Performance analysis of model reference robust tuned 2DoF PI controllers for over damped processes

The aim of the paper is to present a closed-loop performance analysis of robust tuned two-degree-of-freedom (2DoF) proportional integral (PI) controllers for over damped (first- and second-order) plus dead-time controlled processes. A closed-loop model reference optimization method was follow with non-oscillatory and under damped response targets. The analysis shows that the controlled process model parameters (high time constants ratios or high normalized dead-times) impose a constrain on the robustness obtainable when highly oscillating closed-loop responses targets are specified. The non-oscillatory response targets produce the smoothest controller outputs. The regulatory and servo-control performance (integrated absolute error and settling time) may be improved if lightly under damping responses (0.691 ≤ ζ ≤ 0.780) are allowed but affecting the control effort characteristics (its smoothness and maximum values).