xArm7 Gripper can't Grasp Objects

[jonzamora]

Which model is the issue affecting?

• xArm7

What is the issue?

• I'm working on a task where an xArm7 can grasp and lift a cube with the help of mink, however, I ran into an issue with the gripper.

xarm-mink.mp4

Could someone help me debug the xArm7 gripper so it can grasp the cube properly?

I tried all the suggestions mentioned in google-deepmind/mujoco#786 and #54, though my attempts were unsuccessful so far.

Is there any additional context you can provide (e.g., a spec sheet or a URDF to show a value mismatch)?

• My code can be found here https://github.com/jonzamora/mink.
• To reproduce the video above, simply run mjpython examples/arm_xarm7.py

[kevinzakka]

I don't have a lot of bandwidth to fix this right now, but some things that can be done to improve this gripper:

• Custom geom colliders for the finger pads, like in the Robotiq model. Splitting into 2 boxes per pad for more contacts is even better.
• Adding <option cone="elliptic" impratio="10"/>.
• The forcerange on the gripper actuator seems excessively high (100 N?)
• Adding armature to the joints as was done with the Robotiq model for a bit more stability.