Variable Stiffness Soft Knee Exoskeleton for Advanced Space Suits and Planetary Exploration: Energetics Evaluation



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51st International Conference on Environmental Systems


Stiff joints in gas-pressurized space suits have restricted mobility and increase the risk of injury in astronauts during extravehicular activity (EVA). Prior work by Carr and Newman in the Massachusetts Institute of Technology Human Systems Laboratory has established that some level of knee joint stiffness may be beneficial in storing elastic energy, decreasing the metabolic expenditure during ambulation on planetary surfaces. Recently, an airbag-actuated soft knee exoskeleton (SKE) was developed to provide adjustable knee stiffness in parallel with the knee joint using airbag actuators. The SKE was designed to be integrated into the BioSuitTM, an advanced mechanical counterpressure space suit concept, to exert low levels of tunable stiffness to the knee joint to maximize energetics efficiency in suited EVAs during reduced gravity locomotion. In this proof-of-concept pilot study, the SKE is evaluated in a human participant study during hopping. Its impacts on metabolic energetics were assessed via VO2 and heart rate response. Participants completed a single-leg hopping protocol while wearing the inflated/stiff SKE which was compared to a non-exoskeleton/control condition. Metabolic expenditure during the trials was measured using a COSMED K5 metabolic cart system and Garmin chest-mounted heart rate sensor. The SKE V3 was demonstrated as a robust and durable proof-of-concept knee-stiffness exoskeleton during single-leg hopping. The results of this prototype indicate the promising operational feasibility of the SKE hardware. The pilot study investigating metabolic impacts showed that in some individuals the SKE V3 may beneficially impact metabolic expenditure indicators such as VO2 and HR, but the effects of trial order and fatigue should be further investigated to better understand the difference in outcomes between left and right leg hopping. Recommendations for future work include studies involving more participants, increased exercise duration, and other movement tasks motions to fully evaluate the metabolic expenditure impacts of the SKE V3.


Allison Porter, Massachusetts Institute of Technology, US
Katya Arquilla, Massachusetts Institute of Technology, US
Nicole McGaa, Massachusetts Institute of Technology, US
Alvin Harvey, Massachusetts Institute of Technology, US
Rachel Bellisle, Massachusetts Institute of Technology, US
Dava Newman, Massachusetts Institute of Technology, US
Aleksandra Stankovic, Harvard Medical School/Massachusetts General Hospital, US
ICES407: Extravehicular Activity: Emerging Space Suit Technologies
The 51st International Conference on Environmental Systems was held in Saint Paul, Minnesota, US, on 10 July 2022 through 14 July 2022.


Spacesuits, Exoskeletons, Metabolics, EVA