The Occupant Response to Autonomous Braking: A Modelling Approach That Accounts for Active Musculature

Objective: The aim of this study is to model occupant kinematics in an autonomous braking event by using a Finite Element (FE) Human Body Model (HBM) with active muscles, as a step towards HBMs that can be used for injury prediction in integrated pre-crash and crash simulations. Methods: Trunk and neck musculature was added to an existing FE HBM. Active muscle responses were achieved using a simplified implementation of three feedback controllers for: the head angle, the neck angle, and the angle of the lumbar spine. The HBM was compared with volunteer responses in sled tests with 10 ms−2 deceleration over 0.2 s and in 1.4 s autonomous braking interventions with a peak deceleration of 6.7 ms−2. Results: The HBM captures the characteristics of the kinematics of volunteers in sled tests. Peak forward displacements have the same timing as for the volunteers, and lumbar muscle activation timing matches data from one of the volunteers. The responses of volunteers in autonomous braking interventions are mainly small head rotations and translational motions. This is captured by the HBM controller objective, which is to maintain the initial angular positions. The HBM response with active muscles is within +/- 1 standard deviation of the average volunteer response with respect to head displacements and angular rotation. Conclusions: With the implementation of feedback control of active musculature in an FE HBM, it is possible to model the occupant response to autonomous braking interventions. The lumbar controller is important for the simulations of lap-belt restrained occupants; it is less important for the kinematics of occupants with a modern three point seat belt. Increasing head and neck controller gains gives a better correlation for head rotation, while it reduces the vertical head displacement and introduces oscillations