The implementation of PI controller for evaporative cooling system in controlled environment greenhouse

This paper presents the development and a real-time implementation of controlled environment greenhouse by using a proportional plus integral (PI) controller based on the microcontroller STM32 and wireless sensor network by using MATLAB/Simulink program to control temperature and humidity. The modelling of the greenhouse is done by using a System Identification toolbox in MATLAB which is identified approximated to be a first order plus dead time system (FOPDT). The PI controller is designed based on Cohen-Coon tuning algorithm. The temperature and humidity sensors are connected with FiO Glide boards to send data to the micro-controller STM32F4 with radio frequencies to control temperature and humidity appropriately by using the PI algorithm and send signals for control the fan and fog sprayer. The size of greenhouse is 2×3×2 meters. The experimental results show that, the PI controller base on microcontroller STM32 can be controlled the inside temperature is lower than the outside temperature of 4 degrees Celsius. And the environment of greenhouse system has improved significantly.