Opportunistic Replacement Policies for Maintained Systems.

摘要

Consider a unit in continuous operation. When this unit fails,it is immediately replaced. In addition,opportunities arise according to a renewal process when we can either replace this unit at a reduced cost or do nothing. The problem is formulated as a Markov decision process. If the unit has increasing failure rate,the replacement policy that minimizes the expected total discounted cost or the average cost of maintenance is characterized by a single parameter i* :If an opportunity exists,we replace the working unit only if its age exceeds i* . Techniques to compute the minimum discounted cost and the optimal policy are suggested. Under this simple replacement policy structure,the operating characteristics of the system are discussed for the special case where the opportunities arise according to an exponential arrival process. A series system of two units where the failure of either unit is also an opportunity to replace the other unit at a reduced cost is considered. When the units have increasingly failure rate,the structure of the optimal policy is again determined. (Author)