Methods of updating body orientation in crash scenarios based on body’s local angular rate

Accurate information about the body orientation is crucial when engineers and researchers try to describe the three-dimensional (3D) kinematics of that body in a precise manner. Various analytical methods were developed to calculate the body orientation from the body's measured angular rate. All of those algorithms are based on the same underlying physics. Even though they solve the same governing motion equations, they each take a slightly different approach, both analytically and numerically. The objective of this study was to assess the accuracy of the various algorithms by comparing their predictions to reference kinematics data. For this study, the reference data comes from computer simulations as well as from dynamic crash-like experiments that incorporated 3D optical motion capture. Specifically, this study examines these algorithms to determine if they are actually different, which method produces results that are most similar to the reference data, and whether or not there are advantages or disadvantages to using one or the other for applications in crash testing analysis. Two methods, both utilizing an approach involving Euler parameters, were identified as the most accurate from the seven discussed. In addition, it was presented that characteristics of the angular velocity signal (its magnitude, period, etc) affect the magnitude of the error in the calculated orientation. Finally, it was shown that accuracy in the computed orientation is sensitive to the numerical integration algorithms used as part of the methods of obtaining body attitude.