I am trying to extract features from 3 time-dependent principal components signals derived from 15 pressure and temperature sensors of a filling plant. The plant is working batchwise and following a recipe, steps of which depending on the process part have either duration or pressure limits .
I already tried frequency analysis, although it shown some results I am still not able to classify the frequency in classes (frequencies of a batch which is about to fail and good frequencies).
Is there somebody out there, who can give me ideas how the define features of a time-dependent signal without frequency analysis?