed comparable results, but still had significant differences. Costs were also compared between the side reactor system and a more conventional system for methyl acetate synthesis. The side reactor systems were found to be more cost effective than the conventional system. Additionally, an increase in the number of external reactors resulted in lower utility costs (mainly as a result of lower flow rates in the side streams). Overall, the reaction and process conditions are important considerations when deciding whether or not to use a side reactor system. For the gas phase toluene disproportionation reaction, the side reactor systems were not cost effective, when compared to the conventional system. However, the liquid phase methyl acetate reaction proved to be more conducive to side reactor systems in terms of cost. This thesis has shown the applicability of using rigorous disequilibrium distillation models in optimisation studies. The side reactor systems have been found to be complex systems that require a holistic approach to find optimum configurations instead of optimising individual process units.