# A Stair-Climbing Wheelchair with Novel Spoke Wheels for Smooth Motion
However, its complex manufacturing process hinders practical implementation. Overall, existing stair-climbing wheelchairs generally exhibit drawbacks such as structural complexity, inability to maintain user posture, and reliance on external assistance [14]. Therefore, a simple-control, highly adaptive wheelchair is needed to support users in independently completing daily activities. Spoke wheels integrate the functions of both wheels and legs into a single wheel-leg mechanism, offering simple control and excellent terrain adaptability. These advantages make them highly promising for applications in outdoor exploration, material transportation, medical rehabilitation, and home mobility. For instance, TERMES robots developed by Harvard University [15] mimic ant swarm behavior for post-disaster search and environmental monitoring. The Whegs series from Case Western Reserve University [16] demonstrates superior locomotion on uneven terrains, making it suitable for hazardous operations. The ASGUARD platform from the German Research Center for Artificial Intelligence [17] is designed for military and emergency rescue missions, facilitating efficient transport. Additionally, A soft-driven robot developed by Hanyang University [18] achieves gecko-like crawling through coordinated wheel-leg movements, enabling operations in confined spaces for rescue and inspection tasks. These applications highlight the broad potential of spoke-wheel mechanisms. Despite their strong obstacle-crossing performance, maintaining stable motion on flat surfaces remains a challenge for traditional spoke wheels. To address this, researchers have explored transformable spoke wheels that morph into circular wheels for smoother locomotion, such as Texas A&M's \(\alpha\)-WaLTR [19], Shang hai Jiao Tong University's Trimode [20], and Tianjin University's RHex-T3 [21], as well as designs from Hanyang University [22] and the University of the West of England [23]. While these approaches improve performance, they introduce additional structural and control complexity. Without altering spoke-wheel morphology, Virginia Tech's IMPASS [24] employs extendable active spokes to partially mitigate stability issues, albeit at the cost of increased system complexity. Similarly, Hanbat University [25] incorporated springs between spokes and their terminals to enhance compliance, yet this modification does not fully resolve the oscillation problem. In summary, while spoke-wheel mechanisms offer simple control and strong adaptability to uneven terrain, their inherent oscillation during flat-terrain movement limits their practical application in wheelchairs. To overcome this limitation, this paper proposes a novel spoke-wheel mechanism, Flexwheel, designed to achieve smooth wheeled motion while preserving obstacle-crossing advantages. Based on this mechanism, an intelligent stair-climbing wheelchair prototype is developed, featuring simple control, strong terrain adaptability, and the ability to maintain user posture stability (as shown in Figure 1). Software simulations and physical experiments demonstrate that the proposed wheelchair not only mitigates the oscillation issue of traditional spoke wheels on flat surfaces but also integrates multiple sensors to enhance autonomy and intelligence.