Control Notes

This discussion is as old as controller tuning itself: should one tune a controller to respond well to setpoint changes or to do well at rejecting disturbances. Different tuning rules have been developed for the two cases, and much research has been...

What is a Filter? In a modern control system, a filter is an algorithm (or function block) used mainly for the reduction of noise on a process measurement signal (Figure 1). But that is not its only use as we will see later. Figure 1. Noise filter. Types...

Process design flaws often lead to poor control performance. Then all eyes are on the control engineer to make the system work. Case in point is one level control loop at a chemical company that contracted me to improve the control performance of one...

For a long time I suspected that control valves take longer to respond to small changes in controller output than to large ones. I have now confirmed this by doing tests on several control valves and analyzing the results. Most of my control loop optimization...