Guaranteed dominant pole placement with discrete-pid controllers: A modified nyquist plot approach

Guaranteed dominant pole placement problem has already been considered in the literature (Journal of Process Control 19(2009):349-352). For the systems that are higher-order or have dead-time, pole placement procedure with PID controllers via modified Nyquist plot and root-locus has been proposed. Based on this idea, the dominant pole placement problem with discrete-PID controllers in zdomain is studied since it is important to take advantage of discrete-time domain representation during the pole placement procedure for time-delay systems. It is shown that modified Nyquist plot method is still valid in discrete-time domain and it is possible to find relevant discrete-PID controller parameters. Controller zeros are also considered in the study, since in the closed-loop controller zeros can disrupt the dominance. Success of the method demonstrated on example transfer functions.