Reduction of Moan Noise by Frequency Response Function Based Substructuring and Optimization Techniques

Abstract

“Moan” noise in a vehicle causes discomfort and anxiety to passengers. In the previous study, the causes of moan noise were identified, and a coherence analysis of the components was conducted[1]. It was found that moan noise was generated by the attribution of resonance when the exciting force produced by the stick slip motion in a brake system was transmitted to a coupled torsional beam axle (CTBA) module. The analysis involved calculation of the response of the CTBA module on a full suspension brake system reconstructed by consideration of transfer functions and the joint conditions of the CTBA module and brake systems. Each transfer functions are decomposed by a frequency response function based substructuring(FBS) technique. In this study, when using the sensitivity analysis and optimization techniques for moan noise reduction, FBS technique was performed to calculate the response of the modified CTBA module considering the joint conditions and transfer functions of the brake systems. Highly sensitive design parameters regarding the response of the CTBA module were identified after the sensitivity analysis. The most sensitive design parameters were selected to enhance the efficiency and the robustness of optimization. The optimal values for design variables were obtained by applying a progressive quadratic response surface method (PQRSM) as a optimization algorithm. The application of an optimization technique was possible using the FE model and the results of the FE analysis from the previous study[1]. After optimization, a prototype was re-designed, manufactured and tested. Finally, it was verified that the moan noise was reduced, as the natural frequency of 387 Hz for the CTBA module was moved to a higher frequency.