1 Introduction
In China, most of the greenhouse equipments are switch devices, with only on and off states. However, the environment factors are observable but uncontrollable continuous variables. As the difference from the conventional continuous system or discrete system, it is hard to research the system by classical or modern control theory. Furthermore, due to the different skill levels of people who are engaged in the agricultural production and the goal of optimal yield and quality, it is necessary to introduce a new theory to give guidance to the greenhouse development.