Research On Control System Of Drip Irrigation In Greenhouse Based On Transpiration Rate

With the shortage of water resources, the efficiency methods to solve the contradiction between supply and demand of water resources in our country are to development the Irrigation technology of saving water, increase of efficiency of the usage of the water irrigation, as well as the operating management method which are benefit to the environment. In order to get these demand, there are many factors are involved in, such as the drip irrigation combined with advanced Irrigation control technology, the physiological characteristics of the plant ,the climatic conditions and the soil behavior. So that, the irrigation scheduling which is fit to the plant can be set up.From the meteorological factor and the soil moisture, the crop variation law of the transpiration rate and the relationships with each other is studied in this paper. The method base on transpiration rate and size to determine the crop water is put forward. The P-M equation's reliable is validated which is to simulate the transpiration rate when soil moisture between 50% and 70%.The three-level control system is designed base on fuzzy control algorithm. The first-level control system is used to calculate the transpiration rate and the change rate of it, the result of the first-level control system is used to the input to the second-level control system to get the lower limit of the soil moisture. The third-level control system to get the time of the irrigation which will last for. The lower limit of the soil moisture is dynamic alteration towards the transpiration rate, this result can used to forecast the water need rate of the crops.The control system's software design is completed in this paper many functions such as collection, monitor, decision, data storage and so on. The control system is based on CAN bus communication technology, and making the industrial control computer as it's center, the system realized data acquisition and control command output is through the CAN bus, which can efficiently reduce the disturbance and improve the system'stabilities. Now, the control system has been well in used to nearly half a year, compared to the general conditions control, the rate of flowers water is reduced significantly and water is saved about 10%. It shows that the system's design is rational and reliable, and the design meets the requirements of system which are anticipated.