Design and analysis of offset free model based predictive control

• Main Author: Gomez-Gonzalez, Ricardo
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2006
• Subjects: Chemical engineering
• ISBN: 0549175873; 9780549175872

One predictive control design is derived to eliminate the steady state error or offset from a system response. This strategy makes use of a velocity weights based predictor, which inherently works as an integrator. Sufficient conditions to eliminate offset are presented and proved in terms of a matrix rank. Conditions for obtaining offset free behavior are more challenging to obtain for the case of underactuated and nonlinear systems. An ad hoc modification is proposed through the introduction of an aiming distance concept that corrects the reference trajectory in a portion of the prediction horizon. The modification can help to avoid cases where controllability of a state is lost due to the dynamics of the system. Extensive simulation studies are carried out to show the feasibility of the aiming distance correction. A Khepera robot is chosen as a test system since it introduces significant challenges to the controller given that it is underactuated, and controllability can be lost in some of its states. The tests have proved to be successful, showing how the aiming distance correction factor can make the controller account for unseen errors that will otherwise lead to persistent offset in the response of the system. Extensions of the aiming distance into chemical engineering are studied via simulation of a semi-batch reactor for the production of penicillin. The advent of new technologies such as the Internet has posed a challenge in the way engineering is taught at the universities. The Virtual Control Laboratory presents a fast and simple tool for both the designer and the user. It features significant levels of modularity, such that most of the code can be reused and only minor changes are needed to create a new system. Due to its intuitive graphical interface the user can interact with the system in an analogous way to the physical setup. Two laboratories are presented to demonstrate the VCL.