Control Engineering's Process Control Newsletter for March 2001


In this issue:

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Controller tuning problem

Once or twice a month I receive a request to recommend tuning constants for an application. Without fail there is simply not enough information provided to make even an educated guess. When I request more information about process dynamics, you can almost hear someone say, 'What's he talking about?'

I was recently talking to Tien L Chia, president of ControlSoft (Cleveland, O., the folks who make INTUNE), about this problem and we thought it might help if we provided a sample problem and then report the results next month.

Here's the sample problem the folks at ControlSoft came up with.

The following dynamics represent a well-insulated heat sink or extruder barrel temperature process:

Process Model:

G(s)= 0.1*e^-2s / S(30S+1)

Process Description:

Process Gain = 0.01
Process Deadtime = 2 Sec.
Process Lagtime = 30 Sec.
Process Type = Integrating

The process variable range is 0 to 1,000 Deg.F and the controller output is -100% to +100%

Calculate the PI and/or PID variables for a series based controller algorithm.

PID formula:

Series PID = Kc(1+1/Ti S)(1+Td S)

PID settings:

Kc = Proportional gain.
Ti = Integral time constant in seconds.
Td = Derivative time constant in seconds.

So how did you do?

1. What PI settings did you determine?
2. What PID settings did you determine?
3. What tuning method did you use?
4. About how much time did you spend determining these values?
5. What sort of response did you get? % of overshoot? Rise time? Settling time?

ControlSoft said if you want to know the answers INTUNE comes up with, contact them through their web site .


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Pushing the limits with advanced process control

My Feb. 2001 article discussed what it takes to really get the benefits from advanced process control (APC) applications. One of the things I keep learning is it's easy to miss someone who should have been included and innovative solutions show up about a day or two after an article has gone to production. Read the online version.

In the article I should have mentioned that ControSoft (Cleveland, O.) also provide APC solutions in the form of their Mantra model-based, multi-variable controller.

A recent press release from CyboSoft (Ranch Cordova, Calif.) introduced a high-speed model-free adaptive controller solution capable of updating control loops every one to ten milliseconds, depending on the number of loops and hardware used.


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Learning opportunities

* Massachusetts Institute of Technology (Cambridge, Mass.) is holding a summer professional program titled ' Modeling, Simulation and Optimization of Chemical Processes ' August 6-14, 2001.

* Several risk management and process safety training courses are available from ABS Group (Knoxville, Tenn.)

* Bill Bialkowski's company, EnTech Controls (Toronto, Ontario, Canada), has a variety of seminars designed especially for process engineers planned throughout 2001.


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Fieldbus news

I recently attended FOUNDATION fieldbus' general assembly in Vancouver, British Columbia, Canada and attended a couple of short courses conducted by Southern Alberta Institute of Technology (SAIT, Calgary, Alberta, Canada).

SAIT and Fieldbus Foundation have formed an exclusive partnership allowing SAIT to prepare and administer a certified FOUNDATION fieldbus curriculum for users and integrators. Visit for details.

Speaking of fieldbus, if you've been reluctant to introduce fieldbus into your process for fear of single-point fieldbus module failures, Fisher-Rosemount's DeltaV system recently introduced a redundant H1 solution. For more information and to see a live demo, visit

Sign up to receive Fieldbus Foundation or other newsletters.

Read more about the Fieldbus Foundation general assembly.


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Conferences, seminars, and exhibitions

* April 1-4 World Batch Forum Conference (Orlando, Fla.)

* May 22-25 Simatic and APACS+ Users Meeting (Chicago, Ill.)

* June 10-14 Intergraph Process & Building Solutions is sponsoring ' International Process and Power 2001 ' in Orlando, Fl.

* August 7-9 Profibus Trade Organization's General Assembly Meeting will be held in Scottsdale, Ariz. Contact Mike Bryant at (480) 483-2456 or for details.


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March in Control Engineering

Cover: Control Engineering Editors' Choice Awards
For these prestigious, annual awards, Control Engineering editors select the best products of 2000 in all areas of coverage. All products selected must have been mentioned in Control Engineering, Control Engineering Online, or Control Engineering e-newsletters during 2000. Criteria for selection includes technological advancement, impact on the market, and service to the industry.

Safety systems for discrete manufacturing
Discrete manufacturing control engineers now have many opportunities to implement improved safety systems from gate switches to light curtains. A standard methodology for determining risk aids analysis of each machine and system.

Sensorless ac drives
Variable-frequency drives come in several flavors of control capability. Sensorless ac drives offer performance superior to open-loop control and approach that of the best closed-loop (flux vector) ac control methods-at less cost. Some topics to be covered: What are the methods of obtaining tight control without using a feedback device? What's fueling innovations in this fast growing sector of ac drives? The latest drive products will be sampled in an Online Extra article.

Ethernet I/O
Ethernet continues to win mindshare among hardware vendors for plant-floor communications. Here are some things to consider when running Ethernet all the way to I/O connections.

Product Focus: Terminal blocks
Original Control Engineering research examines trends and user issues with terminal blocks. Recent product descriptions from leading suppliers will be included, along with research results.

Back to Basics: Noise and disturbances
Electrical noise can disturb how automation devices operate. Here's how to avoid trouble.

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Dave's public service announcement

Too often, when searching for a URL you get the frustrating '404 Error,' page not found. Here are a couple of things to try.

Searching - Go to the main domain indicated in the URL and try searching for keywords in the original URL 'not found' string.

Snipping - Try snipping off the right end of the URL until you find something that works. Often times you will find a new link.

Notify - When all else fails, send an e-mail to the webmaster. You can almost always contact someone using webmaster@ or support@.


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