Back exo modeling

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1

Dear AnyBody team,

I have a question regarding modeling a back support exoskeleton in AMS. Consider a back exo with two thigh segments and a vest segment. The vest is attached to each thigh segment in specific reference nodes located close to the hip joints. The question is: is it ok to connect the vest segments to both thigh segments using 2 any revolute joints? I mean generally is this an accepted way, or does it cause any close loop problem or similar issues?
Thanks,
Mina

2

Hi Mina,

In theory, it should not be a problem to connect the vest segment to thigh segments with AnyRevoluteJoint. You must be aware that the movement at the human hip is 3dof, so you need to take care of the mismatch somehow. It means that the motion data that you provide must account for the limited movement at the hip.

Best regards,
Dave

3

Thank you, Dave. I think I can account for that by using a combination of hard and soft constraints. However, as I only constraint the movement of the exo leg pads to the translational movement of the human thigh in X direction, there are some moments that I see a mismatch between location of the leg pad and interaction force location on thigh (mainly in Z direction. Is this generally fine or a big issue? I mean the human and exo segments should 100% match at the interaction points or a few centimeter movement is acceptable?

Thanks,
Mina

4

Hi Mina,

I think it is acceptable to have some relative motion between the human and the exoskeleton. That is how it is in reality in most cases.

Best regards,
Dave

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