Androgynous Fasteners for Robotic Structural Assembly

Abstract

We describe the design and analysis of an androgynous fastener for autonomous robotic assembly of high performance structures. The design of these fasteners aims to prioritize ease of assembly through simple actuation with large driver positioning tolerance requirements, while producing a reversible mechanical connection with high strength and stiffness per mass. This can be applied to high strength to weight ratio structural systems, such as discrete building block based systems that offer reconfigurability, scalability, and system lifecycle efficiency. Such periodic structures are suitable for navigation and manipulation by relatively small mobile robots. The integration of fasteners, which are lightweight and can be robotically installed, into a high performance robotically managed structural system is of interest to reduce launch energy requirements, enable higher mission adaptivity, and decrease system life-cycle costs.

Self-replicating hierarchical modular robotic swarms

“…demonstrated that this can be achieved with a captive, interlocking, androgynous fastener 31 , and other possible solutions include electropermanent magnets 32 and bistable latches 33 .…”

Ultralight, strong, and self-reprogrammable mechanical metamaterials

“…1D) using four custom injection-molded genderless reversible fasteners (Fig. 1F) (34) that were held captive in the voxel face (Fig. 1E).…”

“…The external robot faults included motor overcurrent, main joint motor driver communication timeout, main joint target timeout (when the motor did not reach its target within the expected time), encoder mismatch fault (belt skip detection between motor and joint encoders), gripper failure fault, and board synchronization faults. The internal robot faults included bolter modules not reaching the required fastening torque, extension modules not fully contracted, rotation module not reaching its target position, robot global orientation error when the robot was manually placed into the structure in the incorrect orientation, motor overcurrent, and controller board communication loss (29). In the analysis of system faults (Table 1), faults were divided into two categories: those due to mechanical issues with the robots and those due to communication loss timeout or tether interference that was unsuccessfully managed by the operators, requiring a pause in operations.…”

“…The interior fastening robot used in this system is named Mobile Metamaterial Internal Co-Integrator (MMIC-I) and is an inchwormstyle robot that moves between adjacent voxel faces in the interior of the lattice structure (29). It joins newly placed voxels to the existing structure by locomoting to the faces of the unit cell to be added and bolting the four fasteners at the corner of each face.…”

“…Our self-reprogrammable system combines mechanical metamaterial building blocks and two types of robots (29,30) to create a reconfigurable structural-robotic system (fig. S1).…”