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Entry type: Application example Entry ID: 37361207, Entry date: 07/10/2009

Smith Predictor for Control of Processes with Dead Times

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Objective of the application is fast and tight control of processes with dead times. A dead time can be recognized by the observation that after a step excitation of the manipulated variable there is no reaction of the controlled variable at all for a certain time (the dead time).

Objective of the Application
A normal PI controller must be tuned very sluggish for processes with large dead times and the control performance will decrease accordingly. The control performance can be considerably improved with the help of a so-called Smith-Predictor.

The present example shows the realization of a control loop with PI controller and Smith-Predictor starting from the respective process tag type (CFC solution template) of the PCS 7 Advanced Process Library.

Main contents
The following main points are discussed in this application note:

  • How to create an instance and set the parameters of the process tag type.
  • How to calculate the required process model for the Smith-Predictor.
  • Benchmark simulations with and without Smith-Predictor, to show the potential benefits.

This entry was created with SIMATIC PCS 7 V7.1, the procedure is transferable to PCS 7 V7.0 and higher versions.

  Smith Predictor for Control of Processes with Dead Times (857,0 KB) 

07/2009 First release

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