Design of Exoskeleton for Musculoskeletal support of human body under low gravity conditions and its performance evaluation by Fluid Dynamic Analysis Lavanith Togaru Karthik Naganathan Department of Mechanical Engineering Kakatiya Institute of Technology amp Science Warangal Telangana India ID: 1048009
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1. Presented ByLavanith TogaruDesign of Exoskeleton for Musculoskeletal support of human body under low gravity conditions and its performance evaluation by Fluid Dynamic AnalysisLavanith Togaru, Karthik NaganathanDepartment of Mechanical Engineering, Kakatiya Institute of Technology & Science: Warangal, Telangana, India.Thermal & Fluids Analysis WorkshopTFAWS 2020August 18-20, 2020Virtual Conference TFAWS Active Thermal Paper Session
2. Topics to be discussedRisk for humans due to space travelProblems associated with HSF and their present remediesProposed solutionBiological considerationsBiological allowances Working principle of the exoskeletonFeatures of the exoskeletonExoskeleton components & models Fluid circuit – schematic diagramSummary and future workAcknowledgementTFAWS 2020 – August 18-20, 20202
3. Risk involved with human space travelHuman body has evolved and adjusted to our earth’s environment. Any change in those normal conditions can cause mild to severe effects on its functioning which can directly effects its health. Lack of required oxygen levels and change in gravity are the major potential dangers associated with space travel along with many other hazards like Sun’s UV radiation, small floating meteorites, no ambient pressure, etc.,Due to the above reasons almost all the human body systems are going to be affected. TFAWS 2020 – August 18-20, 20203
4. Problems associated with human space flight (HSF)TFAWS 2020 – August 18-20, 20204
5. Present remedies and their issuesExisting solutions to problemsMusculoskeletalTo compensate the loss of bone mineral density and degeneration of skeletal muscle/ muscle atrophy, two methods are adapted:Special diet, extra exercise and medications to ensure there is reduced amount of loss. Considering the person with higher bone density for a mission.CardiovascularTo reduce the orthostatic hypertension and loss of hydrostatic pressure, astronauts are given with pharmacological interveners (medicines targeted to intervene with specific organ/ part of body bring it to normal function during adverse conditions). Artificial gravity creation is also under consideration for solution to these issues. Issues with existing solutionsThere is a potential risk of exercise induced muscle damage due to over and unaccustomed exercise. It is unlikely to find a person with higher bone density all the time.Medicine hinders the brain’s normal functioning and always produces side effects which are inevitable. Creation of artificial gravity is not possible in the near future. TFAWS 2020 – August 18-20, 20205
6. Proposed solutionAs a solution to those issues which are discussed previously, we have took a step to design an exoskeleton for astronauts which can be worn during space exploration. This exoskeleton needs to have some distinctive features like:In any case/ situation, It should only provide additional support to the astronaut. That means it should not be a burden for him/ her.It should be easily worn and removed. It must have the capability to work alongside with human body and other systems designed for space like spacesuits.Most importantly the power/ energy requirements must be as low as possible or nil. TFAWS 2020 – August 18-20, 20206
7. Biological ConsiderationsTFAWS 2020 – August 18-20, 20207
8. Anatomical PlanesTFAWS 2020 – August 18-20, 20208CranialCaudal MedialLateralCoronal Plane
9. Synovial Joints of human bodyTFAWS 2020 – August 18-20, 20209F. Netter’s Atlas
10. Body links and Range of MotionSkeletal muscles are attached to skeleton, work together to put the body in motion, which indeed helps the human body to be in a stable posture during static and dynamic movements. Imagine our body as a series of links or segments joined together using different types of joints discussed before. Now these links are moving or rotating around the axis of rotation of that joint. How far or the range to which each link is allowed to move/ rotate around that joint is given by range of motion. Remember, our muscles always works in tandem with other muscles, this is to restrict the moment for the safety of human body (surprisingly, this is what lead us to the term Range of Motion). TFAWS 2020 – August 18-20, 202010
11. Body linkagesTFAWS 2020 – August 18-20, 202011
12. Body motionsFlexion and ExtensionAdduction and AbductionLateral rotation and Medial rotationCircumduction TFAWS 2020 – August 18-20, 202012
13. Range of motions for different areas of bodyTFAWS 2020 – August 18-20, 202013
14. Range of motion for different areas of bodyTFAWS 2020 – August 18-20, 202014
15. Breathability TFAWS 2020 – August 18-20, 202015Breathability here refers to the skin covering our body not that is related to the general breathing of human lungs.Our skin surface has many operations form protecting the internal organs to sending sensory information, from perspiration with surroundings to protecting our body from foreign organisms and maintaining thermal balance. It is important to ensure all these operations are continued without any disturbance.
16. Load bearing capabilityOur complex human body is always designed to be in a dynamic condition. The musculoskeletal system works to keep our dynamic body in a stable position.So, any additional load shifts the ‘centre of gravity (CG)’ destabilizing the body. Also we cannot add weight wherever we want due to two main reasons:Shift of CGThe nerves can be under compression creating numbness. For this reason, we have decided to add weight/ load only at the well known location ‘shoulders’. TFAWS 2020 – August 18-20, 202016
17. Carrying capability of shouldersTFAWS 2020 – August 18-20, 202017
18. Biological allowances Need is the very first thing that forms as the base for all these considerations. These considerations are never ending.The more you take them into account, the more complex it becomes.These exoskeletons are more specific to the person for whom it is being designed. Mostly, it depends on the user comfort and safety which accounts for major part during design. TFAWS 2020 – August 18-20, 202018
19. Working Principle of ExoskeletonTFAWS 2020 – August 18-20, 202019
20. Need for exoskeletonThis exoskeleton is designed to create the sense of gravity for the person (astronaut) wearing it. At present it can address problems related to loss of bone density, hydrostatic pressure loss, muscle atrophy and orthostatic hypotension. All these problems seems different but in some sense they all are related to one another. Afterall they arise from the same human body. How are they related? Can we make a single device to bring them back to the normal conditions?TFAWS 2020 – August 18-20, 202020
21. Relationship between problemsTFAWS 2020 – August 18-20, 202021Low gravityLoss of contact with groundFree movements Bone Density LossMuscle AtrophyOrthostatichypotensionLoss of Hydrostaticpressure
22. Working principleAs astronauts experience weightlessness everything around them starts to look lighter (easy to handle). They require very less effort to lift any object or move their body compared to on-earth condition. What if we can restrict that free movement so that he/ she will be in need of additional effort to pick, place and move objects or their very limbs itself. This very idea led us to design an exoskeleton as a support for our human body.TFAWS 2020 – August 18-20, 202022
23. Working principleThis exoskeleton will wrapped around the body (just like a wearable suit) way down from foot to shoulders. We want to use fluid power to restrict the body movements of astronauts (mostly limbs). So that he/ she will be in need of additional effort to do their daily activities. Are we really making them immovable? No, this exoskeleton ensures that he/ she will be using the same effort that they generally use to do work on earth even at those reduced and low gravity conditions.TFAWS 2020 – August 18-20, 202023
24. Features of exoskeletonFor inducing hydrostatic pressure, we will be employing a pressurising unit lodged into the shoe’s sole which is connected to the exoskeleton. This exoskeleton carries embedded fluid lines/ conduits which runs all around the body to connect different regions of exoskeleton with the fluid reservoir or accumulator.There are four fluid reserves in this exoskeleton, two primary ones positioned on the shoulders and two secondary placed at the lower limbs for controlling the shoes. TFAWS 2020 – August 18-20, 202024
25. Schematic showing components in Exoskeleton TFAWS 2020 – August 18-20, 202025Primary ReservoirSecondary ReservoirElbow joint ctrl.Hip joint ctrl.Knee joint ctrl.Shoulder joint ctrl.
26. Transverse-section of exoskeleton at elbow regionTFAWS 2020 – August 18-20, 202026Elbow Forearm Arm ExoskeletonDouble acting cylinder
27. Braces at joints holding actuatorsTFAWS 2020 – August 18-20, 202027
28. Sectioned view of exoskeletonTFAWS 2020 – August 18-20, 202028
29. Sectioned view of shoe soleTFAWS 2020 – August 18-20, 202029Surface area of foot sole: 100 cm2Average weight of human body: 82.2kgEarth Gravity:9.81 m/s2 ** Calculated from MSISGround Reaction force on foot:F = m*gF = 82.2*9.81Hydrostatic pressure:P = F/AP = (82.2*9.81)/0.01Hydrostatic pressure:P = 80638.8 pa (or)P = 0.80638 bar (or)P = 0.79584 atm
30. Bellow type Insole TFAWS 2020 – August 18-20, 202030In this bellow type of insole instead of a piston cylinder arrangement a bellow of the above shown shape which can exert pressure at the precalculated regions is arranged into the shoe. The pressure to be exerted is same as the previous case which is of 0.80638 bar
31. General EquationsFlow losses in fluid pressureDouble acting cylinder AccumulatorTFAWS 2020 – August 18-20, 202031
32. Fluid circuit schematicTFAWS 2020 – August 18-20, 202032
33. SummaryThis conceptual exoskeleton design was developed from an idea to create a sense of gravity in space.Presently, this exoskeleton will be addressing problems related with musculoskeletal and cardiovascular systems under the influence of low gravity condition during a space travel. We have discussed many of biological considerations required for preparing a device used for a supporting human body. This exoskeleton uses fluid power for its operational energy requirements. Finally this design was prepared making it compatible with additive manufacturing for the ease of fabrication.TFAWS 2020 – August 18-20, 202033
34. Future work Study on effectiveness of fluid power to operate this exoskeleton will be made along with looking for alternative solutions. During this time standard dimensions are used from man-system integration standards which may not stand in practical sense. We want to use modern human body (of astronauts) dimensioning techniques to make specific designs for an individual.Integration of systems into this exoskeleton to address other problems with space travel will also be considered. TFAWS 2020 – August 18-20, 202034
35. Acknowledgements We are thankful to Dr. P. Yamini Chandrika, M.B.B.S for her suggestions during the evaluation of musculoskeletal system support design parameters. Also to Ms. K. Sreelekha Mahalakshmi, Ms. R. Aamuktha Malyada (House surgeons) and Mr. T. Sudheer Kumar (MBBS) of Kakatiya medical college for their support in clearing our queries related with medical related issues in this design. TFAWS 2020 – August 18-20, 202035
36. TFAWS 2020 – August 18-20, 202036For further queries Contact me: Lavanith TogaruMail: lavanithtogaru@gmail.com