Swarms of straightforward, interacting robots have the potential to unlock hidden abilities to perform elaborate tasks. However, getting these robots to achieve a true hive-like coordination mind has proven to be a hurdle.
In an attempt to change that, a team at MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) has developed a surprisingly straightforward scheme: self-assembling robotic cubes that can climb over each other, jump in the air, and roll along the Earth.
Six years after the first iteration of the design, robots can now “communicate” with each other using a barcode-like system on each side of the block that allows the modules to identify each other. The autonomous fleet of 16 blocks can now perform straightforward tasks or behaviors such as forming lines, following arrows, or tracking featherlight.
Inside each modular “M-Block” is a flywheel that moves at 20,000 revolutions per minute, using angular momentum when the flywheel is braked. There are enduring magnets on each edge and on each surface that allow you to connect any two cubes together.
While the dice can’t be manipulated as easily as, say, dice from the video game “Minecraft,” the team envisions useful applications in inspection and, ultimately, disaster response. Imagine a burning building in which the staircase has disappeared. In the future, you can just imagine throwing M-blocks on the ground and watching them build short-lived stairs that you can apply to climb to the roof or go down to the basement to rescue victims.
“M stands for motion, magnet, and magic,” says MIT professor and CSAIL director Daniela Rus. “Movement” because the cubes can move by jumping. “Magnet” because the cubes can be connected to other cubes using magnets, and when connected, they can move and connect together to create structures. “Magic” because we don’t see any moving parts and the cube appears to be powered by magic.
Although the mechanism is quite elaborate inside, the outside is quite the opposite, allowing for more strong connections. In addition to inspection and rescue, scientists also envision using the blocks for purposes such as gaming, manufacturing and health care.
“What’s unique about our approach is that it is inexpensive, robust, and potentially easier to scale to a million modules,” says CSAIL PhD student John Romanishin, lead author of the modern paper on the system. “M-Blocks can move in general ways. Other robotic systems have much more elaborate movement mechanisms that require many steps, but our system is more scalable.
Romanishin wrote the paper with Rus and graduate student John Mamish from the University of Michigan. They will present a paper on M-blocks at the IEEE International Conference on Bright Robots and Systems in November in Macau.
Previous modular robotic systems typically moved using unit modules with tiny robotic arms called external actuators. These systems require a great deal of coordination for even the simplest movements, with multiple commands for a single jump or hop.
In terms of communication, other attempts have included the apply of infrared featherlight or radio waves, which can quickly become unwieldy: if you have a lot of robots in a tiny area and they are all trying to send signals to each other, it opens the way to a confused channel of conflict and confusion.
When a system uses radio signals to communicate, these signals can interfere with each other if there are many radios in a tiny volume.
In 2013, the team developed a mechanism for M-blocks. They created six-sided cubes that move using so-called “inertial forces.” This means that instead of using movable arms to aid connect the structures, the blocks have a mass inside them that they “throw” onto the side of the module, which causes the block to rotate and move.
Each module can move in four main directions when placed on one of the six walls, giving you 24 different directions of movement. Without the little arms and appendages sticking out of the blocks, it’s much easier for them to avoid damage and collisions.
Knowing that the team had overcome the physical obstacles, the main challenge still remained: how to make these cubes communicate and reliably identify the configuration of neighboring modules?
Romanishin developed algorithms to aid robots perform straightforward tasks, or “behaviors,” which led them to the idea of a barcode-like system in which robots could sense the identity and appearance of other blocks to which they were connected.
In one experiment, the team turned modules into a randomly structured line and observed whether the modules could determine the specific way in which they were connected to each other. If this wasn’t the case, they would have to pick a direction and roll in that direction until they reached the end of the line.
Essentially, the blocks used the configuration of how they were connected to each other to direct the movement of their choice – and 90 percent of the M-blocks managed to line up.
The team notes that building the electronics was quite a challenge, especially when trying to fit elaborate hardware into such a tiny package. To make M-Block swarms a bigger reality, that’s exactly what the team wants – more and more robots that will create larger swarms with greater capabilities for different structures.
The project was supported in part by the National Science Foundation and Amazon Robotics.