A ready-to-use MuJoCo simulation model of the Petoi Bittle X quadruped robot (V1, plastic P1S servos), with OpenCat gait data for trot, walk, crawl, and more.

Mass properties are physically validated from direct measurement of a Bittle X V1 / BiBoard V0_1 unit (2026-06-08):

Total simulated: 273.5 g — matches Petoi spec (265–290 g) ✓

Foot contact sites corrected to Y=0.072 m from shank body origin (previously 0.05 m). Joint damping tuned to 1.5 for stable open-loop trot.

pip install mujoco numpy
python example.py        # pose demo (stand, sit, buttUp, ...)
python example_trot.py   # trot gait demo

All gaits use the same conversion from OpenCat degrees to MuJoCo radians. trF (trot) and wkF (walk) have been visually verified; others are converted from the same source data but not individually tested.

balance, buttUp, calib, dropped, lifted, lnd, rest, sit, str, up, zero

from gaits import convert_gait, convert_pose, list_gaits

# Get all available gait names
print(list_gaits())

# Convert a gait to MuJoCo joint angles (radians)
trot = convert_gait("trF")  # shape: (48, 8)

# Convert a pose
stand = convert_pose("balance")  # shape: (8,)

• Visual meshes from PetoiCamp/ros_opencat (MIT License, Toshinori Kitamura)
• Gait data from OpenCatEsp32 (MIT License, Rongzhong Li)
• MJCF structure adapted from gravesreid/mujoco_mpc_bittle (Apache 2.0)
• MuJoCo model by Marc Hesse

For biologically grounded locomotion learning with spiking neural networks, see MH-FLOCKE.

Apache 2.0 — see LICENSE