MIMO Robust Disturbance Feedback Control for Refrigeration Systems Via an LMI Approach

Abstract This paper proposes Multi Input and Multi Output (MIMO) robust Disturbance Feedback Control (DFC) design using Linear Matrix Inequalities (LMIs). DFC can be added to existing controllers as an additional control loop, to attenuate disturbances and model uncertainties. The extended state space representation of the overall system is considered with parametric model uncertainties. LMIs are formulated to solve the optimization problem such that the DFC satisfies Lyapunov stability and robust performance. DFC was applied in the superheat control and the suction pressure control for a refrigeration system, and experimental results shows that DFC improves disturbance rejection compared to conventional PI controllers.