Understanding the Effects of Age and Safety Countermeasures on Occupant Kinematics

Monday, March 18, 2019

11:00 AM-1:00 PM

BIOMED PhD Thesis Defense

Title:
Understanding the Effects of Age and Safety Countermeasures on Occupant Kinematics in Low-Acceleration, Time-Extended Events

Speaker:
Christine Holt, PhD Candidate
School of Biomedical Engineering, Science and Health Systems
Drexel University

Advisors:
Sriram Balasubramanian, PhD
Associate Professor
School of Biomedical Engineering, Science and Health Systems
Drexel University

Kristy Arbogast, PhD
Co-Scientific Director and Director of Engineering
Center for Injury Research and Prevention
Co-Director
Center for Child Injury Prevention Studies
R. Anderson Pew Distinguished Chair of Pediatrics
Children's Hospital of Philadelphia (CHOP)
Research Associate Professor
University of Pennsylvania

Abstract:
Pre-crash maneuvers contribute primarily to occupant mis-positioning prior to a crash event. The inertial forces during the pre-crash phase have the potential to cause alterations to the occupant’s “state” (initial posture, position, muscle tension), which could have consequences for the restraint. Developmental differences that occur between adolescence to adulthood may also affect occupant kinematic responses. Therefore, the objective of this study is to quantify the kinematic responses of restrained pediatric, young adult and adult human volunteers during a simulated evasive swerving maneuver and evaluate the effects of age, two safety countermeasures (pre-pretensioning and inflated torso bolsters), and muscle responses, on occupant kinematics. It is vital to understand occupant kinematics for a broad range of ages and therefore sizes as it is representative of a real-world occupant population and must be considered to implement vehicle countermeasures properly.

A novel laboratory device was designed to expose subjects to non-injurious loading conditions that mimic real-world evasive swerving events. An oscillatory lateral pulse with a maximum acceleration of 0.73 g was applied. Forty seat belt restrained subjects across four age groups (9-11 years (n=10), 12-14 years (n=10), 15-17 years (n=10) and 18-40 years (n=10)) were exposed to a series of test conditions (baseline, pre-pretensioned seat belt, sculpted vehicle seat with and without inflated torso bolsters) while their kinematics were captured using 3D motion‐capture and muscle activity was recorded. Reaction loads were collected from the shoulder belt and footrest. The results show that a significant reduction in occupant lateral displacement is possible when safety countermeasures are activated. Of the specific countermeasures evaluated, pre-pretensioning led to the most reduction in peak lateral head and trunk kinematics independent of age. The pre-pretensioned seatbelt provided sufficient load to restrict multiplanar trunk motion. The sculpted seat countermeasure, when the torso bolsters were inflated, showed similar, though not as substantial reductions in lateral motion. Bracing was studied as a volunteer induced countermeasure, and it significantly reduced peak lateral head and trunk excursion independent of age. Last, some subjects employed transverse trunk rotation during the cyclic maneuver to restrict large lateral displacements. However, this kinematic strategy was most likely subject-specific as it did not have age-specific implications.

This study is the first to provide insights into dynamic kinematic responses of restrained pediatric and adult volunteers subjected to oscillatory lateral perturbations. Findings from this study can help guide the design of safety countermeasures that are relevant to the pre-crash phase. The data provided from this study not only contributes to the automotive field but also provides fundamental biomechanical knowledge of pediatric and adult subjects for comparative analysis.

Contact Information

Ken Barbee
215-895-1335
barbee@drexel.edu