Work Envelope Analysis A work envelope is a region in three-dimensional space in which a person can comfortably work. In planning EVAs and designing EVA work areas, it is crucial to determine in advance whether a crew member can reach a work site from the available foot restraints. The work envelope currently used for these analyses is a cylindrical volume centered on the body centerline, which was determined from experiments with suited test subjects. Later experiments have shown that the current work envelope may be conservative in some regions, while other areas of the current work envelope are probably not visible to the suited person. In addition, the experimentally-determined work envelope is not resizable for different individuals. The space suit torque-angle model allows a more advanced work envelope analysis to be done using inverse kinematics analysis. First, the visible areas in front of the suited person are mapped out. Then, for a mesh of target points in the visible volume, inverse kinematic analysis is used to determine the shoulder and elbow joint angles needed to place the hand on the target point. The torques that are required to hold this arm position are calculated from the space suit model. Finally, target points that require less than 15% of the maximum isometric strength at all joints are considered to be inside the work envelope.
Work Envelope Comparison between calculated work envelope boundaries and cylindrical NASA work envelope.