Multivariable fuzzy control with its applications in multi-evaporator refrigeration systems

Abstract

Multi–evaporator refrigeration (MER) system is a cost–effective device for a building with different cooling requirements because it is comprised of a single compressor and a single condenser but multiple evaporators each operating at a specified temperature to simultaneously cater to different cooling loads such that the efficiency can be improved and the economic cost can be reduced. Compared with a single–evaporator refrigeration system, an MER system is more difficult to control due to its complex structure with cross–coupling effects among different evaporators. This thesis presents a series of novel Type–1 and Type–2 Takagi–Sugeno (T–S) fuzzy model based studies for multivariable process control to manipulate MER systems, including 1) loop pairing based on both Type-1 and Type-2 T-S fuzzy models to determine a control configuration for decentralized control; 2) Type-1 and Type-2 Effective T-S fuzzy model (ETSM) to describe the interactions among control-loops to facilitate decentralized controller designs; 3) sparse control structure selection and ETSM based sparse controller design to handle the interactions when the decentralized control may not provide satisfied performance. Finally, the proposed methods are applied on an experimental MER system to validate their practicality and effectiveness.