A Robust Design Process of Exhaust System for Idle Vibration of a Vehicle

This paper presents a robust design process for the idle vibration in a passenger vehicle. Except global modifications of a body structure, chassis system or engine mounting system, it is difficult to find the local countermeasures that can work for the idle vibration. It is a major goal of this paper to develop the local countermeasures for the idle vibration. A process for robust design is proposed, which consists of 4 steps, that is, a) problem definition, b) cause analysis, c) countermeasure development, and d) validation. In order to simplify complexities of a robust design, it is more efficient to divide the step for countermeasure development into two small phases. In the first phase for movement to the target, a deterministic design is carried out to shift the resonance frequency of exhaust far from the critical frequency range of idle. In the second phase for reduction of quality deviation, a probabilistic design is executed to minimize deviation of attenuation of internal forces, which is transmitted from the exhaust to the body structure. Meanwhile, it is general that a robust design requires lots of iterative computations and higher accuracy. This study tries to overcome these requirements by applying the substructure synthesis method using a FRF (Frequency Response Function) based hybrid model. It is validated that the proposed design decreases the level of idle vibration more over 5 dB.