A Comparison of Sensor Systems for Measuring Three-Dimensional Crash Dummy Motion
Published May 13, 1996 by National Highway Traffic Safety Administration in United States
Tracking angular motion of dummy components, such as the head, is important in understanding body response during violent force exposures. This paper compares four methods of measuring angular motion of a Hybrid III dummy head during a series of tests using a horizontal accelerator sled and a head/neck pendulum. The Hybrid III head was instrumented with three orthogonal magnetohydrodynamic (MHD) angular rate sensors and with nine linear accelerometers arranged in a 3-2-2-2 array. The motion of the head was monitored using a Selspot optical target tracking system and a high-speed video camera during the horizontal accelerator sled tests. A two-potentiometer device and a high-speed camera were used to monitor the head motion during a series of head/neck pendulum flexion and extension tests. Software routines were written to calculate the head rotation and angular velocity from the head-mounted sensors. Comparisons of the angular velocity and rotation, determined using the MHD, nine accelerometer array, and Selspot system, were made for each of the horizontal accelerator sled tests. For each pendulum test, the two-potentiometer data were differentiated to determine the angular velocity and these data were compared to the angular velocity determined using the MHD sensors and the nine accelerometer array. The angular rotation of the head from the three sensor technologies was also compared for each pendulum test. Rotational motion of the head in the principal direction of motion using all four sensing technologies compared well for each of the horizontal sled tests and for the head/neck pendulum tests in which there was no head impact. When the head, attached to the base of the pendulum, was subjected to impact against a wooden board, analysis of the accelerometer array resulted in calculated rotations greater than those which actually occurred. The MHD angular rate sensors proved to be the superior of the tested techniques in determining the three-dimensional angular velocity of a rigid body.