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 Centre for Bits and Atoms (CBA), has been pursuing as his doctoral thesis work. It’s now reached the point that prototype versions of such robots can assemble small structures and even work together as a team to build up a larger assemblies.
The new work appears in a paper by Jenett, Gershenfeld, fellow graduate student Amira Abdel-Rahman, and CBA alumnus Kenneth Cheung, who is now at NASA’s Ames Research Centre, where he leads the ARMADAS project to design a lunar base that could be built with robotic assembly.
“This paper is a treat,” said Aaron Becker, an associate professor of electrical and computer engineering at the University of Houston, who was not associated with this work. “It combines top-notch mechanical design with jaw-dropping demonstrations, new robotic hardware, and a simulation suite with over 100,000 elements,” he added.
“What’s at the heart of this is a new kind of robotics, that we call relative robots,” Gershenfeld said. Historically, he explained, there have been two broad categories of robotics — ones made out of expensive custom components that are carefully optimised for particular applications such as factory assembly, and ones made from inexpensive mass-produced modules with much lower performance. The new robots, however, are an alternative to both. They’re much simpler than the former, while much more capable than the latter, and they have the potential to revolutionise the production of large-scale systems, from airplanes to bridges to entire buildings.
According to Gershenfeld, the key difference 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,” he said. 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, 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.
The underlying vision is that just as the most complex of images can be reproduced by using an array of pixels on a screen, virtually any physical object can be recreated as an array of smaller three-dimensional pieces, or voxels, which can themselves be made up of simple struts and nodes. 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 minimised. 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. Jenett has dubbed the little robots BILL-E (a nod to the movie robot WALL-E), which stands for Bipedal Isotropic Lattice Locomoting Explorer.
Click here to read about a MIT/NASA collaboration further examining wing manufacture.