[Question] Implementing soft terrain for legged locomotion

[jnskkmhr]

My question is somewhat similar to this issue #90.

I am currently working on implementing a soft terrain contact model (more like a force model) based on resistive force theory described in this paper: https://arxiv.org/abs/1303.7065.

As an initial test, I dropped a robot foot from a height of 0.5m and observed that the terrain can support the object with a certain level of penetration.

My question is: what could be a promising approach to simulate this soft terrain model for legged robot locomotion, particularly for bipedal locomotion?
I found that simply applying force to the foot does not work effectively due to the resulting moments causing the robot to flip.
Do you think increasing contact points will help?
I already tried with 5 points (one at the center, 4 at the corner), but this did not work.

I can share my current code, which essentially computes the contact force based on the paper's formulation and applies it to the robot using the articulation API.

rft.mp4

[RandomOakForest]

Thank you for posting this. The best solution we found for this, currently, is that you can use WARP to model a soft terrain. There is an example script here that may be of help. Also, in our showroom page, there is some information about procedurally generated terrains with different configurations.

[jnskkmhr]

Hi @RandomOakForest
Thank you for the response.

I thought about that too, but I did not understand how to reflect the physics done in warp to IsaacLab simulation (how to integrate robot-particle interaction done by warp to Isaac?)
Also, as far as I tried both warp and PhysX particle system, running particle sim is really expensive.

Is there a way to apply force computed in warp to every vertices of mesh (like foot)?
It would be great if I can run sort of like reduced order terrain model (kind of like model which approximate foot-terrain interaction).
Then apply forces computed by this terrain model to foot mesh, that is my idea.

[RandomOakForest]

Thanks for following up. I'll move this into our Discussions section for the team to follow up.