.IndustrialControlSystems.Applications.ControlProblems.SmithPredictor

Smith predictor controller for delayed processes

Information

Description

The aim of this example is to show how classic control strategy can be implemented with the models contained within the ControlLibrary.
The system to be controlled is a delayed second order one

          Y(s)           1           -8T
   P(s) = ----  =  ---------------- e
          U(s)       (1+0.2s)(1+s)

In this case the delay is too high in order to control the process with a simple PI controller. However, the same simple
controller can be used within a more complex structure called Smith predictor. This scheme is based on the knowledge of the process
since it is a model based control strategy. The control scheme follows, and can be replicated with the blocks contained in the library



Two different scheme have been tested. In the first scheme the Smith predictor is based on a model that is equal to the
real process (M(s) = P(s)), while in the second one the model is an approximation of the process. The step responces are reported below

The red line is the process responce without the controller action, the green line is the process controlled with the Smith predictor (M(s) = P(s)) while the pink one is the responce of the Smith predictor with an approximate model.
Every 8 seconds (the time delay) there is an action due to the uncorrectness of the model M. However, the amplitude
of these peacks decrease with time. The control signal of the two controllers are reported below.

Revisions

Industrial Control Systems (v 1.0.0) : April-May 2012
List of revisions:
  • 11 May 2012 (author: Marco Bonvini)
Main Authors:
Marco Bonvini; <bonvini@elet.polimi.it>
Alberto Leva <leva@elet.polimi.it>
Politecnico di Milano
Dipartimento di Elettronica e Informazione
Via Ponzio 34/5
20133 Milano - ITALIA -
Copyright:
Copyright © 2010-2012, Marco Bonvini and Alberto Leva.
The IndustrialControlSystems package is free software; it can be redistributed and/or modified under the terms of the Modelica license.
Generated at 2026-04-01T18:18:38Z by OpenModelicaOpenModelica 1.26.3 using GenerateDoc.mos