Abstract:
This paper presents the formulations of the expected long-run cost per time unit
for a system monitored by a static control chart and by an adaptive control
chart respectively. The static chart has a fixed sampling interval and a fixed
sample size. The adaptive chart has a fixed sample size but variable sampling
intervals. The system is supposed to have three states, normal working state,
failure delay time state, and failed state. Two levels of repair are used to
maintain the system. A minor repair is used to restore the system if a
detectable defect is confirmed by an inspection. A major repair will be
performed if the system fails. The expected cost per time unit for maintaining
such a system is obtained. The objective of such analysis is to find an optimal
sampling policy for the inspection process. An artificially generated data
example and a real data example are used to compare the expected cost per time
unit for both the static and adaptive control charts.
