[Sara]

Hi Hugo,

Thanks for your reply. Yes, I have been actually having trouble setting the alarm distance, contact distance and time step. So far, I have managed by trial and error, but as you can imagine this is very time consuming and still gives me a slow simulation with lag as well as occasional contact failure. Each time I make an adjustment to the CAD file of the gripper, I have to again keep changing these three variables randomly until the gripper can safely make contact with the breast tissue model.

Any advice you can give me regarding how I can best choose these variables would be very helpful. I have supplied meshes, controller and main script for my SOFA scene in the file below, in the case that numerical settings are not the main issue here:

https://1drv.ms/u/s!ApELNE0leU38gkKmAH7Cr73U_dco?e=4MzJfu

My best regards,

Sara

[Sara]

It was the fixing boxes… It’s solved!

[Sara]

I am having some problems again as I add more elements to the scene:

I have assembled the gripper fingers with the full scene, but something is wrong with my animation again during bending. I think I might be forgetting to solve a constraint or have defined something incorrectly. I am printing the cable constraint values to terminal, and they are increasing and decreasing as they should, but the actual model itself is not bending, only flickering between the visual model and the mesh (I will post a link to some pictures below for clarification).

https://1drv.ms/u/s!ApELNE0leU38gje5AYDDvvPYROEP?e=HlWRtJ

I checked my code (especially the controllers and where they are attached and implemented) but I can’t find what could be wrong. I have put the meshes and *.py files in a the link below.

https://1drv.ms/u/s!ApELNE0leU38gighSP97f_BdaPeS?e=WEY5kP

Any advice on what I could do to solve this or what might be wrong is really appreciated.

Thanks!

Sara

[Sara]

Hi Elie,

It works!!! I kept having problems until I added print(self.cableconstraintvalue.value) as well as print(c) like you recommended.

Thanks so much for your help,

Sara

[Sara]

Hi Elie,

Thanks for getting back to me so quickly! I have used your exact code and it has solved my translation issue- the finger moves in the plane, it is just not bending. I am sure the implementation is now correct, it is just not working in my scene. I am using mac OSX- do you think it could be a hotkey issue? Even though I am using [cmd + “-“] or [cmd + “M”], it has no effect on the finger. Sorry to to trouble you with this, any advice you can give me on what I could do would be helpful.

Also, I have added in the fixes to my bounding box and it seems to be behaving better during actuation- thanks again!

Sara

[Sara]

Hi Elie,

Thanks very much for your help! You’re right, I have forgotten to include that mesh. I am able to move the finger in the plane now after implementing your code, but it will not close or open (bend inwards or outwards). I have had this similar problem when I tried the CableGripper/PneunetGripper SoftRobots tutorials; is it something to do with my definition of the cable or cable points?

Many thanks,

Sara

[Sara]

Hi SOFA,

I am trying to debug my code to find out why my gripper finger is not moving. I have simplified it down to just one finger with all the basic components necessary to simulate cable actuation. I am not getting any results, I think I am missing something important or doing something wrong. I’ve attached a file below that contains both version of my code (The full gripper and the newer test code with just one gripper finger), as well as the mesh files I am using.

https://1drv.ms/u/s!ApELNE0leU38gjAAcZSebNS-RrPr?e=cbPkWN

If anyone has the time to have a look at the code, it would be very appreciated.

Thanks!

Sara

[Sara]

Hi again RowingMK2,

I have used your linked files to create surface and volumetric meshes and loaded them into SOFA. I did not seem to face any problems and they appeared to be fine.

I have included my mesh files in the same link you provided:

https://dgistackr-my.sharepoint.com/:f:/g/personal/550160_dgist_ac_kr/EtkCoIapFw9NtGidQxGkx0ABu4aSrdH6O6O8fQxgzFE4_Q?e=dftJ5D

Could you try load them into your scene and check if they work?

Good luck!

Sara

[Sara]

Hi RowingMK2,

I was facing this problem last week, and have recently resolved it. I will walk you through step-by-step what I did. I roughly followed the instructions given here:

From design to mesh generation using FreeCAD and GMSH

You must first export your design file in *.brep format. This will depend on the CAD software you are using; for me, I am using SolidWorks, and so I exported my drawing as a *.igs file (keeping only the contours of my 3D body). Open this file in Gmsh, and select Tools > Options and set your 2D algorithm to MeshAdapt. You may also choose to decrease your element size to obtain a courser or finer mesh.

Then, from the left hand bar, select Modules > Mesh > 2D and this should produce a triangular and fairly homogeneous surfacic mesh. Save this as a *.msh file. Gmsh will offer you an options pop-up and there you must select ASCII Version 2. Follow the same Modules > Mesh > 3D to obtain your tetrahedral (volumetric) mesh, and save this in the same way.

I hope this helps you!

Sara

[Author]

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