"kick" in barkour example

[yuichiro-student]

In the following tutorial on the quadruped barkour,
https://github.com/google/brax/blob/main/brax/experimental/barkour/tutorial.ipynb
there is a kick in the step function as follows.

  # kick 
    push_interval = 10 
    kick_theta = jax.random.uniform(kick_noise_2, maxval=2 * jp.pi)
    kick = jp.array([jp.cos(kick_theta), jp.sin(kick_theta)])
    kick *= jp.mod(state.info['step'], push_interval) == 0
    qvel = state.pipeline_state.qvel  # pytype: disable=attribute-error
    qvel = qvel.at[:2].set(kick * self._kick_vel + qvel[:2])
    state = state.tree_replace({'pipeline_state.qvel': qvel})

It seems that this kick is injecting some noise to the velocity of the state in certain frequency.
Would you tell me the purpose of the kick? Is it for exploration during training or for something else? Thank you.

[btaba]

Hi @yuichiro-student , this was inserted to make the policy robust for sim2real transfer onto a robot