Examenspresentation av Oscar Wallin och Andreas Andersson

Abstract:
Growing plants with hydroponics can reduce the use of water to 10\% of that of traditional farming. Hydroponics puts high demands on the pH and nutrient levels of the water. Therefore, a major challenge is the control of pH and nutrients, often measured as electrical conductivity (EC).

This master thesis goes through experiments that has resulted in a model of EC and pH, for a hydroponic farm, as well as a fuzzy-logic control system and PID control system for pH and EC.

The PID controller outperforms the fuzzy logic controller when used for pH control, in both speed and stability. For EC the PID controller was faster but less exact when compared to fuzzy logic control. Both a fuzzy control system and a PID control system could be suitable for hydroponics depending on the tuning. The tuning along with the capabilities of the pumps is the determining factor for how large or small the system can be. For a small system of 20 liters the system developed in this report works well and could also be used for larger systems, but with a slower response.