An important part of the swarm-bots project
consists in the physical construction of at least one swarm-bot, that
is, a self-assembling and self-organising robot colony made of a number
(30-35) of smaller devices, called s-bots. Each s-bot is a fully
autonomous mobile robot capable of performing basic tasks such as autonomous
navigation, perception of its surrounding environment, and grasping
of objects. A s-bot is also able to communicate with other peer units
and physically join either rigidly or flexibly to them, thus forming
a swarm-bot. A swarm-bot is supposed to be capable of performing exploration,
navigation and transportation of heavy objects on very rough terrains,
especially when a single s-bot has major problems at achieving the task
alone. The hardware structure is combined with a distributed adaptive
control architecture inspired upon ant colony behaviours.
The s-bot design is shown in figure 1. The mobility is ensured by a
differential treels© drive system, composed
by tracks and wheels.
Each treel© is controlled by a motor so
that a robot can freely move in the environment and rotate on the spot.
Treels allow each s-bot to move even on moderately rough terrain, with
more complex situations being addressed by swarm-bot configurations.
The motor base with the treels© can rotate
with respect to the main body by means of a motorised axis.
S-bots can connect to each other with two types of possible physical
interconnections: rigid and semi-flexible.
Rigid connections between two s-bots are implemented by a gripper mounted
on a horizontal active axis. This gripper has a very large acceptance
area that can securely grasp at any angle and lift (if necessary) another
Semi-flexible connections are implemented by flexible arms actuated
by three motors positioned at the point of attachment on the main body.
The three degrees of freedom allow to move the arm laterally and vertically
as well as extend and retract it.
Using rigid and flexible connections, s-bots can form a swarm-bot having
1D or 2D structures. These structures can bend and take 3D shapes.
Rigid and flexible connections have complementary roles in the functioning
of the swarm-bot. The rigid connection is mainly used to form rigid
chains that have to pass large gaps, as illustrated in Figure 4. The
flexible connection is adapted for configurations where each robot can
still have its own mobility inside the structure. The swarm-bot can
of course also have mixed configurations, including both rigid and flexible
connections, as illustrated in figure 2.
Potential application of this type of swarm robotics are, for instance,
semi-automatic space exploration, search for rescue or underwater exploration.