Development of a Multi-Body Systems Approach for Analysis of Launch Shudder in Rear Wheel Driven Vehicles

Driveline shudder is a low-frequency (10 Hz - 30 Hz) vibration issue of vehicles that can occur under various test conditions. Specifically, launch shudder is an issue that can be prevalent under vehicle take-off conditions. Factors that typically contribute to launch shudder include stick-slip excitation of friction materials (clutches) and driveline excitations, in particular, on rear wheel drive (RWD) vehicles. Shudder caused by the driveline excitation is generally related to the universal joints (Cardan joints) in the driveline system. In this case, the u-joint forces and kinematics induce a 2^nd order excitation when operated under a driveline angle.

This document focuses on launch shudder phenomena resulting from driveline system excitation on a RWD vehicle. An initial treatment of the physics governing launch shudder and typical factors influencing the shudder levels in vehicle are provided. Following this, the development of a multi-body systems (MBS) based approach is described. The results from the model are shown to correlate well with experimental measurements on a test vehicle. Upon demonstrating good correlation, the MBS model is utilized to conduct sensitivity analyses with respect to key design factors that influence launch shudder. Finally, the results are summarized and suitable conclusions provided.