Lee Jae-Young, Han Seongji, Kim Munyu, Seo Yong-Sin, Park Jongwoo, Park Dong Il, Park Chanhun, Seo Hyunuk, Lee Joonho, Kim Hwi-Su, Bak Jeongae, Rodrigue Hugo, Kim Jin-Gyun, Cheong Joono, Song Sung-Hyuk
Advanced Robotics Research Center, Korea Institute of Machinery and Materials, University of Science and Technology, Daejeon 34103, Korea.
School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea.
Sci Robot. 2024 Aug 14;9(93):eadl2067. doi: 10.1126/scirobotics.adl2067.
Wheels have been commonly used for locomotion in mobile robots and transportation systems because of their simple structure and energy efficiency. However, the performance of wheels in overcoming obstacles is limited compared with their advantages in driving on normal flat ground. Here, we present a variable-stiffness wheel inspired by the surface tension of a liquid droplet. In a liquid droplet, as the cohesive force of the outermost liquid molecules increases, the net force pulling the liquid molecules inward also increases. This leads to high surface tension, resulting in the liquid droplet reverting to a circular shape from its distorted shape induced by gravitational forces. Similarly, the shape and stiffness of a wheel were controlled by changing the traction force at the outermost smart chain block. As the tension of the wire spokes connected to each chain block increased, the wheel characteristics reflected those of a general circular-rigid wheel, which has an advantage in high-speed locomotion on normal flat ground. Conversely, the modulus of the wheel decreased as the tension of the wire spoke decreased, and the wheel was easily deformed according to the shape of obstacles. This makes the wheel suitable for overcoming obstacles without requiring complex control or sensing systems. On the basis of this mechanism, a wheel was applied to a two-wheeled wheelchair system weighing 120 kilograms, and the state transition between a circular high-modulus state and a deformable low-modulus state was realized in real time when the wheelchair was driven in an outdoor environment.
由于结构简单且能源效率高，轮子在移动机器人和运输系统中一直被普遍用于移动。然而，与在正常平坦地面上行驶的优势相比，轮子在克服障碍物方面的性能有限。在此，我们展示了一种受液滴表面张力启发的可变刚度轮。在液滴中，随着最外层液体分子的内聚力增加，向内拉动液体分子的合力也会增加。这会导致高表面张力，使液滴从由重力引起的变形形状恢复为圆形。同样，通过改变最外层智能链块处的牵引力来控制轮子的形状和刚度。随着连接到每个链块的钢丝辐条的张力增加，轮子的特性反映出普通圆形刚性轮的特性，这在正常平坦地面上高速移动时具有优势。相反，随着钢丝辐条的张力减小，轮子的模量降低，并且轮子会根据障碍物的形状容易变形。这使得轮子无需复杂的控制或传感系统就能适合克服障碍物。基于这种机制，一个轮子被应用于一个重达120公斤的两轮轮椅系统，并且当轮椅在户外环境中行驶时，实时实现了圆形高模量状态和可变形低模量状态之间的状态转换。
