To provide a conceptual view of the capabilities of a team of robots, we composed a scenario that was designed to exploit the features of a group of Millibots and emphasize the heterogeneous nature of the team.
Imagine a scenario in which a team, consisting of seven Millibots and a single tank robot, is deployed to investigate an office building or lab for which only a rudimentary floor plan is provided. It is known that there will be spaces unreachable by the larger tank robot. Therefore, a team that includes Millibots is deployed to explore the given space and detect any objects or persons not found in the plans.
To accomplish the mission, a team of Millibots is constructed with various sensor modules. Many modules will be common to each Millibot while others will be specific to Millibots performing a specialized task. To provide mapping ability for the spaces covered by the Millibots, each Millibot is equipped with either a short range or long range sonar range module. Since the space will mostly be open hallways and offices, most of the robots will carry the long-range sonar modules. However a few will be equipped with short range sensors to provide information from tightly spaced obstacles or corridors. Along with sonars, each robot will also carry an infrared proximity module to provide low level obstacle avoidance. The proximity module is necessary because the sonar use is limited due to interference with the localization system and cannot provide continuous protection.
Some robots are equipped with specialized modules. For example, one robot is equipped with a second communication module that allows the robot to act as a repeater. When this robot detects a message on one channel, it repeats it on the other. The ability to repeat messages allows the Millibot group to maintain communications with its team leader even if it the group moves out of range. Additionally, one Millibots is designated to carry a camera module. This module provides the group with the ability to identify and classify detected obstacles. However, because of the power requirements of the camera module, the camera will remain powered off until it is needed by the group for identification.
The specific mobility platform is task dependent also. Since the Millibots will be travelling on a tiled floor, they are equipped with a track driven mobility platform equipped with rubber treads. To complete the robot, a main processor and communication link are attached. Finally, a localization module is added to each robot to provide position estimation.
Figure 7 shows an example of the progression of the team of robots in this scenario. The tank robot has stopped on the left of a set of obstacles blocking its progress. The team of Millibots has moved between the obstacles and fanned out to surround and map the blocking obstacles. The camera robot was positioned and a video image was used to identify the obstacles. The group continued to move and has begun exploration into a room containing more obstacles. Several robots have positioned themselves to provide localization coverage while the remaining robots are moving in and out of the coverage to build a map of the area. When the low-level map has provided enough detail, the camera robot will again be called to provide a video image for classification. The robot with the second set of radio modules has been positioned to provide communications between the group in the room and the tank robot down the hall.
