ISHS Acta Horticulturae 719: International Symposium on Greenhouse Cooling
GREENHOUSE DIURNAL TEMPERATURE CONTROL WITH NATURAL VENTILATION BASED ON EMPIRICAL MODELS |
| Authors: | M. Berenguel, F. Rodriguez, J.L. Guzman, D. Lacasa, J. Pérez-Parra |
| Keywords: | temperature control, natural ventilation, empirical model |
| Abstract:
Natural ventilation is a mechanism that reduces the greenhouse air temperature. Its control is characterized by the following features: (a) the relationship of the temperature with the vent position, which is nonlinear; (b) the external weather strongly influences the effect of ventilation on the temperature, because the speed of the internal air renewal depends on the external air temperature (stack effect) and wind conditions (wind effect), and (c) the actuator (vent) has two nonlinear phenomena: saturation (between 0% and 100%) and output resolution (the vent implementation is performed using racks with gears, which permits a vent minimum movement of about 5%). This paper presents the development of a kind of feedback linearizing controller for a parral-type greenhouse diurnal temperature control. These controllers are mainly based on models and measured data and are discussed in terms of their suitability for disturbance cancellation and nonlinear control purposes. The schemes are based on a previously developed nonlinear empirical model of a typical Mediterranean greenhouse. Some results and conclusions are presented that show the main features of the controllers develped in order to account for the nonlinear characteristics of the system and disturbance cancellation. | |
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