| Water-saving irrigation is great importance to solve the imbalance between supply and demand of water resources, as underwater resources shortage appeared with continuous improvement and development of the living standard and the industry. Traditional flooding irrigation has been still employed in most dry farmlands of our country, however, its relatively low moisture utilization, backward irrigation way and equipment, low-level automation, reliance on import equipment and excessive cost are not fit for China’s situation. Therefore, we took the soybean drip irrigation as the research subject against the deficiency of present irrigation to develop the wireless monitoring system of soil moisture content, conducted the threshold control test for drip irrigation and consequently took the data collected as the sample to carry out a test to drip irrigation fuzzy controller by simulating. The content on study mainly includes:(1) Analyzed common water-saving irrigation control methods and irrigation ways at present. Determined the research program about the water-saving irrigation system according to actual demands from the experiment unit. The wireless monitoring system of soil moisture content consists of threes parts, the principal computer remote control center, the lower computer controller and sampling nodes. The site drip irrigation control employed threshold control method and experienced fuzzy control simulation test for drip irrigation.(2) Finished development to the wireless monitoring system of soil moisture content. The principal computer is mainly responsible for surveillance, memory and inquiry to data, and achieving the telecommunication between it and the lower computer controller via the GPRS200 wireless module. While the lower computer controller is mainly responsible for field environmental parameter collection and irrigation control. Sampling nodes are mainly responsible for the soil humidity collection and data transfer. The lower computer controller and sampling nodes through the XL4463 wireless module transfer data and follow the Modbus communication protocol.(3) Conducted a system field test, verified the accuracy of collected data and the irrigation effect of the threshold control. Compare and analyze collected data with the actual measurement, whose results indicated that: the soil humidity error for both is at-0.35%~0.21%, which illustrated a high accuracy of collected data. When we use the threshold method to control the irrigation, the soil moisture content raised from 22.12% to 28.24%(after irrigating from the number below lower limit value to that of reaching the ceiling limit), which exceeded the optimum humidity scope(24%-26%)for the growth of crop, then generated a large overshoot and finally could not provide suitable soil humidity environment for crop growth.(4) Designed the irrigation system for fuzzy controller according to the soybean branching period demands to water, and output the irrigation volume via fuzzy inference by taking the soil humidity error and its rate of change as the decision factor of fuzzy controller.Simulated in the Matlab software with the Simulink simulation and fuzzy logic toolbox, whose results showed that, when the soil humidity reached 22%, its error and rate of change are 3% and 2% respectively, and the output irrigation volume could make the soil moisture content reach 25.34% to satisfy demands of crop growth.Therefore, the system could efficiently regulate and control the soil humidity, satisfy the desired level of crop growth to soil moisture, which is of great importance to the yield and quality of soybean crop and could reach the goal of water-saving. |
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