DMC-PD cascade control method of the automatic steering system in the navigation control of agricultural machines

In the navigation control of agricultural machines, in order to improve the precision and response speed of the steering control system, an automatic steering control method based on DMC-PD cascade control was proposed. The model of automatic steering driving mechanism was built through analyzing the mechanism and electric control principle. The model of steering mechanism for agricultural machines was identified in time-domain according to dynamic response data. A steering control model was built by combining both models. Based on this model, adopted cascade control structure, the inner loop designed a DMC controller for steering angular velocity, and the outer loop designed a PD controller for steering angle. A steering angular velocity control simulation was taken by Matlab MPC toolbox, and an automatic steering control experiment was carried out in a YANMAR VP6 rice transplanter. The experimental result indicates, the absolute value of steering angle tracking error is 0.5 degrees, and tracking delay is 0.25s. Therefore, the DMC-PD cascade control method can satisfy the requirement of automatic navigation control for agricultural machines.