A wheel drive mechanism is simple, stable, and efficient, but its mobility in unstructured terrain is seriously limited. Taking inspiration from art- and mathematics-based origami techniques, a team of engineers, has recently designed a set of high-load capacity, shape-shifting wheels. Hankook’s R&D department has been working with biorobotics experts from Seoul National University and Harvard engineers on the project.
The transformable wheel based on membrane origami can drastically change its diameter when transporting heavy loads or overcoming obstacles. With simple fabrication, high weight-to-payload ratio, and large shape variation, enabling softness and flexibility, the kinematic mechanism neutralizes joint distortion, absorbs shocks from the ground, and is capable of bearing more than a 10-kilonewton load.
It took a team of engineers almost ten years to get four fully functional wheels that can be fitted to various prototype vehicles. As a result, the team built a fully functional set of convertible wheels and installed them on demonstration vehicles, showing the wheels can change diameter from 46 to 80 cm while supporting the weight of a full-size body.
Hankook’s experimental wheels are made up of three layers based on a thick, flexible composite membrane designed to fold along lines similar to origami. For increased structural strength and durability, the rigid panels are clamped with laser-cut aluminum facet panels that retain most of the membrane stiffness except for fold lines. In the basic state, the wheels are at a minimum diameter – but when squeezed horizontally, they fold up to their maximum diameter, and the internal locking plates add stiffness to the structure.
In the video, the team shows how the transformable wheels can be used so that small robots can move neatly and low to dive under obstacles or high to move faster and smoother. Previous prototypes also included retractable bars that unfold as the wheels expand, effectively attaching a kind of climbing device to the wheels that can pull the vehicle over lugs well beyond the wheel’s diameter.
The researchers note that the new design’s multifaceted surface is certainly much smoother than earlier prototypes but still looks bumpy compared to a conventional tire. On the other hand, such a transformable capability can come in handy in extreme off-road conditions, especially in vehicles like rovers designed to explore the alien landscapes of extraterrestrial bodies – like Mars or the moon.