Comparison study of PID controller tuning for greenhouse climate with feedback-feedforward linearization and decoupling

The interest in ensuring optimal growth climate conditions is sustained by the increasing demand in greenhouse products, which in turn, leads to an increasing demand of high efficiency greenhouse control systems. The greenhouse climate control is complex due to the high nonlinear interaction between the biological subsystem and the physical subsystem, and due to strong coupling of the two main controlled variables: temperature and humidity. In this context, the paper presents an equivalent greenhouse climate model based on feedback-feedforward compensation technique responsible for linearization, decoupling and disturbance compensation of the greenhouse complex model. Based on this equivalent model reduced to integral plus dead time decoupled processes, a comparison study of associated PI/PID controllers employing different tuning techniques is performed by simulation.