Validation and Reliability Testing of a New Hybrid III 6-Year-Old Lower Extremity
Principal Investigator: Laura Boucher, PhD, The Ohio State University
Previous CChIPS-sponsored research has succeeded in collecting data directly from a pediatric population to help inform the design and development of a prototype 6-year-old Hybrid III anthropomorphic test device lower extremity (ATD-LE). The resulting ATD-LE has a tibia load cell and a more biofidelic ankle.
Based on results from the first project using the new prototype ATD-LE in static and dynamic assessments, the objectives of this project were to:
1) Evaluate the repeatability of the tibia force, tibia moment, range of motion (ROM), and stiffness of the new prototype ankle (ATD-LE) across a range of loading conditions; and
2) Quantify the injury response of the ATD-LE by performing Knee bolster air bag (KBA) tests and compare the injury responses between the updated ATD-LE and previous prototype.
In Aim I, a pneumatic ram impactor was used to evaluate the repeatability of the ankle in response to various loading parameters at 1.3 meters/second (m/s) without shoes, and 2.3 m/s with and without shoes. The tibia force transmission, bending moment, ankle ROM, and stiffness was quantified and evaluated for consistency. In Aim II, a dynamic assessment in out-of-position scenarios took place using KBA tests using the same protocol as in previous research. The ATD was positioned in a front seat to mimic three “worst case scenarios” including toes on the mid-dashboard, toes on the lower dashboard, and feet flat on floor. The impact responses in the femur and tibia were collected and compared with published injury threshold values. Results were then compared to the previous ATD-LE KBA tests using an earlier prototype.
Results of the ram impact testing indicated repeatable responses; tibia load, tibia moment, and ankle ROM had a maximum coefficient of variance of 2.7 percent. Calculated ankle stiffness was not as repeatable, with a maximum coefficient of variance of 15.6 percent. Interestingly, the repeatability tests performed with shoes resulted in decreased tibia force and moments, suggesting that the shoes absorbed force during the impact. The KBA test results placed the prototype ATD-LE in a realistic and dynamic environment, and indicated that the toes on lower dashboard position was the most injurious due to the high bending moments in the tibia, above injury threshold.
This work has demonstrated continued improvement in the biofidelity of the ATD-LE, indicating positive steps towards validating the new design of the Hybrid III 6-year-old ATD ankle. The device allows researchers to collect data that were previously difficult to capture, thus providing new information which may lead to injury reduction and thus help advance the safety of children.
At left: The set-up for the repeatability tests is pictured.
At right: The ram impactor making contact with the ATD-LE.
Student: Yeonsu Ryu, The Ohio State University
IAB Mentors: Doug Longhitano, American Honda Motor Co., Inc.; Eric Dahle, Evenflo Company Inc.; Phil Przybylo, Evenflo Company Inc.; Jerry Wang, Humanetics Innovative Solutions Inc.; Hiromasa Tanji, TK Holdings Inc.; Schuyler St. Lawrence, Toyota USA; Jason Gainey, Volkswagen Group of America