Handling Analysis of a Light Commercial Vehicle Considering the Frame Flexibility

Abstract

This paper presents a complete multibody model of a light commercial truck considering the frame flexibility for handling characteristics studies. The flexible multibody model was developed using a multibody package, and it includes a complete primary suspension, the steering system, the power train, a tire model (Delft) and the flexible frame. The directional response behaviour, the drivability and the vehicle/road interaction are the factors that define vehicle handling performance. The most important parameters concerning lateral behaviour are: longitudinal velocity, tire cornering stiffness, suspension system elasticity, steering systems elasticity, lateral load transfer, mass centre location and aerodynamics properties. Consequently, regarding lateral load transfer, the use of a flexible frame is very important. The complete model was validated with experimental results and for the purpose of vehicle analyses, typical standard handling manoeuvres were undertaken including constant radius turn, constant velocity turn and double lane change. The results obtained were lateral acceleration, yaw rate, side slip angle, roll angle and the understeer gradient. Analysing the results, the vehicle showed a changing behaviour concerning steer. At low velocities and lateral accelerations, the vehicle is slightly understeer. However, at higher velocities and lateral accelerations, it can become oversteer.
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