Range of Motion (ROM) Analysis for Pressure Garments (EVA and LES) using 3D Photogrammetric Motion Capture
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Understanding work envelope (reach) and range of motion (ROM) is a critical component of pressure garment (EVA and LES) design. In comparison to methods used in the Apollo program involving the use of goniometers and 2D still photography, methods for evaluating suit ROM have significantly advanced in the past two decades with the utilization of 3D motion capture. These methods more accurately model the constraints that an EVA suit, for example, applies to nominal human ROM and reach. Current research methods for evaluating suit ROM utilize a Vicon camera system to track reflective markers placed on a subject performing a motion sequence, which are then identified as coordinatized points in a 3D space. The Aerospace Human Systems Laboratory (AHSL) at Texas A&M University has developed a new process for visualizing and analyzing ROM and reach volume envelopes utilizing a 3D photogrammetric scanning instrument. Specifically, a 10-camera scanning system is used to capture a 20-second motion sequence of a human subject at 10 images/second resulting in 200 3D images. Coupled with supporting computer programs, any anthropometric point of interest can be landmarked on the human body or suit scan, coordinatized, automatically tracked across the motion sequence, and then plotted to analyze the subject’s reach and ROM in unsuited, suited unpressurized, and suited pressurized configurations. Any decrements to performance for any size of subject in any suit size could theoretically be modeled by this method. The application of this strategy to a scanned human in an unpressurized and pressurized Russian SOKOL launch and entry suit is also discussed.