Using the Instantaneous Center of Rotation to Examine the Influence of Yaw Rate on Occupant Kinematics in Eccentric Planar Collisions

The biomechanical injury assessment for an occupant in a planar vehicle-to-vehicle collision often requires a kinematic analysis of impact-related occupant motion. This analysis becomes more complex when the collision force is eccentric to the center of gravity on a struck vehicle because the vehicle kinematics include both translation and potentially significant yaw rotational rates. This study examines the significance of vehicle yaw on occupant kinematics in eccentric (off-center) planar collisions. The paper describes the calculation of the instantaneous center of rotation (ICR) in a yawing vehicle post-impact and explores how mapping this quantity may inform an occupant’s trajectory when using a free particle “occupant” analysis. The study initially analyzed the impact-related occupant motion for all the outboard seat positions in a minivan using several hypothetical examples of eccentric vehicle-to-vehicle crash configurations with varying PDOF, delta-V, and yaw rate. The ICR and free particle occupant trajectories were calculated for six different simulated crash examples to illustrate which seating positions were most influenced by post-impact vehicle yaw. The process was repeated for all the outboard seat positions in a sedan using the vehicle kinematics from a staged two-vehicle crash test. It was found that the ICR can provide the crash analyst or the biomechanist a useful mechanism to visualize the relationship between vehicle and occupant kinematics in an eccentric planar vehicle collision.