Some Results Concerning the Effect of Stochastic Parameters on Engine Mount System Behavior

Vehicle noise, vibration, and harshness (NVH) development typically assumes that the vehicles behave deterministically, both individually and among vehicles of the same model line and equipment level. While the deterministic assumption is true in neither case, for NVH development on an individual vehicle, the vehicle can be considered as a deterministic system responding to stochastic inputs. However, even among nominally identical vehicles, the allowable assembly and parameter tolerances result in some variability in vehicle characteristics and responses. Characterizing the expected variability would provide a number of benefits, such as helping to identify system parameters that NVH behavior is sensitive to, determining how well a NVH vehicle system model should be expected to correlate with test, and providing guides to determine when vehicle NVH behavior is significantly abnormal enough to merit a diagnostic investigation.

This work investigates one aspect of vehicle system variability, the dynamic characteristics of the engine mount system due to stochastic mount stiffnesses. Both closed form analytical methods and numerical simulations are addressed as evaluation methods. Results are presented for a number of mount system configurations and illustrate the range of variability of mount system natural frequencies.