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A new kind of robotics, called relative robots, have the potential to revolutionize the production of large-scale systems, from airplanes to bridges to entire buildings. Today’s commercial aircraft are typically manufactured in sections, often in different locations — wings at one factory, fuselage sections at another, tail components somewhere else — and then flown to a central plant in huge cargo planes for final assembly.

But what if the final assembly was the only assembly, with the whole plane built out of a large array of tiny identical pieces, all put together by an army of tiny robots?

That’s the vision that graduate student Benjamin Jenett, working with Professor Neil Gershenfeld in MIT’s Center for Bits and Atoms (CBA), has been pursuing as his doctoral thesis work. 

Prototype versions of the BILL-E robots can assemble small structures and even work together as a team to build up larger assemblies.

Aaron Becker, an associate professor of electrical and computer engineering at the University of Houston, who was not associated with this work said the project “combines top-notch mechanical design with jaw-dropping demonstrations, new robotic hardware, and a simulation suite with over 100,000 elements.” 

The key difference between the new relative robots and the current ones lies in the relationship between the robotic device and the materials that it is handling and manipulating. With these new kinds of robots, “you can’t separate the robot from the structure — they work together as a system,” Becker says. For example, while most mobile robots require highly precise navigation systems to keep track of their position, the new assembler robots only need to keep track of where they are in relation to the small subunits, called voxels (like pixels on a screen) that they are currently working on. Every time the robot takes a step onto the next voxel, it readjusts its sense of position, always in relation to the specific components that it is standing on at the moment.

According to, the underlying vision is that virtually any physical object can be recreated as an array of smaller three-dimensional pieces, or voxels. 

The team has shown that these simple components can be arranged to distribute loads efficiently; they are largely made up of open space so that the overall weight of the structure is minimized. The units can be picked up and placed in position next to one another by the simple assemblers, and then fastened together using latching systems built into each voxel.

The robots themselves resemble a small arm, with two long segments that are hinged in the middle, and devices for clamping onto the voxel structures on each end. The simple devices move around like inchworms, advancing along a row of voxels by repeatedly opening and closing their V-shaped bodies to move from one to the next. 

One advantage of such assembly is that repairs and maintenance can be handled easily by the same kind of robotic process as the initial assembly. Damaged sections can be disassembled from the structure and replaced with new ones, producing a structure that is just as robust as the original. 

“For a space station or a lunar habitat, these robots would live on the structure, continuously maintaining and repairing it,” says Jenett. 

The new work appears in the October issue of the IEEE Robotics and Automation Letters.