Title: A simulation study on the use of co-state variables as strategic setpoints for tomato greenhouses

Authors: Raphael Linker; Marc Lousky

Addresses: Faculty of Civil and Environmental Engineering, Technion – Israel Institute of Technology, 32000 Haifa, Israel ' Faculty of Civil and Environmental Engineering, Technion – Israel Institute of Technology, 32000 Haifa, Israel

Abstract: Modern greenhouses include a large number of control actuators. Such a situation leads to the question of how to divide the control effort between these actuators. This question can be answered using optimal control theory and more particularly the system co-states. By modifying the value of these co-states the grower can control the greenhouse climate and correct deviations due to imperfect modelling or unexpected weather. This work presents a simulation study of this concept for a greenhouse with a tomato crop. For the specific scenarios investigated, by adjusting the co-state two to five times during the season, it was possible to maintain the yield within 6% of its target value. The control costs were on average 10% higher than the control costs that could be achieved if perfect weather forecasts were available at the beginning of the season.

Keywords: TOMGRO; optimal control; greenhouse climate control; simulation; co-state variables; tomato greenhouses; control actuators; target yield.

DOI: 10.1504/IJSAMI.2015.070749

International Journal of Sustainable Agricultural Management and Informatics, 2015 Vol.1 No.2, pp.163 - 177

Received: 14 May 2014
Accepted: 07 Oct 2014
Published online: 23 Jul 2015 *

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