OPT FOR SECURITY AND PERFORMANCE
Improve the security and performance of your plant with alarm management, performance supervision, asset supervision, web-based data visualisation, optimisation, advanced control, and tuning with the new TaiJi tool.
Rethink your working methods and obtain immediate results thanks to our services, trainings, and consulting expertise. Manage changes intelligently with our proven solutions.
certified service providerSeptember 2004
In this issue
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About us |
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Classes and seminars |
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Trick for this month |
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To contact us |
See our previous issues :
http://www.topcontrol.com/techinfo/news.php
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ISA Expo 2004
See us at ISA Expo 2004 in Houston, October 5-6-7; our booth is 1605.
We will also present many papers…
Visite nuestro nuevo sitio web en español : http://www.topcontrol.com/top/accueil.php?lang=es
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Classes & seminars
See our calendar for 2004 Classes & Seminars
See at http://www.topcontrol.com/training/tcalendar.php
Milwaukee, September 28-29-30,
ExperTune - Theory and UseEX-501-3 -- Detailed Loop Analysis with ExperTune
http://www.topcontrol.com/training/tlistcourses.php?idcours=10
Quebec City, October 19-20-21,
EX-502-3 -- ExperTune Advanced Tools
http://www.topcontrol.com/training/tlistcourses.php?idcours=11
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Trick for this month: Feedforward?
When should we use feedforward?
We should use feedforward when it is possible to measure a disturbance and hence to eliminate its impact on the process variable. Many examples exist but the control in a reservoir where one can measure net flow (all flows going in minus all flows going out) is easy to understand; this error flow signal becomes the feedforward signal sent to the valve to "help" ( in this case, the net flow is add to the controller output) the PID controller. When the net flow varies, this signal directly manipulates the control valve. Using feedforward will ensure a quick response contrary to the PID controller which has to "wait" to see a change in level; this will delay the PID controller response.
Feedforward can be additive or multiplicative. It is sometimes a simple gain (static) or a time function to compensate for delays, leads or lags in the system (dynamic feedforward). PID Tuner and PlantTriage from ExperTune can calculate gain and time constants based on process tests.
If the gain is set too high, this will generate oscillations; if the gain is set too low, then the feddforward impact will be reduced.
Performances are greatly improved and if the signals are available, we only need minutes to implement it!
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Comments, suggestions and requests are welcomed. Please e-mail us at: info@topcontrol.com
You are welcomed to visit our web site :http://www.topcontrol.com
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49 Bel-Air Street, Lévis, QC
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4734 Sonseeahray Drive
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