This effort can however be significantly reduced if the error detection is included in the control program as it is written via a suitable control description. Only additional language elements are required for this purpose.
Figure D 10: Diagnostic system with integrated error monitoring
Figure Table D 1: Alternative solutions for diagnostic systems
Special form of expert system that is designed to cover all realistically possible errors and that is capable of preparing a cause-effect analysis to suit the requirements and criteria of the user.
Diagnostic systems operate as automatic monitoring processes for the detection and notification of damage that has occurred or that is starting to occur in a system (Figure D 10). Specifically, this means:
- Checking the settings and operation for errors in the dialogue with the user,
- Detection of errors in the function of devices and systems,
- Localisation of errors, i.e. detecting the location of the error and the cause of the error,
- Detection of changing operating states, e.g. due to malfunctions from wear (early detection of damage),
- Indication or errors in the dialogue with the user.
There is a series of possible solutions for setting up diagnostic systems - depending on the emphasis of the task (Table D 1).
Unambiguous diagnostics are often only possible if several measured signals are evaluated at the same time; pre-defined evaluation strategies are necessary to identify errors during this process. All these aspects signify significant effort for sensors. The result from diagnostic systems is either displayed or it is used to stop the machine or to correct the process in the context of feedback.
The additional effort for diagnostic programs can be very high (up to 100 % of the control program). It is nevertheless worthwhile if the value of increased availability and reliability is valued highly enough.