The effect of inerter and relaxation spring on passive suspensions of electric vehicles with in-wheel motors

The increased unsprung mass caused by the in-wheel motor influences the ride performance of the vehicle. In order to reduce the impact, passive suspension components such as inerter and relaxation spring can be introduced. A linear quarter-car model is used to represent the vehicle corner. The suspension architectures featuring inerter and/or relaxation spring are compared with conventional passive suspension by considering three performance indices. The suspension performance indices, namely, discomfort index, road holding index, and working space index are derived analytically. It is proven that the suspension architectures with inerter and/or relaxation spring provide improved performance when they are arranged in specific layouts.