Robots build strong structures, reconfigurable like LEGO

Significant advancement

Over the past ten years, researchers have engineered microscale robots capable of autonomous reshaping through programmable materials like DNA. Nevertheless, creating self-reconfiguring systems on a scale suitable for larger endeavors, such as sustainable construction in space, has presented significant challenges.

In this project, the team introduced a robotic structural system as an example of programmable matter, demonstrating mechanical capabilities and scale comparable to traditional high-performance materials and truss systems.

A "voxel" structural unit is a mechanical metamaterial building block mass-produced from high-performance fiber-reinforced composites. These voxels offer diverse material properties by recombining constituent materials and geometry. 

Comprising three mobile robots (two for transportation and one for fastening), a path-planning algorithm, and 30-centimeter mechanical metamaterial units reinforced with fibers, a self-assembling robotic system was employed.

The transport robots positioned the lattice units externally, while the fastening robot internally secured each newly placed block to the structure, according to researchers.

The two mobile robots that navigate the system's outer surface and interior are responsible for tasks such as transporting items, placing objects, and securely fastening components. They leverage the inherent lattice periodicity of the system for indexing and metrology, ensuring precise and reliable execution of their functions.

Simple robots use passive alignment features to achieve precise locomotion within the structure without external sensing or control systems.

The closely integrated design ensures robust reconfiguration and assembly, forming a joint robotic-structural system. According to researchers, this innovative approach shifts the complexity of autonomous assembly from hardware to software, relying on sophisticated planning and scheduling algorithms rather than intricate perception requirements. 

Promising results 

In a test scenario, the system efficiently arranged 256 units to construct a shelter characterized by ultra-light density, substantial strength, and stiffness. This structure was built within a continuous runtime of 4.2 days. 

The autonomous capabilities of each robot were evident as they successfully executed numerous operations, encompassing tasks such as locomotion, voxel placement, and fastener bolting.

Researchers claim that the distance traveled varied among robot roles, with cargo transport covering 4624 body lengths (equivalent to 3.15 kilometers), crane transport spanning 522 body lengths (0.35 kilometers), and the fastening robot moving 754 body lengths (0.23 kilometers), mainly stationed at the building front. 

The team claims both robot types also demonstrated fault-monitoring capabilities, promptly pausing operations upon detection. In the event of a fault, the system notified the operator, who could initiate remote issue resolution (no-touch recovery) or opt for manual intervention before restarting autonomous operations.

"These low-cost and relatively imprecise robots achieved assembly and reconfiguration with very high repeatability and consistency and minimal required state estimation resources (sensors and computation)," said a statement. 

The details of the team's study were published in the journal Science Robotics on January 17.