Application of Inerters to Vehicle Suspensions

Abstract

Passive vehicle' suspensions have typically been limited to arrangements of springs and dampers. However, it is well-known that mechanical admittances (transfer-function from velocity to force) realized in this way are restricted to having lagging phase. A new mechanical network element called the inerter has been introduced for which the applied force is proportional to the relative acceleration across its two terminals; thus the inerter is the network dual of the spring. The wider class of positivereal (i.e. passive) mechanical admittances may be now realized. In this paper, we investigate the performance of a quarter-car model and two fixed-structure suspension arrangements which incorporate inerters. We take as our measures of performance the overshoots of step responses of the quarter-car. We find that, compared to conventional passive suspension, only one overshoot can be reduced by these inerter schemes. However, we investigate the effect of trading off the reduction of one overshoot at the expense of another and find that the inerter schemes can provide significant performance advantages.