PI controller design based on generalized stability boundary locus

The paper introduces a generalized approach to identify all stabilizing PI controllers for processes with time delay. The approach depends on modeling higher order plant transfer functions by a first order plus dead time model. Then, the normalized form of the obtained model and controller transfer functions are used for plotting the stability boundary locus plane. After that, the all stabilizing values of tuning parameters for PI controllers are being calculated from the obtained plots. This approach brings the advantage of not needing to plot the stability boundary locus each time when the process transfer function changes, which is the case for the so far reported studies in the literature. Simulation examples are provided to illustrate the usefulness of the proposed approach.