22.7.2013 – The Damping ratio software

EUSAMA principle suspension testers (or resonant adhesion principle suspension testers) based on their specification mostly measure only minimum adhesion or road holding, the Eusama value. But this value is unfortunatelly especially on small cars rear axles strongly influenced by incorrect tire inflation or nonstandard axle load.
On that account we implemented on EUSAMA suspension testers in years 2009-2010 in cooperation with GOCA in Belgium another method of wheel damping evaluation – calculation of the Minimum phase shift.
Further on based on several years of development we implemented in the software version 2.30 another extended method of wheel damping evaluation – calculation of the wheel Damping ratio.
In engineering the Damping ratio is a generally used dimensionless measure describing how oscillations in a system (wheel on the car body) decay after disturbance.
It is necessary to point out that on a car there exist two different damping ratios, one related to the car body (damping ration ζs of the sprung mass = Boge test) expressing driving comfort and second related to the wheel (damping ration ζu of the unsprung mass = EUSAMA test) expressing driving safety.