P-I and I-P controllers in a closed loop for DC motor drives

The traditional proportional-integral (PI) controller, which has been widely used for the speed control of DC motor drives, has been compared with the relatively new integral-proportional (IP) controller which were first discussed in 1978. This paper presents some improvements in this important industrial field. Theoretical studies for PI and IP controllers in the S-domain are presented, and the transfer functions for both are derived. Simulation results due to step response in the S-domain and Z-domain are presented for both controllers. Experimental studies are discussed in detail. The performance of the two controllers due to step input reference and their behavior due to sudden changes in reference speed and load are discussed. The simulation and the experimental results indicate the superiority of IP over PI controllers.