Research On Greenhouse Automatic Control System Based On PIC16F877A

Greenhouse is an important part of installation agriculture. Crop production in domestic and overseas greenhouses shows that advancing the ability of automatic control and management for greenhouse will improve the efficiency of agriculture production. With the rapid development of sensor, computer and communications technologies, the design of intelligent monitoring and controlling system for greenhouse environment has attracted people's attention increasingly. It has become a research tendency with important significance. Therefore, the greenhouse automatic control system based on PIC is designed, which can control the greenhouse environment to create suitable growing condition for plants. Then it can make the crops obtain high yield to improve the economic benefits of the agriculture production.A general description about development on greenhouse environmental control technology at home and abroad is given and the greenhouse internal mechanism is analyzed in this dissertation. The temperature and humidity models of greenhouse being adopted are also given and the approximate mathematical model of greenhouse temperature control system is obtained based on analysis of the history environmental data in the greenhouse.As for the control of temperature and humidity, fuzzy control algorithm is applied. The fuzzy control theory is studied in detail and the table about fuzzy control rule of several kinds of executive mechanisms is established. The method of T-S model is used in fuzzy reasoning, the control rule established by this method is easy to adjust and its engineering significance is clear. The fuzzy algorithm of temperature control system is simulated in MATLAB. The simulation result indicates that the fuzzy control algorithm has advantage in decreasing overshoot, strengthening stability and improving the compatibility. The anticipated control effect can be achieved by this way. So it is a deal control method. Hardware of the automatic control system is composed of PC and single-chip computer PIC16F877A and periphery circuit. The unified management of the greenhouse is realized by PC called epigyny computer through the communication with the hypogyny computer. PIC16F877A and periphery circuit realize the function of measuring, display and real time control of the greenhouse environment parameters. The controller which takes PIC16F877A as the core, can realize the parameter monitoring independently in the situation without PC.As for the software design aspect, the fuzzy control algorithm is introduced and its corresponding procedure flow chart is designed, such as master routine flow chart, fuzzy algorithm flow chart, communication procedure flow chart. The communication between the epigyny computer and the hypogyny computer is accomplished by using the ActiveX control named MSComm. In addition, The man-machine interface is designed by VB6.0 which makes the procedure simple and clear, providing a friendly direct-viewing management platform for the user. The entire system whose software and hardware collocation is reasonable, has convenient design, development, maintenance and a high performance-to-price ratio.