Feasibility study for the estimation of a motorcycle helmet Centre of Gravity accelerations with 6 Degrees of Freedom (6DOF) system

Traumatic Brain Injury (TBIs) is the most frequent cause of serious and fatal road crashes. European Community has adopted an automatic emergency call system (eCall) and made it mandatory for new cars since 2018. eCall was adapted also to motorcycles, which are worldwide linked to significant mortality and trauma rates in crashes. In this context, the development of a helmet fitted with sensors, capable to estimate biomechanical crash consequences and to transmit the information over the eCall system, has the potential to reduce motorcycle crashes severity. The aim of this study is to adapt the 6 Degrees of Freedom (6DOF) method to the estimation of the linear and rotational accelerations of a helmet Centre of Gravity (CoG) during an impact and check the fitness of the method for the scope. The research was performed with virtual testing tools, reproducing three impacts of the helmet on a deformable structure at 8 m/s. The results indicate that the 6DOF estimates the peak values of the linear acceleration components with good approximation, while the peak values of the rotational acceleration components and the time histories of all the components present large errors. The 6DOF cannot be extended beyond the application to rigid bodies and another prediction method has to be identified for the accelerations of the helmet centre of gravity.