The two-door direct-cooling refrigerator currently on the market includes a freezing compartment and a refrigerating compartment. The freezing compartment is usually used for freezing at a temperature of -6 to -18 ° C; the refrigerating compartment is used for storing food at a relatively high temperature in a relatively freezer compartment. It is required to have a certain preservation effect, and it is not allowed to freeze the food. The room temperature is generally 0 to 10 °C. The traditional refrigerator temperature is generally controlled by the refrigerating chamber. The different temperatures of the refrigerating chamber and the freezing chamber are realized by adjusting the size of the evaporator in the two chambers. The temperature adjustment is completely controlled by the opening and closing of the compressor. However, the temperature in the refrigerator is affected by many factors, such as the initial temperature of the refrigerator, the heat dissipation characteristics of the storage and the heat capacity, the filling rate of the refrigerator in the refrigerator, the temperature of the environment, and the frequency of opening the door. Therefore, it is difficult to establish a standard mathematical model for the temperature control of such controlled parameters and random factors, and it is impossible to implement with conventional PID adjustment. A high-quality refrigerator should have high temperature control accuracy and optimal energy-saving effect, and the use of fuzzy control technology to achieve this design is undoubtedly the best choice. 2 Refrigerator refrigeration system improvement In order to improve the temperature control accuracy and energy saving effect of the refrigerator, we have improved the traditional refrigerator refrigeration system, designed a fuzzy controller, and realized dual temperature dual control, automatic frost, fault alarm, temperature display and other functions. At the same time, the optimal distribution of the cooling capacity can be determined according to different usage conditions, the cooling performance of the direct cooling refrigerator is greatly improved, and the energy saving effect is obtained. The flow chart of the improved refrigerator refrigeration system is shown in Figure 1. As shown, a bistable solenoid valve 1 is connected in parallel with the evaporator of the original refrigerator compartment of the refrigerator, and a bistable solenoid valve 2 is directly connected to the evaporator of the original freezer compartment. The working principle is as follows: firstly, according to the refrigerator compartment And the temperature of the freezer and the temperature setting determine whether to open the compressor. When the temperature of the refrigerating compartment and its rate of change are higher than a certain value, the compressor starts to operate. At this time, the valve 1 and the valve 2 are closed, and the refrigerant is condensed by the condenser, and the capillary is throttled and depressurized, and then evaporated and cooled in the evaporator; When the temperature of the refrigerator compartment meets the requirements, the valve 1 is opened. The resistance generated by the expansion of the refrigerant as it evaporates in the evaporator of the refrigerating compartment causes the refrigerant to start to flow, and enters the freezing compartment through the valve 1 to rapidly lower the temperature of the freezing compartment; once the temperature of the freezing compartment reaches the requirement, the compressor is stopped. Valve 1 is closed; when valve 1 is opened, the refrigerant may be incompletely vaporized in the freezer evaporator, and some liquid remains. The function of the liquid storage tank is to recover the remaining liquid so as not to flow directly back to the compressor. Liquid blow. The function of the valve 2 is to automate the frost, and the valve 2 is normally closed. When the frost thickness detecting circuit detects the defrosting, the valve 2 is opened, and the high-temperature and high-pressure gas flowing out of the compressor directly enters the freezer evaporator to make the surface frost rapidly. Dissolve; after a period of defrosting, valve 2 is closed and the refrigerator resumes normal operation. 3 refrigerator fuzzy control system structure The structure of the fuzzy control system of the refrigerator is mainly composed of a single chip, a power supply, a detection circuit, a keyboard, a display circuit, an alarm circuit and the like. The system MCU uses the high-performance M C6805R6 produced by MOT OROLA as the central processing unit. The chip has built-in A/D conversion and has 8 analog input ports, which provides a powerful guarantee for the operation and signal detection of the fuzzy control program. . The input part of the system is mainly used to input the internal and external state of the refrigerator, the power state, the door opening state and the temperature set by the user. The system mainly has the status detection of the freezer compartment, the refrigerating compartment, the ambient temperature, the power supply, etc. Through the detection and processing of the temperature and the opening state, the compressor and the corresponding valve are controlled to start and stop according to the fuzzy inference decision. The output part of the system is mainly used to control the opening of the compressor, the bistable solenoid valves 1, 2 and the temperature display and fault alarm, so the output circuit includes the compressor on/off control circuit and the bistable open control line and the temperature display circuit. And fault alarm circuit. 4 fuzzy control principle During the operation of the refrigerator, due to the difference in the type of food stored, the difference in the ambient temperature, the number of door opening times, the fluctuation of the power supply voltage, etc., the overall cooling capacity and distribution relationship of the refrigerating room and the freezing room are constantly changing, so it is necessary to control the compression. The opening and closing relationship between COM P, valve V 1 and valve V2 optimizes the overall cooling capacity and its distribution between the two chambers. There are only two defined states for COM P, V1, and V 2 to turn on and off, but when the switch is affected and restricted by many factors, it has certain ambiguity. Based on conventional knowledge, a large number of experiments and expert experience, we have summarized a set of control rules, and based on these rules, we designed a controller to use fuzzy control technology to infer the optimal opening and closing point of the compressor, valve 1, valve 2 The best opening point, thus achieving the control of the operating state of the refrigerator. For example, the control rule for determining whether the compressor is turned on is (in this case, COM P = OFF, V1 = OFF): (1) If the freezing and refrigerating chambers have a high temperature and a large rate of change, and the ambient temperature is also high, the compressor is turned on. (2) If the temperature of the refrigerating compartment is high and the rate of change is large, the temperature and rate of change of the freezing compartment are low, and when the ambient temperature is high, the compressor is turned on. (3) If the temperature and rate of change of the refrigerating compartment are both low, and the temperature and rate of change of the freezer compartment are high, but the ambient temperature is low, the compressor is turned on. (4) If the temperature and rate of change of the two compartments are both moderate and the rate of change is low, the compressor stops. (5) If the temperature and rate of change of the refrigerating compartment are moderate, the temperature and rate of change of the freezer compartment are high, and the compressor is opened when the ambient temperature is moderate. (6) If the temperature and rate of change of the refrigerating compartment are moderate, the temperature and rate of change of the freezer compartment are low, and the compressor is opened when the ambient temperature is moderate. The defrosting circuit uses M OTOROLA's dedicated semiconductor sensor MT S102 to detect the frost thickness, and the valve 2 is closed by fuzzy inference to realize the automatic frost. 5 Conclusion The fuzzy control technology is used to improve the refrigeration system of the refrigerator, realizing the dual-temperature dual control in the true sense, which can make the refrigerator quickly and reasonably adjust the distribution of the cooling capacity according to the change of the use conditions, and avoid the area distribution of the two-chamber evaporator. Improper use or changes in the use conditions result in waste of cooling, thereby achieving energy savings. Volkswagen Car Audio,Volkswagen Car Radio,Volkswagen GPS Navigation Universal Car DVD/GPS Co., Ltd. , http://www.flow-toyotacardvd.com
Pre-set discussion on the simulation control system of the straight refrigerator
1 control requirements for the refrigerator