Multi Body Dynamics Modeling of Launch Shudder in Electric Vehicles

The continued push for faster automotive design cycles while maintaining high product quality requires increasing fidelity in virtual analysis. One vibration disturbance load case that has been targeted for virtual analysis improvement is launch shudder, particularly in electric vehicle (EV) applications. Launch shudder can be caused by halfshaft constant velocity joint (CVJ) excitation of a powertrain mounting resonance. It is heavily dependent on the CVJ friction characteristics, axle torque, dynamic operating angles of the halfshafts, the mounting system of the powertrain and the transfer path of vibration to the occupant’s seat. The need to model these parameters accurately makes a full vehicle, multi body dynamics model a great candidate for this load case. This study introduces an approach to modeling, analysis and applications of launch shudder simulation at General Motors. With this model, variation studies can be completed to fully understand vehicle performance and vehicle designs optimized to reduce the launch shudder vibration response the customer feels. It also allows for a deeper understanding of the unique set of challenges that electric vehicles introduce to launch shudder, such as low tire slip and the operating torque profiles of the drive unit(s).