The Magnitude-Optimum Design of the PI Controller for Plants with Dead Time and Oscillatory Modes

Abstract

The design of the PI controller for stable linear plants based on the magnitude-optimum criterion can be applied directly for high-order linear models with dead time, without need of the model reduction. This paper discusses key properties of this method, especially considering oscillating plants. Even though the closed-loop response is specified only for low frequencies and the robustness requirements are not explicitly formulated in the design objective, in the case of plants without zeros a large closed-loop stability margin is ensured automatically regardless the dead time value, under the assumption that the damping coefficients corresponding to the oscillatory modes of the plant are sufficiently high.