LAUSR

Abstract Dead times affect many industry processes and are mainly caused by the time required to transport mass, energy or information. In process with dead times the performance of classical PID controllers may be significantly decreased, especially when the dead times are large and higher than the dominant time constant of the process. Several solutions have been presented over the years to improve the control in such cases. The paper contributes in this direction by presenting an extension to second order stable processes of the predictive PI controller introduced by Hagglund in 1996 for first order processes. Both real and complex poles cases are considered. The solutions are derived in special forms in which the classical PID controller is maintained and a new linear block, which just requires one additional parameter, is inserted. In this way, the flexibility of the PID is conserved and control performances improve. For the sake of coherence with respect to the Hagglund’s controller, the proposed solutions are called Predictive PID controllers (PPID). Simulation examples show the good performance of the PPID controllers.