Shipped: Hrobot: a small humanoid robot that learns to walk

Hrobot is a 230 mm, 20-DoF humanoid robot built from Dynamixel XL330 servos. Its walking, get-up, and rough-terrain policies are trained with reinforcement learning (PPO in mjlab, MuJoCo physics) and run directly on an ESP32-S3 at 50 Hz, using only the IMU and the servo encoders. Each policy is a small MLP that fits in 63 kB. The videos show the policies in MuJoCo physics. The open firmware is verified against ONNX Runtime on a PC but has not yet been tested on the physical robot.