Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 33-38). Also available via the Internet.

by Edward Y. Chow, Alan S. Willsky. / "October, 1982." / Bibliography: p. 43-44. / Office of Naval Research Contract No. N00014-77-C-0224 NASA Ames Research Center Grant No. NGL-22-009-124

Two well-known methods of improving the reliability of a system are (i) provision of redundant units, and (ii) repair maintenance. In a redundant system more units made available for performing the system function when fewer are required actually. There are two major types of redundancy - parallel and standby. In this dissertation we are concerned with both these types. Some of the typical assumptions made in the analysis of redundant systems are (i) the repair facility can take up a failed unit for repair at any time, if no other unit is undergoing repair (ii) the system under consideration is needed all the time However, we frequently come accross systems where one or more assumptions have to be relaxed. This is the motivation for the detailed study of the models presented in this dissertation. In this dissertation we present models of redundant systems relaxing one or more of these assumptions simultaneously. More specifically it is a study of stochastic models of redundant systems with 'vacation period' for the repair facility (both standby and parallel systems), and intermittently used systems. The dissertation contains five chapters. Chapter 1 is introductory in nature and contains a brief description of the mathematical techniques used in the analysis of redundant systems. In Chapter 2 assumption (i) is relaxed while studying a model of cold standby redundant system with 'vacation period' for the repair facility. In this model the repair facility is not available for a random time immediately after each repair completion. Integral equations for the reliability and availability functions of the system are derived under suitable assumptions. In Chapter 3, once again assumption (i) is relaxed while studying a model of parallel redundant systems with the same 'vacation period' for the repair facility, explained in the above paragraph. In Chapter 4, the detailed review of intermittently used systems have been studied. In Chapter 5, assumption (ii) is relaxed. This chapter is devoted to the study of an intermittently used 2-unit cold standby system with a single repair facility. This study was carried out using the 'correlated alternating renewal process' and the joint forward recurrence times. All the above models have been studied, when some of the underlying distributions have a non-Markovian nature. They have been analysed using a regeneration point technique. / Mathematical Sciences / M. Sc. (Statistics)

by Lam Ngok. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 111-114). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview --- p.1 / Chapter 1.2 --- Organization outline --- p.2 / Chapter 2 --- Fundamentals of reliability theory --- p.4 / Chapter 2.1 --- State vector --- p.4 / Chapter 2.2 --- Minimal path sets --- p.4 / Chapter 2.3 --- Minimal cut sets --- p.7 / Chapter 2.4 --- Structure functions --- p.7 / Chapter 2.5 --- The structure functions and the systems reliability --- p.10 / Chapter 3 --- Literature review --- p.12 / Chapter 3.1 --- Introduction --- p.12 / Chapter 3.2 --- Approximation schemes --- p.13 / Chapter 3.3 --- Heurisitic search schemes --- p.14 / Chapter 3.4 --- Exact solution schemes --- p.16 / Chapter 3.5 --- Software reliability --- p.17 / Chapter 4 --- Characteristics of Series-parallel network --- p.18 / Chapter 4.1 --- Series-parallel network problem formulation --- p.18 / Chapter 4.2 --- Characteristics of series-parallel networks --- p.19 / Chapter 4.3 --- Some further properties of Maximal Monotonicity --- p.20 / Chapter 4.3.1 --- Definitions and the background --- p.20 / Chapter 4.3.2 --- The proper and the improper MMPs --- p.22 / Chapter 4.4 --- Examples --- p.37 / Chapter 4.5 --- Computational results --- p.39 / Chapter 4.6 --- New progress --- p.40 / Chapter 5 --- Extensions for the series-parallel reducible networks --- p.43 / Chapter 5.1 --- Some new notations for computation --- p.44 / Chapter 5.1.1 --- Notation --- p.44 / Chapter 5.2 --- Problem formulation --- p.46 / Chapter 5.3 --- The series-parallel reducible networks --- p.46 / Chapter 5.4 --- The algorithm --- p.54 / Chapter 6 --- "On ""Successive Solution Scheme For Constrained Redun- dancy Optimization In Reliability Networks"" [1]" --- p.56 / Chapter 6.1 --- Introduction --- p.56 / Chapter 6.2 --- The contents --- p.56 / Chapter 6.2.1 --- The motivation --- p.56 / Chapter 6.2.2 --- The Successive Solution Scheme --- p.57 / Chapter 6.3 --- Illustrative examples --- p.62 / Chapter 6.3.1 --- Example 1 --- p.62 / Chapter 6.3.2 --- Example 2 --- p.67 / Chapter 7 --- Conclusions --- p.76 / Chapter 8 --- Appendix --- p.79 / Chapter 8.1 --- Computational results --- p.79 / Chapter 8.2 --- Programme codes --- p.97

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / Includes bibliographical references. / by Xi-Cheng Lou. / M.S.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Edward Yik Chow. / Sc.D.

Fault tolerant motor drives are becoming more important in safety critical applications. Although a single motor module fault tolerant drive may be sufficient in some applications, this motor drive only offers limited redundancy. This thesis investigated the dual motor module fault tolerant drive system in which two motor modules were connected electrically in phase and on a common shaft provide redundancy and to increase the reliability of the entire drive system. A general phase current mathematical model to produce the desired output torque was developed to minimize copper loss and torque ripple in the motor drive, which is applicable to both sinusoidal and trapezoidal brushless permanent magnet motor types. A detailed fault effect investigation was performed in this thesis and it is concluded that switch short-circuit fault is the most serious fault since it reduces the electromagnetic torque output significantly and generates larger torque ripple in the motor drive due to the presence of large drag torque. Three fault remedial strategies were proposed to compensate the torque loss and to reduce the torque ripple under different faulty conditions. It is concluded from the analytical results that fault remedial strategy 3 is the tradeoff algorithm in which the zero torque ripple factor can be achieved with only a modest increase in copper loss comparing with the minimum possible value. Two practical dual motor module fault tolerant brushless permanent magnet drive test arrangements with different motor structures were developed in this thesis. The computer simulation studies using the MATLAB Simulink were performed to verify the effectiveness of the proposed fault remedial strategies. The efficiency of the motor drive was predicted based on torque loss measurements and the results were verified in the simulation study. The effect of faults on the drive efficiency was investigated as well. The entire fault tolerant motor drive control system was also developed to verify the analytical and simulation results. A fault detection and identification method to detect switch open-circuit faults, switch short-circuit faults, and the winding short-circuit faults was also proposed. Its advantages are the simplicity of the implementation and reduction of the cost of the drive system. The experimental results demonstrated that the proposed fault remedial strategies can be implemented in real time motor control and are effective to compensate the torque loss and reduce the torque ripple. / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2008

Fault tolerant motor drives are becoming more important in safety critical applications. Although a single motor module fault tolerant drive may be sufficient in some applications, this motor drive only offers limited redundancy. This thesis investigated the dual motor module fault tolerant drive system in which two motor modules were connected electrically in phase and on a common shaft provide redundancy and to increase the reliability of the entire drive system. A general phase current mathematical model to produce the desired output torque was developed to minimize copper loss and torque ripple in the motor drive, which is applicable to both sinusoidal and trapezoidal brushless permanent magnet motor types. A detailed fault effect investigation was performed in this thesis and it is concluded that switch short-circuit fault is the most serious fault since it reduces the electromagnetic torque output significantly and generates larger torque ripple in the motor drive due to the presence of large drag torque. Three fault remedial strategies were proposed to compensate the torque loss and to reduce the torque ripple under different faulty conditions. It is concluded from the analytical results that fault remedial strategy 3 is the tradeoff algorithm in which the zero torque ripple factor can be achieved with only a modest increase in copper loss comparing with the minimum possible value. Two practical dual motor module fault tolerant brushless permanent magnet drive test arrangements with different motor structures were developed in this thesis. The computer simulation studies using the MATLAB Simulink were performed to verify the effectiveness of the proposed fault remedial strategies. The efficiency of the motor drive was predicted based on torque loss measurements and the results were verified in the simulation study. The effect of faults on the drive efficiency was investigated as well. The entire fault tolerant motor drive control system was also developed to verify the analytical and simulation results. A fault detection and identification method to detect switch open-circuit faults, switch short-circuit faults, and the winding short-circuit faults was also proposed. Its advantages are the simplicity of the implementation and reduction of the cost of the drive system. The experimental results demonstrated that the proposed fault remedial strategies can be implemented in real time motor control and are effective to compensate the torque loss and reduce the torque ripple. / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2008

Thesis (Ph. D.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains ix, 185 p. : ill. Includes abstract. Includes bibliographical references (p. 87-91).

Thesis (M.S.)--Missouri University of Science and Technology, 2010. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed July 26, 2010) Includes bibliographical references (p. 96-102).