Control Global

Control Talk Blog

The Control Talk Blog provides guidance from a user's viewpoint on the design of automation systems, equipment, and piping for process control improvement. Details are offered on the selection and installation of PID controllers, control valves, variable speed drives, and measurements to maximize loop performance. The blogs are often more intensive and extensive and less vendor specific than a white paper. The goal is an advancement of the profession by sharing conceptual principle based knowledge.

Greg McMillan is a retired Senior Fellow from Solutia/Monsanto and an ISA Fellow. At present, McMillan is a part time modeling and control consultant in Technology for Process Simulation for Emerson Automation Solutions specializing in the use of the Virtual Plant for exploring new opportunities. He spends most of his time writing, teaching and leading the ISA Mentor Program he founded in 2011. He received the ISA Kermit Fischer Environmental Award for pH control in 1991, received the Control magazine Engineer of the Year Award for the Process Industry in 1994, was inducted into the Control magazine Process Automation Hall of Fame in 2001, was honored by InTech magazine in 2003 as one of the most influential innovators in automation, and received the ISA Life Achievement Award in 2010.

Also, you can read McMillan's monthly Control Talk Column printed in Control magazine.

When is Reducing Variability Wrong?

Submitted by Greg McMillan on Sun, 09/02/2018 - 15:26
Having the blind wholesale goal of reducing variability can lead to doing the wrong thing that can reduce plant safety and performance. Here we look at some common mistakes made that users may not realize until they have better concept of what is really going on.

How to Prevent Acceleration, Jumping and Oscillation of Unstable Processes

Submitted by Greg McMillan on Sat, 07/14/2018 - 18:13
Inverse response, negative resistance, positive feedback and discontinuities can cause processes to jump, accelerate and oscillate confusing the control system and the operator. Not properly addressing these situations can result in equipment damage and plant shutdowns besides the loss of process efficiency.

Solutions to Prevent Harmful Feedforwards

Submitted by Greg McMillan on Thu, 03/08/2018 - 21:20
Here we looks at applications where feedforward can do more harm than good and what to do to prevent this situation. This problem is more common than one might think. In the literature we mostly hear how beneficial feedforward can be for measured load disturbances.

Surprising Gains from PID Gain

Submitted by Greg McMillan on Sat, 09/16/2017 - 17:36
We learned in control theory courses that too high a PID gain causes oscillations and can lead to instability. Operators do not like the large sudden changes in PID output from a high PID gain. Operators may see what they think is the wrong valve open in split range control...

How to Motivate Management and Millennials (M&Ms)

Submitted by Greg McMillan on Mon, 08/14/2017 - 19:00
The key to a much brighter future of our profession depends upon management providing the funding and support and millennials seeking to improve process performance by the use of the best automation and process control. There are some common approaches to these seemingly very different groups.