In steel and paper rolling mill industrial plants, where dc drive systems are widely used, improving dynamic and steady state performance properties plays a significant role in achieving a good quality of product. In this paper we intend to study the steady state performance of those systems in response to changed input reference, where an optimized transfer function based feed-forward compensating technique is proposed and applied to enhance their order of astatism without inserting additional integrators in the forward path of the closed loop system and therefore achieving improvement of the corresponding tracking error accuracy performance. The simulation results have shown a noticeable and important achievement in accuracy performance of the studied system when subjected to changing input reference.

Keywords: Direct current (dc) drive control system, Proportional-integral (PI) controller, Reduced order state observer, Accuracy performance, Order of astatism, Feed-forward compensation