Environmental Parameter Control Of Greenhouse

As one of the important way of the modern agriculture development, facility agriculture has become one of the most important research subjects of the world. And as to the complexity of the greenhouse system, we have some difficult problems to solve. Such as how to provide the most suitable environment for crop growth through setting the appropriate control objectives as well as make the maximum use of natural resources to reduce the energy losses.Through the comprehensive analysis, I summarized the roles of the four factors in crop growth within the greenhouse, including temperature, humidity, light intensity and CO₂ concentration. I take both the changing characteristics and the correlations of the four factors into account, and set the ideal control objectives. By using the principle of thermal equilibrium and material balance relations, and through the mechanism analysis of greenhouse model, the mathematical model of temperature and humidity is established. Thus the basis for the control strategy and control algorithm is built.The maximum crop yield is set as target. Through employing AHP we get the relationship of the three factors (temperature, humidity, light intensity) with crop yield and that of the three factors with the seven measures (covering or uncovering the hull, switching on or off the heating equipment and spraying equipment etc) respectively. Thus we obtain the relationship of the seven measures with the crop yield. This helps maximize the use of natural resources for the ideal environment of crop growth and reduce the energy losses to a certain extent.Aiming at the high-precision mechanism model of the greenhouse and the problem of the nonlinear strong coupling between temperature and humidity, this paper employs the method of accurate linearization in the nonlinear system. The exact linearization of the system is realized through state feedback,and then realizes the gradual tracking of the ideal output of this system. It is proved by the simulation of MATLAB software that the controller designed has favorable performance, and is able to track and adjust the objective curves of temperature and humidity. Finally, the results and conclusions are summarized, and the forward works are presented.