Steering the Last Trailer as a Virtual Tractor for Reversing Vehicles With Passive On- and Off-Axle Hitches

The paper reports on a practical backward motion strategy for a vehicle pushing several passive trailers with any combination of on- and off-axle hitches. The last trailer is defined as a virtual tractor that can be guided along paths of varying curvature like a single non-holonomic vehicle. Then, kinematic relationships are proposed to translate the resulting motion commands to the actual tractor. The paper extends previous work by specifically addressing propagation of virtual set-points through on-axle hitches. This case is difficult because direct propagation cannot be achieved due to kinematic restrictions imposed by current joint angles. The method has been experimentally applied for both autonomous path-tracking and online operator steering using a tracked mobile robot with two different off- and on-axle combinations of dissimilar trailers. Results indicate applicability in autonomous vehicles and advanced driver assistance systems.