Detection of Oscillating Control Loops

Abstract

Since a control loop may exhibit poor performance for various reasons, it is not only important to detect poor performance, but the challenge is to trace the bad performance to its root cause. Not only controller design and tuning but also other elements in the control systems, such as sensors and actuators, are often responsible for the poor performance. There are many reasons for poor control performance, which can be detected using specialised methods and indices, without requiring the knowledge of time delays or model identification. Attempt of this chapter to review and suggest procedures for semi- or fully automatic detection of oscillating control loops. For each method described, the basic assumptions, limitations, strengths and weaknesses will be clearly stated. The parameterisation of the methods is thoroughly discussed to give default settings for real applications. Industrial examples from different industrial fields (chemicals, refining, petro-chemicals, pulp & paper, mining, mineral and metal processing) are presented throughout the chapters to demonstrate the applicability of the methods.