Greg: Freedom to find the best opportunities, access to the best technical minds, the time to explore problems conceptually on a first-principle basis, and the right to publish meant the most to me. In instrument design and construction, my supervisor was always at least 500 miles away, so I had to pretty much decide on my own what was best. In Engineering Technology (ET) it was up to the individual to define the job. I worked on both biological and chemical processes as Monsanto moved towards being a life sciences company.
If I had an intelligent question, I found quickly that going directly with an open mind to the expert, no matter where the person resided, was mutually beneficial. Often the person was in ET, but other times he was in the plant or at an instrument manufacturer.
The access to the mind of Greg Shinskey through his many books was particularly influential because he analyzed every problem based on fundamental chemical and physical relationships. Other books on control were mostly a reiteration of the math of control theory (frequency response and state space).
The compilation of applications in handbooks was helpful, but a lot of the problems didnt fit the script. I needed to know conceptually how to find the solution by the first-principle approach to cause and effects. I also found it much more satisfying to understand the basic nature of the problem.
Dynamic simulation provided me the experimental laboratory to build, test and analyze what is really under the hood. A good part of the effort was to emulate the control system in the simulation. It was a formidable task to exactly replicate the proprietary PID algorithms that represented many years of development besides all the functional capability in a DCS. The development of dynamic simulation software that could link to the DCS was a step forward to eliminate this duplication of effort, but the interface, initialization and speeding up the real time factor was another challenge. Now these issues are gone with the virtual plant where the actual control system and dynamic process model reside in the same laptop or desktop PC. This leads me to the following Top Ten List.
Top Ten Reasons I Prefer a Virtual Plant to a Real Plant
10. You cant freeze, restore and replay an actual run or batch
9. No separate programs to buy, learn, install, interface and support
8. No waiting on lab analysis
7. No raw materials
6. No environmental waste
5. Virtual instead of actual problems
4. Batches done in seconds or minutes instead of hours or days
3. Can operate plant on a tropical beach
2. Last time I checked my wallet, I didnt have $100,000,000
1. Actual plant wouldnt fit in my suitcase.
Stan: While there are virtually no situations where you couldnt benefit from a virtual plant, except perhaps retirement, when is it most advantageous to virtually explore process scenarios and prototype process control improvements?
Greg: I especially appreciated a plant at my finger tips for testing when dynamics are incredibly fast (e.g. compressor surge control), incredibly slow (e.g. fermentor cell growth rate control), or unstable (e.g. exothermic reactor temperature control).
Stan: Nothing is perfect and every model, like every measurement, has errors. What are the watch-outs?
Greg: There are thousands of chemical compounds, and many compounds used and produced in specialty chemical processes dont have enough information on how the physical properties change with temperature, pressure, composition or interaction with other physical properties.
For distillation, the physical properties are exceedingly important and complex. Column models are numerical hogs. I was more than content to leave these problems my close friend and associate Terry Tolliver (see The best of the best, Part 1, January Control, p. 111), who is industrys foremost expert on distillation column control.
A big issue for me is models for process design that evolve into dynamic models. They are often a magnitude low in dead time−a killer for control. The models I build focus more on process dynamics and do not have all the complexities needed for process design.
For a practical review of the state of the technology, check out Virtual Plant Reality in The Light at the End of the Tunnel is a Train in the 2005 August issue of Control. www.controlglobal.com/articles/2005/442.html) My latest article on a virtual plant is available electronically at http://tinyurl.com/2qkfgf.
Stan: What are some of the improvements accomplished in actual plants?
Greg: The strange, but true stories of my experiences in the 1980s are in a free E-book at http://tinyurl.com/2nj5jq. Ill conclude this odyssey with saying that I got to play a significant role conducting opportunity assessments of major plants in the 1990s. I got the biggest benefits from process control improvement in the areas of pH and reactor control.
The technical path for advancement offered at Monsanto by the Fellow program helped provide Stan and me with the environment and recognition to pursue a purely technical career. The last thing anyone would have wanted was for one of us to become a supervisor. We can barely supervise ourselves.
Excellent technical people have become managers because of circumstances and still managed to keep their skills, perspective and sense of humor. One such person is Soundar Ramchandran , whose real love is process control, but who is also responsible for process technology for a large monomer plant.
The following Top Ten List from Soundar provides an early warning for others on the road to executive stock options.
This Months Puzzler: Dont Feed the Forwards
When does a feedforward control system do more harm than good?
Send an e-mail with your answer to the Puzzler, CONTROL questions, or comments to [email protected].