Modelling and control of an alfalfa rotary dryer

A dynamic model of an alfalfa rotary dryer was developed and used to test the performance of two different feedback controllers. One controller is a conventional PI (Proportional-Integral) controller with fixed tuning parameters whereas the other is a gain-scheduled PI controller with automatically adjusted tuning parameters. The performance of the two controllers was compared with the performance of the dryer under manual control. The gain-scheduled PI controller was found to be superior in the sense that it used less control action and achieved the same control performance as the fixed tuning parameter PI controller. The use of the gain-scheduled controller was shown to reduce energy consumption, increase dryer throughput and had an estimated pay-back time of nine months.