Army Ant Inspired Adaptive Self-Assembly with Soft, Climbing Robots

Abstract

Social insects, including army ants (genus Eciton) self-assemble dynamic structures which allow them to perform more efficiently and achieve otherwise impossible feats. Army ant bridges, for example, grow and shrink according to traffic levels because they incorporate smart, flexible materials (i.e. living ants) and emerge from local behavior.

Similarly, self-assembled structures that respond to local stimuli could allow robots to adapt to new conditions when exploring unknown or rapidly changing environments. While many robot systems use rigid modules to create pre-determined structures, the work of my thesis, Eciton robotica, takes a new approach: inspired by army ants, soft robots create amorphous structures whose size and shape can adapt to the needs of the group.

Eciton robotica incorporates several novel features: the soft body, the gripping mechanism, communication through vibration, and the self-assembly algorithm. The robots’ corkscrew gripper connects and disconnects easily to Velcro loop and supports loads in tension, sheer and peel; it allows E. robotica robots to climb over other robots and attach to them at any point. In simulation, a simplified model of the robot was used to test a local control rule for adaptive self-assembly: robots stop and become part of a structure when stepped on. Using only local rules and information, simulated robots built and dissolved bridges in response to traffic and varying terrain. To implement this in hardware, the robots send vibration pulses as they walk, and sense this vibration if they are stepped on by other robots. Using vibration sensing and the local control rule, I used two E. robotica robots to form and dissolve adaptive structures in a 2D vertical plane.

This work includes a number of firsts: The Flippy robot, an early robot module, is one of the first soft climbing robots, and highly capable though limited to Velcro and fabric based surfaces. The E. robotica platform, to my knowledge, is the first use of soft mobile robots for any collective behavior, including self-assembly, and the first case of adaptive self-assembly in a vertical plane.