Modular Kinematic Modelling of Articulated Buses

Development of compact and easy to use mathematical models of articulated vehicles for the motion planning, control, and localization purposes becomes more and more important in the era of intelligent transportation systems, especially when there exists a need of reliable predictions of motion for multi-body (semi-)automated freight and public transportation vehicles of various kinematic structures. We propose a modular algorithmic approach to kinematic modelling of nonholonomic (multi-)articulated buses, including the N-trailer vehicles as a special case, comprising a car-like prime-mover passively interconnected with arbitrary number of segments (wagons/trailers) equipped with fixed or steerable wheels, and with various locus of a driving axle in a kinematic chain. Kinematic models are valid under an assumption of a pure rolling of all the vehicle wheels (no skid/slip motion), which is practically justified for the low-speed maneuvering conditions. The proposed approach leads to compact nonlinear models which, thanks to their modular construction, preserve clear geometrical interpretation of velocity couplings between the vehicle segments. Derivations of kinematic models for popular structures of articulated and bi-articulated urban buses are presented for various driving-axle locus and steering capabilities. Experimental model validation, conducted with a full-scale wagon-driven articulated bus, illustrates utility of the approach.