PID control in terms of robustness/performance and servo/regulator trade-offs: A unifying approach to balanced autotuning

In this article, we address the model-based tuning of single-loop PID controllers in terms of the robustness/performance and servo/regulator trade-offs. Although the robustness/performance compromise is commonly considered, it is not so common to also take into account, for example, the conflict between input and output disturbances, referred to here as the servo/regulator trade-off. This is a distinguishing feature of the presented approach, in which the final tuning expressions show how to shift each compromise. Another remarkable feature of the proposed methodology is that stable and unstable plants are dealt with in a unified way. Finally, at the light of the obtained expressions for the controller's parameters, we concentrate on giving tuning guidelines with an emphasis on balanced servo/regulation operation. For that purpose, two different performance indices are investigated.

► We consider PID tuning in terms of robustness and servo/regulation issues.
► We examine how these trade-offs interact and how to achieve an overall balanced tuning.
► Both stable and unstable plants are considered in a unified way.
► The overall conclusion is that regulatory control is normally the preferred option.
► Regulatory control is specially preferred when considering unstable plants.