PI/PID controller design for FOPDT plants based on the modulus optimum criterion

We present the PI/PID controller settings for the first order systems with dead time, based on the modulus optimum criterion. The settings provide fast closed-loop response to changes of the reference input. Unlike most other tuning methods, the parameters are obtained without approximation of the delay term, so they remain valid for long dead time. Besides the performance indices, quality of the settings is also evaluated by the stability margin. Although optimal values of the parameters are valid for the reference tracking problem, a compensation of the disturbance lag that preserves the stability margin is proposed for the disturbance rejection problem.