Fuzzy controller decreases tomato cracking in greenhouses

Sunlight heats the greenhouse air temperature during the day and can encourage tomato cracking and decrease marketable product. A fuzzy controller was designed to control greenhouse climate to reduce tomato cracking using as variables solar radiation, substrate temperature and canopy temperature. A movable shade screen reduced incoming radiation during warm and sunny conditions; meanwhile irrigation was controlled according to canopy and substrate temperature. The shade screen was opened or closed with a gear motor driven by a photovoltaic system. The motor controlled by a pulse width modulated inverter started softly decreasing its starting current. The fuzzy system injected additional water and nutrients between 12:00 and 15:00 h; irrigation cycles were removed during very cloudy days. Tomato cracking decreased from 52% to 17% using the fuzzy controller and canopy temperature never exceeded 30 °C.

► The controller reduced tomato cracking.
► Radiation, substrate and canopy temperatures were the monitored variables.
► The fuzzy controller controls irrigation scheduling and shading.
► A solar panel supplied the energy for the system.
► Pulse width modulated applied reduced voltage for soft motor starting.