Known as M-Blocks, the robots are
cubes with no external moving parts. Nonetheless, they’re able to climb over
and around one another, leap through the air, roll across the ground, and even
move while suspended upside down from metallic surfaces. Inside each M-Block is
a flywheel that can reach speeds of 20,000 revolutions per minute; when the
flywheel is braked, it imparts its angular momentum to the cube. On each edge
of an M-Block, and on every face, are cleverly arranged permanent magnets that
allow any two cubes to attach to each other. Researchers studying
reconfigurable robots have long used an abstraction called the sliding-cube
model. In this model, if two cubes are face to face, one of them can slide up
the side of the other and without changing orientation, slide across its top.
The sliding-cube model simplifies the development of self-assembly algorithms,
but the robots that implement them tend to be much more complex devices. To
compensate for its static instability, the researchers’ robot relies on some
ingenious engineering. On each edge of a cube are two cylindrical magnets,
mounted like rolling pins.
When two cubes approach each
other, the magnets naturally rotate, so that north poles align with south, and
vice versa. Any face of any cube can thus attach to any face of any other. The
cubes’ edges are also beveled, so when two cubes are face to face, there’s a
slight gap between their magnets. When one cube begins to flip on top of
another, the bevels, and thus the magnets, touch. The connection between the
cubes becomes much stronger, anchoring the pivot. On each face of a cube are
four more pairs of smaller magnets, arranged symmetrically, which help snap a
moving cube into place when it lands on top of another. But the researchers
believe that a more refined version of their system could prove useful even at
something like its current scale. Armies of mobile cubes could temporarily
repair bridges or buildings during emergencies, or raise and reconfigure
scaffolding for building projects. They could assemble into different types of
furniture or heavy equipment as needed. And they could swarm into environments
hostile or inaccessible to humans, diagnose problems, and reorganize themselves
to provide solutions.
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