Research On The Control System Of Heat Pump Dryer

China not only is densely populated, but depends heavily on agriculture as well. The quality of agricultural byproducts processing is influencing benefit of agricultural production directly, and agricultural byproducts must be carried on drying before transported and processed into the food. The dry operation generally consumes a large amount of energy. In order to reduce the energy consuming and improve the quality of the processed goods, the dry technology of the heat pump is applied to the dry homework of the agricultural byproducts. In China, it becomes increasingly important to improve the drying machines, because the old and the less automatic drying machines cannot satisfy us with its poor quality of dryness. With the development at full speed of technology of the computer and industrial control, It is feasible to apply the technology of computer and programmable logic controller into the heat pump dryers.By using microcomputer, the experiment studied the monitoring and controlling system of dryers about the content of the temperature, the humidity and the amount of wind in the room of dryer. The conclusions are as follows. The monitoring and controlling system contains three parts: sensors, controllers and executors. Sensors are used to detect the content of the temperature and the humidity of the heated air, to measure the amount of wind in the drying machines respectively. The experiment adopts the method that PID controller combines with fuzzy controller. Fuzzy control is introduced in the control process, and by using it, strengthening the adaptability of the system to some unstable factors. The experiment uses S7-200 series PLC CPU266 of SIMENS Company to control the computer as the present controlling computer. The on-the-spot man-machine interface selects TD200 text monitor. With TD200 we can monitor the temperature, the humidity and the control state of each valve, and establish essential control parameter. We use the configuration software of industrial monitor and control to accomplish the data interchange between PC/PLC, accomplish the man-machine interface, accomplish to monitor and control the temperature and the humidity in time. At last, the experiment analyses the controlled result of this system. We also conclude that it is good to control the system and have reached the anticipated result.This system can be used on both old and new model-drying machines. This project hasvery important meanings to the dry technology that improves the agricultural byproducts, and also has the wide development prospects.