Case Studies: Cloning Crash Test Dummies
September 30, 2009
First Technology Safety Systems Inc. (FTSS, Plymouth, MI), maker of crash test dummies and computer crash simulation models for automotive, military and aerospace applications, uses the HandHeld laser scanner from NVision Inc. (Coppell, TX) to ensure the accuracy of its crash dummies. The dummies are crucial in evaluating the performance of side curtain airbags in a rollover.
The need for scanning arose when a mathematical formula was developed to define the geometry of a dummy that was originally based on a physical mold. “Crash dummies have been developed over the years largely as physical molds,” says FTSS Engineer Steve Goldner. “The geometry of the dummy has a major impact on crash test results, but it has become essential to convert the original designs to mathematical models in order to enable improvements in manufacturing technology. It also helps avoid damage to the original mold.”
FTSS engineers designed a new dummy based on the mathematical model. Because physical measurement methods could not provide the level of accuracy needed to confirm that the new design matched dummies built from the original mold, they used laser scanning to measure the new dummy. FTSS selected the NVision HandHeld scanner for this task because of its wide-stripe laser, speed, accuracy and ease of use. The scan data is quickly converted to a stereolithography (STL) file, which can be easily compared to a computer-aided design (CAD) model.
A key advantage of the scanner is that it is mounted on a mechanical arm so it can move freely around parts of many sizes. The mechanical arm keeps track of the scanner’s location so all data is collected within the same coordinate system. As FTSS, technicians scanned the dummy, the scanner generated a point cloud consisting of the coordinates of individual points. FTSS technicians used integrated software that is included with the scanner to convert the point cloud to an STL polygon mesh. Reverse engineering software then converted the STL data to a surface model. Then, technicians overlaid both the scanned model and the CAD geometry based on the mathematical formula to see how closely they matched.
Technicians used this process to fine-tune the mathematical formulae until they were able to create a new dummy and confirm it exactly reproduced the original mold designs. To date, FTSS has reverse engineered between 30 and 40 dummies with the NVision HandHeld scanner. This process ensures that current test dummies are consistent with those used in the past, which in turn ensures the accuracy of the crash tests that are used to evaluate automobile safety.