| China is a country with lack of irrigation water resources and serious fertilizer pollution,In order to maintain the sustainable development of agriculture,the study of the control and management technology of fertigation is more and more attention. With the rapid development of science and technology,more new technology is widely used in agricultural fertigation.Many researches about the control and management technology of agricultural fertigation were made at home and abroad. However, compared with advanced foreign technology, domestic research started relatively late and the technology is relatively backward.There is a big gap. Although foreign countries have more mature equipments, the crop-growth factor, climate environment, soil condition and so on are different from China, therefore, these foreign equipments are difficult to meet the actual needs of China.Moreover, the domestic reseach mainly limit in the laboratory, and the system construction is expensive. Thus, it is necessary to design a set of cheap and fine fertigation prepapration control system to meet the needs of society.A set of precise fertigation prepapration control system is designed by studying the system structure, control algorithm, software and hardware design and so on, to make up water and fertilizer solution which could meet the demand of crop growth by adjusting the concentration EC value and the acidity pH value of water and fertilizer solution, in order to improve crop yield and quality, save energy and protect environment.Firstly,the mathematical models of electric proportional regulation valve and sensors are established by analyzing the working principle of electric proportional regulation valve and sensors.Then composition structure of controlled system is combined to set up the mathematical model of controlled system.Secondly,based on the mathematical model of controlled system,the fuzzy PID controller of the precise fertigation prepapration control system is designed,and the simulation experiment is carried out.Then the simulation results of the fuzzy PID controller are compared with those of the traditional PID controller. The simulation results show that the fuzzy PID controller can make the controlled system for better performance than traditional PID controller.Finally,the hardware and software of the precise fertigation prepapration control system are designed. According to ’hardware-in-the-loop’, this control system mainly includes: a host computer as control processing center(including the Simulink model and the monitoring center),a MCU STM32F103 as data acquisition system, power supply module, sensor module and actuator. Among them,the power supply module mainly provides energy for the whole system, and it can meet the operating voltage of each part of the system through the DC/DC buck circuit. The CM-230 K conductivity sensor, pH electrode, flow sensor and BP801 pressure transmitter are used to acquisite the parameters of water and fertilizer solution. The MCU STM32F103 is used to process the data.Then the data is sent to the host computer for analysis and processing by the data transmission module. The collected data is transmitted to the Simulink model for analysis and calculation by the host computer. After the reasoning calculation of the fuzzy PID controller, the inference results are sent to the MCU through the data transmission module to control valve opening of the actuator, and then adjust the EC value or the pH value of water and fertilizer solution until makes up the target concentration or acidity of water and fertilizer solution. The monitoring center interface of the precise fertigation prepapration system, which is created programmatically by the Matlab/GUI graphical user interface, is used to display the collected data in real time to make data monitoring more clear at a glance.The experimental results show the precise fertigation prepapration control system can make up the target concentration or acidity of water and fertilizer solution, and the maximum error absolute value is less than 5%,meeting the requirements of actual control. And the system interface is user-friendly and easy operation, which can achieve real-time display of the various parameters of water and fertilizer solution and the working state of the actuator. It can meet the practical requirement of precise fertigation prepapration. |
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