CONTROL OF MIXED-FLOW GRAIN DRYERS - AN IMPROVED FEEDBACK-PLUS-FEEDFORWARD ALGORITHM

A feedback-plus-feedforward control algorithm for moisture control in mixed-flow grain dryers has been further developed to compensate both terms of the algorithm when changes in drying air temperature occur during operation. This eliminates any influence of drying air temperature on output grain moisture content when the controller is operating. The gains in both terms of the algorithm were expressed as functions of temperature so as to correct the discharge rate of grain whenever a change in drying air temperature, which would change the drying rate of the grain, was detected. The modified algorithm was validated by simulation and experiment. Means of applying the algorithm to dryers other than the dryer for which the control algorithm was first designed and to crops other than wheat are described. The use of the algorithm during drying while recirculating grain and the transfer from manual to automatic control of the grain discharge rate are discussed. © 1993 Silsoe Research Institute.