Vehicle suspensions with parallel inerter: effectiveness in improving vibration isolation

Inerter is an additional suspension element to spring and damper with the property that the force generated is proportional to the relative acceleration between its two terminals. This study investigates the effectiveness of a parallel inerter in various vehicle suspension systems to provide superior vibration isolation. In the study, the inerter was paired in parallel to passive, semi-active and active vehicle suspension systems, and the systems were solved with a quarter vehicle model to obtain suspension responses due to ground excitations in the form of step and random road profiles. From the analysis, it was observed that inerter force and spring force were anti-phase to each other, and in parallel layout the cancellation of the two forces gave better vibration isolation to a sprung mass. This provided superior ride performance in vehicle suspension application as indicated by the reduction in vertical sprung mass acceleration. It was also found that the effectiveness brought by parallel inerter was independent on the various vehicle suspension systems; however, the improvement was only slight as the cancellation of forces was insignificant relative to the damping force associated with the specific vehicle model used in the study.