Recognizing Integrating (Non-Self Regulating) Process Behavior
By Bob Rice and Doug Cooper
ABSTRACT: The case studies on this site largely focus on the control of self regulating processes. The principal characteristic that makes a process self regulating is that it naturally seeks a steady state operating level if the controller output and disturbance variables are held constant for a sufficient period of time. But some processes where the streams are comprised of gases, liquids, powders, slurries and melts do not naturally settle out at a steady state operating level. Process control practitioners refer to these as non-self regulating, or more commonly, as integrating processes.
A Design and Tuning Recipe for Integrating Processes
By Bob Rice and Doug Cooper
ABSTRACT: As has been discussed elsewhere in this e-book, it is best practice to follow a formal recipe when designing and tuning a PID controller. A recipe lets us move a controller into operation quickly. And perhaps most important, the performance of the controller will be superior to one tuned using an intuitive approach or trial-and-error method. Additionally, a recipe-based approach overcomes many of the concerns that makes control projects challenging in an industrial operating environment. Specifically, a recipe approach causes less disruption to the production schedule, wastes less raw material and utilities, requires less personnel time, and generates less off-spec product.
Analyzing Pumped Tank Dynamics with a FOPDT Integrating Model
By Bob Rice and Doug Cooper
ABSTRACT: Integrating (or non-self regulating) processes display counter-intuitive behaviors that make them surprisingly challenging to control. In particular, they do not naturally settle out to a steady operating level if left uncontrolled. To address this distinctive dynamic character, we modify the controller design and tuning recipe to include a FOPDT Integrating model and slightly different design rules and tuning correlations as discussed here.
PI Control of the Integrating Pumped Tank Process
By Bob Rice and Doug Cooper
ABSTRACT: The control objective for the pumped tank process is to maintain liquid level at set point by adjusting the discharge flow rate out of the bottom of the tank. This process displays the distinctive integrating (or non-self regulating) behavior, and as such, presents an interesting control challenge.