Gripper Setup Guide

This guide walks you through the process of setting up a custom gripper for use with GraspDataGen. We'll use the Robotiq 2F-85 gripper as an example, but the same principles apply to other grippers.

Prerequisites

• Isaac Sim installed and configured
• Access to the Isaac Sim USD assets
• Basic familiarity with Isaac Sim interface

Step 1: Load and Save the Gripper

1. Load the gripper from Isaac Sim assets:

   • Open Isaac Sim
   • Load the gripper from: omniverse://isaac-dev.ov.nvidia.com/Isaac/Robots/Robotiq/2F-85/Robotiq_2F_85_edit.usd

2. Save the gripper locally:

   • Use File -> Save Flattened As...
   • Save to bots/robotiq_2f_85.usd
   • Important: Make sure to open the saved file before making any edits

Step 2: Ungroup the Robot

GraspDataGen does not handle nested robots yet, so we need to move the robot to the root USD path.

1. Select and ungroup the robot:

   • Select the Robotiq_2F_85 (defaultPrim) prim
   • Right-click and select "Ungroup Selected"
   • Caution: Don't select the one under that - you need the IsaacRobotAPI on that level
   

2. Set the default prim:

   • Right-click on the Robotiq_2F_85 prim
   • Set it as the defaultPrim from the right-click menu

Step 3: Add Root Joint

A root joint is needed to hold the hand steady throughout the simulation.

1. Create a fixed joint:

   • Select the Robotiq_2F_85 (defaultPrim) prim
   • Go to Create -> Physics -> Joint -> Fixed Joint
   • Name it root_joint or another name that won't clash
   

2. Configure the joint:

   • In the Properties window, set Physics | Joint | Body 1 to /Robotiq_2F_85/base_link

3. Add root_joint to the IsaacRobotAPI:

   • Select the Robotiq_2F_85 (defaultPrim) prim
   • On the Property tab find IsaacRobotAPI | robotJoints and click Add Target then select the root_joint

Step 4: Configure Finger Collision Detection (Optional)

Repeat these steps for both right_inner_finger and left_inner_finger.

Enable CCD (Continuous Collision Detection)

1. Select the finger:

   • Select Robotiq_2F_85/right_inner_finger

2. Enable CCD:

   • Check the box for Physics | Rigid Body | Enable CCD
   • Note: This won't actually be enabled during GPU simulation, but it's a parameter in grasp_sim.py for CPU-based simulation

Improve Collision Geometry

1. Make the finger non-instancable:

   • Select Robotiq_2F_85/right_inner_finger/visuals
   • Uncheck the box for "Instancable" directly under the prim path in the Property tab

2. Change collision approximation:

   • Find the Physics | Collider attribute on the /Robotiq_2F_85/right_inner_finger/visuals/Defeatured_2F_85_PAD_OPEN_fingertipsstep_01/Defeatured_2F_85_PAD_OPEN_fingertipsstep prim
   • Change the approximation from "Convex Hull" to "Convex Decomposition"
   

3. Enable shrink wrap:

   • Check the Physics | Collider | Advanced | Shrink Wrap checkbox

Visualize Collision Objects

You can visualize the collision objects as they will be simulated:

1. Click on the Eye icon at the top of the viewport
2. Check: Show By Type -> Physics -> Colliders -> Selected

Step 5: Repeat for Other Fingers

Apply the same configuration steps to the left_inner_finger.

Step 6: Save and Configure

1. Save the USD file after making all changes

2. Add gripper configuration:

   • Add your new gripper configuration to GRIPPER_CONFIGURATIONS in scripts/graspgen/gripper_configurations.py

   Here is an example of what the configuration should look like. At minimum, you need to set gripper_file, finger_colliders, and base_frame. Note that we set bite to half the size of the pad to show you can customize all the other configuration parameters:

   'robotiq_2f_85': {
       'gripper_file': 'bots/robotiq_2f_85.usd',
       'finger_colliders': ['right_inner_finger', 'left_inner_finger'],
       'base_frame': 'base_link',
       'bite': 0.0185,  # half of 37mm
   },
   

3. Test the configuration:

   • Your gripper should now be ready for use with the Gripper Definition tool (create_gripper_lab.py)

Important Notes

The Robotiq 2F-85 gripper from the Isaac Sim assets already has several important parameters configured that we didn't need to change:

• Mass values are set on the links to real-world masses
• Force and velocity limits are set on the driving joint (finger_joint)
• Mimic joints are properly configured for the remaining joints

These parameters ensure the gripper simulates correctly in the physics engine.