DEVELOPMENT OF A pH CONTROL SYSTEM FOR NUTRIENT SOLUTION IN EBB AND FLOW HYDROPONIC CULTURE BASED ON FUZZY LOGIC

摘要

This paper outlines the development of a fuzzy-based control system for maintaining a proper acidity (pH) level of nutrient solution in ebb and flow hydroponic cultures. The nutrient solution pH is kept at a desired set point by controlling two valves: (1) acid valve (to control the addition of acid solution necessary) and (2) base valve (to control the addition of base solution necessary). The control algorithm has been developed based on membership functions of fuzzy set. In order to get smoothness, the fuzzy rules have twenty-one linguistic statement which are determined by methods of trials and errors using the membership functions based on the skilled operator's experienceApplying the fuzzy logic to control the pH of the nutrient solution increased the smoothness of the pH the during control course. Performance of the control system is discussed and recommendations are provided for future work.