Siemens PCS 7 1 Preface

Preface

6 MPC Level

V 1.0, Beitrags-ID: 42200753

1 Preface

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 of this Application Note

The following issues are discussed in this application:

• 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.