How to modify configuration at reset in the gym environment?

[perrin-isir]

Hi, I wonder how one could set the initial configuration (including orientations) at reset in the gym env.

upkie_base_env (https://github.com/tasts-robots/upkie_locomotion/blob/main/envs/upkie_base_env.py) has a bullet interface (cf https://tasts-robots.org/doc/vulp/BulletInterface_8h_source.html) in which there's a position_init_base_in_world (see also https://tasts-robots.org/doc/vulp/structvulp_1_1actuation_1_1BulletInterface_1_1Parameters.html#a47b738f18c99bebd00ee742ff024569a) but for instance no orientation_init_base_in_world. Similarly, I don't see how to modify the initial joint values.

What would be the best solution for that?

[stephane-caron]

The best way is to pass the initial orientation to the spine via the configuration dictionary. The orientation part was indeed not wired 😉 This is now fixed with upkie/vulp#33, so that we can write examples such as this one:

"""Genuflect while lying on a horizontal floor."""

import gym
import numpy as np
from loop_rate_limiters import RateLimiter

import upkie.envs

nb_genuflections = 10
genuflection_steps = 200
amplitude = 1.0  # in radians

config = {
    "bullet": {
        "orientation_init_base_in_world": [0.707, 0.0, -0.707, 0.0],  # [qw, qx, qy, qz]
        "position_init_base_in_world": [0.0, 0.0, 0.1],  # [x, y, z]
    }
}

if __name__ == "__main__":
    upkie.envs.register()
    with gym.make("UpkieServosEnv-v1", config=config) as env:
        observation = env.reset()
        action = np.zeros(env.action_space.shape)
        rate = RateLimiter(frequency=200.0)
        for step in range(nb_genuflections * genuflection_steps):
            observation, _, _, _ = env.step(action)
            x = float(step % genuflection_steps) / genuflection_steps
            y = 4.0 * x * (1.0 - x)  # in [0, 1]
            A = amplitude  # in radians
            action[[0, 1, 3, 4]] = A * y * np.array([1.0, -2.0, -1.0, 2.0])
            rate.sleep()

It looks like this:

genuflections.mp4

Hoping this helps 😃

[perrin-isir]

Thanks a lot!

What about the joint values? Can they also be modified via the config for all resets?

[stephane-caron]

This makes sense 👌 It should be a straightforward change → #64.

[perrin-isir]

I see, thanks!