Online Measurement And Control System Of Multiple Channel Nutrient Solution

Since the 20 th century, with the increasing of population, declining of arable land, worsening of environmental pollution, more and more serious of food safety, 18 billion of arable land red line worrying, a shrinking labor force in rural areas, making the non-soil cultivation with high nutrient composition, space occupancy and less utilization has been more attention.Soilless culture nutrient solution include nutrient solution cultivation, rock cultivation and so on. Among them, nutrient solution cultivation is an important method for controlling plant growth according to nutrient liquid composition and content. Nutrient solution for the growth and development of plants provides all the necessary nutrients, the concentration of nutrient solution and quantity provided critical protection for healthy plant growth. Therefore, design a system of accurating detection and allocating of nutrient solution which has become key problems in the nutrient solution cultivation technology.Main research contents and results:(1) The online detection system of nutrient solution was constructed. The concentration of various ions in the nutrient solution was detected by different ion-selective electrodes, and the change between ion concentration detected and the results of ion measurement were analyzed. The results showed that the detected ion concentration can reach 95.5%.(2)The nutrient liquid inhalation measurement system was constructed. The amount of liquid is closely related to the opening time of the solenoid value. Through the relationship between the inhalation flow of the nutrient solution and the proportion of the solenoid valve opening time, the variation trend of the intake flow and the difference of the flow between the channels were analyzed. The results showed that the extremely significant linear relationship.(3)Through analyzing the characters of PID control and fuzzy control, control scheme of controlling nutrient solution was obtained. The fuzzy rule table is formulated, and the fuzzy PID control of the p H value of the nutrient solution is realized.The system was designed by modular. The main achievement of the online testing for each ion concentration in the nutrient solution and the control functions. The module of ion concentration detection, using multiple component on line detection to detect the ion concentration. According to the detected data to receive a comprehensive analysis of each element, understanding the situation of each element in plant growth during absorption, also to avoid the traditional single inaccuracy only according to EC measured values(total salinity) to determine the absorption of nutrients. In the modular of the amount of nutrient solution, by analyzing each ion in plant growth during absorption, multiple channel online fuzzy control was used. According to the data of each ion concentration detected by the analysis, using fuzzy control theory, drawing on the expertise to determine whether to add the nutrient solution.