Seedling Nutrient Solution Ph Control System

Floating seedling technology is a large-scale, industrialized methods and new nursery, which has been widely used in many plants nursery such as flue-cured tobacco, vegetables and flowers. Process of the breeding, pH of nutritional fluid in an optimyuum range is used of the development of roots and absorption of most of the mineral nutrient. Therefore, pH control is significant has a direct impact on the quality of seedlings.Nowdays, pH control in our country is very lag which is controlled by manpower. So the limitation is low efficiency, lack of guarantee and offline calibration. Therefore, this paper developed a control system for pH of the nutritional fluid which play a positive role in energy conservation, improvement the management level and the quality of the seedlling.This thesis attempts to using advanced control algorithms to solve the eaupractical problem. According to the existing seedling industry in c rural area, designs a simple and effective neutralization equipment to make the neutralization reaction quickly and evenly.Based on reading, analysis and research domestic and foreign literaturesat about pH control,this paper advances a new method of pH control-Fuzzy-Smith predictive control which is specific to the hysteresis, nonlinear and time-varying parameters. Fuzzy control is fit for the object without mathematical model. And the predictive control is fit for the object with hysteresis. So the Fuzzy-Smith predictive control combined the advantages of Fuzzy control and predictive control. Simulation results show that the Fuzzy-Smith predictive control system for pH control in floating seedling has good control effects, which is an ideal intelligent control method.Based on the analysis of the requirements of pH control system,this paper developed pH controller with the mi croprocessor-LPC2132 which is the key part of the controller. It can accomplishes data acquisition,transmission,display and online modification. Meanwhile, it can setup parameter according as different crops. The monitor computer can display the field data. And manage the storage of historical records and the monitor of the whole system.The result shows that the design of the system which has advantages such as reasonable structure, low cost and strong practicability, satisfies the requirement of the automatic control for pH control in nutritional fluid.