Update hand collision mesh due to the collision issues in Octomap and MoveIt

[oguzhanbzglu]

Problem

This MR updates the hand collision mesh (STL) to address collision issues observed in ROS 2 MoveIt when using OctoMap-based environment perception.

We are running the bimanual v1.0 robot in Isaac Sim with a top-mounted camera. The camera captures both the gripper and part of the hand assembly:

OctoMap generates collision objects from the depth image and is expected to ignore geometry that belongs to the robot itself. However, as shown below, OctoMap incorrectly creates collision voxels around the metal section at the base of the gripper:

The root cause is that the curved portion of the metal component is not fully represented in the current collision mesh. As a result, this geometry is not filtered out by the self-collision masking and is perceived as an external obstacle. The same issue could potentially lead to inaccurate collision checking on real hardware.

Solution

The hand collision mesh has been slightly extended based on the curved size to fully cover the missing curved section of the metal component.

This update resolves the OctoMap self-filtering issue while keeping the mesh lightweight. The resulting STL file size remains effectively unchanged.

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[kou]

@stevenaya Could you take a look at this?

[stevenaya]

We will first merge #64, then see if this problem remains.

[stevenaya]

I think we may consider updating the collision mesh for v1.0 later to provide more detailed collision handling. Let me discuss this with our team member.

[oguzhanbzglu]

Hello, thank you for considering this change. However, even though this change is independent of #64, if you expand the collision area, you might also want to consider modifying the inertia properties of the link defined in #64 to account for the change in mass.