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Chapter 4
The cost of repair
This section will introduce the cost distribution and the expected cost of repair,
ECR. The ECR is used as a measure of how cost effective a TS-strategy is. In the
final section the TS-problem is defined as an optimization problem.
What we are looking for in a TS-process is to repair a malfunctioning device. This
can be done by performing tests, observations and repair actions until the device is
working properly. But we are not only interested in repairing the device by following
some TS-strategy but rather to follow the best TS-strategy.
In this context the best TS-strategy will not only repair the device but will also do
this by arranging actions in such a way that they make the average TS-cost as low
as possible.
4.1
Cost of repair
The TS-costs include the repair cost CR = (C R1 , C R2 , . . . , C Rn ) which includes
costs arising from repair time, spare parts, configuration changes, software updates
and the cost of repair tools exposed to wear. It also includes the observation cost
CO = (C O1 , C O2 , . . . , C On ) which describes costs arising from determining whether
or not a specific component is causing the system malfunction. There is also the
cost of performing tests CT = (C T1 , C T2 , . . . , C Tm ), where C Tj includes all costs
that are associated with concluding the answer of a specific test Tj . The total cost
of a TS-sequence is simply the cost of all performed observations together with the
cost of performed tests and the cost of the final repair. The total cost of a specific
TS-strategy is not obvious but will be disused later in this chapter.
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