XXXII NATIONAL SYSTEMS CONFERENCE, NSC 2008, December 17-19, 2008 AVAILABILITY OPTIMIZATION OF A SERIES-PARALLEL SYSTEMS USING GENETIC ALGORITHMS S.P. Sharma, Dinesh Kumar and Ajay Kumar Abstract—Due to complicated structure of industrial systems, system-availability has become an increasingly important issue. If the reliability of a complex system is increased, the related cost will also increase. The objective of this paper is to improve the design efficiency and to find the most optimal policy for MTBF (mean time between failures), MTTR (mean time to repair) and related costs. Pulping system, the main functionary part of paper industry, is the subject of study. MTBF and MTTR of various components, during the design phase, are obtained using genetic algorithms (GAs), in a cost effective manner, which helps the system analyst to formulate optimal design policies and repair policies. Index Terms—Availability, Genetic algorithm, Optimization & Reliability. R I. INTRODUCTION eliability/availability of an industrial system may be enhanced using highly reliable structural design of the system or system components of higher reliability, or both of them may be performed simultanously. The system structure is designed under many constraints such as weight, volume etc., so the reliability cannot be further improved. In such a case, reliability can only be improved by replacing the components of higher reliability. While improving the reliability of system/components, the associated costs will also increase. Thus, it is very important issue for system analyst to consider the profit as well as the qulality requirement. Failure is nearly an unavoidable phenomenon and so the reliability analysis has become an increasingly important issue. Unfortunately, the component failure/repair rates, used in the calculations are inaccurate and very often dependent on the configuration and environment, and thus known only approximately. Further, age, adverse operating conditions and the vagaries of the system affects each unit of the system differently [1]. The reliability of the system is affected by various factors such as design, manufacturing, installation, commissioning, operation and maintenance [2]. Due to advances in technology and growing complexity in technological systems, the job of system analyst has become Prof. S.P. Sharma is with the Department of Mathematics, Indian Institute of Technology, Roorkee, India, (e-mail:
[email protected]). Prof. Dinesh Kumar is with the Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee, India, (e-mail:
[email protected]). Ajay Kumar (Research Scholar) is with the Department of Mathematics, Indian Institute of Technology, Roorkee, India, (corresponding author, Mobile No.: +91-9410326672, e-mail: