Detection of valve stiction in integrating processes

A simple method for detection of static friction (stiction) in control valves was presented in [6]. However, that method cannot be used for control loops with integrating processes. This paper presents a new method to handle these cases. The main idea is to detect abrupt changes (which are typical in the case of stiction) in the loop output. This is done by considering the probability distribution of the second derivative. In the stiction case the distribution is close to Gaussian, otherwise it will have two peaks.