Research Of Greenhouse Control System Based On Wireless Sensor Networks

Greenhouse is an important component of the agricultural facilities, and it is one of the priorities of modern agricultural development. It can change natural conditions for crop growth, create a suitable environment, shorten the crop cycle, and increase economic benefits. Temperature and humidity are the most important environmental factors in the greenhouse, they are strong coupling nonlinear, and increasing the difficulty of control. To solve this control problem, an intelligent greenhouse control system based on WSN and fuzzy PID is designed in the thesis.Greenhouse climate modeling is the key to achieving greenhouse control. First, the main thermodynamic process of the greenhouse environment is analyzed a general mechanism and greenhouse model is established. According to the model, collection nodes are laid. The values of temperature and humidity are calculated by the collecting information in order to get a suitable range of environmental factors of crop growth. For optimizing greenhouse control a structure of the greenhouse control system has been designed and hardware has been selected.Second, according to analysis of coupling relationship of temperature and humidity, controller of temperature and humidity based on fuzzy PID are designed. The controller are respectively designed according to whether the coupling of temperature and humidity or not. Without taking into account coupling between temperature and humidity, the controller design principle is changing the order of the implementing agencies based on the change speed of temperature and humidity. The pseudo decoupling controller of the temperature and humidity is designed according to the impact of humidity change on temperature change; the heat generated by the humidity change will be feedback to the temperature controller, so that the temperature can be compensated. At the same time fuzzy controller and PID controller are combined, through the threshold switching, to promote the accuracy and flexibility of the controller while a PID control or a fuzzy control is adopted only. Then, MATLAB software is used, and the controller in both cases are tested. Test results show that the decoupling controller of the temperature and humidity have better response curves, it is able to achieve the desired control effect.Finally, the results and conclusions are summarized, and the forward works are presented.