[Feature]: Add support of time integration to kinematic entity.

[Nodevon-WS]

Bug Description

I tried to use "set_dofs_velocity" to set the joint velocity, but after calling scene.step(), when I checked the velocity with the "get_dofs_velocity" function, I found that the velocity at this time was inconsistent with the value I had set. Could you please tell me the reason for this?

Steps to Reproduce

for i in range(len(plate_euler)-1):
turntable.set_dofs_velocity(velocity = (plate_euler[i+1, 2]-plate_euler[i, 2])fps/1803.1415926535, dofs_idx_local = 0, skip_forward = True)
scene.step()
print(turntable.get_dofs_velocity(0))

Expected Behavior

Set velocity takes effect immediately.

Screenshots/Videos

No response

Relevant log output

Environment

• OS: Ubuntu 20.04.6 LTS
• GPU/CPU: NVIDIA Corporation TU116 [GeForce GTX 1660 Ti] 11th Gen Intel® Core™ i7-11700 @ 2.50GHz × 16
• GPU-driver version: 470.256.02
• CUDA / CUDA-toolkit version: 11.4

Release version or Commit ID

version number 0.4.0

Additional Context

No response

[duburcqa]

It should work. Can you share a self-contained repro script?

[Nodevon-WS]

turntable.xml

test.py
I set dofs_velocity to a constant 1 rad/s in the test script, but the output shows that it does not take effect immediately.

[duburcqa]

It does take effect immediately. Just do:

    turntable.set_dofs_velocity(velocity = 1, dofs_idx_local = 0, skip_forward = True)
    print(turntable.get_dofs_velocity())

[duburcqa]

Use dt = 0.00001 and you will see it is applied. It just gets updated during step(), so it is no longer equal to the set value after it.

[Nodevon-WS]

Thanks for your reply. Setting dt = 0.00001 does work, so I understand that the velocity set by set_dofs_velocity is not actually constant during the step; it participates in dynamics interactions that are affected by the time step.
However, a time step of 0.00001 is far too small for my simulation. Are there other methods to keep the joint velocity constant throughout the step?

[duburcqa]

No, because it is not physical. Maybe we could extend our new KinematicEntity to support this. It should not be too hard.

[Nodevon-WS]

Thanks. Looking forward to the support of new features.