FWD Halfshaft Angle Optimization Using 12 Degree of Freedom Analytical Model

This paper describes the development of an analytical method to assess and optimize halfshaft joint angles to avoid excessive 3^rd halfshaft order vibrations during wide-open-throttle (WOT) and light drive-away events. The objective was to develop a test-correlated analytical model to assess and optimize driveline working angles during the virtual design phase of a vehicle program when packaging tradeoffs are decided. A twelve degree-of-freedom (12DOF) system model was constructed that comprehends halfshaft dynamic angle change, axle torque, powertrain (P/T) mount rate progression and axial forces generated by tripot type constant velocity (CV) joints. Note: “tripot” and “tripod” are alternate nomenclatures for the same type of joint. Simple lumped parameter models have historically been used for P/T mount optimization; however, this paper describes a method for using a lumped parameter model to also optimize driveline working angles. The 12DOF model results enable evidence-based decisions during the virtual vehicle phase for driveline working angles, powertrain mount rate and locations relative to P/T center of gravity. Several challenges were encountered and addressed during the 12DOF model development and correlation process, including halfshaft dynamic angle determination, P/T lateral rigid body mode frequency determination and subjective rating prediction.