Index Ratio Diagram - A New Way to Assess Control Performance

This paper presents a new way to conduct the control performance assessment (CPA). The measurement of control quality is a multi-criteria task from a practical point of view. Generally, the tuning of any controller means reaching a compromise between the accuracy and speed. The required (optimal) ratio between these two contradictory factors depends on the process demands, limitations and the engineering skills. Two basic indexes: the overshoot and settling time fit perfectly into such defined requirements. This research follows these path, but with the use of modern measures: robust statistical scale and shape factors, tail index and ARFIMA filter fractional order estimator. The assessment uses two dimensional Index Ratio Diagram (IRD), which allow to compare contradictory measures. Moreover, they allow to define new multi-criteria index able to compare different loops. The validation is compared against commonly used integral indicators.