Abstract: Combine is a higher-order system with time-varying characteristics, nonlinear characteristics, and large delay time. Its working condition is complex. The mathematical model of combine and the internal, external disturbance are analyzed briefly in this paper. There are many problems in load control system using one controller, such as too many disturbances affecting the controller, mutual influence between parameters, difficulties in adjusting the parameters, and the dynamic performance is not good enough. A double loop control system was studied. Combine is divided into walking part and operating part. The walking part is controlled by vehicle speed controller and the operating part is controlled by threshing cylinder controller. The vehicle speed controller use single neuron PID. Controller adjust the system parameters according to the changes of the walking condition to keep the vehicle speed is equal to the desired value. The threshing cylinder controller use direct generalized predictive control. The controller can automatically adapt to the changes of the system parameter and working conditions and keep the cylinder’s rotate speed constant at the optimum speed. The algorithm in the controllers has smaller computation load, and can meet the real-time requirements. The simulation and test show that the system can access to higher control accuracy and better dynamic characteristics.

Key words: Double loop Direct generalized predictive control, Load control of combine, Threshing cylinder speed, Vehicle speed