Data and simulation model files for: Variable-stiffness morphing wheel inspired by the surface tension of a liquid drop

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.