Cable Gripper cannot grasp objects

[SoftRobots3]

Hi everyone,
I'm using the tutorial "Cable Gripper" to simulate a soft cable gripper.
I'm using the same code; I just changed the gripper files (.stl and .vtk) and the cable.json file.

The gripper can move and bend without problem in a realistic way, but it's impossible to grasp the object.

The collision between the gripper and the object is detected; however, as soon as the gripper enters contact with the cube, the cube starts flying around. This is strange because when I started the animation, the cube fell down on the floor because of gravity.

My only guess is that there is a problem with the mesh of my gripper (the design is a little bit complex, and the size of the elements is a little bit smaller than the size of the elements in the tutorial). But I could be wrong as I tried to make them bigger, reducing the complexity of the design, but I didn't solve the problem (and in any case, I'm losing interesting information about the interaction between the gripper shape and the object).

I'm designing the gripper in Inventor, and then generating the .vtk file using FreeCAD and GMSH.

Any suggestion will be really appreciated!

Thank you!

[hugtalbot]

Hi @SoftRobots3

The collision between the gripper and the object is detected; however, as soon as the gripper enters contact with the cube, the cube starts flying around. This is strange because when I started the animation, the cube fell down on the floor because of gravity.

Is you own gripper mesh colliding with the cube at first step?
You are correct it could also be an issue with the mesh itself.
Would you have a recording / video of the phenomenon you describe?

Cheers

[hugtalbot]

Hi @SoftRobots3 could you send me your files again please?

[hugtalbot]

Hi @SoftRobots3

• could you try to take a screenshot of the contacts between the pliers and the cube please? I can not really see them
• could you try increasing the friction coefficient ?
• the prefab ContactHeader() is using a LocalMinDistance as proximity, I would like to test another one like MinProximityIntersection could you try it ?

Cheers

[hugtalbot]

Hi @SoftRobots3

Are your fingers and the cube all rigid bodies?

[SoftRobots3]

Hi @hugtalbot,
The cube is a rigid body, I'm importing it from stlib3.physics.rigid.
The fingers are not rigid as I'm using the function "ElasticMaterialObject".

[hugtalbot]

Hi @SoftRobots3

have you tried to define smaller steps for closing the fingers?
It could be that the position of your soft fingers significantly changes from one time step to another regarding the relative mass of both the fingers and the cube.

Do you have a full scene that we could test ourselves?

[github-actions[bot]]

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@SoftRobots3
Feedback has been given to you by the project reviewers, however we have not received a response from you. Without further news in the coming weeks, this discussion will be automatically closed in order to keep this forum clean and fresh 🌱 Thank you for your understanding

[github-actions[bot]]

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@SoftRobots3
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