Tracking time-discrete quasi-sliding mode variable structure controller for temperature and humidity of greenhouse

The greenhouse climate control was to meet the requirements of the cultivation of various plants at different stages. Based on the greenhouse climate model, the tracking control defined by the two variables of temperature and humidity was discussed. A mathematical model was built for representing the mechanism of the greenhouse environment according to mass and energy balance. Because the relationship of the two variables of the internal climate system was nonlinear and it was strongly coupling and sensitive to the external environment, it was proposed to design a high performance temperature and humidity tracking variable structure controller based on the quasi-sliding mode equivalent control with provision for equivalent control. To solve the nonlinear problem of the greenhouse control system, Taylor expansion was used to linearize the nonlinear system model at reasonable operating points. Simulation results indicated that the controller had the favorable performance and the capability of tracking the target value of temperature and humidity. The stability and robustness of the tracking control system were discussed and verified in the paper.