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The main tasks for condition diagnostics, both functionally without any changes in machine operation mode and in testing under the influence of external controlled vibration exciters, also can be divided into three main groups. This division is based on the method used for determining diagnostics standards. These standards are used for defect detection, identification, and development prediction. The first group uses standards based on a group of consecutive measurements of diagnostic signals for each machine (history based standard). These methods were traditionally used in condition monitoring systems and the main type of vibration signal analysis was narrow band spectrum analysis. The second group of tasks used the standards formed by single vibration measurements conducted on a group of identical machines’ units (set based standard). These tasks are typical for the final output control at repair or production shops. A number of signal analysis techniques can be applied in this connection, but the most powerful method is similar to the previous case using spectrum analysis of the vibration signal. The third group contains the tasks with the most complex solutions for development, but are most efficient in practical diagnostics with prior known standards. Thus condition diagnostics can be done using a single vibration measurement. Typically, the solution of most complicated problems is based on the analysis of signal modulation processes, for example, using the spectrum analysis of low frequency oscillations of high frequency signal power, including vibration excited by periodic shock pulses. In this case the standard of the defect free state is most typically considered the absence of certain features in the analyzed signal. The new generation of condition monitoring and diagnostics systems reliably detect, not only potentially dangerous defects of any of above groups at the initial stage of their development, but also identify the exact defect type and its severity. Only in this case and, taking into account prior known development rates for each of defect types, is it possible to provide long term condition prediction and residual service life of the machine or its unit. This task is considered to be the main one for the new generation of the condition monitoring and diagnostics systems.
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