Suction Gripper API Documentation

Hi all,

I’m currently implementing a suction gripper in Isaac Sim using a standalone script and the SurfaceGripper class (link). However, none of the parameters seem to be documented - they all have either [description] or [summary] as their documentation.

I was hoping this would be fixed in 2023.1.0, but it is still that way.

Apart from the obvious ones, like usd_path, translate, or direction: Can anyone explain these parameters in a bit more detail or link me to some sort of documentation?

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Yeah, it’s really rough. It seems to work fine if you ignore the offset rotation/orientation. Not sure why. The grip theshold I believe is the distance in meters within which the gripper will make a fixed joint. So 0.01 is 1 cm. The parentPath is the prim you’re putting the gripper on. The d6JointPath is what you’re naming the joint, which should be under the parentPath. I set the forceLimit, torqueLimit, stiffness and damping to 1e9. Don’t really understand what they do, but it works. retryClose will keep trying to close it, but only IIRC if you call update on the gripper. Otherwise you can just call close() every time step. Oh, and I think it’ll only auto-close if you explicitly call close() on the gripper once.

Anyway, this is from memory. Getting it to work was really frustrating.

Well at least I’m not the only one with this issue :D

I think the force_limit, torque_limit and bend_angle are parameters of the joint - i.e. if there is a force or torque applied to the joint that is larger than either one of these, the joint will break. And since it is probably a fixed joint, the kp and kd are probably the stiffness and damping of that joint to calculate the force applied to displacements away from it.

It would be really nice if we somehow got this confirmed officially instead of having to rely on guesswork, and I’m kind of surprised that this class is so badly documented, given how pervasive suction grippers are in industry applications.

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Indeed. I had guessed bend_angle specified the maximum possible angle between the gripper and the thing being gripped. There’s a kp and kd? Anyway, fun times :)

Here’s some documentation: Surface Gripper — Omniverse IsaacSim latest documentation

Glad you guys are digging into this since I will need it too eventually. :)