Correlation of Axle Build Parameters to End-of-Line NVH Test Performance Part I: Preparing the Data for Multivariate Regression Analysis

The first part of a detailed examination of multivariate correlation of several axle assembly and component parameters to the assembly NVH performance (vibration) measured at the end of the assembly process is presented focusing on preparing the data for multivariate regression analysis. The study is based on test results and measurements acquired from multiple axle assemblies built with the same hypoid gearset, thus effectively eliminating the affect of gearset variation on the test result. Several major components within the axle are considered including the differential housing (that controls wheel differentiation during turns), the axle housing, and several assembly parameters. In Part I (this work), details are presented of the preparation of the data for multivariate regression analysis include assessment of variation within the variables (their candidacy for regression analysis) necessary transformations, examination of univariate and multivariate normality, assessment of univariate and bivariate outliers, and presentation of the final multivariate data set that satisfies the assumptions for proceeding with linear regression. In Part II, the multivariate linear regression model is developed and analyzed.