| In recent years,the level of agricultural modernization in my country has been continuously improved.In the cultivation process,water waste and low fertilizer utilization use have been reduced but still persist.At present,the domestic production of light and simple water and fertilizer integrated equipment has automatic irrigation efficiency and the low precision of the ratio of water and fertilizer has restricted the development of my country’s agriculture to a large extent.Regarding the issue above,there is a great need to develop an integrated water and fertilizer control system that can perform better.This thesis is based on the STM32 microcontroller,an integrated water and fertilizer control system was developed,the control system is integrated into the microcontroller control technology,Interactive screen configuration technology and intelligent algorithm to an automatic and precise distribution of solutions realize irrigation.This system has taken STM32 MCU to achieve the information collection and equipment action control;F series serial port screen has been used to realize the information exchange function between human and equipment;The system has selected PSO-Fuzzy PID method to adjust the EC and pH of solution by regulating the open degree of the ball valve,therefore agricultural production needs have been met.The work and research results of this thesis are as follows:(1)The control process models of conductivity and pH of solution were built respectively.The results show that the control process of conductivity and pH of the mixed solution is nonlinear,delayed and time-varying,it can also be affected by uncertain factors such as irrigation flow and the concentration of mother liquor.(2)A simulation model was developed for the control of EC and pH,the control algorithms of PID,Fuzzy PID and PSO-Fuzzy PID were simulated.The results show that the PSO-Fuzzy PID control which can achieve fast accurate regulation has more advantages than the first two,which can meet the system’s requirements for the mixing precision of water and fertilizer solution.(3)Determined the hardware design and component of the control system.With STM32 MCU as the main controller,various information was collected,which includes the EC value,pH value of solution,the pipeline flow,pressure and other parameters were been collected,and realizes the manual/automatic of various pumps,electric ball valves and solenoid valves control;Based on the functional block design thinking,an software control program was developed,including system initialization,data acquisition and processing,output control.The user is able to control the system of the device and view real-time/historical data and curves through the touch screen.(4)Under different irrigation output flow rates,the control effects of Fuzzy PID and PSO-Fuzzy PID on the EC and pH of water and fertilizer solutions were verified.The results show that the PSO-Fuzzy PID control method has significantly reduced overshoot in the control process,harvested more ideal adjustment speed and root mean square error,which can better adapt to changes in system output flow,have better dynamic adjustment and maintain static stability,and better meet the needs of the system for precise fertilizer distribution.The water and fertilizer integrated control system can construct stable and reliable operation,easy to operate and can develop more functions,which is able to achieve the expected performance and accuracy requirements in the agricultural irrigation process and fertilization equipment and has a broad application prospect. |
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