Data driven performance monitoring and retuning using PID controllers

This paper presents a joint methodology for performance assessment and retuning of PID controllers. The methods are data-driven and based on the set-point response collected during operation or tests, using as reference input steps, ramps, and other signals. For each set-point response, the IAE (Integral of Absolute Error) is computed and a statistical test is evaluated to check if performance is below a given threshold. A data-driven design method is applied if new controller gains are required to resume the performance, using closed-loop data and a reference model obtained also from data under operation with good performance. Both monitoring and design require only closed-loop data, and statistical tests are used to provide evidence that monitoring and retuning were successful. Three applications for two different pilot plants are presented, evaluating: (i) flow, level, and pressure loops, (ii) outer and inner loops, (iii) validation of closed-loop data, (iv) performance recovery after introducing faults that reduce performance, (v) performance monitoring and retuning for three levels of performance. As illustrated, the proposed methodology can be applied directly to closed loops even in the presence of very noisy signals, with no assumptions about the design method used for the controller design.