Control Notes

Overview Gain-Anchored Tuning (GAT) is a PID tuning method for integrating processes, developed by Jacques Smuts of OptiControls.

Background A few weeks ago, a refinery got me out to tune the control loops on their thermal oxidizer.

Controller gains of properly tuned loops are typically within the range of 0.1 to 10.

A customer of mine owns a combined-cycle power plant that runs well most of the time, but when they start up or shut down the power augmentation system, the latter oscillates wildly.

Weird control strategies are sometimes used in lieu of proper tuning to address process interactions.

Once in a while you’ll have to tune a control loop on a process that takes seemingly forever to settle out at its final value.

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.

What is a Filter?

Process design flaws often lead to poor control performance.

For a long time I suspected that control valves take longer to respond to small changes in controller output than to large ones.