| With the arrival of the 21st century, water resources crisis has become a global outstanding issue to which people pay more and more attention all over the world. Our country is one of 13 countries in world which are suffering from shortage of water, and has less than a quarter of the world's average per capita water capacity. While the water resource is faced with shortage, the waste of water is very serious in the department of agriculture which consumes the most of water in China. At present, the utilization rate of agricultural irrigation water is only about 40%, which is less than 1/2 of that in developed countries. Therefore the development of water-saving irrigation technology and improvement of the utilization rate of agricultural irrigation water is the only way to solve the problem of shortage of water resource in future as well as the basic requirement of modern agriculture. The premise of forming the formation of agriculture with efficient use of water must be the transformation of agricultural irrigation technology in china.Facility agriculture is an important component of modern agriculture. Development of greenhouse water-saving irrigation techniques has a great significance for improving the utilization rate of agricultural water. The technology of the greenhouse water-saving irrigation is still in its early stages, low automation level and short history. The overwhelming majority of domestic greenhouse equipments are relatively simple, and the greenhouse irrigation is still manually based on the experience of the traditional irrigation methods which has restricted the improvement of production and quality of greenhouse crops. The article aims at designing a set of control system which can automatically monitor the soil humidity of greenhouse crops growth, which could irrigate the crops timely with a proper quantity of water, and also play a role of highly efficient irrigation, water saving, and energy-saving.In this paper, we mainly research the drip irrigation control system of greenhouse based on virtual instrument technology, which consists of the relations of soil humidity and irrigation quantity and the irrigation control technology and each part of software and hardware of system equipment. The sensor technique, computer information technology, virtual instrument technology and database technology are organically combined by comparing the virtual instrument with the traditional instrument. The overall plan of system is that sensor's humidity signals were gathered and transmitted to PC Computer by the data acquisition card, then PC Computer is used as host computer to output control signals to irrigation actuator after calculation, treatment and fuzzy decision. The signal storage and demonstration are realized at the same time. In terms of hardware, equipment selection and performance indicators are described in detail, and the irrigation valve drive circuit is also designed. In the software aspect, the LabVIEW virtual instrument is used as the development platform and the modular design method is adopted in order to realize the detection signal real-time gain, the gathering information real time display, data processing, the control signal accurate output, sound warning and gathering signal data management function and so on. In terms of control algorithm, considering characteristic of the greenhouse environment system which consists of nonlinear, time-variant, time delay, the precise mathematic model was hardly to be established. The fuzzy control method is adopted to realize the control of the greenhouse irrigation system in the paper. The fuzzy control is a nonlinear control system, which has excellent robust stability and poor sensitive to the change of system parameters. The design of fuzzy controller and the formation of the fuzzy control list are realized by employing MATLAB software in this paper, and the fuzzy controller is simulated by applying Simulink software. Finally, the irrigation system can meet the requirements of design by the drip irrigation experiment... |
