A multibody model to assess the effect of automotive motor in-wheel configuration on vehicle stability and comfort

Motor in-wheel topology is an optional configuration for electric-powered vehicles which has some advantages over the conventional standalone motor configuration, like improved modularity when designing different drivetrains (FWD, RWD, AWD) and increased usable interior space of the vehicle. However, drawbacks are also present due to the added unsprung mass, which directly affects to vehicle road holding and ride comfort, and may increase the suspension design cycle, as there is no data available from similar designs. In this work, a multibody model of a B-class car has been developed in order to assess the effect of motor in-wheel configuration on vehicle stability and comfort. The car is modeled in relative coordinates, being the suspensions described as macro-joints by means of lookup tables thus yielding a tree-like structure, and a semi-recursive formulation is applied to derive the equations of motion, which are numerically integrated in time through the trapezoidal rule. Three tests are carried out to compare the behavior of conventional and motor in-wheel configurations: sine sweep, obstacle avoidance and constant radius. A number of motion indicators are obtained from these maneuvers so as to measure the ride, handling and steering characteristics.