Tuning of controllers for integrating time delay processes

Presents an identification method and a simple control strategy for open loop integrating processes with time delay. From a symmetrical relay test the open-loop integrating process model transfer function is estimated. A control strategy involving an inner loop in the feedback path and a proportional integral controller in the feedforward path is proposed. The inner feedback loop with a controller plays an important role in stabilizing the integrating processes. Then the PI controller in the outer loop is designed to control the stabilized process efficiently. Simple tuning formulae interims of the estimated process model parameters have been derived for the controllers based on user-specified gain and phase margins. A comparison of the performances of the proposed design settings with those given by earlier workers is presented.