Abstract
The study of the kinematic of vehicle occupants during collision is of interest both for car manufacturers in terms of designing and making vehicles with a higher level of passenger security, and for those who investigate car accidents, as the degree of the occupants’ injuries, the place and configuration of their injuries represent important facts for the study of the kinematic and dynamic of the colliding vehicle. The occupant’s kinematic during the impact has as a point of reference the occupant’s position before the collision. It is not the normal driving position for the car diver, but it is a modified position caused by collision avoiding manoeuvres. Collision avoiding manoeuvres, braking and steering, may be encountered singularly or simultaneously in case of real crashes and include additional factors such as posture change and the movement of the occupant’s body, which should be considered with the analysis of the accident results. Such position and behaviour differences of the occupant’s body before the collision represent data that cannot be recorded in real-life accidents, and therefore it is hard to measure the differences between injury mechanisms from data gathered in retrospective analysis of car crashes only. The aim of this study is to anticipate the behaviours of the human body before the collision. Predicting the position and the behaviour of the body of the occupant – car driver – is based on the results of the impact tests with active human models, collision tests where crash test dummies have been used not being conclusive in this case because of the absence of collision avoiding human reactions. In order to simulate the real situation before the collision of a car, which occurs when the brakes or pre-crash safety systems are activated in an emergency situation, impact tests have been performed at a lower speed as compared to the speed encountered in real accidents, with human voluntaries using a test sledge. The study is focused on the driver’s behaviour of a frontal impact before the crash. The driver’s posture on braking just before the impact has been examined on two different muscle positions: the muscles completely relaxed, and the muscles completely tense, respectively. Data on the occupant’s posture and activation of his body muscles have been measured by the use of a 3D movement capture system, namely the technique of muscular electromyography. In order to monitor the movement of the voluntaries during the impulse, 2 accelerometers have been placed on the surface of both the occupant’s body and on the sledge. Prediction of the driver’s body position and position maintaining mechanisms auto have been investigated based on the results of these experimental studies. It was concluded that the process of muscle tensioning before the crash influenced the physical movement of the occupant with slight collisions, and this muscular effect is greatly linked to the rotating angle of the head, neck and trunk. Where the subject’s muscles have been initially relaxed, muscular responses started to activate about 100 ms after the start of the acceleration variation. The kinematic of the head-neck-trunk system has been strongly influenced by the activity of the muscles. In case of relaxed muscle structure, the flexion movement of the pelvis is dominant but no extension movement of head or lower limbs have been detected. The purpose of the study is to make an injury forecast based on how the change in human body postures influence the occupant’s injuries in a car crash. This study indicates that the muscles may react quickly enough to achieve significant control over the driver’s behaviour during lower speed impact, considering his position just before the collision.
Keywords: Pre-crash, Occupant Kinematics, Muscle Reaction, Occupant Posture, Bracing