On the Control Allocation Performance of Longer Combination Vehicles

This paper investigates the hierarchical vehicle dynamics control performance for path-following of a longer combination vehicle. The vehicle, an A-double, has four units – tractor, two semi-trailers and a dolly between the trailers. In the upper-level, LQR control is used to command the total forces and moments (virtual control inputs - V) for path-following. The lower level uses a weighted pseudo-inverse control allocation method to distribute the desired virtual controls to the multiple steering axles. It is found that there is a degree of redundancy in the definition of the V, and the paper focuses on the effects of choosing different sets of V on vehicle responses. It is found that the magnitude of constraint forces at the articulation joints and the robustness of the response are both heavily influenced by the choice of V. The evaluation is carried out by simulation using both linear and high-fidelity truck models.