a high-frequency first-principle model of a shock absorber and servo-hydraulic tester

the aim of this paper is to present the model of a complete system, consisting of a variable damping shock absorber and a specialized servo-hydraulic tester, used to evaluate the vibration levels produced by a shock absorber. this kind of evaluation is used within the automotive industry to investigate shock absorbers, as an alternative to vehicle-level tests. the purpose of such testing is to quantify a shock absorber's ability to transfer the mid- and high-frequency content of the vibrations passing from the road profile, through the suspension, to the vehicle body. the first-principle non-linear model formulated, derived and validated in this paper allows laboratory test conditions to be reproduced. it also provides an understanding of structural vibrations in regard to the dynamical interactions between the shock absorber, its basic components (e.g. valve systems), mounting elements, and the hydraulic actuator. the model is capable of capturing important dynamical properties over a wide operating range, yet is only moderately complex. the model has proved to be qualitatively suitable and quantitatively accurate based on validation work performed for the entire frequency range of interest, i.e. 0–700 hz. the application scope of this study covers the engineering need to develop a simulation tool for high-frequency shock absorber design optimization.