كنترل كامپيوتري شرايط محيطي گلخانه : قسمت دوم - آزمون و بررسي عملكرد سيستم

A Computer-Based Control System for Greenhouse Environment: Part it - Results and System Validation

Recently, a computer-based control and monitoring system for greenhouse environment was designed. In this paper details about the design and implementation of the monitoring part of the system is provided, first. A graphical user interfiacc (Gtl) was designed using Visual Basic, The GUI was developed to carry out the monitoring tasks. The software implements the control algorithms, compares the received data with set points and sends out control signals to the microcontroller in order to change the states of actuators, i.e., heater, fan, etc., to reach the desired conditions. Flow chart and snap shot of the software are given. A series of experiments were carried out in Fall 2003 in order to validate the system. Performance of the system, controller as well as the GUI, was evaluated by installing the system in a model greenhouse. Two sets of experiments were carried out. For the uncontrolled experiment, it was found that the outside temperature was always less than the inside one. For the second set of experiments the controller was put in operation. It was found that contrary to the previous case. the rate of temperature change at lower part ofʹ greenhouse was greater than the rate of temperature change near the ceiling. This is partly due to the use of re-circulating fan with an attached perforated polyethylene tube in guiding the air toward the plant root zone. The time constant of mist and fog system was rather long, about 30 min, in reaching to the desired humidity.