Modeling, Optimal Control Design and Testbench Development of Home Refrigerator

Abstract

In this work, a nonlinear model of Home Refrigerator has been formulated. A two region lumped model of evaporator and condenser considering the time varying boundary has been formulated. The assumptions for the same are stated. The compressor and expansion device model are also furnished. The nonlinear model is simulated with Single speed control and Discrete speed control using MatLAB. The non-linear model has been linearized around the steady state operating point obtained by simulating the non-linear model by discrete control algorithm. The linear model is used for Optimal control design. A performance function formulated as a part of the LQR design takes into consideration the minimization of error and control input. Considering discrete control as the baseline, the results show an improvement in overall energy reduction of 2 watts. An automated testbench using LabVIEW environment has been developed consisting of Data Acquisition system using Agilent DAQ device and NI hardware. The discrete control algorithm has been integrated in the testbench. A unique state machine based compressor control strategy developed in order to prevent frequent startup and shutdown of compressor has been included as a part of testbench.