Using Stretch with dex-wrist in Gazebo

Hello everyone,

I’ve been running into some issues trying to use the simulated Stretch in Gazebo with the added dex-wrist to try to pick up an object and failing. Right now the robot has just been teleoperated. I wonder if there are any plugins for the gripper that got deconfigured when I made the changes to the URDF to add the dex-wrist. I have tried both with models of objects (e.g. a can) or with just a cube or cylinder from Gazebo default objects.

Any information on this would be greatly appreciated!

Hey @umlmecu, I don’t know of any gripper plugins that may have been deconfigured, but @Mohamed_Fazil knows the Gazebo stack better, so he may know. Mohamed is out of office atm, but I can definitely try to reproduce and possibly solve the issue you’re seeing. Would you take a video of the behavior you’re seeing? Steps to reproducing it myself would be helpful as well.

My students sent me a 30sec video and I added a 4sec cropped one that just shows the robot wobbling and the object flying off. For this video, they launched the empty world (using stretch_gazebo gazebo.launch), added the table and can, and they used the keyboard teleop.

I have seen this same behavior when you use the moveit_config sending poses through RViZ.

Full 30sec video

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Great thanks, let me look into this and get back to you shortly.

Hi @umlmecu, Sorry for the very delayed response as I was out of the office for a while. As you suggested, I tried reproducing the issue within the Stretch in the Gazebo environment. I tried to pick up a Cup from the surface using the DexWrist and the standard gripper. I couldn’t reproduce the issue of the object flying. But I was able to see the robot wobbling a lot and the object kept slipping away. I suspect this issue is due to the inaccurate Internia and friction coefficient values that are set for the robot links. We are looking forward to fixing this issue with our URDF for gazebo in the near future.

Alternatively, as a quick fix for now, you can try to use the gazebo GraspFixPlugin that would enable an object stick to the arm link when force is applied from two gripper finger links onto the object. I still haven’t tried implementing this quick fix, but I can share the code here once it is ready.