AUTONOMOUS MANEUVERS OF A FARM VEHICLE WITH A TRAILED IMPLEMENT IN HEADLAND Christophe Cariou, Roland Lenain, Michel Berducat Cemagref, UR TSCF, 24 avenue des Landais, 63172 Aubi` ere, France {christophe.cariou, roland.lenain, michel.berducat}@cemagref.fr Benoit Thuilot Clermont Universit´ e, Universit´ e Blaise Pascal, LASMEA, BP 10448, 63000 Clermont-Ferrand, France benoit.thuilot@lasmea.univ-bpclermont.fr Keywords: Guidance system, Mobile robot, Path planning, Motion control, Agriculture. Abstract: This paper addresses the problem of path generation and motion control for the autonomous maneuvers of a farm vehicle with a trailed implement in headland. A reverse turn planner is firstly investigated, based on primitives connected together. Then, both steering and speed control algorithms are considered. When the system is driving forward, the control algorithms are based on a kinematic model extended with additional sliding parameters and on model predictive control approaches. When the system is driving backward, two different steering controllers are proposed and compared. Real world experiments have been carried out with an experimental trailer hitched to a mobile robot. At the end of each row, the reverse turn is automatically generated to connect the next reference track, and the maneuvers are autonomously performed. Reported experiments demonstrate the capabilities of the proposed algorithms. 1 INTRODUCTION For many years, researchers and manufacturers have widely pointed out the benefits of developing au- tomatic guidance systems for agricultural vehicles, in particular to improve field efficiency while relea- sing human operator from monotonous and dange- rous operations. Auto-steering systems are becoming common place (e.g. Agco AutoGuide, Agrocom E- drive, Autofarm AutoSteer, Case IH AccuGuide, John- Deere AutoTrac) and focus on accurately following parallel tracks in the field. However, more advanced functionalities are today required, in particular for headland driving. In fact, the operator must still ma- nually perform maneuvers at the end of each row be- fore reengaging the automatic guidance system on the next path to follow. In order to benefit of fully auto- mated solutions, and therefore reduce the operator’s workload (and even enable to consider driverless agri- cultural vehicles), the automation of the maneuvers in headland has to be studied with meticulous care. Very few approaches have been proposed in that way, mainly based on loop turns (e.g. John-Deere iTEC Pro, see figure 1(a)). The drawback of such an approach is that it involves excessive headland width for turning on the adjacent track, all the more if a long trailer is used. It is thereby not adapted for small fields and far from optimal in term of productivity, head- land being usually either low-yield field areas due to high soil compaction or wasted areas as they cannot be used for planting agricultural products. (a) Loop turn. (b) Fish-tail. (c) With trailer. Figure 1: Different types of maneuver in headland. Another solution is to perform reverse turns, i.e. maneuvers executed with stop points and a reverse motion as depicted in figures 1(b) and 1(c), leading to reduced headlands. However, although more in accordance with European agricultural practices, au- tomation of such maneuvers in headland has rarely been considered in the literature. In fact, numerous approaches devoted to road applications have been proposed for the autonomous maneuvers of a vehi- cle, even with one or several trailers, see (Altafini C., 2001), (Lamiraux F., 1998), (Hermosillo J., 2003), 109