  The emerging behaviors of swarms have fascinated scientists and gathered
significant interest in the field of robotics. Traditionally, swarms are viewed
as egalitarian, with robots sharing identical roles and capabilities. However,
recent findings highlight the importance of hierarchy for deploying robot
swarms more effectively in diverse scenarios. Despite nature's preference for
hierarchies, the robotics field has clung to the egalitarian model, partly due
to a lack of empirical evidence for the conditions favoring hierarchies. Our
research demonstrates that while egalitarian swarms excel in environments
proportionate to their collective sensing abilities, they struggle in larger or
more complex settings. Hierarchical swarms, conversely, extend their sensing
reach efficiently, proving successful in larger, more unstructured environments
with fewer resources. We validated these concepts through simulations and
physical robot experiments, using a complex radiation cleanup task. This study
paves the way for developing adaptable, hierarchical swarm systems applicable
in areas like planetary exploration and autonomous vehicles. Moreover, these
insights could deepen our understanding of hierarchical structures in
biological organisms.
