Greenhouse multi-variables control by using feedback linearization decoupling method

Greenhouse system is a MIMO(multi-input, multi output), non-linear, strong coupling system. Nowadays, most of the greenhouse control methods using PID control cannot relieve the coupling between variables, so the effects of these controls are not ideal. Aiming at these problems, a feedback linearization decoupling method is designed for the coupling between CO2 concentration, temperature and humidity, which are main factors in greenhouse environment control. Firstly, the model of greenhouse system is converted into an affine nonlinear model, and the original system is precisely linearized by coordinate transformation and nonlinear state feedback, so that the coupling relationship between CO2 concentration, temperature and humidity is relieved. Then, the PID controller is designed for the decoupled system in order to make sure the state variables of the system track the set values effectively. Finally, the simulation results show that the feedback linearization decoupling method proposed can relieve the coupling relationship between CO2 concentration, temperature and humidity, and the decoupled system based on PID controller can track the set values effectively.