Digital controller fluctuation-source tracing using power spectral decomposition technique

In a digital controller, the outputs may have large fluctuations due to the quantisation noises. If the digital controller is part of a closed-loop system, then the fluctuations will propagate to everywhere and it is difficult to locate the primary source of the fluctuations by studying only the plain data. In this paper, a power spectral decomposition technique is applied to resolve this problem. To make the application viable, the data taken from the digital controller are modified to reflect the cause- consequence calculation-sequence. A successful application in a real digital controller debugging case confirms the usefulness of the technique.