Asti Model info for structural Analysis

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vigneshkc
Posts: 8
Joined: 08 Dec 2018, 14:41

Asti Model info for structural Analysis

Post by vigneshkc » 10 Dec 2018, 17:59

Hi everyone,

I recently started using V-rep and I am still in the learning process.

I have a few queries regarding the inbuilt Humanoid Robot : Asti. For my Master's Project I am working on Structural analysis of Humanoid robot. So I need the Dynamic loads acting on it.

My approach as a preliminary step was to use the mass-inertia properties of human being and use the values in Asti Robot.
For this:
1. I scaled Asti by 1.4 times to increase the height to 1.77m
2. Used the human mass inertia properties for most of the parts

I was looking for a way to find out the forces experienced by the body parts. For that I tried using force sensors (example : rightLowerLeg---> forcesensor---> auxiliary mass) Auxiliary mass and rightLowerleg has same mass i.e .5*mass of original rightLowerLeg

But the problem I am facing is that the force o/p I am getting form the sensor is very small (avg of only 20N) which doesn't seem to be right.

Please help me out with the above issue.

Thanks and Regards,
Vignesh K.C.

coppelia
Site Admin
Posts: 7199
Joined: 14 Dec 2012, 00:25

Re: Asti Model info for structural Analysis

Post by coppelia » 12 Dec 2018, 10:55

Hello,

for that, try to use the Vortex engine for more reliable data. Make also sure to compare the data from one engine to the other t get a feeling which engine provides better/worse data.

If you introduce auxiliary masses, then the results are also a bit biased. But you often do not have a choice.
But you can also read the force/torque acting along/around a joint with sim.getJointForce

Cheers

vigneshkc
Posts: 8
Joined: 08 Dec 2018, 14:41

Re: Asti Model info for structural Analysis

Post by vigneshkc » 12 Dec 2018, 18:39

Hi ,

Thanks a lot for your reply. I tried using the Vortex engine as suggested. But the results didn't change much (Average Force was about 21 N)

Is there something I am doing wrong. Please let me know after reviewing :

https://drive.google.com/open?id=1Qv1i2 ... 4UjgXVGcbS

I have already tried sim.getJointForce. But this is the same as the joint torques(for revolute joints) I guess. It doesn't give the the net force and moment experienced by the joint (which is what I want as an input to the stress analysis)

Thanks and Regards,
Vignesh

coppelia
Site Admin
Posts: 7199
Joined: 14 Dec 2012, 00:25

Re: Asti Model info for structural Analysis

Post by coppelia » 14 Dec 2018, 08:26

Your force sensor is only connecting to rightLowerLeg0, which has no children. Additionally, you have broken your model: look at your model by enabling all visual layers and you'll see that something's fishy.

Cheers

vigneshkc
Posts: 8
Joined: 08 Dec 2018, 14:41

Re: Asti Model info for structural Analysis

Post by vigneshkc » 14 Dec 2018, 12:26

Hi,
Thank you for your reply.

I added the lowerlegjoint as a child and the results came out good.
Thanks again

Regards,
Vignesh

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