MODERNIZATION OF THE MODEL OF SHIP REFRIGERATION UNITS USING FUZZY LOGIC FOR TEMPERATURE CONTROL

The paper considers modernization of digital temperature regulators of ship refrigerating units. The comparative analysis of the existing temperature regulators has been carried out, their advantages and disadvantages being determined. The author proposed to use fuzzy logic principles to determine the temperature mode of the refrigeration system and to control the operation of variable-output compressors. There has been developed a temperature control unit based on fuzzy logic in MATLAB/Simulink environment. The control unit processes input signals that are the temperature mismatch value and the temperature mismatch differential. Using a set of logic rules, the control unit generates a control signal and sends it to a variable performance compressor. By means of the model of the refrigeration unit presented in the Simulink mathematical modeling environment operation of the plant is compared in two modes: using temperature control on fuzzy logic and using the relay temperature control. The fuzzy logic controller has been stated to be more efficient due to its higher sensitivity to temperature changes, a logical forecast of the temperature change, and little difference between the required and real temperature of the unit. In terms of fuzzy logic, regulation process is smooth, with a little delay. The simulation results showed significant differences between the temperature logics used to control temperature of a ship refrigerating unit, advantages of fuzzy logic over relay logic.