The complexity and accuracy of a vehicle model depend on the purpose of modeling. A nonlinear 5-degree-of-freedom (5-DOF) tractor semi-trailer model is proposed in this paper for bifurcation analysis of the vehicle system dynamics. Both yaw and roll motions are taken into account in the model. A nonlinear tyre model is adopted for capturing the nonlinear behavior of the system. Lateral load transfer of wheels due to lateral acceleration and roll of sprung masses and hysteresis behavior of suspensions are also taken into account to improve model accuracy. Parameters of the 5-DOF model are extracted from a TruckSim model. Comparison between the responses of the two models shows that the proposed nonlinear 5-DOF model has a high accuracy and is thus believed to be capable for design of vehicle state/parameter estimators or active chassis controllers.

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