无需电力的可变半径轮子，靠结构设计自动响应扭矩变化。
MORPH Wheel: A Passive Variable-Radius Wheel Embedding Mechanical Behavior Logic for Input-Responsive Transformation
- 通过柔性结构与扭矩耦合器，纯机械实现半径自动调节。
- 半径可在80mm至45mm间变化，输出扭矩超10N，精度高且可重复。
- 适合无人控制或环境复杂的机器人移动系统，如崎岖地形探测。
本文提出一种全被动的可变半径轮子——MORPH轮，其通过几何结构与柔顺设计嵌入机械行为逻辑，实现对输入扭矩的自适应响应。与依赖执行器、传感器和主动控制的传统变速系统不同，MORPH轮仅通过自身结构在无电条件下完成半径调节（80 mm → 45 mm）。该设计集成扭矩响应耦合器与弹簧加载连杆，具备三大特性：（1）通过对称耦合器实现双向无限旋转；（2）驱动模式下传动刚性，承载扭矩超过10 N；（3）基于确定性运动学的精确重复传动比控制。建立了完整的解析模型，揭示了直驱与半径变换模式切换的阈值条件。实验验证表明，在1.8–2.8kg轮重范围内，实测扭矩-半径及力-位移特性与理论预测高度一致。机器人级测试在0–25kg负载、坡道及非结构化地形上证实，该轮能被动调整半径以实现最优传动比。MORPH轮体现了机械编程理念，将智能、情境感知行为直接嵌入物理结构，为不确定或控制受限环境下的机器人移动系统提供了被动变速与机械智能的新范式。
原文摘要 · Abstract (English)
This paper introduces the Mechacnially prOgrammed Radius-adjustable PHysical (MORPH) wheel, a fully passive variable-radius wheel that embeds mechanical behavior logic for torque-responsive transformation. Unlike conventional variable transmission systems relying on actuators, sensors, and active control, the MORPH wheel achieves passive adaptation solely through its geometry and compliant structure. The design integrates a torque-response coupler and spring-loaded connecting struts to mechanically adjust the wheel radius between 80 mm and 45 mm in response to input torque, without any electrical components. The MORPH wheel provides three unique capabilities rarely achieved simultaneously in previous passive designs: (1) bidirectional operation with unlimited rotation through a symmetric coupler; (2) high torque capacity exceeding 10 N with rigid power transmission in drive mode; and (3) precise and repeatable transmission ratio control governed by deterministic kinematics. A comprehensive analytical model was developed to describe the wheel's mechanical behavior logic, establishing threshold conditions for mode switching between direct drive and radius transformation. Experimental validation confirmed that the measured torque-radius and force-displacement characteristics closely follow theoretical predictions across wheel weights of 1.8-2.8kg. Robot-level demonstrations on varying loads (0-25kg), slopes, and unstructured terrains further verified that the MORPH wheel passively adjusts its radius to provide optimal transmission ratio. The MORPH wheel exemplifies a mechanically programmed structure, embedding intelligent, context-dependent behavior directly into its physical design. This approach offers a new paradigm for passive variable transmission and mechanical intelligence in robotic mobility systems operating in unpredictable or control-limited environments.
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