Strange Behaviours of the Robot When Running with Flex backend

Autonomous Machines Robotics - Isaac Isaac Gym
1

Hi,

I just realized that both the kuka robot and my own custom robot behaves very strangely when running with --flex. You can reproduce this issue by running the kuka_bin.py example.

With Flex, several joints of the kuka move unpredictably, which looks completely different from when running with PhysX

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I also reproduced the problem with my own custom robot. Indeed, my robot also had issues with gym.set_actor_dof_position_targets(...) and gym.set_attractor_target. Sometimes, the robot in Flex cannot follow the targets, even though in PhysX, it works normally. Sometimes, the links even fall apart.

Could you give me some advice?

Thanks a lot,
Bradley

2

Hi Bradley,

I think this is likely due to some poorly conditioning of in the Allegro fingers. Flex uses a maximal coordinate solver which is more sensitive to these issues. Increasing the asset_options.armature 0.01 appears to help, but will also change the dynamics a little. If you’re doing rigid body manipulation then I would recommend PhysX for this scenario since it uses a reduced coordinate solver which is less sensitive to this issue.

Cheers,
Miles