[Question] How to change the transformation direction of gripper

[harshp1509]

Question

i am trying lift the cube using myarm m750 but arm is not able to lift the cube . so i was thinking that it was because of frame transformation direction .

in the Franka robot case blue color array direction is in the finger direction but in my case it is in opposite direction.

i have follow the franka usecase and franka is working fine but in myarm m750 case it is not lifting cube.

what is the reason behind this problem????

reference:

ee_frame: FrameTransformerCfg = FrameTransformerCfg(
            prim_path="{ENV_REGEX_NS}/Robot/myarm_m750/base",
            debug_vis=False,
            visualizer_cfg=FRAME_MARKER_CFG.replace(prim_path="/Visuals/FrameTransformer"),
            target_frames=[
                FrameTransformerCfg.FrameCfg(
                    prim_path="{ENV_REGEX_NS}/Robot/myarm_m750/gripper",
                    name="end_effector",
                    offset=OffsetCfg(
                        pos=[0.0, 0.0, 0.1034],
                        rot=[1, 1, 0, 0],  # Rotation in radians (ZYX Euler angles)
                    ),
                ),
            ],
        )

[RandomOakForest]

Thank you for posting this. It may have to do with how your robot was imported. I'll move this to our Discussions section for the team to follow up.

[RandomOakForest]

Following up, your myArm M750 is likely not lifting the cube because the end-effector frame’s orientation does not match the convention expected by your control code. Adjust the frame transform in your configuration, and check the gripper’s physical parameters. Here is a summary with some guidance and troubleshooting for you to consider.

1. Frame Transform and Coordinate System Direction

Background

• Each robot arm in Isaac Sim has a unique coordinate system for its end-effector (gripper) frame.
• The Franka Emika Panda (commonly used in Isaac Sim examples) uses a coordinate convention where the Z-axis of the end-effector points in the direction of the gripper fingers.
• If your myArm M750 robot’s end-effector frame is oriented differently (for example, the Z-axis points away from the fingers), the same control code will not work correctly.
• If the frame transform is misaligned, the robot will approach the object incorrectly, making grasping and lifting fail.

How to Diagnose

• Use the Frame Visualizer in Isaac Sim to display the axes of the end-effector frame.
• Check the direction of the axes (X, Y, Z) relative to the gripper’s physical opening direction.
• Compare this with the Franka’s frame convention as shown in the Isaac Sim documentation and Isaac Lab robot integration guide.

How to Fix

• Adjust the frame transform in your robot’s configuration so the end-effector frame matches the convention expected by the controller.
• In Isaac Lab, this is typically done by setting the correct offset (position and rotation) in the robot’s configuration file.
• For example, if your gripper’s approach direction is -Z instead of +Z, you may need to add a 180-degree rotation about the appropriate axis in the transform.

Example:

# This is a generic example; adjust the rotation as needed for your robot
from omni.isaac.core.utils.rotations import euler_angles_to_quat

ee_offset = OffsetCfg(
    pos=[0.0, 0.0, 0.1034],  # Adjust as needed
    rot=euler_angles_to_quat([0, 0, 3.1416]),  # 180 degrees about Z
)

• See Isaac Lab Frame Transformer documentation for more on setting up transforms.

2. Gripper Physics and Contact Properties

• Even with correct transforms, the robot may fail to lift the cube if the gripper’s contact geometry, friction, or force settings are not suitable.
• Make sure your gripper has:
  • Sufficient closing force
  • Adequate friction between the gripper and the cube
  • Properly defined collision meshes for both the gripper and the cube

How to Check

• In Isaac Sim, select your gripper and the cube. Inspect their Physics > Collision and Physics > Material properties in the GUI.
• Increase friction coefficients if the cube slips.
• Ensure the gripper closes tightly enough to hold the cube.

3. Summary of Action Steps

1. Visualize and confirm the end-effector frame direction using Isaac Sim’s frame visualizer.
2. Adjust the frame transform (position and rotation) in your robot’s configuration so the end-effector’s approach axis matches the convention expected by your grasp planner/controller.
3. Check and tune gripper physics: friction, force, and collision geometry.
4. Test grasp and lift manually in simulation to verify.