Robotic "particles" swarm together to move towards the light
Most robots are usually made to do one particular job, so they're not very adaptable to new situations. But that might change with a set of robots developed by researchers at MIT, Harvard, Columbia and Cornell Universities. These "particle robots," as the team calls them, are simple, circular devices that can connect to each other magnetically to move and work as a swarm.
Individually, the robots are pretty basic. Each one is made up of a ring of panels that can expand and contract like an aperture ring on a camera, growing from a diameter of 6 to 9 inches (15 to 23 cm). This is driven by a small motor, a battery and a microcontroller in the base. They also each have a light sensor and a communicator built in.
Each unit alone can't do much else besides expand and contract, but stick them together and they can communicate to move around as a whole. They all have magnets along their edges allowing them to loosely cling to each other, and through coordinated expanding and contracting, the entire swarm can shuffle towards a light source and even be made to carry or push objects.
The system itself can be made up of essentially any number of particle robots and configured into any shape that's needed. They could be arranged into a straight line to squeeze through tight gaps, or spread out to get more leverage and move faster. And because they aren't directly relying on each other, a single faulty unit won't compromise the rest of the pack.
"We have small robot cells that are not so capable as individuals but can accomplish a lot as a group," says Daniela Rus, an author of the study. "The robot by itself is static, but when it connects with other robot particles, all of a sudden the robot collective can explore the world and control more complex actions. With these 'universal cells,' the robot particles can achieve different shapes, global transformation, global motion, global behavior, and, as we have shown in our experiments, follow gradients of light. This is very powerful."
Particularly fascinating though are the algorithms that drive these group motions. Each particle will sense the intensity of the light and broadcast that figure to its buddies, while listening out for the same signals from the robots around it. The particles are programmed to move in a certain order, like a Mexican wave: those furthest from the light source will expand and contract first, followed by the next-furthest, all the way up to the closest.
"This creates a mechanical expansion-contraction wave, a coordinated pushing and dragging motion, that moves a big cluster toward or away from environmental stimuli," says Shuguang Li, first author of the study. "If you mess up the synchronized clock, the system will work less efficiently."
In physical experiments, the team demonstrated how 24 particle robots could work together to move around, crawling towards light bulbs and changing direction as different ones were switched on and off. At the same time, they were able to navigate around and through obstacles.
To show how the system is basically endlessly scalable, the researchers then ran simulations of up to 10,000 individual particles. Again, the quirky method worked to get the swarm to the goal, even when as many as 20 percent of the units had failed.
This is far from the first time we've seen swarming-style robots. Some of the researchers on this study started with robotic cubes back in 2013, while other teams have developed robots that model insect swarms. A Harvard team managed to get as many as 1,000 tiny "particles" arranging themselves into preset shapes, and we've seen blocky bots able to assemble into 57 different configurations depending on the task at hand.
In future, the team plans to try to make the particle robots more true to their name. The long-term goal is to shrink the components down so that swarms could be made of millions of microscopic particle robots.
The research was published in the journal Nature, and the particle robots can be seen in action in the video below.