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Networking of Sensors and Contr ol Systems in Manufacturing
FIGURE 4.5 Program fault categories. 203
Programming faults:
• Comparison of local variables of different types
• Omission of comment marks
This categorization provides significant insight into the location of
fault conditions, the reasons for their occurrence, and their severity. If
the faults are in either a hardware (mechanical) or software category,
then the frequency of failure by month can be summarized as indicated
in Fig. 4.4. Two major and unexpected milestones in the program rep-
resented in Fig. 4.4 are the routine introduction of revised cell control
software and revised robot control software. In both cases, a substan-
tial increase occurred in the downtime of the flexible manufacturing
cell. In an industrial environment, this would have been very costly.
In this study, it was found that interface faults (mismatched data
transfer between modules and hardware) were the major cause of
