Kinematics Bionic Concept Structure Design and Optimization of Vehicle Crash Dummy’s Knee Joint: Bionics and Biomechanics Applied in Collision Safety of Cars

Abstract

The structural bionicism of the knee joint of an automobile crash dummy is an important factor affecting the accuracy of the dummy’s knee displacement and knee flexion angle measurements in automobile crash tests. This study focused mainly on the optimization of the bionic structure of the knee joint of an automobile crash dummy to ensure that the dummy has a kinematic response closer to that of the knee joint of a real human. Forty sets of high-speed photographic images of the sphyrion were acquired by performing a trajectory-measurement test at the lower tibial point. Subsequently, the high-flexion motion trajectory of the knee joint was obtained by solving vector equations and by multicurve fitting. This trajectory, combined with the bionic structure design method, optimized the structure of the existing dummy’s knee joint. Thereby, its motion can be altered from a fixed-axis rotation to a non-fixed-axis curve motion close to how the human tibial plateau rotates around the femoral condyle. This increases the degrees of freedom of the dummy’s knee joint from two to three. The knee joint structures before and after the optimization were simulated kinematically using a multibody dynamics method. The results showed that the peak of the motion trajectory deviation of the optimized sphyrion decreased from 3.7% to 1.9%, and the average deviation decreased from 2.0% to 0.2%. This indicates that the structural optimization scheme improved the motion bionics of the crash dummy’s knee joint.