Deciding Dynamic Inspection Frequency: A Fuzzy Set Approach
Volume 4, Number 1, January 2006 - Paper 4 - pp. 45 - 59
A. K. VERMA1, A. SRIVIDYA1 and RAJESH S. PRABHU GAONKAR21Reliability Engineering Group, Indian Institute of Technology Bombay, Powai, Mumbai – 400076, India
2Mechanical Engineering Department, College of Engineering, Goa, Farmagudi, Ponda, Goa - 403401, India
(Received on May 4, 2005)
Deciding inspection frequency and choosing appropriate type of maintenance method are the two principal actions in maintenance program of all industries. It is well known that dynamic or variable inspection frequency is advantageous as against fixed inspection interval. For deciding the inspection schedule and maintenance type, the degradation behaviour of the deteriorating or mechanical system is a foremost criterion. Uncertainty of the information about degraded condition of the system is the hindrance to arrive at the optimal inspection/ maintenance decision. Fuzzy set theory is a viable solution to overcome such a problem. In this paper, the degraded states (degree of deterioration) of the system are modelled in the form of linguistic terms. Expert inspection engineers judge the condition based on linguistic variables that are pre-defined fuzzy sets. The opinions of the experts are then merged to arrive at a single resultant fuzzy set, which represent the present state of the deteriorating system. Distance measures and credibility score method are used to 'map' the resulting fuzzy set on to the pre-defined fuzzy sets. An illustrative maintenance decision-making strategy is devised that shows the next inspection date and the type of the maintenance to be carried out. The whole procedure is demonstrated with diverse examples.
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