Reliability and profit analysis of some models on sophisticated systems

Abstract

The present thesis entitled “Reliability and Profit Analysis of some Models on Sophisticated systems” is an attempt to analyse the reliability and profit of some modern sophisticated systems by computing various measures of system effectiveness. A sophisticated system may be mechanical, electro-mechanical, electronic system e.g. computer, automobile engine, electric motor, electric meter, electric boilers, refrigerators, washing machine, UPS, PLC system, combat aircrafts, missiles, satellites etc. Many such one-unit or two unit systems are being used in day to day life in various industry, companies and households. These systems may have different operational stages, different types of failures and repairs. Further, most of the systems are under some warranty policy for some specified period provided by the system provider. The present study investigates various stochastic models corresponding to such one-unit and two- unit cold standby systems considering different operational stages with different failure rates. The main emphasis is on cost optimization and reliability. The work done is useful to study life times, improvement in reliability, minimization of operational costs, reliability and profit analysis of various systems viz. emergency power systems, computer systems, nuclear power plants, communication network, combat aircraft, missiles and satellites etc. The thesis consists of eight chapters. Here is a brief summary of these chapters: Chapter I includes the fundamental concepts and definitions related to the work done in the thesis to make it sufficient in itself. Chapter II deals with the information/data collected related to a sophisticated system-UPS (uninterrupted power supplier) system to develop models for such systems. For the purpose, a manufacturing plant of some electrical appliances such as UPS system, electric meters etc. was visited and information/data was collected regarding structure, functioning, failure, repair and various operational stages of UPS system from the plant, company area sales manager, system distributor/supplier and the service engineer. Chapter III analyses a single unit sophisticated system under warranty having different operational modes. It is assume that the failure rate of the unit during its installation is high (burn-in period) and after the proper installation the failure rate decreases, i.e. the unit improves and reaches to its useful life period. After acquiring certain age the failure rate of the unit starts increasing, i.e. the unit deteriorates, due to wear out of its components (wear-out period). It is assumed that the unit is under ordinary failure free warranty policy up to its useful life period. Under the warranty policy, during the warranty period, the system provider through its service engineer provides service(s) free of charges to the system user that includes maintenance; repair or replacement of the unit or its component(s).