Use of Photogrammetry in Extracting 3D Structural Deformation/Dummy Occupant Movement Time History During Vehicle Crashes

The ability to extract and evaluate the time history of structural deformations or crush during vehicle crashes represents a significant challenge to automotive safety researchers. Current methods are limited by the use of electro-mechanical devices such as string pots and/or linear variable displacement transducers (LVDT). Typically, one end of the transducer must be mounted to a point on the structure that will remain un-deformed during the event; the other end is then attached to the point on the structure where the deformation is to be measured. This approach measures the change in distance between these two points and is unable to resolve any movement into its respective X, Y, or Z directions. Also, the accuracy of electro-mechanical transducers is limited by their dynamic response to crash conditions.

The photogrammetry technique has been used successfully in a wide variety of applications including aerial surveying, civil engineering and documentation of traffic accidents. It has the potential to be used as a method to extract the time history of structural deformations during vehicle crash testing from film analysis without resorting to physical measurement of the points of interest. The procedure consists of first placing coded targets at the points of interest. Each targets motion is recorded using two digital high speed video cameras positioned at discrete angles to capture the motion of each target from two perspectives. Processing and analysis of the captured motion will yield the X, Y, and Z coordinates of these targets in a three dimensional space as a function of time.

This paper describes in detail, the application of photogrammetry in crash safety analysis. It demonstrates the technique through examples carried out in dummy occupant motion and structural deformation analyses for a variety of crash tests and modes.