Frequency-dependent automotive suspension damping systems: State of the art review

Configuration of a passive suspension of a passenger vehicle most often requires a compromise between its handling, road-holding, and ride (passenger) comfort. Nowadays, car manufacturers (automotive OEMs) are forced to develop ways for enhancing the functionality of shock absorbers and yet keeping their costs low. The use of so-called frequency-dependent (FD) valves in hydraulic passive suspension dampers, which allow the damping force to vary with the frequency of the excitation (or its change rate), is a satisfactory solution to the problem by means of adaptive passive valves. In this study, the effectiveness of the FD technology in passenger vehicles is demonstrated on the basis of a quarter-car simulation model. This is followed by a comprehensive review of several FD type valve structures currently offered by various automotive damper suppliers. Their advantages as well as potential drawbacks are shown and hydraulic circuits are formulated for each of the considered designs. Exemplary characteristics of a FD shock absorber obtained from own measurements are shown, too. The results of subjective qualitative evaluation of analyzed cases are presented and appropriate directions for further development steps are proposed. Finally, simulation results of functional model of FD shock absorber are presented.