Ergonomic Assessment of a Space Suit - PDF document

1 Ergonomic Assessment of a Space Suit: F
Ergonomic Assessment of a Space Suit: From the Perspective of Population Analysis, Fit, Accommodation, Comfort, and Performance Sudhakar Rajulu , PhD NASA Johnson Space Center EXPLORATION CAMPAIGN 2 Space Suits and Exoskel

2 etons • Protection • S afety • Pop
etons • Protection • S afety • Population variation Fit, Mobility, Reach, E xertion Performance • Potential Injury and Discomfort Restrictions Movement Excursion Incompatibility Compensatory adjustment issues Safe L

3 imits Population based Assessment is Cri
imits Population based Assessment is Critical Apollo A7LB, Shuttle EMU, MK III History of NASA Space Suits Space Suit Design for Diverse Body Sizes Crewmembers in 1960’s Crewmembers in 2000’s • Body sizes used be “ho

4 mogeneous” in early space program •
mogeneous” in early space program • Today, crews are in a wide variety of body size, shape, and physical skill • Smaller population needs to be included from early design stage Smaller Population Accommodation Apoll

5 o Sizing EV TLSA (Torso Limb Suit Assemb
o Sizing EV TLSA (Torso Limb Suit Assembly): The torso portion of the TLSA is custom sized and the limb portions are graduated in size and adjustable to accommodate individual crewman limb lengths Shuttle EMU (Extravehicu

6 lar Mobility Unit) MK III Sizing Kosmo e
lar Mobility Unit) MK III Sizing Kosmo et al., 1988. Development of the NASA ZPS Mark III 57.2 - kN/m 2 (8.3 psi) Space Suit Anthropometric Measurements for Suit Design Early Technique based on Linear Measurements: • Take

7 critical body measurements (stature, sho
critical body measurements (stature, shoulder breadth, etc.) • Compare linear dimensions between suit and crewmembers • However, linear measurements do not represent 3 - D body and suit geometry Special Consideration fo

8 r Suit Fit and Accommodation Shoulder cl
r Suit Fit and Accommodation Shoulder clearance in the suit Restricted shoulder motion by hard upper torso (HUT) assembly Shoulder irritation immediately after extravehicular activity training Shoulder - to - Suit Clear

9 ance and Interactions: • Space suits
ance and Interactions: • Space suits have a very restrictive space and if not properly sized can result in discomfort, pain or injury • Suboptimal suit fit, in particular at the shoulders, has been identified as one of

10 the predominant risk factors for shoul
the predominant risk factors for shoulder injury while wearing a space suit. 3 - D Body Scan Technique Vitus 3 - D Laser Scanner “Average” 3 - D Body Shapes 3 - D Virtual Suit Fit Assessment • Overlay 3 - D body sca

11 ns with suit CAD drawing to assess overl
ns with suit CAD drawing to assess overlap and clearance • Greatly improved design process for suit fit and mobility • However, scans do not represent the entire ranges of crewmember body shapes • Scans are essentiall

12 y static: Diverse poses are necessary to
y static: Diverse poses are necessary to fully assess suit - to - body interactions Medium Size Suit Large Size Suit X - Large Size Suit 3 - D Body Scan Overlaid with Hard Upper Torso Geometry Shoulder Shape Variations from

13 Different Poses • Elevation of the acr
Different Poses • Elevation of the acromioclavicular joint occurs after 90 degrees of abduction • Resultant variations in shoulder geometry induces tissue compression at scye openings Parametric Reposable Model for Sui

14 t - to - Body Interaction Assessment Bod
t - to - Body Interaction Assessment Body Shape = f (anthropometry, posture ) • Subjects were scanned in multiple different poses • Developed a resizable and reposable model Expansion Into Current and Future Crew Popula

15 tion • A statistical model developed u
tion • A statistical model developed using the US Army data • Model can predict body shape as a function of any anthropometry dimensions body shape =  0 +  1 stature +  2 body weight + … + error deter

16 mine � 0 , � 1 ,
mine � 0 , � 1 , … , � � , which minimize error Suit - to - Body Interaction Assessment (Cont’d) • Model - estimated body shapes were incorporated with the CAD drawings of

17 a medium - size Extravehicular Mobility
a medium - size Extravehicular Mobility Unit (EMU). • CAD incorporation enables the quantification of the contact volume and clearance between the suit and body surfaces. Expansion Into Current and Future Crew Populati

18 on Body Dimension B Body Dimension A Unl
on Body Dimension B Body Dimension A Unlikely to fit Likely to fit Suit Type A Suit Type B Virtual suit fit test for all permutations of suit size and body shapes Monte - Carlo Suit Fit Analysis: Automatic Body Positioning &

19 Quantifiable Suit Fit Metrics • Devel
Quantifiable Suit Fit Metrics • Develop quantifiable suit fit metrics using suit - to - body clearance and overlap measurements • Automatically calculate the suit - to - body overlap area, volume and penetration depth O

20 verlap Area and Volume Assessment Penetr
verlap Area and Volume Assessment Penetration Depth (mm) Suit - to - Body Penetration Depth Calculation Preliminary Results: Overlap Volume Estimation Male (n=1,743) Female (n=628) • Suit - to - body overlap volumes were

21 estimated from a large number of samples
estimated from a large number of samples • Preliminary analysis revealed the trend of overlap volume covarying with anthropometry Virtual Population Fit Analysis Fit Unfit Fit Unfit Small - Size HUT (Hard Upper Torso) Asse

22 mbly Fit Assessment Outcome Constrained
mbly Fit Assessment Outcome Constrained Mobility of Space Suit Motion in the suit can be substantially different from “natural” unsuited motions due to: - Suit weight (200 lbs ) - Pressurization - Mechanical limitatio

23 ns - Sub - optimal size matching Suited
ns - Sub - optimal size matching Suited Posture and Mobility Capacity (MK III) Mobility Assessment and Modeling Conclusion Exoskeletons and Space suits share the common needs A ccommodate a major portion of the eligible popu

24 lation C omfortable to wear and perform
lation C omfortable to wear and perform functional tasks A djustability features do not expose the user to unsafe conditions As such, Virtual evaluation of the entire population is a must Insufficient to test a small sample

25 of users who may or may not represent t
of users who may or may not represent the entire range of the user population Contact Information Sudhakar Rajulu, PhD. Anthropometry and Biomechanics Facility NASA Johnson Space Center Office : 281.483.3725 Email: Sudhaka