Abstract: In order to improve the noise, vibration and harshness (NVH) level of the whole vehicle, a multi-objective optimization design was carried out for the intermediate support of the drive shaft, and the stiffness value of the support was calculated,simulated and analyzed.Firstly, the process and optimization theory of frequency ratio calculation and design were introduced, and the suspension mass, natural frequency and frequency ratio of a certain transmission shaft were calculated and analyzed. Then, based on multi-objective genetic algorithm (NSGAⅡ), the objective function was constructed, which used the vibration transmissibility, first order modal change rate, rubber damping ratio and frequency ratio as the objective function‘’s constraints. The multi-objective optimization theory was used to re-match and optimize the stiffness of the intermediate support, and the optimal stiffness value was obtained. Finally, the original intermediate support and the new intermediate support with the optimized stiffness values were simulated. Both the intermediate supports were tested with the electric light bus by NVH test program. The vibration acceleration of the improved intermediate support was decreased by about 19% at 80km/h speed. The optimized intermediate support with optimal stiffness value, can well reduce the vehicle vibration, and decrease the negative impact of the transmission shaft on the vehicle vibration, which proves the effectiveness of the optimization method.

Key words: drive shaft vibration; support stiffness; noise,vibration, harshness(NVH) test; multiobjective genetic algorithm; stiffness matching; vibration transmission rate