Simulation of Vibrating Vehicle Structures as Part of the Design Process of Engine Mount Systems and Vibration Absorbers

A vehicle's structure vibration leads to perceivable accelerations at the steering wheel, the seat rails and the floor panels; additionally, these vibrations cause structure borne noise which contributes to the sound pressure level in the passenger's compartment. The perceivable structure accelerations and the sound pressure level constitute criteria for evaluating a vehicle's noise and vibration behavior. Consequently, improving the noise and vibration behavior is tantamount to reducing the vibration amplitudes of the vehicle structure.

The operating engine causes engine mount forces which provoke the structure vibration. After the engine mount forces are calculated, the structure vibrations are simulated with a vehicle structure model described by transfer functions that relate the engine mount forces to the accelerations of all selected structure points where the vibration is supposed to be analyzed. The transfer functions can be measured in a vehicle or derived from a Finite Element model of the structure. Based on transfer functions, the seat rail accelerations are simulated with and without a vibration absorber attached to the vehicle structure.