Valve backlash and stiction detection in integrating processes

Valve nonlinearities are responsible for producing limit cycles in the loop and consequently decreasing plant performance. In the case of an integrating plant, once the loop oscillation is detected, the engineer should distinguish between stiction and backlash, but no method is available in the literature to address this class of problem. In this paper, it is proposed a data-driven method to distinguish between loop stiction and backlash for integrating processes. The closed-loop pattern provides enough information to verify when either stiction or backlash is available. The efficacy of the proposed technique is corroborated by simulation case studies.