Wheels have been commonly used for locomotion in mobile robots and transportation systems due to their simple structure and energy efficiency. However, the performance of wheels in overcoming obstacles is limited compared to their advantages in driving on normal flat ground. Here, we present a variable stiffness wheel inspired by the surface tension of a liquid drop. In a liquid drop, 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 the wheel can be controlled by changing the traction force at the outermost smart chain block. As the tension of the wire spokes connected to each chain block increases, the wheel characteristics reflect 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 decreases as the tension of the wire spoke decreases, and the wheel can be easily deformed according to the shape of obstacles. This makes the wheel suitable for overcoming obstacles without requiring complex control or sensing. Based on this mechanism, the wheel is applied to a 2-wheeled wheelchair system weighing 120 kg, and the state transition between a circular high-modulus state and a deformable low-modulus state is realized in real-time when the wheelchair drives in an outdoor environment.

This dataset is the raw data gathered from the experiment using the stiffness-variable morphing wheel in the article titled "Variable-stiffness morphing wheel inspired by the surface tension of a liquid drop". For measurements of wheel modulus, the two load cells (CSBA-50L, CAS Ins.) at the hub structure and one load cell (CSBA-50L, CAS Ins.) at the indenter were used in the experiment. A laser displacement sensor (ODSL 96B M, Leuze) was used to measure the positions of the indenter and hub structure. The data was collected with the NI DAQ module (cDAQ-9172, NI-9215, National Instrument) and LabVIEW software. Computer-aided design (CAD) files provide detailed shapes and dimensions of the major components of the morphing wheel and mobile platform that were used to generate this dataset. The simulation model files were developed to simulate the deformation characteristics of the morphing wheel both on a flat surface and while overcoming obstacles, focusing on changes in its modulus.