Why the grippers are not in the middle of the gripper base and the grippers sinking into the cube when gripping?

[sophia.chen2013]

Isaac Sim Version

[v] 4.5.0
4.2.0
4.1.0
4.0.0
4.5.0
2023.1.1
2023.1.0-hotfix.1
Other (please specify):

Operating System

[v] Ubuntu 22.04
Ubuntu 20.04
Windows 11
Windows 10
Other (please specify):

GPU Information

NVIDIA GeForce RTX 4070
NVIDIA-SMI 535.183.01

Topic Description

Detailed Description

Grippers are not in the middle of the gripper base and the grippers sinking into the cube when gripping.

Steps to Reproduce

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Error Messages

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Screenshots or Videos

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Additional Information

What I’ve Tried

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Related Issues

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Additional Context

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[michalin]

Hi there thank you for your question.

1. Why are the grippers not in the middle?
   You want to make sure that one of the robot finger joints is mimicing the other finger for them to close towards the center. You can find an example in this URDF. If set up correctly you should be able to see on Isaac Sim GUI Windwos>Physics>Physics Inspector that the joint is set to “Mimic joint” as shown in the screenshot (“panda_finger_joint2”).
   

   

2. Why are the gippers sinking in?
   There are two possibilities. One is that the collision mesh assigned to your robot finger is actually smaller in shape than the visualization mesh. You can check through the GUI by clicking on the eye symbol at the top like this:
   

   
   
   Second possibility is that you can set a non-zero collision offset
   You can read more about contact offsets here: Advanced Collision Detection — PhysX SDK Documentation

[sophia.chen2013]

The gripper has joint7 and joint8, I have set joint8 to mimic joint7 in urdf file ,and the usd file’s joint 8 can mimic joint 7 in isaac sim UI. But when I use the new urdf and usd files in my python code . There is a error as below:
Exception: Prim path expression [‘/World/piper_description/link6’] is invalid, a prim matching the expression needs to created before wrapping it as view

The link6 is the end_effector of the robotic arm.

[michalin]

Hi Sophia, thank you for the additional information. Would you be able to share your setup or steps to reproduce your problem? I may be able to help faster that way.