An independent steering driving system to realize headland turning of unmanned tractors

• A 360°steering auxiliary wheel is installed on the tractor to realize efficient turning at the headland. • The auxiliary wheel system has the functions of automatic steering, lifting and driving. • The minimum turning radius of the modified tractor is 0 m. • The auxiliary wheel steering method decreases the ground space occupancy at the headland by 50 %. Headland turning is one of the factors that affect the efficiency of automatic tractors. The tractor turns in headland following a curved trajectory based on the minimum turning radius and drives into the next row, in most cases. However, the efficiency of the tractor with this turning method is limited by the steering angle range of the front wheels. In this paper, an auxiliary wheel is designed to achieve efficient headland turning by equipping a 360° steering auxiliary wheel at the front of the tractor, which includes auxiliary wheel structure, hydraulic drive system and electro-hydraulic servo controller. The designed electro-hydraulic system can realize automatic steering, lifting and driving of the auxiliary wheel. Finally, field experiments are conducted to verify the superiority of the proposed auxiliary wheel turning method compared with the existing turning methods. Experimental results show that the auxiliary wheel turning method improved the efficiency of the automatic tractor in headland by 50%, 80% and 50% respectively in terms of time efficiency, travel distance and appropriation of space compared with the conventional turning method.