Synchronous Tracking Control for Agricultural Wide-Span Implement Carrier (WSIC)

Abstract

Abstract. The mobile operating mode of agricultural Wide-Span Implement Carriers (WSICs) requires accurate synchronization of the forward motions of the two supporting tractors. The guidance task for WSIC operations is currently performed by human operators, which is labor-intensive and can be inaccurate. To replace the traditional human steering and control process, an automatic guidance system adapted to the mobile mode of the WSIC was designed and tested. A master-slave cooperative control method was applied, and the steering angle control law for both the master and slave vehicles and the velocity control law for the slave vehicle were derived. A scaled-down robotic platform was developed by integrating two heavy-duty mobile robots, a dual-rover real-time kinematic GPS (RTK-GPS), two inertial measurement units (IMUs), two XBee-PRO wireless communication modules, and two groups of control processors. Validation experiments were performed using the robotic platform on a flat and firm surface. Results of the single-robot path-following experiment verified the effectiveness of the steering angle control law. Results of the two synchronous tracking experiments, one with a constant reference velocity of 0.3 m s-1 and one with a varying reference velocity of 0.2 to 0.6 m s-1, showed that the two robots could perform their individual path-following tasks accurately while keeping their relative offset to less than 0.1 m. In the experiment with a constant reference velocity, the average, root mean square (RMS), maximum lead, and maximum lag of the offset errors were 0.01, 0.03, 0.05, and 0.06 m, respectively. Slightly larger average, RMS, and maximum lead offset errors were observed in the experiment with a varying reference velocity, which were 0.02, 0.04, and 0.09 m, respectively. These experimental results confirmed that the designed control laws for the synchronous tracking of the WSIC vehicles were effective and the developed automatic guidance system was reliable and applicable. Keywords: Automatic guidance, Master-slave control, Synchronous tracking, Wide-Span Implement Carrier (WSIC).