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Entry type: Application example Entry ID: 42200753, Entry date: 04/08/2010
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Model Predictive Control including integral transfer functions

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Objective of the Application
The area of application of the model predictive controller provided in SIMATIC PCS 7 (function block ModPreCon and MPC respectively) is restricted by the following fact: The control algorithm only works for stable processes with a step response settling to a constant value in a finite time horizon.
If the process is not stable or shows an integral action (e.g. level control, position control), the respective sub transfer functions have to be stabilized by slave con-trollers. The objective of this application note is to describe how to proceed in such cases.
This application note is an extension of the application note "Multivariable Model Predictive Control – the Distillation Column as an Application Example", containing basic information how to apply the MPC.
The application example considered here shows an MPC with two manipulated and two controlled variables in combination with a simulated process of which the sec-ond main control loop shows integral action.

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

  • The stabilization of unstable processes using P(ID) controllers
  • The integration of a subordinated PID controller in an MPC application
  • Simulation example

Validity
Valid for PCS 7 V7.0 SP1 or later versions

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Model Predictive Control including integral transfer functions 42200753_MPC_Level_en.pdf ( 674 KB )

History

Version

Modification

04/2010    V1.0 First release
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