A modified empirical mode decomposition (EMD) process for oscillation characterization in control loops

This paper focuses on a new method for characterizing oscillations in measurements from control loops in chemical processes. The proposed method uses a modified empirical mode decomposition (EMD) process to uncover all the zero-crossings in the data. It is shown that this procedure characterizes the following attributes of the oscillations: (i) non-constant mean, (ii) time instances when the oscillations are present, (iii) strength of the oscillations at different times, (iv) time period of each sweep of oscillation. The proposed approach is tested on more than 150 industrial control loop data and results obtained for 10 loops are discussed. The utility of the characterization approach in the area of oscillation analysis is also discussed. (c) 2007 Published by Elsevier Ltd.