Extremum seeking control of the CANON process - Existence of sub-optimal stationary solutions
2012 (English)In: 8th IFAC International Symposium on Advanced Control of Chemical Processes, IFAC , 2012, 19-26 p.Conference paper (Refereed)
The paper considers extremum seeking control (ESC) for on-line optimization of the CANON process, a new and potentially highly effective process for ammonium removal from wastewater. For gradient estimation we employ the classical method based on periodic excitation. From simulations we find that the ESC scheme can lock onto sub-optimal stationary solutions, far removed from the optimal solution, and that the ESC may have multiple stationary solutions for given controller parameters. The cause of this is investigated through analysis of a general dynamic model. Based on the analysis, it is shown that for systems for which the optimum corresponds to the input-output transfer-function having a transmission zero at the origin, there will in general exist a number of stationary solutions to the ESC with periodic excitation. The solutions are characterized by the phase lag of the system, rather than a zero gradient of the objective function, and are hence in general not related to the optimality conditions. For systems that can be described by Hammerstein or Wiener models, as typically considered in ESC, the solution will in general correspond to the zero gradient condition fulfilled at the optimum. As shown, the CANON process can not be described by Hammerstein orWiener models, and this then explains the observed existence of sub-optimal stationary solutions.
Place, publisher, year, edition, pages
IFAC , 2012. 19-26 p.
, IFAC Proceedings Volumes (IFAC-PapersOnline), ISSN 1474-6670 ; 8
Adaptive control, Extremum seeking, Periodic excitation, Real time optimization, Wastewater treatment plant
IdentifiersURN: urn:nbn:se:kth:diva-88005DOI: 10.3182/20120710-4-SG-2026.00128ScopusID: 2-s2.0-84867058437ISBN: 978-390282305-2OAI: oai:DiVA.org:kth-88005DiVA: diva2:502073
8th International Symposium on Advanced Control of Chemical Processes, ADCHEM 2012; Singapore; 10 July 2012 through 13 July 2012
FunderICT - The Next Generation
QC 201211222012-02-142012-02-142013-04-19Bibliographically approved