Controller performance assessment in set point tracking and regulatory control

Recent critiques of minimum variance benchmarking for single‐input–single‐output (SISO) control loops have focused on the need for assessment of performance during set point changes and also on the need to pay attention to the movements in the manipulated variable. This paper examines factors that influence the minimum variance performance measure of a SISO control loop. It discusses the reasons why performance during set point changes differs from the regulatory performance during operation at a constant set point. The results demonstrate how regulatory performance is influenced by the nature of a disturbance, and that correlation of signals within a control loop can indicate whether the disturbance is random or deterministic. The paper is illustrated with simulated, experimental and industrial examples. Copyright © 2003 John Wiley & Sons, Ltd.