Prediction of Suspension Fundamental Mode Frequency with Extraction of Dynamic Properties of Automotive Shock Absorbers and Tire

The automotive shock absorber has various functions in car performance. Particularly, it is a dominant tuning parameter to get good primary and secondary ride characteristics within 1-35Hz ranges in car development. Thus, understanding of characteristics of shock absorber in this frequency range is indispensable to both test and analysis engineers for an effective and systematic approach. In this study, tire is also investigated from the same point of view. Frequency dependent stiffness and damping coefficient are extracted by discrete sine swept test under constant velocity of 25, 50, 100mm/sec which represent typical road surface conditions[1]. The responses are analyzed on frequency domain and the basic theoretical background for this approach is introduced. Also, frequency dependent stiffness and damping coefficient of the shock absorber and tire are interpolated by 1^st or 2^nd order function of frequency and used for prediction of fundamental suspension mode frequency with simple calculation. The results of this calculation are compared with test results to verify its usefulness.