Adaptive frontal structure design to achieve optimal deceleration pulses. volume 05-0243

To minimize the injury of car occupants during a frontal crash not only the restraint system must be optimized, but also the crash pulse generated by the vehicle structure. It is clear that a low velocity crash with full overlap requires less structure stiffness than a high velocity offset crash. Ideally for each serious crash situation the whole available deformation length must be used and all the impact energy must be absorbed without deforming the passenger compartment. For compatibility it is necessary to have a stiffer structure in case of a heavy opponent and a softer structure in case of a lighter opponent. This paper discusses possibilities to design an adaptive vehicle structure that can change the stiffness real time for optimal energy absorption in different crash situations. Besides that all the energy is absorbed it is also important to manage the intensity during the crash time, because the resulting crash pulse has a large influence on the injury level. Especially at high crash velocities a stiff structure in the first phase of the crash followed by a softer part is effective but difficult to realize with traditional structures. Therefore a comparison between several energy absorbing methods is made and friction is found as the best controllable way for adaptable energy absorption. In a proposed new concept design the right amount of energy could be absorbed by means of friction generated by hydraulic brakes on two rigid backwards moving beams. In case of an offset or oblique crash a mounted cable system moves the missed beam backwards. With this new intelligent design with interactive control, an optimal vehicle deceleration pulse can be possible for each crash velocity independent on the struck car position, yielding the lowest levels of the occupant injury criteria, also in case of compatibility problems