Parallel Redundant System Research Articles

Estimation of Stress - Strength Reliability for Parallel Redundant System Via Burr of type X Distribution

Estimation for the reliability of a parallel redundant system with independent stress and strength Burr distribution (type ) probability density functions is considered. Estimation of the reliability parameters is conducted according to the non-Bayesian estimation methods, namely the maximum likelihood and shrinkage methods. The Bayesian estimation is also considered using the Jeffery and Gamma priors with squared error, quadratic and weighted loss functions. Finally, the reliability estimate is calculated and the best method for estimation for each case is given using the mean squared error criteria.

Photovoltaic Inverter Reliability Study through SiC Switches Redundant Structures

Reliability is a very important issue in power electronics; however, sometimes it is not considered, studied, or analyzed. At present, renewables have become more popular, and more complex setups are required to drive this type of system. In the specific case of inverters in photovoltaic systems, the user’s safety, quality, reliability, and the system’s useful life must be guaranteed. In this paper, the reliability of a full bridge inverter is predicted by calculating metrics such as failure rates and Mean Time Between Failures. Reliability is obtained using different types of structures for SiC MOSFETs: serial systems, active parallel redundant systems, and passive parallel redundant systems. Finally, the reliability study shows that a system with a passive parallel redundant structure is more reliable and has a higher useful life compared to the other structures.

A Note on the Time to Failure of a Two-Unit Parallel Redundant System with Deterioration on a Lattice

In this paper, we consider a two-unit parallel redundant system with deterioration on a lattice, where each unit has multi-stage deterioration levels, say, n levels. The transition from one deterioration level to the subsequent level occurs following the well-known Marshall-Olkin bivariate exponential distribution. We derive the closed form of the Laplace transform of the time to system failure in the two-unit parallel redundant system with deterioration on n×n lattice without repair and simultaneous failure, as well as the simple system on 3×3 lattice.

A generalized Freund bivariate model for a two-component load sharing system

Motivated by reliability systems whose components fail one by one and share a common load, this work provides a generalized Freund bivariate class of distributions for modeling the two component lifetimes of a parallel redundant system. When a component fails, such load-sharing systems can be repaired meanwhile the surviving one endures the total load, modifying its two-dimensional lifetime model, which is of interest in maintenance and stress-strength reliability modeling. The proposed model is based on the overload of the surviving component after the first failure, causing both the proportional failure rate parameters and the baseline distribution of the component to change. A genetic algorithm is employed to find the maximum likelihood estimation, and a simulation study illustrates its implementation and efficiency. Applications in three real engineering data sets are carried out, revealing the usefulness of the proposed class for modeling the load-sharing effect.

RELIABILITY AND COST ANALYSIS COMPARISON BETWEEN TWO-UNIT PARALLEL SYSTEMS WITH NON-IDENTICAL AND IDENTICAL CONSUMABLE UNITS

In this paper, reliability and cost analysis of two different two-unit parallel redundant systems with non identical and identical consumable units respectively have been done by employing Semi – Markov Processes and Regenerative Point Technique and a comparison is made between both the systems. The systems being considered are two inkjet printers with different cartridge arrangements. The first system contains two non-identical consumable units, colour and black cartridges, wherein, failure of one unit results in system being operative under reduced efficiency. However, the second system contains two identical consumable units, both colour cartridges, wherein, failure of any one of the units does not affect efficiency of system. The system may also fail due to other technical failures. Various system efficiency indicators such as Mean Time to System Failure (MTSF), Availability and Expected Down-Time of the System, Busy Time Period of Repairman, and Average Number of (damaged) Unit Replacements are estimated. Using data collected from industry, the parameters are used to estimate reliability parameters of both the printers and a comparison of profits of both systems with respect to time has been done. Subsequently, the differences in behavior of Availability and Profitability of both systems due to variations in its parameters have been analyzed.

Reliability modeling and optimal random preventive maintenance policy for parallel systems with damage self-healing

Materials with intrinsic self-healing phenomenon possess the ability to heal in response to external random shocks. Introducing a recovery factor to quantitatively measure the damage self-recovery efficiency, this paper designs a self-healing mechanism corresponding to both damage load and shock arrival numbers for a parallel redundant system consisting of multiple non-identical components. From the actual engineering perspective, each shock arriving on the system selectively affects one component or more but not necessarily all units in parallel, and consequently, random shocks are categorized according to their sizes, attributes and affected components. This study investigates novel reliability models and schedules optimal preventive maintenance policies, in which the closed-form reliability quantities are derived analytically and the optimum preventive replacement interval is demonstrated theoretically. In addition, a Nelder-Mead downhill simplex method is introduced to seek the optimal replacement age in minimizing the long-run average maintenance cost rate for the condition system failure distribution is rather complex. A micro-electro-mechanical system (MEMS) whose constitutional materials are integrated by microcrystalline silicon, where polymer binders with self-healing capability are always synthesized, is designed to verify the results we obtained numerically, illustrating the significance of considering damage self-healing phenomena.

Optimal periodic maintenance policies for a parallel redundant system with component dependencies

In this paper, we investigate modified periodic maintenance policies for a parallel redundant system with three types of dependencies including stochastic dependence, structural dependence, and economic dependence, where they are seldom taken into account simultaneously in previous researches. More specifically, the stochastic dependence is modelled when multiple external shocks selectively affect the distinct components according to their sizes, attributes, and functions, leading to the existence of common cause failure. In addition, the structural dependence is considered as the parallel system is packaged and just systematic preventive maintenance is available. Finally, the economic dependence is introduced when developing preventive maintenance models, where the replacement costs among all items are associated. System reliability function is derived analytically in terms of cumulative shock damage theory and Laplace transform, and then four modified periodic maintenance policies are developed, in which the expected maintenance cost rate is minimized to seek the optimal replacement interval. An illustrative example of a silicon micro-electro-mechanical system (MEMS), which is composed of multiple non-identical resonators in parallel, is arranged to validate the theoretical results and to show the significance of considering component dependencies when scheduling preventive maintenance policies.

English

English

An extension of the Freund's bivariate distribution to model cascading failures

ABSTRACTThe notion of cascading failures is a common phenomenon we observe around us. Here the initial failure alters the structure function of the system, which leads to subsequent failures within a short period of time referred to as threshold time. The concept of cascading failures within the framework of reliability theory and the Freund bivariate exponential distribution to model cascading failures has been studied by few authors. The Freund bivariate exponential distribution allows modelling a parallel redundant system with two components. In this system, the lifetimes of the two components behave as if they are independent, until one of the components fail, after which the remaining component suffers an increased/decreased stress. In this article, we further generalize this model to accommodate cascading failures. Various properties of the model are investigated and statistical inference procedures are developed using L-moments and method of moments. A practical application of this model is illustrated using data from www.espncricinfo.com. Also well analysed Diabetic Retinopathy Study (DRS) data is further analysed using this model and our findings are presented.

Mean time to failure of systems with dependent components

We consider first a system of two components that are possibly dependent. Two simple reliability structures can be formed: series system and parallel (redundant) system. The exact formulas and two-sided bounds for the MTTF of systems are provided. We extend some of the results of Kotz et al. (2003) [8] on the effect of redundancy or competing risk when component lifetimes are no longer independent. The main results are illustrated by some useful distributions. The new (r,s)-out-of-n system is also discussed. In addition, a new concept of dependence ordering (more diagonal dependent) between bivariate distributions is introduced and used to compare the system lifetimes. Finally, the extension of the main results to the three-component systems and multi-component systems are also briefly investigated.

Maintenance scheduling for a parallel system subject to exponential power hazard

This paper presents equations, which can be used to evaluate the failure frequency and the failure rate of a two identical component parallel redundant system in which each component can operate in its wear out period, and the failure rate of each component is exponential power distribution. The optimum maintenance interval for a two identical component parallel redundant system can be obtained using these equations. The proposed approach is presented and illustrated using several numerical examples. The optimum maintenance interval for each component in a two identical parallel redundant system will depend on factors such as: failure rate, repair and maintenance times of each component in the parallel redundant systems.

A series—parallel redundant reliability system for cellular manufacturing design

This paper presents a novel, multi-objective mixed-integer programming model for designing a cellular manufacturing system (CMS) that minimizes the total cost and maximizes the overall system reliability. In general, it is impossible to avoid production interruptions while handling machine breakdowns. In this situation, changing the process route dynamically can provide a quick response to meet production requirements. By assuming alternative process plans for operation—part requirements, the concept of the ‘reliable route’ proposed in the literature is extended. In a redundant reliability system with a series—parallel configuration, each reliable route is associated with an operation of a part (i.e. an operation—part) as a parallel subsystem. This route consists of a number of units or alternative machines allocated to cells in such a way that parts are processed with the maximum reliability for a given period of time. When an alternative machine breaks down, unprocessed parts are transferred to the next predetermined machine on the reliable route in order to complete their processes. While the reliable route approach increases the overall system reliability, the operational costs of the system also increase. To assess the present proposed model as a useful decision tool for the manager, various numerical examples are solved and analysed. Finally, the related computational results are reported.

M out of n inspected systems subject to shocks in random environment

Consider a parallel redundant system, consisting n components, that is subject to shocks. The shocks cause the components to fail with certain probabilities. Shocks arrival rate and components’ failure probabilities may depend on an external Markovian environment. We consider warm and cold stand-by systems. Systems’ failures are silent. The system is maintained through inspection and repair/replacement. We propose several state-dependent maintenance policies and derive system availability and cost function.

Economic analysis of an n-unit parallel redundant system based on a Stackelberg game formulation

A parallel redundancy has been researched in a great amount of literature on reliability theory. In the real circumstances, however, it is seldom observed except some systems that require much higher reliability. This is because most of the literature only look at the manufacturer’s point of view. The present study carries out an economic analysis of an n-unit parallel redundant system against a single unit system based on a Stackelberg game formulation considering both the consumer’s viewpoint and the manufacturer’s one. It clarifies quantitatively in what situation the manufacturer can increase his profit by dealing in the parallel redundant system.

Failure Bunching Phenomena in Electric Power Transmission Systems

The physical environment in which a component resides can have a significant effect on the resulting reliability of the system. This is particularly true in electric power systems containing overhead transmission lines. Extreme weather conditions can create significant increases in transmission element stress levels leading to sharp increases in the component failure rates. The phenomenon of increased transmission line failures during bad weather is generally referred to as ‘failure bunching’. This condition should not be misconstrued as a common mode failure. This is an entirely different phenomenon and one that is important for multi-circuit transmission lines on single tower structures. This paper illustrates the inclusion of weather conditions in the reliability analysis of parallel redundant systems. A series of weather models are presented with application to electric transmission lines. The reliability effects of incorporating common mode failures in multi-circuit tower structures and independent events incorporating normal, adverse, and major adverse weather considerations in separated parallel line configurations are illustrated and examined. The applications described in this paper are to electric power transmission lines. The concepts of stress related failure bunching and common mode failures are, however, applicable to a wide range of engineering systems.

Reliability analysis of a two-unit parallel redundant system considering the mission profile of the system

Reliability analysis of a two-unit parallel redundant system considering the mission profile of the system

ユニット式UPSの開発

Parallel redundant operation system using multiple power supply modules is suitable and acceptable for power supply system used in high reliability system. Three types of power supply modules have been developed: single-phase 100V 2kVA module, single-phase 200V 3kVA module, and three-phase 200V 2.5kVA module. Any desired number of these modules can be connected in parallel and are capable of redundant operation. Using these modules makes it possible to economically configure high-performance, high-reliability UPS (Uninterruptible Power Supply) capable of parallel redundant operation.

Development of a Parallel Redundant STATCOM System

This paper presents a new concept of parallel redundant STATCOM system. This system consists of a number of medium capacity STATCOM units connected in parallel, which can achieve a high operational reliability and functional flexibility. The proposed STATCOM system has such redundant operation characteristics that the remaining STATCOM units can maintain their operation even though some of the STATCOM units are out of service. And also, it has flexible convertibility so that it can be converted to a BTB or a UPFC system easily, according to the diversified change of needs in power systems. In order to realize this concept, the authors developed several important key technologies for the STATCOM, such as the novel PWM scheme that enables effective cancellation of lower order harmonics, GCT inverter technologies with small loss consumption, and the coordination control scheme with capacitor banks to ensure effective dynamic performance with minimum loss consumption. The proposed STATCOM system was put into practical applications, exhibiting excellent performance characteristics at each site.

Stochastic programming models for general redundancy-optimization problems

This paper provides a unified modeling idea for both parallel and standby redundancy optimization problems. A spectrum of redundancy stochastic programming models is constructed to maximize the mean system-lifetime, /spl alpha/-system lifetime, or system reliability. To solve these models, a hybrid intelligent algorithm is presented. Some numerical examples illustrate the effectiveness of the proposed algorithm. This paper considers both parallel redundant systems and standby redundant systems whose components are connected with each other in a logical configuration with a known system structure function. Three types of system performance-expected system lifetime, /spl alpha/-system lifetime and system reliability-are introduced. A stochastic simulation is designed to estimate these system performances. In order to model general redundant systems, a spectrum of redundancy stochastic programming models is established. Stochastic simulation, NN and GA are integrated to produce a hybrid intelligent algorithm for solving the proposed models. Finally, the effectiveness of the hybrid intelligent algorithm is illustrated by some numerical examples.

Application of Monte Carlo simulation to optimal maintenance scheduling in a parallel-redundant system

A modified distribution function is created based on the assumption that the component useful life phase is associated with an exponential distribution and the wearout period is subject to a Weibull distribution (/spl beta/>1). Using the modified distribution function, a Monte Carlo simulation approach is used to obtain the total failure frequency and optimum maintenance interval for a parallel-redundant system where each component can enter its wearout period. Two examples are used to illustrate the simulation procedure. The effect of the Weibull parameter /spl beta/ on the optimum maintenance interval for a parallel-redundant system is illustrated.