Manufacturing Tolerances and Axle System NVH Performance

A study of axle system noise, vibration, and harshness (NVH) performance using design for six sigma (DFSS) methods is presented with a focus on system robustness to typical product variations (manufacturing-based tolerances). Instead of using finite-element analysis (FEA) as the simulation tool, a lumped-parameter system dynamics model developed in MATLAB/Simulink is used in the study. This provides an efficient way to conduct large analytical design of experiment (DOE) and stochastic studies. The model’s capability to predict both nominal and variance performance is validated with vehicle test data using statistical hypothesis test methods. Major driveline system variables that contribute to axle gear noise are identified and their variation distributions in production are obtained through sampling techniques. Through analytical DOE and analysis of variance (ANOVA) analyses, the critical design parameters that control system NVH variations with respect to product variations and variations due to operating conditions are covered. Design criteria of axle systems with respect to robust NVH performance are also discussed. Axle gear whine is a major NVH concern in vehicle driveline systems. The noise source is typically the hypoid-gear-mesh, first-harmonic transmission error, which further transforms into dynamic gear mesh force under operation. The dynamic characteristics of the mesh force are controlled by the gear train torsional dynamics. The driveline system translational dynam