Precise Control System Design And Experiments Of Water-fertilizer Integration Sprinkler Irrigation

The integrated water and fertilizer equipment and its precise control technology are effective means to improve the utilization rate of agricultural water and fertilizer.The combination of water and fertilizer integration equipment and sprinkler irrigation system is simple and flexible to ensure the uniformity of irrigation.In the domestic water and fertilizer integrated system,the related equipment has low fertilization accuracy,unstable automatic control,and low intelligence.This paper designs a PLC as the control center and combines the water and fertilizer demand information of different crops to integrate fertilizer,The integrated water and fertilizer equipment and its control system with multiple functions of fertilizer mixing,fertilizer injection and sprinkler irrigation.The main research contents are as follows:(1)Design the overall control scheme and intelligent algorithm model of the integrated water and fertilizer system.Based on crop water nutrition monitoring and irrigation and fertilization requirements,an overall control plan is proposed that integrates irrigation,fertilizer solution allocation,and water and fertilizer mixed spraying functions.Analyze the pipeline structure and the principle of concentration control,and study the change mechanism of the water and fertilizer mixing process from a theoretical perspective.In view of the multi-variable,nonlinear,hysteresis and other problems in the process of water and fertilizer mixing,the control model in this paper is determined,and the automatic irrigation algorithm,the proportional fertilization algorithm,the water and fertilizer concentration control algorithm and the fertilization time algorithm are designed.(2)The hardware and software design of the water and fertilizer integrated mixing equipment and its control system are carried out.Based on the hardware requirements of the control system,equipment selection was made.The variable addresses of the equipment are allocated,and the drive circuits of the power supply module,expansion module,drive module,TCP communication module,and RS485 module are designed.The peristaltic pump is used as the key equipment of sprinkler irrigation,water and fertilizer integrated fertilizer and fertilizer injection,and the output performance under different working modes has been experimentally studied.The results show that the output flow and voltage are linear in the fertilizer mixing mode;the voltage can be adjusted in the water and fertilizer mixing mode.The maximum adjustment range is 15 V,and the maximum output flow range is 0.18m3/h,which satisfies the quadratic polynomial relationship.The mathematical model at a pressure of 0.25 MPa has the highest degree of fit,which provides algorithm support for software development.The programming of the PLC controller and the construction of the interactive software for the touch screen are carried out on the software.The PLC adopts manual/automatic mode,and has designed automatic irrigation,fertilizer solution,water and fertilizer mixed spraying modules,as well as programs for initialization,automatic mixing,over-alarm and other auxiliary modules.It has completed the transplantation of Modbus communication protocol and the digital simulation of sensor signals.Conversion,establishment of touch screen TCP communication.A touch screen interface is designed for the monitoring of crop water nutrition and the adjustment of irrigation and fertilization parameters,which realizes the information and intelligence of the integrated water and fertilizer control system.(3)Taking the sprinkler irrigation water and fertilizer integrated system as the research object,the irrigation performance,fertilization performance and control effect were tested,and the change law of the system sprinkler irrigation uniformity and fertilization uniformity was obtained.The results show that: 1)The working pressure has a highly significant impact on the hydraulic performance of the system.As the pressure increases,the average point sprinkler irrigation intensity and range increase,and the water distribution is more uniform.When the pressure reaches0.25 MPa,the range of the nozzle is basically stable at 9.8 about m.2)When the pressure is 0.25～0.3MPa,the uniformity coefficient of combined sprinkler irrigation under different spacings are all above 75%,and when the pressure of 0.275 MPa and the combined spacing coefficient is 1.3,the maximum sprinkler irrigation uniformity coefficient is 86.99%.3)For water and fertilizer spraying in different concentration modes,the system can maintain a relatively stable fertilizer solution concentration output except for the 0.1% concentration mode,and the variation range is roughly controlled within ±0.02%.4)The uniformity coefficient of fertilization of the system under the same concentration mode.When the combined spacing coefficient is 1,the uniformity coefficient of fertilization is the largest,reaching 80%.When the fertilizer solution concentration is 0.2%,the uniformity coefficient of fertilization is the highest,and the variation difference is the smallest,which is 6.39%.In general,the designed water and fertilizer integrated sprinkler irrigation system has stable output of fertilizer solution and high accuracy of water and fertilizer concentration control.