X2-N: A Transformable Wheel-legged Humanoid Robot with Dual-mode Locomotion and Manipulation

2026-04-23

AI Summary

This work addresses the limitations of conventional wheeled-legged robots, which suffer from insufficient stability and maneuverability in legged locomotion and lack upper limbs for dexterous manipulation. To overcome these challenges, we present X2-N, a high-degree-of-freedom morphing robot capable of seamless transitions between humanoid and wheeled-legged modes through joint reconfiguration. We develop a unified reinforcement learning-based whole-body control framework that integrates hybrid locomotion, morphological adaptation, and manipulation tasks within a single policy. Experimental results demonstrate that X2-N efficiently performs dynamic skating, stair climbing, and package delivery, exhibiting exceptional terrain adaptability and robust coordination between locomotion and manipulation.

Technology Category

• Intelligent Robots: Manipulation
• Machine Learning: Imitation Learning & Inverse Reinforcement Learning
• Planning, Routing, and Scheduling: Replanning and Plan Repair

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Search and Retrieval-Augmented AI: Multilingual and cross-lingual Web search

Abstract

Wheel-legged robots combine the efficiency of wheeled locomotion with the versatility of legged systems, enabling rapid traversal over both continuous and discrete terrains. However, conventional designs typically employ fixed wheels as feet and limited degrees of freedom (DoFs) at the hips, resulting in reduced stability and mobility during legged locomotion compared to humanoids with flat feet. In addition, most existing platforms lack a full upper body with arms, which limits their ability to perform dexterous manipulation tasks. In this letter, we present X2-N, a high-DoF transformable robot with dual-mode locomotion and manipulation. X2-N can operate in both humanoid and wheel-legged forms and transform seamlessly between them through joint reconfiguration. We further propose a reinforcement learning (RL)-based whole-body control framework tailored to this morphology, enabling unified control across hybrid locomotion, transformation, and manipulation. We validate X2-N in a range of challenging locomotion and manipulation tasks, including dynamic skating-like motion, stair climbing and package delivery. Results demonstrate high locomotion efficiency, strong terrain adaptability, and stable loco-manipulation performance of X2-N, highlighting its potential for real-world deployment.

Problem

• wheel-legged robot
• humanoid locomotion
• dexterous manipulation
• mobility
• stability

Innovation

• transformable robot
• dual-mode locomotion
• wheel-legged humanoid
• reinforcement learning control
• loco-manipulation