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Homework Help: Knee Exoskeleton Design

  1. Sep 27, 2012 #1
    Hey All,

    I've been a long time viewer of these forums but only just joined because I'd like to get some other viewpoints. For one of my biomechatronics assignments, I was asked to design an active knee exoskeleton for assembly and use in the developing world.

    I've already conducted a literature review and although there are many papers out there about the pros and cons of various actuator types (whether they be electric motors, hydraulic actuators, pneumatic artificial muscles, MR fluids, etc.), there doesn't seem to be much in the form of cheap and readily available technology for the Third World. My question to you is: can you think of any technology that would be suitable for the design of such an exoskeleton?

    A few ideas that have come to mind for the actuator are a series of bicycle pumps, however I'm not sure that these would generate sufficient power to function a full knee exoskeleton. Other possibilities included old scooter or motorcycle motors. As far as power sources are concerned, old batteries from power tools could be used, while I have no real idea about control-feedback mechanisms such as sensors.

    For the exoskeleton frame, raw materials such as wood, leather, etc would be obvious choices. Does anyone have any ideas as far as technology that could be used? My assignment asks for the inclusion of sketches, force and energy requirements and wiring diagram for control-feedback mechanisms.

  2. jcsd
  3. Sep 27, 2012 #2


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    When you say "exoskeleton" do you mean it also has to be powered? How are you going to capture motion input? Why not just a support frame like a knee brace and depend on the user's muscular strength for movement? What are you trying to accomplish?
  4. Sep 28, 2012 #3
    Yeah, it needs to be powered by some sort of actuation mechanism. We are told that it should be based on a hinged knee brace already as the "blank canvas" you could say. I was thinking something like old smart phones like iPhones or Samsung Galaxys could be used to capture motion input because they have gyros and accelerometers already in them, but not sure if it would work. I guess it's all theoretical anyway, we just have to design one, not actually physically build it.
  5. Sep 28, 2012 #4


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    I'm also a bit confused. What are the "use cases" for a powered knee brace? You need more like a full lower-body exoskeleton in order to help folks walk. What is the purpose of assisting in knee movement?
  6. Sep 28, 2012 #5


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    BrianSum, I am surprised that you show no evidence of having researched this question. A Google search produces a plethora of articles by researchers and developers of exactly what you are asking for. One example:

    This paper reports on the mechanical design of an active knee orthosis, powered by pleated pneumatic artificial muscles. The orthosis is intended as a proof-of-concept rehabilitation device for the assessment of mechatronical design principles and testing of different control strategies. The general focus of this research is on the development of a step rehabilitation robot prototype consisting of a powered exoskeleton for the lower limbs.
  7. Sep 28, 2012 #6
    I have completed a literature review, the fact of the matter is that most, if not all, current knee exoskeletons are designed in the developed world for the developed world. The task involves designing something that is cheap and made from technology that is available and affordable for the developing world. A pneumatic muscle actuation mechanism such as the one you've highlighted Bobbywhy, is an alternative, however, pleated artificial muscles can be expensive to make. The materials necessary to build something like this may not be cost-effective. I have the background of various current knee exoskeletons, I was just asking for other people's inputs for possible materials that could be used "around the house" in a sense - left over parts that can be manufactured.

    Obviously, a device essentially made from spare parts would not be as effective as a device that is built in the First World. I suppose the goal involves thinking laterally. For example, this Mexican student http://www.unboundedmedicine.com/2007/01/24/prosthetic-arm-developed-by-a-mexican-engineer/ developed a make-shift prosthetic arm from left-over parts that was cheap to build (old electronic hardware).
  8. Sep 28, 2012 #7


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    Excuse me, I tried, without success, to remove my post #5 above after I re-read your Opening post: "cheap and readily available technology for the Third World". Clearly what I referred to does not meet the limits you set. Sorry for the error.

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