Stiction compensation in process control loops: A framework for integrating stiction measure and compensation

In this paper, a framework that utilizes a stiction measure for effective stiction compensation in process control valves is proposed for the first time. The performance of a friction compensator termed the "knocker" proposed in the literature is studied. It is observed that the choice of knocker parameters has a significant influence on the performance of the compensator. It is shown that the choice of the knocker parameters can be automated based on the stiction severity exhibited by the loop. We propose the use of a combination of two approaches for estimating stiction severity. Experimental and simulation case studies are used to demonstrate the efficacy of the proposed approach. Results indicate that a reduction of 6 - 7 times can be obtained for the output variability.