Tag Archives | pid controllers

Brewery contol display

Tip #95: Use External-Reset Feedback for Cascade Control and Slow Final Control Elements

The value of the external-reset feedback feature in PID controllers is becoming increasingly apparent to me. I got a preview of its importance when I found that 1980s vintage DCS required a fix for override control that was addressed in the next generation of DCS by this feature. This wakeup call was followed by the […]

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Fig. 1. The Smith predictor control scheme.

Autotuning of a new PI-PD Smith predictor based on time domain specifications

Abstract: The paper extends a recent work on a modified PI-PD Smith predictor, which leads to significant improvements in the control of processes with large time constants or an integrator or unstable plant transfer functions plus long dead time for reference inputs and disturbance rejections. Processes with high orders or long time delays are modeled […]

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How do you handle manual operations?

In the ISA Automation Week Mentor Program, I am providing guidance for extremely talented individuals from Argentina, Brazil, Malaysia, Mexico, Saudi Arabia, and the USA. We will be sharing a question and the answers each week. If you would like to provide additional answers, please send them to Susan Colwell at ISA. The twelfth question […]

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Fig. 1. Block diagram of a cascade control system.

Improving performance using cascade control and a Smith predictor

Abstract: Many investigations have been done on tuning proportional-integral-derivative (PID) controllers in single-input single-output (SISO) systems. However, only a few investigations have been carried out on tuning PID controllers in cascade control systems. In this paper, a new approach, namely the use of a Smith predictor in the outer loop of a cascade control system, […]

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