How to add force at one point?

[Aristomo]

I have a robot and I want to add forces at one point on this robot. Just like there is a hand to push it, but I do not want others see it. Ho w to do this? I wish the point where will be push can be given according to the coordinate. Thanks!

[yuvaltassa]

Write into xfrc_applied to apply the force/torque at the body com, or use mj_applyFT is you want an arbitrary point.

[Kcygt]

Hi,
Do you have any example for mj_applyFT ?
Thank you

[yuvaltassa]

Isn't there something in the tutorial? Maybe not

[Kcygt]

I don't know which tutorial you referenced. There are a number of videos on this link ( https://www.youtube.com/watch?v=j1nCeqtfySQ ), but I didn't notice any examples. Could you share any other tutorials you may know of?

[yuvaltassa]

I meant the introductory tutorial, of course. Not clear how you missed it, that's a pretty prominent location. Do you think there is a place it should be mentioned where it isn't? It's also here, so I don't know where else I can put it...

That said, mj_applyFT is not mentioned in the tutorial. In the second cell under "Simulation", you would do something like:

frames = []
mujoco.mj_resetData(model, data)
bodyid = model.body('box_and_sphere')
while data.time < duration:
  mujoco.mj_applyFT(model, data, my_force, my_torque, point_on_body, bodyid, data.qfrc_applied)
  mujoco.mj_step(model, data)
  if len(frames) < data.time * framerate:
    renderer.update_scene(data, scene_option=scene_option)
    pixels = renderer.render()
    frames.append(pixels)

[Kcygt]

That's useful. Thank you.