Environmental control for plants using intelligent control systems

Abstract

Greenhouses provide a protected environment in which crops can be grown under a tightly controlled climate. The efficiency of plant production in greenhouses depends significantly on the adjustment of optimal climate growth conditions to achieve high production at low expense, good quality and low environment load. To achieve these goals several components, temperature and air humidity, must be optimally contro, lled through heating, ventilation, humidification and/or dehumidification. This paper focuses on the control of greenhouse air temperature and humidity ratio by means of simultaneous ventilation and humidification. The control process is divided into two distinct control loops, one maintaining the temperature by adjusting the ventilation rate, and the other maintaining the humidity ratio by adjusting the water capacity of the fog system. Several types of conventional control structures are employed to control the greenhouse environments, however, their parameters should be tuned if the operating conditions are changed. Fuzzy logic controllers are more flexible compared with these conventional controllers. This paper introduces Fuzzy Pseudo-Derivative Feedback (FPDF) controller that results from the fertelization of the PDF controller with fuzzy set theory. The parameters of the classical PDF and the FPDF controllers were optimized using a genetic algorithm (GA). Best results were achieved using the proposed controllers compared with the conventional PDF controller