Concept Design of a 4-DOF Pedestrian Legform

The new European car-to-pedestrian impact safety protection regulation has prompted many research efforts in this area. For knee and lower leg protection, the current regulation requires using a legform that consists of 2 degrees-of-freedom (DOF) for injury assessment. It mimics the shear and bending about the knee joint when the lateral side of a pedestrian is impacted by a vehicle. However, in a smaller portion, non-lateral impact accidents also exist in the real world. Moreover, even in a purely lateral impact, once the legform contacts with the bumper, it could rotate towards the other directions due to the curvatures of the bumper shape and the deformation of the bumper foam, causing the legform taking load from other directions. For assessing injuries under omni-direction impact, a concept design of a 4-DOF pedestrian legform is developed. The two added DOFs represent the natural human knee rotation and the shear with respect to the knee joint when a pedestrian is impacted from the front or the back. The bio-mechanical requirements of the 4-DOF legform are adopted from the existing 2-DOF pedestrian legform and the Hybrid III dummy knee. The challenge is to design all the 4-DOF mechanisms, including the motion and stiffness mechanisms, in a limited space of the legform. Design methodology is also documented in this paper.