_apply_drag_force() seems unused, and unstable reward curve during trainning

[utomm]

Question about _apply_drag_force() method and reward stability:

Hi, thanks for sharing the source code of such an interesting and impressive work!

I've been exploring the code, and I noticed something that raised a question. In the LeggedRobot class, there is an _apply_drag_force() method. However, it seems this method is actually unused during simulation, which is different from what's described in the original paper. Is the open-sourced code is a modified version or it is just because the force is forgotten to be applied in the code?

Additionally, when attempting to reproduce the results using the provided training script, I encountered some issues with the stability of the reward curve. Is this expected behavior, or is there something I might be missing?

Thank you for your attention to this issue.

[gmargo11]

Hi @HuSha3k ,

There was indeed an issue with the apply_drag_force function. I have fixed it in the latest commit 8e743ac to match the implementation from the paper. You should find that it significantly stabilizes training. Thanks for your patience!

-Gabe