Study On The Theory And Experiment Of Intelligent Control Method For Grain Dryer

The grain drying is a complicated heat and substance exchange course, and grain itself is also a kind of complicated biochemistry matter. Not only is its drying process influenced by material property and medium parameter (hot wind temperature, humidity and speed etc), but also the climate conditions, drying technology and structure of drying tower have the important effects on the drying result. The grain drying is not only a physical course, but also a biological and chemical process.The grain drying system is one big time lag and strong nonlinear system with much interference. It costs about 8 hours in the drying course that the grains go through the dryer. Moreover, the temperature and humidity of environment, hot air temperature and humidity as well as the moisture content and equality of unprocessed grains all have the important influence on final grain moisture content. It is impossible to describe this complicated drying process with the accurate mathematical model of this system. As for this system, feedback and feed forward control of the classical control theory both cannot resolve this problem, but experienced workers can operate satisfactorily the grain drier.The research object of this paper is grain drier. The structure of 300 tons of grain drying tower is the living example. A lot of experiments have been carried out in grain depot. In theory, grain drying technological parameter data acquired by experiments are analyzed by orthogonal experiment method. Dynamic coupling and heat and mass coupling are analyzed on heat and mass transfer for porous enclosure in the process of grain drying. The regression model of main influencing parameters is built in the process of grain drying. Expert system of grain drying is developed by combining result of orthogonal experiment with regression model. The results of industrial experiments show that expert system can analyze synthetically real time technological parameters of grain drying, and take suitable control strategy to obtain more satisfactory output grain moisture. The main contents are numerated in the following.(1) The influencing factors on drying process is studied, such as hot air temperature, hot air flow rate, inlet grain moisture content, circumstance temperature, relative humidity, grain flow speed, etc, and the relation of factors is obtained. By orthogonal experiment method, the best matching relations of grain drying technological parameters are found out.