农业工程学报2016，Vol.32Issue(8)：27-32,6.DOI:10.11975/j.issn.1002-6819.2016.08.004
温室水肥一体化营养液调控装备设计与试验
Design and test of regulation and control equipment for nutrient solution of water and fertilizer integration in greenhouse
摘要
Abstract
Excessive amounts of fertilizers and irrigation water are used in agriculture, which will lead to some negative effects. Not only the resource utilization rate is reduced, but also the liquid nitrate content exceeds because of drainage, and the underground water source is polluted finally. Integration technology of water and fertilizers can improve the resource utilization, while the pollution of the surrounding natural environment can be also reduced. Automatic control and regulation of irrigation water and fertilizers integration have been implemented in the greenhouse production in Europe and North America, the resulting result is reasonable fertilizers and water application, and the control accuracy is higher. However, excessive irrigation and use of fertilizers still exist in China’s greenhouse production. The result of this production mode is that the proportion of nutrient inputs is unreasonable and the nutrient is in serious loss due to excessive irrigation. It is necessary to conduct the thorough research on the integration technology of water and fertilizers to develop the regulation technology and equipment of water and fertilizers integration suitable for Chinese actual situation and with low cost. Preparation of nutrient solution is a process that fully mixes fertilizers and water and makes the nutrient solution reach the preseted value. There are 2 different modes in the mixed tank, including advection and ideal mixing, where all kinds of liquids are mixed, and the actual system can be considered as the combination of these 2 modes. Moreover, considering the time delay caused by the flow of liquid in the pipers, the process of the preparation of the nutrient solution can be simulated by using a first-order lag transfer function model. However, in order to achieve higher control accuracy the mixing tank should have sufficient space. Such nutrient solution’s electric conductivity (EC) value will not change dramatically when injected into the liquid fertilizers, and therefore, the mixing tank should have a larger space. But it will bring a lot of other problems, for example, EC values’ adjustment speed and flexibility will become worse. To resolve this conflict, a Venturi device is added to the mixing tank in this paper, so a virtual volume is added to the mixing tank, and the whole nutrient solution preparation system is converted to a second-order lag system. According to the theoretical analysis of the nutrient solution preparation system, a regulation and control equipment of water and fertilizers integration nutrient solution is designed in this paper. Besides the nutrient solution preparation function, the equipment also has irrigation control and environmental control functions, and the system structure is composed of computer, master control module, wireless transmission module, EC and pH measurement module and driver control module. The wireless transmission module includes 433 MHz wireless transmission, third generation (3G) wireless transmission and short message service (SMS) alarm; the drive control module is divided into nutrient solution ratio drive, environmental control drive and irrigation control drive; and EC and pH value of the nutrient solution are detected by the EC and pH measurement module. The control of nutrient solution is implemented in the following ways: first, the EC and pH values of the nutrient solution in mixing tank are detected online in realtime, and then the detection results are sent to the master control module through the RS-485 bus. The different value between computer’s set value and current detection value is calculated by the master control module, and the nutrient solution ratio drive module is controlled by master control module according to the calculated results, so the injection ratios of fertilizer mother liquid are controlled by solenoid opening and closing. The nutrient solution adjustment process is executed finally. The regulation algorithm of nutrient solution is realized by the incremental PID (proportion, integration, differentiation) algorithm and a gain adaptive Smith predictor. The experimental results show that the system enters a stable stage in about 30 s and is infinitely close to the set value of the 2.0 mS/cm EC. This shows that the nutrient solution regulation equipment is not only faster, but also more accurate for the system response.关键词
温室/灌溉/水/肥/水肥一体化/营养液/调控/装备Key words
greenhouses/irrigation/water/fertilizers/the integration of water and fertilizers/nutrient solution/regulation/equipment分类
农业科技引用本文复制引用
袁洪波,李莉,王俊衡,王海华,N.A. Sigrimis..温室水肥一体化营养液调控装备设计与试验[J].农业工程学报,2016,32(8):27-32,6.基金项目
国家自然科学基金（青年）项目（31301240）；河北省高等学校科学研究计划青年基金项目（QN20131083）；河北省自然科学基金项目（C2014204025）；保定市科学研究与发展计划项目 （）
