Signal Preprocessing for Stiction Detection Methods

Oscillation in control loops is a problem of high incidence, stiction in control valves being the most frequent cause. In the last two decades, many automatic stiction detection methods were proposed. These methods require certain signal preprocessing for proper use, where the choice of the appropriate preprocessing technique and parameters depends on the detection method and signal characteristics and, due to the lack of information about its automatic application, are mostly led manually. The need for user interaction turns an automatic into a nonautomatic detection method, which makes the application unfeasible to an entire plant with hundreds or even thousands of control loops. This work proposes techniques for automatic preprocessing according to the demands of each detection method. The techniques cover the main problems related to stiction identification: removal of noise excess, identification of peaks and valleys, and removal of variable mean and zero-crossing identification. Satisfactory results are obtained for both simulated and industrial data