Modular voxel tech could bring swimming robots into the mainstream

Bioinspired underwater robots that swim by undulating their bodies may be more energy-efficient than their rigid counterparts, but they’re also quite difficult to build. That could soon change however, thanks to a new modular robotics system.

Currently in development at MIT, the system incorporates individual building blocks known as voxels.

These are basically hollow plastic boxes made up of multiple narrow struts, which are stiff and load-bearing when pushed in one direction, but soft and flexible when pushed in others. This combination of characteristics allows robots to maintain their overall body shape while simultaneously flexing it from side to side – all without requiring complex custom-designed hardware.

In one demonstration of the technology, the scientists built a ~1-meter (3.3-ft)-long snake-like robot made up of 20 voxels joined end-to-end.

Actuators within its body pull on the sides of those voxels via steel cables, causing the voxels to sequentially compress and relax to one side or the other, producing undulations that travel from the front of the body to the rear (a tight-fitting neoprene skin makes it more hydrodynamic). Tow-tank tests showed that the robot is indeed able to efficiently swim through the water in this fashion.

A closer look at the Hydrosnake, with its neoprene skin taken off
A closer look at the Hydrosnake, with its neoprene skin taken off


And while the voxel-built “Hydrosnake” robot is made up of only about 60 individual components, the researchers state that a snake-like robot previously built by NASA (using conventional components) was made up of thousands. Additionally, whereas MIT’s own fish-like RoboTuna robot took two years to design and build, the Hydrosnake was put together in just a couple of days.

The voxels were also used to build a wing, the profile (cross-sectional) shape of which can morph to alter its lift-to-drag ratio. An array of overlapping scale-like tiles on its exterior maintain a watertight seal, even as the wing’s curvature is in the process of changing. Such wings could conceivably be used in systems that generate power from ocean waves, or that allow ships to move through the water more smoothly.

This underwater wing uses voxels to change shape
This underwater wing uses voxels to change shape


Additionally, because the voxel system in general can be easily scaled up to large applications, the scientists believe it could one day even be used in whale-inspired submarines that move by flexing mechanical flukes.

A paper on the study – which is being led by research assistant Alfonso Parra Rubio, Prof. Michael Triantafyllou and Prof. Neil Gershenfeld – was recently published in the journal Soft Robotics.

The Hydrosnake and the morphing wing can both be seen in action, in the video below.

Modular Morphing Lattices for Continuum Robotic Structures

Source: MIT

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