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Heterogeneous Teams of Modular Robots for Mapping and

Exploration (Grabowski et al.)

A team of Millibots (centimeter-scale robots) collaborate to map and explore

unknown environments

To provide two-way communications within the group, each Millibot is equipped

with a radio frequency transmitter and receiver. These units can exchange data at4800 bps at a distance of up to 100 meters (size and power consideration).

Three sensor modules: short-range sonars (0-0.5m), long-range sonars (0.15-1.8m),

and infrared proximity (0-0.25m).

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Heterogeneous Teams of Modular Robots for Mapping and

Exploration (Grabowski et al.)

Collaboration

To overcome their individual limitations and accomplish important tasks

ranging from localization to surveillance, mapping, and exploration Self-localization is critical for the success of collaboration

o dead-reckoning, vision-based localization, GPS, landmarks, or map-based

positioning?

o Millibot localization is based on the trilateration: determine the position based ondistance measurements to

known landmarks or beacons

Collaborative localization

o Localization module

Use ultrasound and radio pulses

to measure the distance between

itself and other robot

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Heterogeneous Teams of Modular Robots for Mapping and

Exploration (Grabowski et al.)

Mapping and exploration

A group of Millibots can be equipped with similar sensors to cover more

area in less time than a single robotDuring operation, each robot collects information locally about is

surroundings

This data is transmitted to the team leader where it is used to build a

local map centric to that robot

The team leader (or human operator) can utilize the robots lcoal map

information to direct the Millibot around obstacles, investigate

anomalies or generate new pathsIn an unknown environment, robots move to collect new information

about the environment and build composite maps. In turn, the maps

provide clues about the most viable areas of exploration that will furtherincrease the knowledge about the environment

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Heterogeneous Teams of Modular Robots for Mapping and

Exploration (Grabowski et al.)

Mapping and exploration

Keep line-of-sight to maintain positions

The team leader can merge the informationfrom several local maps into a single global

map using an occupancy grid with a

Bayesian update rule

This method allows the combination ofsensor readings from different robots and

different time instances.

Zero corresponds to a free cell and one isoccupied. Initially, all cells are 0.5.