| In the process of research on the development of modern facility agriculture in China,solar greenhouse has become a new type of greenhouse structure in China.It has been developing vigorously in the north and has become the main body of modern agriculture in China.Ventilation system is the main measure of cooling and dehumidification in solar greenhouse.It can not only adjust the temperature and humidity of solar greenhouse,but also increase the concentration of carbon dioxide.It is helpful to photosynthesis of green plants and increase the output of crops.In addition,it can also prevent high temperature in the greenhouse and reduce the possibility of diseases and insect pests.At present,the development of greenhouse ventilation mechanization in China is uneven.Generally speaking,the low mechanization and automation of greenhouse ventilation will lead to unreasonable ventilation time.It is not conducive to the growth of greenhouse crops and will reduce the yield of crops.This paper focuses on the design and development of a ventilation control system suitable for solar greenhouses,which can be used to improve greenhouse ventilation efficiency and increase crop yields.The characteristics of solar greenhouse lead to closed or semi closed greenhouse environment,its internal environment is complex.There are various types of environmental impact factors,including illumination,carbon dioxide,and so on.In addition,the coupling between factors is large,and the impact of taking control measures on the greenhouse is not immediately effective,but has a time delay.Based on the research of solar greenhouse ventilation,this paper proposes to use fuzzy PID control algorithm to control greenhouse ventilation to automate greenhouse ventilation.Its main research work and innovations are as follows:(1)This paper analyzes the research and progress of greenhouse ventilation control at home and abroad,and summarizes the shortcomings.And briefly summarize the characteristics of conventional PID control algorithm and fuzzy control algorithm.On the basis of analyzing the basic principles of the two control algorithms and the actual use cases,a fuzzy controller is designed by combining the fuzzy control and PID control technology.And simulate it with MATLAB software.(2)The overall scheme of ventilation control system construction in solar greenhouse was determined.The system mainly includes two parts:mechanical structure design and algorithm theory research.Algorithm theory research part includes traditional PID control algorithm and fuzzy control algorithm research;The mechanical structure design mainly includes the design of the execution system and the design of the control system.(3)The master-slave-node structure is used to control the greenhouse ventilation.Input a given temperature parameter through the host computer,use the sensor to monitor the temperature in the greenhouse,and use the flat-pull mechanical structure to adjust the size of the greenhouse ventilation,so as to control the temperature inside the greenhouse.(4)In the aspect of fuzzy PID control algorithm,the input and output fuzzy sets of greenhouse are defined.The input of the system is set as temperature error e and error change rate ec,and the output is the size of the greenhouse vent.And define membership function and input and output language threshold,establish fuzzy control management rule table,carry out fuzzy reasoning and defuzzification,calculate the current K_p,K_i,K_d,and output through PID controller.This project has been successfully debugged and operated in the solar greenhouse.According to the analysis of experimental research results,the ventilation system of the solar greenhouse using fuzzy PID algorithm can adjust the temperature within the set value range,so as to ensure the normal growth of crops at the appropriate temperature.The size of the ventilation holes also can be adjusted according to the temperature difference between the inside and outside of the greenhouse to improve the efficiency of greenhouse ventilation. |
PDF Full Text Request