An automatic controller for a greenhouse using a supervisory expert system

The commercial production of crops and cut-flowers is a very labour intensive industry. In order to meet the high standards, the plants need to experience the least possible stress, i.e. requiring the environmental conditions to be as close as possible to an ideal one. To create an ideal environment, the main environmental parameters that need to be controlled are temperature, humidity, light intensity and carbon dioxide concentration. Because of the dead times and extreme interdependence of these four parameters, the control problem can be classified as nonlinear and multivariable. Two control techniques, PID-control and fuzzy logic control, are investigated in order to establish the applicability of each technique. In order to fully automate the control process, a supervisory expert system is implemented in conjunction with the controller, to serve as a user friendly interface with the operator.