Simplified architecture of a type-2 fuzzy controller using four embedded type-1 fuzzy controllers and its application to a greenhouse climate control system

Uncertainty is an inherent part of control systems used in real-world applications. The use of new methods for handling incomplete information and to cope with large amounts of uncertainties is of fundamental importance. The traditional type-1 fuzzy sets (T1FSs) used in conventional fuzzy logic systems (FLSs) cannot fully handle the uncertainties present in control systems. The type-2 FSs (T2FSs) used in T2FLSs can handle such uncertainties in a better way because they provide more parameters and more degrees of freedom. In spite of the features of the T2FS, it has not received the attention it deserves because of its implementation complexity. In this paper, a simple architecture of the T2FLS using four embedded T1FLSs is introduced. The performance of the proposed T2FLS is assessed by applying it to a multi-input multi-output (MIMO) greenhouse climate control system. Simulation results showed that the simplified architecture is able to cope with the complexity of the plant and has the ability to handle measurement and modelling uncertainties. The performance of the proposed T2FLS is comparable with the computationally costly T2FLS and outperforms its traditional T1FLS counterpart.