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An application of variation simulation for predicting vehicle interior driveline vibration is presented. The model, based on a “Monte Carlo”-style approach, predicts the noise, vibration and harshness (NVH) response of the vehicle driveline based on distributions of imbalance and runout derived from manufacturing production variation (the forcing function) and the vehicle's sensitivity to the forcing function. The model is used to illustrate the change in vehicle interior vibration that results when changes are made to production variation for runout and imbalance of driveline components, and how those same changes result in different responses based on vehicle sensitivity.

The second 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 the multivariate linear 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. Details of the multivariate regression include formulation of the linear regression model, model refinements through analysis of subsets of the variables, tests of significance and residual 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.

Ideally, the calculation of driveline component imbalance sensitivity is a straightforward operation of normalizing the changes in dynamic responses that occur when a known imbalance is added to a rotating component. In practice, however, overlapping driveline component orders (and wheel order harmonics) often prohibit the measurement repeatability required to distinguish these changes. A solution to the measurement repeatability issue is presented for chassis dynamometer testing, based on prescribing minor adjustments to the roll speeds for different wheels in order to separate the orders of various rotating components.

Driveline components are designed to meet customer component-level NVH requirements as measured on a dynamometer in a laboratory environment. It is desired to evaluate the NVH characteristics of driveline components at the end of the manufacturing process and predict how this performance will compare to the component-level specification as measured on the dynamometer in the laboratory environment. A test method is presented for establishing the correlation of the NVH performance of light duty truck axles measured at the end of the manufacturing process on the plant floor to the NVH performance of the same axles measured on a dynamometer in a laboratory environment.