Monthly Archive: October 2006

Oct
30

Control of Deadtime Dominant Processes

A small fraction of the control loops in industry are characterized by the process deadtime being dominant i.e. greater than the process time constant. In most cases the source of the process deadtime is associated with transport delay or analyzer sample time for the process measurement. In many cases the loop directly impacts final product …

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Oct
30

Use of PID and MPC for Parental Advisory Control

Since we tend to learn by examples and we can all relate to the challenges of parenting, I came up with the following discussion of the relative advantages of PID and model predictive control (MPC) of a teenager for my Control Talk column in the September issue of Control Magazine. Would Proportional-Integral-Derivative (PID) or Model …

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Oct
23

Control Performance of Fieldbus Installations

When planning or designing a fieldbus installation, it is important to consideration where the control will reside. The function block set supported by fieldbus devices may be used to address many common control applications. If you are dealing with a slow process then where the control is done may have little impact on the observed …

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Oct
23

Use of Model Predictive Control to Eliminate Split Ranged Control

Terry described an innovative technique of using the PID block for combining split ranged control and valve position control (see Terry’s Oct 16 entry). This technique eliminates the limit cycle at the split range point caused by the increase in nonlinearities and the decrease in resolution imposed by backlash, backfilled pipes and dip tubes, rangeability …

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Oct
16

Combining Split Range and Valve Position Control

When designing a control strategy you may be faced with the challenge of there being an extra degrees of freedom. One of the most common examples is where one control parameter may be maintained at setpoint through the adjustment of two manipulated parameters. Often the solution is to address the control design using split range …

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Oct
16

How to Become Rich and Famous as a Technical Book Author

Well, you may not become rich and famous in the conventional sense. You may not make it into the best seller list or your favorite book club but you can impress your friends, relatives, and associates and increase the marketability of your skills. More important is the sense of accomplishment in adding your expertise to …

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Oct
09

How Process Control Education Should be Changed in the Universities

Professor Tom Edgar of the University of Texas and Joseph Alford from Eli Lilly and Co. have been collecting data and opinions regarding the current syllabus of the typical undergraduate Chemical Engineering Process Control Course and its relevance to the skills and knowledge needed in today’s industrial process control environment. An upcoming issue of Intech …

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Oct
09

Basics of Fieldbus

When the Fieldbus Foundation was established, I lead the team that wrote the Function Block Application Process Specifications. This was a unique experience since it offered a rare opportunity to work with and to get to know some of the best control engineers from Siemens, Yokogawa, Honeywell, Leeds and Northrup, Foxboro, ABB, Smar and others …

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Oct
02

Basics of Advanced Control

In the early 1990’s, I helped establish Emerson’s advanced control program. As part of this initiative, a technical advisory committee was formed to periodically review the program and to help provide technical direction. This committee was made up of leaders in process control such as Professors Karl Astrom, Lund University, Tom Edgar, University of Texas, …

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Oct
02

Techniques to Improve pH Measurement Performance

At a luncheon meeting of Automation Xchange in Park City on August 22, many key users from the biopharmaceutical industry were interested in doing a better job of pH measurement. Many bioprocesses are adversely affected by a change as small as 0.2 pH. During the course of a fermenter batch, which can take up to …

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