Walker2d
State and action spaces
The default 17-value observation is qpos[1..] followed by all velocities clipped to \([-10,10]\); retaining root x produces 18 values. The default action is six controls in \([-1,1]\).
Dynamics and reward
\[ r=w_fv_x+r_{healthy}-w_u\lVert u\rVert_2^2. \]
Health requires root height strictly inside healthy_z_range and torso angle strictly inside healthy_angle_range. Info contains x position/velocity, z displacement from reset, and forward/control/survival components.
Episode end
Unhealthy state terminates when configured; the horizon truncates.
Configuration
| Field | Default | Meaning |
|---|---|---|
xml_file, frame_skip | embedded, 4 | Model and action duration |
| forward/control weights | 1, 0.001 | Reward coefficients |
| healthy reward | 1 | Survival reward |
| terminate unhealthy | true | Enable health termination |
| healthy z/angle ranges | (0.8,2), (-1,1) | Strict health tests |
| reset noise | 0.005 | Uniform qpos/qvel noise |
| exclude root x | true | Observation switch |
| horizon | 1000 | Truncation limit |
Reference: Gymnasium Walker2d.