Today's commercial aircraft are typically manufactured in sections and 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. If the entire plane could be built out of a large array of tiny identical pieces, all put together by an army of tiny robots, costs in manpower and transportation could be slashed.

Prototypes of these robots have been developed to assemble small structures and even work together as a team to build up larger assemblies. At the heart of the system is a new kind of robotics called relative robots.

Historically, there have been two categories of robotics — those made from expensive custom components that are carefully optimized for particular applications such as factory assembly and those made from inexpensive, mass-produced modules with much lower performance. The new robots, however, are an alternative to both. They are much simpler than the former while much more capable than the latter and they have the potential to revolutionize the production of large-scale systems, from airplanes to bridges to entire buildings.

The difference lies in the relationship between the robotic device and the materials it is handling and manipulating. With these new kinds of robots, the robot cannot be separated from the structure — they work together as a system. 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.

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 (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 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. The robots are called BILL-E, which stands for Bipedal Isotropic Lattice Locomoting Explorer.

Several versions of the assemblers were built as proof-of-concept designs, along with corresponding voxel designs featuring latching mechanisms to easily attach or detach each one from its neighbors. The prototypes were used to demonstrate the assembly of the blocks into linear, two-dimensional, and three-dimensional structures.

As it works on assembling the pieces, each of the tiny robots can count its steps over the structure. Along with navigation, this lets the robots correct errors at each step, eliminating most of the complexity of typical robotic systems. While it's missing most of the usual control systems, as long as it doesn't miss a step, it knows where it is. For practical assembly applications, swarms of such units could be working together to speed up the process using control software that can allow the robots to coordinate their work and avoid getting in each other's way.

This kind of assembly of large structures from identical subunits using a simple robotic system has already attracted the interest of some major potential users, including NASA and the European aerospace company Airbus SE.

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. The unbuilding process can also be used to make modifications or improvements to the system over time.

This sequence of photos shows an assembler robot at work, carrying one structural unit over the top and down the other side of a structure under construction. (Image courtesy of Benjamin Jenett)

Ultimately, such systems could be used to construct entire buildings, especially in difficult environments such as space, or on the Moon or Mars. This could eliminate the need to ship large preassembled structures all the way from Earth. Instead it could be possible to send large batches of the tiny subunits or form them from local materials using systems that could crank out these subunits at their final destination point.

Robots don't get tired or bored, and using many miniature robots seems like the only way to get this critical job done. This work could be used in the construction of dynamically adjustable airplane wings, enormous solar sails, or even reconfigurable space habitats.

For more information, contact Karl-Lydie Jean-Baptiste at This email address is being protected from spambots. You need JavaScript enabled to view it.; 617-253-1682.