Modeling and control for greenhouse temperature system based on hybrid automata

Most of the greenhouse climate control equipments in China are on-off control. The control variables are discrete while the disturbance inputs (the outside air temperature, relative humidity and solar radiation, etc.) are continuous, so the microclimate system in greenhouses is a typical hybrid system. The outside air temperature and relative humidity are used as the disturbance inputs and the inside air temperature is used as the output of the system. The actions of ventilation window are used as driving variables. In this way the hybrid automata model for greenhouse temperature system is built. Every mode of the hybrid automata model for temperature system is described with Auto-Regression Moving Average model with external input (ARMAX). The model structure is selected by model fitness analysis, and gradually oblivious recursive extended least squares (RELS) method is adopted to identify every submodel parameters. The model of hybrid system is derived using the input data, output data and the on-off state of the control equipments. Then, the simulation control test is carried out by using zone control method. Realtime data modeling and simulation control results show that the method can simulate the energy balance and control the device switch state inside the greenhouse. The algorithm is an effective measure to control the temperature system without hardware transformation.