Title page for ETD etd-10032011-163823


Document Type Master's Dissertation
Author Campher, Andre Herman
Email andre.campher@lonmin.com
URN etd-10032011-163823
Document Title A systematic approach to model predictive controller constraint handling : rigorous geometric methods
Degree MEng
Department Chemical Engineering
Supervisor
Advisor Name Title
Mr C Sandrock Supervisor
Keywords
  • constraint handling
  • model predictive controllers
  • geometric methods
  • operability index
Date 2011-09-06
Availability unrestricted
Abstract
The models used by model predictive controllers (MPCs) to predict future outcomes are usually unconstrained forms like impulse or step responses and discrete state space models. Certain MPC algorithms allow constraints to be imposed on the inputs or outputs of a system; but they may be infeasible as they are not checked for consistency via the process model. Consistent constraint handling methods - which account for their interdependence and disambiguate the language used to specify constraints would therefore be an attractive aid when using any MPC package.

A rigorous and systematic approach to constraint management has been developed, building on the work of Vinson (2000), Lima (2007) and Georgakis et al. (2003) in interpreting constraint interactions. The method supports linear steady-state system models, and provides routines to obtain the following information:

  • effects of constraint changes on the corresponding input and output constraints,
  • feasibility checks for constraints,
  • specification of constraint-set size and
  • optimal fitting of constraints within the desirable input and output space.

Mathematical rigour and unambiguous language for identifying constraint types were key design criteria.

The outputs of the program provide guidance when handling constraints, as opposed to rules of thumb and experience, and promote understanding of the system and its constraints. The metrics presented are not specific to any commercial MPC and can be implemented in the user interfaces of such MPCs. The method was applied to laboratory-scale test rigs to illustrate the information obtained.

2011 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Campher, AH 2011, A systematic approach to model predictive controller constraint handling : rigorous geometric methods, MEng dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-10032011-163823/ >

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