ON SOME ASPECTS OF SYSTEM RELIABILITY OPTIMIZED DESIGN

Abstract

The present work deals with the optimal. design of a system from the reliability point of view. Due to increased complexity and sophistication in the modern systems, the system reliability always tends to decrease, Therefore, some means must be provided for enhancing the system reliability. System reliability can be improved by employing structural redundancy at the subsystem level, and/or by practising. planned maintenance and repair by QVYS schedules. This ,however. is oonetrained,jwhiOb are limited. and pose a problem to the design and maintenance engineer. Consequently# the problem of optima,; allocation of redun-dancies and of the optimal , nu}nber of repair-Crews arises. The constraints on the system are the overall cost, weight, availability of the system and, power consumption, etc An attempt has been made to _find the optimal allocation of redundancies and the optimal number of repair crews, for maximizing the system reliability or the system availability. In chapter I, . up-to-date, literature about the aspects of reliability optimization has been surveyed and is reviewed in brief. The availability models of the maintained systems with• different repair facilities are discussed in chapter II. A problem of finding the optimal number of repair-crews is solved by. assuming the necessary data. The problem of finding the optimal maintenance interval is also discussed in brief. The mathematical modelling of, the optimal design of a system having active redundancy is presented in seat-ion 2.5. The problem of redundancy allocation to the series and bridge systems has been discussed. The computer programs for these problems are developed in FORTRAN-1I and a number of problems have been salved on IBM 1620 and TDC-31 2 computers. Chapter III deals with the optimization techniques for maximization of the system reliability subject to the given constraints* The techniques discussed in this chap.. ter are Variat ona . method,, Penalty function method-; i agrange' s Multiplier Method, and Lawler and Bell's opti-mization. method. The constrained reliability problem is converted into unconstrained problem by the use of penalty function and is solved by the steepest ascent method. ,lawler and Bel.'s method is.made.use of in solving the constrained redundancy problem by transforming. the problem into binary variables. At the end, various methods discussed have been compared so as to help, the system designer to apply the appropriate techniques. Future avenues of research are also discussed, in short. The