Shock absorber dynamics : A parameter study of damper physical quantitiesand their effect on automobile comfort and control

Abstract:   Damper performance is most commonly characterized by the damper’s forcevelocity behaviour. Different damper layouts and valving methods for creating oil flow constrictions bring different physical properties, outside of this conventional measure. The objective of this report is to find which parameters outside of the conventional force/velocity measure can be used to add better comfort and/or control to road- or track-going vehicles. To fulfil the objectives, vehicle comfort and control needed to be defined. Following this, an extensive parameter study was performed, using a full vehicle model in the software CarSim in combination with an Öhlins-written damper model in MATLAB, which was run through a Simulink model connecting the two. The study was performed for two vehicles: a BMWM4 GT4 and a VW ID.3, with five parameters proposed by Öhlins, varied in compression and rebound (giving a total of 10 parameters). Further on, some results were evaluated based on recorded data from a track test with the BMW, where the conclusions from the parameter study were evaluated through physical changes to the dampers. The parameter study showed that parameters P1-2, P9-10, and P5-6 has significant effect, in that order of magnitude. P1-2 and P9-10 all affect comfort and control, whilst P5-6 has minimal effect on control but a larger effect on comfort. The others, P3-4 and P7-8 have minimal effect on almost all metrics used in this study, with merely a few exceptions. In future studies, an analysis of data in time series format could be done. Moreover, a well prepared verification of the parameter study results could also be done.