Offset backing path planning of tractor-semitrailer vehicles based on qualitative rules and geometric methods considering uncertainties

The backward behavior of tractor-semitrailer vehicles is particularly challenging compared to passenger vehicles, causing many difficulties not only for drivers but also for autonomous driving. Offset backing, which is one of the most important backward scenarios for articulated vehicles, can be applied to various path planning in a confined space, such as parking, and can be used for Advanced Driver Assistance Systems (ADAS) and autonomous driving. First of all, by analyzing the slow movement of a tractor-semitrailer vehicle in a confined space, standard unit motions and compound motions for general posture adjustment were defined. By approximating the offset backing driving paths of expert tractor-semitrailer drivers with a geometric method, qualitative path planning was completed by combining compound and unit motions. In addition, complementary motions were added to respond to errors that occur due to the simplicity of the qualitative path planning based on the geometric method. The usefulness of the developed offset backing path planning for tractor-semitrailer vehicles was demonstrated through repeated experimental tests with a model autonomous vehicle.