Design And Research Of Monitoring System For Heat Pump Drying Device

In view of the problems and shortcomings in the processing of vegetable dehydrating in current China, this research applies the heat pump dry technology in the processing of vegetable dehydrating. Using the advanced computer technology and configuration control technology, the research has designed the automatically monitor computer systems for the heat pump drying device, makes the real-time monitoring and regulation to the processing of vegetables dehydrating. This research has mainly done the following work:1) It designs the general structure of the computer monitoring and controlsystem——the system adopts PC being as the superior machine, and adopts S7-200series programmable logic controller being (made by Siemens Company) as the lower position machine. Then they are formed monitoring system of the whole computer through RS485 bus. As the management level, the superior machine uses the Century Star General Industrial Automation Configuration Software to its monitoring software configuration, and makes the real-time recording and the monitoring to the field data, and designs the temperature and humidity control and related parameters set, real-time humidity demonstration, drawing drying curve, drawing drying rate curve, alarm information table shows, print statements and so on. As scene control level, the lower position machine PLC uses the matching programming software STEP7, completes data collection and processing, loop control and fuzzy control algorithm implementation and other functions through the monitoring system. In according to the requirements of operator, the combination compressors can control the switching, adjust control fault detect protect automatically.2) The process is non-linear, time variable, temperature and humidity strongly coupled, and it is difficult to achieve satisfactory results for using the conventional method of control, so the research makes the design not relies on the object model of fuzzy decoupling control. Using temperature and humidity and their deviation error rate of change as input parameters, utilizing fuzzy inference decoupling control algorithms, it can complete the online track to the dynamic characteristic of controlled plant, revises the controlled variable promptly, realizes to the drying in transit humiture decoupling control.3) Using carrot as experimental subject, the research takes the dehydration tests through the design heat pump drying device. The results prove that the automatic monitoring system is in good condition. Temperature and humidity control are stable in the range. The requirements to the processing of vegetables dehydrating are also basically meet.