Identification of Intermittent Dryring of Grain and Adaptive Control

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To develop the controlling method which accomplish efficient drying with good quality of dried grain and suppress the influences of variations of initial moisture content of grain and drying air temperature, the followings were investigated :1.System indentification of drying processSpace state models were investigated of thin-layr drying, drying of the thick-layr assumed as series of a thin-layr and thick-layr drying expressed by an approximated drying equation. As a result, moistrure content of grain in drying could be stably estimated by Kalman filter from the measurement of the inlet and outlet air temperature.2.Quality modellingGeminability of grain was adopted as a quality index and the relationship between geminability of grain, initial moisture content and temperature of grain was formulated. With the formulated equation, the allowable temperature of drying air was obtained to maintain a high geminability with a decrease in moisture content of grain.3.Design and estimation of multivariables controlling systemRule oriented adaptive control system was investigated which control drying control drying air temperature determined by the quality model and the residence time of grain in a drying chamber determined by the two-tank model. As a result, the control system of residence time of grain by a PI feedback method was developed in which the moisture content of grain at the outlet of drying chamber is estimated from the inlet and outlet air temperature and the grain temperature, and the moisture content of grain is controlled at the estimated value. The control system shows the good responsibility to the variation of initial moisture content and drying air temperature.As future problems, modelling of other quality indexes to extend application of the control system and the improvement of estimation accuracy remain. The author is planning and preparing a developmental study as the application of the control system to actual fields.