Robotic Joint Torque Testing: A Critical Tool in the Development of Pressure Suit Mobility Elements

Abstract

Pressure suits allow pilots and astronauts to survive in extreme environments at the edge of Earth's atmosphere and in the vacuum of space. One obstacle that pilots and astronauts face is that gas-pressurized suits stiffen when pressurized and greatly limit user mobility. As a result, a critical need exists to quantify and improve the mobility characteristics of pressure suits. A historical survey and critique of pressure-suit testing methodologies is first presented, followed by the results of recent pressure suit testing conducted at the MIT Man-Vehicle Laboratory (MVL). MVL researchers, in cooperation with the David Clark Company (Worcester, MA), used an anthropometrically-realistic robotic space suit tester to quantify pressure suit mobility characteristics of the S1034 Pilot Protective Assembly (PPA), a pressure suit worn by U-2 pilots. This suit was evaluated unpressurized, at a vent pressure of 5.5 kPa (0.8 psi), and at an emergency gauge pressure of 20.7 kPa (3 psi). Joint torque data was collected for elbow flexion/extension, shoulder flexion/extension, shoulder abduction/adduction, and knee flexion/extension motions. The aim of this study was to generate a robust baseline mobility database for the S1034 PPA to serve as a point of comparison for future pressure suit designs, and to provide recommendations for future pressure garment testing.

A Review on Human-Spacesuit System Mobility Measurement and Modeling

“…Because these available techniques have their own limitations, a hybrid method absorbing the merits of them needs to be developed in the future. The future spacesuit mobility measurement should be a skin-tight, lightweight, non-invasive and instructed garment that can be worn inside the spacesuit [18]. Such a garment should measure human's joint angles in real time that could be compared with external measurements of spacesuit joint angles.…”

“…However, as human body takes up most of the volume within a spacesuit thereby dramatically reducing the volume that potentially changes with body movement, and as pressured volume effects make up the largest part of joint torque, it is not clear how realistically a measurement in unsuited condition reflects the suited condition [18].…”

“…[17] VI. BIOMECHANICAL MODELING Understanding and predicting exactly how much torque an astronaut must exert to conduct a task would enable task planners to model and plan EVAs so as to estimate physical workload, optimize and maintain low metabolic rates, reduce fatigue, maintain consumables and make schedules [18]. One of the key problems is to estimate the joint torques and muscle forces performing tasks.…”

Revisiting Decompression Sickness Risk and Mobility in the Context of the SmartSuit, a Hybrid Planetary Spacesuit

“…Due to gas pressurization, spacesuits constrain mobility and increase the metabolic cost of movement. Our group has performed biomechanical analyses using OpenSim and have quantified the impact that the EMU has on metabolic rate 35,38 , using joint torques obtained from experimental spacesuit testing 2,39,40 . Simulations included a walking motion in which external EMU joint torques were applied to the hips, knees, and ankles.…”

Characterization of Joint Resistance and Performance Degradation of the Extravehicular Mobility Unit Spacesuit

“…However, the latter data are not discussed as part of this study. All of this information could potentially be used to design EVA workflow to reduce fatigue, assist in task modeling, develop EVA work schedules, as well as to provide future suit engineering design guidance in developing more efficient suits (Meyen et al, 2011).…”