摘要: A commonly used definition of a repairable system (Ascher and Feingold 1984) states that this is which, after failing to perform one or more its functions satisfactorily, can be restored fully satisfactory performance by any method other than replacement the entire system. In order cover realistic applications, much recent literature on subject, we need extend include possibility additional maintenance actions which aim at servicing for better performance. This referred as preventive (PM), where may further distinguish between condition based PM planned PM. The former type due when exhibits inferior while latter performed predetermined points in time.