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Diagnosing the Beam Propeller Movement
of the Frontal Stand
5.2 Scope of the Target System
part in the row Info that enumerates all kinds of parameters. These parameters all say something
about the state of the system.
The scope of the target system depends on considerations, that are specific for PMS, this particular
subsystem, and motives of the modeler. Not all components that could cause a failure of the
beam propeller movement are included in the target system. The architecture of the system that contains
components that are considered is described in Appendix B.1. The considerations to decide if
components are included or excluded in the target system are as follows. For all known components
the following questions are asked:
1. Could a PMS service engineer replace this component with a healthy one? In other words, is
the component a FRU?
2. Does the malfunctioning of this components causes an error 11 message to be logged?
3. Could an expert think of any (hypothetically) produced error 11 log data, of which any conclusions
about the component’s state could be derived?
4. Does including the component lead to superfluous complexity of the model?
5. Is the component part of a control loop?
If, for a certain component, all answers on these questions are positive, the component is included
in the scope of the target system. The last consideration is special to this specific subsystem. The
beam propeller movement is implemented by means of three nested control loops, respectively a
position loop, speed loop, and current loop. These three control loops play an important role, and
therefore this question is of importance (see Section 5.3).
Table 5.2 shows the components that are excluded (see Appendix B.1 for the place of a component
within the architecture). The discussed fault diagnosis only addresses the components that are
Component
Failing Consideration
All components that propagate or influence (the cloud in Figure 5.2) the requests 2
speed signal until it enters the backpanel control unit.
backpanel control unit 3
LUC 3
Power Supply 4
Table 5.2: Components that are excluded from the target system.
part of the subsystem Geometry. All components of other subsystems that might lead to a failure
of the beam propeller movement do not cause an error 11 message to be logged. The backpanel
control unit and the LUC are not included. The reason for this is that in the current technical setup
it is impossible to differentiate if faults are activated by the backpanel control unit, LUC or its
corresponding LUC_Extension. Because the LUC_Extension has, by far, the highest a priori failure
probability, it has been chosen to include this component in the target system. The power supply
is not included, because adding it leads to superfluous complexity of the model. Note that the fault
diagnosis process proposed below could be extended to enable the diagnosis of these, currently,
omitted FRUs as well.
Table 5.3 names the set of components that are within the scope of the diagnostic process. Each
of them has been given an a priori component failure. These values only determine the order of
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