Optimization of Female Head-Neck Model with Active Reflexive Cervical Muscles in Low Severity Rear Impact Collisions.

ViVA Open Human Body Model (HBM) is an open-source human body model that was developed to fill the gap of currently available models that lacked the average female size. In this study, the head-neck model of ViVA OpenHBM was further developed by adding active muscle controllers for the cervical muscles to represent the human neck muscle reflex system as studies have shown that cervical muscles influence head-neck kinematics during impacts. The muscle controller was calibrated by conducting optimization-based parameter identification of published-volunteer data. The effects of different calibration objectives to head-neck kinematics were analyzed and compared. In general, a model with active neck muscles improved the head-neck kinematics agreement with volunteer responses. The current study highlights the importance of including active muscle response to mimic the volunteer's kinematics. A simple PD controller has found to be able to represent the behavior of the neck muscle reflex system. The optimum gains that defined the muscle controllers in the present study were able to be identified using optimizations. The present study provides a basis for describing an active muscle controller that can be used in future studies to investigate whiplash injuries in rear impacts.