Time-minimal set point transition for nonlinear SISO systems under different constraints

• Autores: Andreas Himmel, Sebastian Sager, Kai Sundmacher
• Localización: Automatica: A journal of IFAC the International Federation of Automatic Control, ISSN 0005-1098, Nº. 114, 2020
• Idioma: inglés
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• Resumen

  • Set point transition of nonlinear plants plays an important role in many applications where dynamic process management has to be considered. This transition should be rapid – as operation in the new set point increases the economical benefit – but in compliance with all safety regulations. We present a feedforward approach for a time-minimal set point transition of single-input, single-output nonlinear plants with respect to input, state and output constraints. The conceptual idea is based on the design of an optimization problem utilizing a coordinate change of the plant and a special setup function for the output trajectory. This allows the simultaneous planning of the trajectory and determination of the corresponding control signal. The formulation of the set point transition as an optimization problem provides a flexible design with respect to the integration of inequality constraints. Additional flexibility is provided by the type of setup functions, which permit any adjustment of the output trajectory between the set points. In contrast to other works, we focus on the stationarity of the system output, which allows a faster transition compared to the requirement to reach a steady state of all states. Finally, we present an example from the field of process systems engineering to demonstrate the applicability of the proposed methodology.