How to gravity conpensate for typical parts in robot?

[exaFLOPs26]

I wanted to do gravity compansation of robot in simulation.

#529

I tried to follow the same process of this but seems it is not working. The arms are falling down.

Or is there gravity compensation for DifferentialInverseKinematicsActionCfg?

` gravity_flags = env.scene.articulations['robot'].root_physx_view.get_disable_gravities().clone()

# Find body indices for the links you want to disable gravity for
index_a, _ = env.scene.articulations['robot'].find_bodies('arm.*')
index_l, _ = env.scene.articulations['robot'].find_bodies('link.*')
arm_bodies = index_a + index_l

# Assume articulation index is 0 (if you only have one robot)
articulation_index = 0

# Disable gravity for selected link indices
for link_index in arm_bodies:
    gravity_flags[articulation_index, link_index] = 1  # 1 = disable gravity

# Convert articulation_index to tensor of indices
indices = torch.tensor([articulation_index], dtype=torch.uint32)

# Send new gravity flags to backend
env.scene.articulations['robot'].root_physx_view.set_disable_gravities(gravity_flags, indices)

# Print to verify
print(env.scene.articulations['robot'].root_physx_view.get_disable_gravities())`

[exaFLOPs26]

I found out that even I did not set anything for DifferentialInverseKinematicsActionCfg gravity compensation force was not zero as you can see in the below.

But the arms are falling!!!

ipdb> env.scene.articulations['robot'].root_physx_view.get_gravity_compensation_forces()
tensor([[-0.0000e+00, -0.0000e+00, 8.1209e+02, -5.7220e-06, 7.9388e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 1.4901e-08, 0.0000e+00,
-0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00,
0.0000e+00, 0.0000e+00, 0.0000e+00, 0.0000e+00, 6.9268e-01,
-6.9268e-01, -3.9284e+00, -3.9284e+00, -1.3000e+01, -1.3000e+01,
-1.5951e+00, -1.5951e+00, 8.3648e-02, -8.3649e-02, 0.0000e+00,
0.0000e+00, 1.5188e-01, -1.5188e-01, -1.6276e-01, 1.6276e-01]],
device='cuda:0')

[exaFLOPs26]

I don't want to use super big stiffness and damping as they are not realistic.

[exaFLOPs26]

To give more info,

• I tried OSC with gravity compensation, it did not work.

• I found out that for DifferentialIK, automatically giving gravity compensation as above.

• Isaac Sim works well with reasonable stiffness and damping with target position but IsaacLab does not.