Lightweight Humanoid Locomotion with Minimal Sensing: IRSE X1's Design and Reinforcement Learning Control

This paper presents IRSE X1, a lightweight humanoid robot designed for robust blind locomotion using only proprioceptive sensing. IRSE X1 stands 1.2 meters tall, weighs 12 kilograms, and features a minimalistic design combining aluminum sheet metal, machined parts, and 3D-printed components. It utilizes an inertial measurement unit (IMU) as its sole sensor, eliminating reliance on exteroceptive devices such as LiDAR or depth cameras. Locomotion policies are trained via reinforcement learning in Isaac Gym and transferred to MuJoCo for high-fidelity validation, achieving stable walking across challenging terrains, including slopes, stairs, and uneven ground. The robot's electrical and mechanical architecture prioritizes simplicity, cost-effectiveness, and maintainability, with all components (except the power board) sourced off-the-shelf. Experimental results demonstrate that IRSE X1 achieves reliable blind walking while significantly lowering weight, system complexity, and development barriers compared to conventional humanoid platforms. This work highlights a pathway toward affordable, robust, and adaptable humanoid robots for diverse real-world environments.