Dynamic Modeling, Optimal Control Design and Comparison between various control schemes of Home Refrigerator

Several conventional methods present in refrigerators today consider varying actuators between its minimum and maximum values (Single speed control) or at several values between minimum and maximum values (Discrete speed control). The work done here presents an organized control design method based on appropriate modeling techniques to co-ordinate control inputs in order to achieve improvement over the conventional control schemes. A moving boundary lumped parameter model has been developed to describe the dynamics of heat exchangers. Single speed and Discrete speed control strategies are simulated with this dynamic model. A low order model has been established of the entire system integrating the compressor and expansion valve model which is in good agreement and reflects major dynamic characteristics of vapor compression cycle. LQR control has been applied by appropriate objective function formulation followed by simulation and comparison with other control strategies.