A graphical method for designing PD controller for IPDT processes

A new technique is presented to design proportional-derivative (PD) controller for integrator plus dead time (IPDT) processes. For developing this technique a graphical approach is used. More precisely speaking, five loci are established and plotted in the controller parameters plane, so that on each locus a performance index such as stability margins and crossover frequencies to be constant. Then it is assumed that the characteristics of the desired feedback system are stated in the form of two of these loci. After that by sketching the two under considering loci the intersecting point of them is obtained and hence the values of the controller coefficients are determined. The proposed method is illustrated by an example.