rollin' rollin' rollin'

Scientists just reinvented the wheel, literally

This origami-inspired shape-shifter might change how we roll.

car on another planet sci fi

Thousands of years ago, the invention of the wheel rolled humans toward civilization. While it has gone through some minor changes over the course of history in terms of use (the first wheels might have been used to make pottery rather than for transport) and materials, the basic concept itself supposedly cannot be improved upon.

Except, perhaps, it can.

What’s new — In a paper published Wednesday in Science Robotics, researchers detail their design for an origami-inspired, shape-shifting tire that can change its own structure, switching between the more traditional, tall-and-skinny shape to a short-and-fat form. In so doing, the tire could offer drivers interesting advantages static tire structures just can’t manage.

The “high-load capacity origami transformable wheel” is not a catchy name, but the wheel uses something called the waterbomb tesselation origami pattern (which is an awesome name) to transition between small and large forms as it is being used.

Origami wheels similar to this one are not new, but these past designs weren’t very good at actually carrying loads during the transition process. A transforming wheel isn’t particularly useful to a driver if you first have to take all your gear off your rig to use it.

The new wheel, however, is capable of bearing more than 2,248 pounds in weight — even when transitioning between wheel shapes.

This image — from the paper — shows how the wheel transforms and how the diameter of the wheel changes from approximately 0.8 to 0.46 meters.

D. Lee et al, Sci. Robotics (2021)

How it works — The trick to the new wheel design is how it manages load during the transition stage. The origami tire design features flexible membranes that can puff out like a bellows between rigid constraints. In other words, the edges of the wheel have some flex in them, but the faces of the wheel are stiffer. The team determined that, by increasing the size of the membranes, they could give the wheel enough strength to bear a heavy load even during the transition phase between more stable wheel shapes.

The new membrane concept provides enough softness and flexibility in the wheel to absorb distortions and shock coming up from the ground, much in the same way as a traditional rubber tire. The tire’s tread also helps it to handle different terrains — the skinnier, taller state may be useful for going over ground littered with obstacles, for example, while the shorter, fatter state could be useful for going over sand, for example.

Why it matters — It’s unlikely that your next crossover will come with these trick wheels, but the wheels do have potential applications across a wide variety of use scenarios — like for vehicles wandering on extraterrestrial bodies, for example.

If a lunar or Mars rover had the ability to switch between wheel shapes when moving from rocks onto soft sand, it could help their wheels perform more optimally and extend their lifespan. It would also negate the need to design a single wheel shape for every possible outcome — a task that is rather difficult to do when your road surface is a hundred million miles away on another planet.

What's next — The team, which involved researchers from Harvard University, Seoul National University, and Hankook Tire and Technology Co., admits that the wheel prototype is not commercially competitive right now. But they believe its commercial value could be improved by integrating the new concept with typical rubber tire manufacturing processes.

Other airless tire technologies like this one, also designed by Hankook, could also be incorporated into future iterations of the design, which makes for even more exciting possibilities.

Tire technology continues to evolve, thanks to dramatic advancements in materials and compounds, new tread designs — the innovation is driven in part by the new challenges presented by the aerospace industry and military. An origami-inspired tire may be too complex for anything we’ll be driving down the highway any time soon, but for ultra-specialized applications — say on other planets — it could be just the ticket.

Abstract: Composite membrane origami has been an efficient and effective method for constructing transformable mechanisms while considerably simplifying their design, fabrication, and assembly; however, its limited load-bearing capability has restricted its application potential. With respect to wheel design, membrane origami offers unique benefits compared with its conventional counterparts, such as simple fabrication, high weight-to-payload ratio, and large shape variation, enabling softness and flexibility in a kinematic mechanism that neutralizes joint distortion and absorbs shocks from the ground. Here, we report a transformable wheel based on membrane origami capable of bearing more than a 10-kilonewton load. To achieve a high payload, we adopt a thick membrane as an essential element and introduce a wireframe design rule for thick membrane accommodation. An increase in the thickness can cause a geometric conflict for the facet and the membrane, but the excessive strain energy accumulation is unique to the thickness increase of the membrane. Thus, the design rules for accommodating membrane thickness aim to address both geometric and physical characteristics, and these rules are applied to basic origami patterns to obtain the desired wheel shapes and transformation. The capability of the resulting wheel applied to a passenger vehicle and validated through a field test. Our study shows that membrane origami can be used for high-payload applications.

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