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AnyBody / SitToStand_Exo

Simple Exo model of Sit to stand, from old webcast
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What’s the function of this Force? #1

Open Taejun001 opened 2 years ago

Taejun001 commented 2 years ago

Hi, nowadays I'm working on the modelling of exoskeletons in AnyBody.But I don't know the meaning or the purpose of this driver. Could you give me some hints?

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Another question is why they created this torque between the human body and exoskeletons? I think 1000N is too large.

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Thank you! Best, TJ

melund commented 2 years ago

@mathauto Sorry, I think we have completely overlooked your old post here. I think I can quickly answer your questions, but I can very much recommend that you ask question like this on the anyscript forum: https://forum.anyscript.org

But I don't know the meaning or the purpose of this driver. Could you give me some hints? It adds kinematic constraint to the trunk posture. I.e. the angle between the pelvis segment and the thorax segment. Internally, the model has rhythm that distribute the angles between the different vertebra.

Another question is why they created this torque between the human body and exoskeletons? I think 1000N is too large.

It is not a direct force. Otherwise, you would be right. 1000 N would be too much. But it a adds a actuator which the muscle recruitment algorithm can use to balance the external forces. It is similar to how muscles forces are found in musculoskeletal models. The "strength" of the 'recruited actuator' determines how much the algorithm uses the force. A very strong actuator means a low penalty for the algorithm to use it. Hence force will act more like a 'reaction' force in a free-body diagram. If the strength is very low the algorithm will only use the force if nothing else can balance the external forces.