Axion¶
A GPU-accelerated physics simulator with non-smooth contact and exact friction.
Axion is a rigid body simulator built for robotics research where contact accuracy matters. Unlike simulators that smooth or approximate the friction cone, Axion solves the non-penetration contact constraints exactly and handles non-smooth friction — making it particularly well-suited for skid-steer locomotion, flipper robots, and any scenario where slip behavior drives the dynamics.
Key properties:
- Stable at large timesteps — 5×10⁻² s works well in most scenes; some contact-heavy scenes remain stable at 1×10⁻¹ s
- Parallel worlds — run thousands of independent simulations simultaneously on a single GPU
- Maximal coordinates — makes it straightforward to model unconventional robot morphologies accurately
- CUDA-accelerated — built on NVIDIA Warp and Newton
Helhest — 3-Wheeled Skid-Steer Robot¶
Helhest is a three-wheeled skid-steer robot that can also flip itself upright. Accurate friction is critical here: skid-steer turning depends entirely on the difference in lateral friction forces between wheels, and the flip maneuver requires correct contact dynamics throughout.
Skid-steer turning
Self-righting flip
Dense obstacle field
Motor realism on incline — P-velocity controller drifts under load as expected
Marv — Flipper Tracked Robot¶
Marv is a tracked robot with four articulated flippers — each flipper carries its own track. The combination of track contacts, flipper joints, and varying terrain makes this a demanding test for any simulator. Maximal coordinates make the morphology easy to express without hacks.
Skid-steer turning
Flipper articulation
Dense obstacle field
Large obstacle traversal
Getting Started¶
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Set up Axion and its dependencies
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Run your first simulation
Aleš Kučera — kuceral4@fel.cvut.cz Czech Technical University in Prague