Handling and driving characteristics for six-wheeled vehicles

Handling performance of six-wheeled special-purpose vehicles is investigated in this study. Six-wheel drive (6WD) vehicles are believed to have good performance in off-the-road manoeuvring and to have fail-safe capabilities when one or two of their tyres are blown. However, the handling performance of six-wheel steering (6WS) vehicles is not yet well understood in the relevant literature. In this paper, six-wheeled vehicles are modelled as an 18 degree-of-freedom (DOF) system that considers non-linear vehicle dynamics, tyre models and kinematic effects. The vehicle model is constructed into a simulation tool using MATLAB/SIMULINK so that input/output and vehicle parameters can be changed easily using the modulated approach. Handling performance is analysed not only from the frequency domain but also from the time domain. Simulation results demonstrate that the effect of middle-wheel steering is not negligible from the viewpoint of handling characteristics such as yaw rate, lateral acceleration, etc. The simulation tool is also utilized for the manoeuvring analysis over a rough rigid surface, where the separation between the wheels and the road can be considered. In addition, a new 6WS control law is proposed in order to minimize the sideslip angle. Lane change simulation results show the advantage of 6WS vehicles with the proposed control law.