Application of intelligent control based on fuzzy logic to the optimal control for accelerating calcium ion uptake of tomato plants in hydroponics

点击翻译按钮获取中文摘要

There are many physiological disorders, e.g.blossom-end rot of fruits, caused by calcium deficiency in a hydroponic tomato cultivation. In order to obtain better quality of fruits in a tomato cultivation, effective control of the hydroponic system is neccessay. However, the control system is characterized by complexity and fuzziness. In this study, intelligent control techniques based on fuzzy logic, neural networks and genetic algorithm are developed and then applied to the optimal control of hydroponic tomato cultivation.(1) In the tomato cultivation, marked calcium ion uptake was observed during the reproductive growth. So, the calcium deficiency in tomato fruits seems to be caused by rather low calcium ion transportaion to the fruits than low calcium ion uptake.(2) A newly developed adaptive control technique combining with the feedback control based on fuzzy logic and the feedforward control based on neural networks was effective for the time-varying control problem of the hydroponic nutrient solution. Applying the fuzzy logic increased flexibility and smoothness of the control performance. Furthermore, applying the inverse system model based on neural networks, more speedy and adaptive control performances were obtained.(3) A newly developed optimal control technique combining with neural networks and genetic algorithms was useful for optimization of net photosynthetic rate of a plant. In the method, the net photosynthetic rate to intermittent solution supply is at first identified by using neural networks and then optimal values of 4-step drainage and supply times for intermittent solution supply are determined through the model simulation by using genetic algorithms. The use of neural networks made it possible to identify such complex systems as net photosynthetic rate. Furthermore, the genetic algorithms enable us to quickly search the optimal values.