Estimating modal coordinates from damper displacements: a system-identification approach

For modal damping systems, estimations of the modal coordinates are crucial. This article shows how the identification of time-domain system can be used to obtain better estimations of the modal coordinates in bounce, pitch and roll for a heavy vehicle. Low-order multiple-input-single-output models used for modal coordinate estimation are identified on data both from multi-body systems' simulations and from vehicle measurements. The identified models show considerable improvements in accuracy when compared with the previously used geometric calculations. Although good models are obtainable for all tested load cases, their validity is somewhat limited to load cases of similar excitation type because driver-induced manoeuvres such as braking and steering wheel action provide different vehicle excitation in comparison to road bumps. A compromise would be to identify an estimation data containing all relevant load cases.