ISHS Acta Horticulturae 417: International Symposium on Greenhouse Crop Models
NORMALIZED COSTATE VARIABLE FOR SEASONAL OPTIMIZATION OF GREENHOUSE TOMATO PRODUCTION |
| Authors: | I. Ioslovich, I. Seginer |
| Keywords: | Tomato model, greenhouse crops, environmental control, sub-optimal control |
| Abstract:
Optimal control of the greenhouse environment requires a model of the greenhouse-crop system. Detailed crop models contain many state variables, which makes complete optimization impractical. We chose to search for a sub-optimal solution, which utilizes a single costate variable. In this approach the simulation and performance criterion are still based on the complete model, but the control decisions are approximate. In analogy with a simplified tomato model, normalization of the costate variable with respect to the sunlit leaf-area-index (LAI) was expected to yield a simple sub-optimal control policy. The normalization is of the form P = [p + kg] h, where P is the the normalized costate, p is the (proper) dry-matter production costate (effort to produce the marginal unit of dry matter), k is the price of tomato, g is the fraction of dry matter converted to fruit and h is the sunlit LAI. It is assumed that in vegetative stage g = 0 and in the reproductive stage k, g and h are constant. Computational experiments with a complex tomato model (TOMGRO) showed that the P is almost constant for a growing season. | |
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