Chain formation experiments with LEGO Mindstorm©
Figure 1 shows the configuration of the robots used in our experiments (a) and of the arena were they were performed (b). The two boxes are the aggregation sites were the robots nucleate they chains. These chains may take different forms like in the following pictures (c and d).
Figure 1. Setup of the robot (a) and of the arena (b), and some examples of final configurations.
The signature of collective choice is an asymmetrical distribution of robots on both sites, as shown in Fig. 2. The empirical distribution is compared with the the theoretical distribution if the two sites were equally probable (which is a Gaussian). In this system, the selection of one site (i.e. asymmetry) grows with the group size, as shown in the distributions of the robots on both sites for all the experiments, for 2, 4 and 8 robots.
Figure 2. Empirical and theoretical distributions of the number of robots
on the two sites for groups of 2, 4 and 8 robots.
At the end of each experiments different patterns of aggregation were observed. Some of them are shown in Fig. 3. The patterns can be describes in terms of the connections between robots. When a robot is connected to the back of another, the connection is labelled C1; when two robots are connected at the same point, it is labelled C2; C3 in case of three connections and C0 if the back of a robot remains without connections (Fig. 4). We found that whatever the experimental parameters are (group size, time of the experiment or number of sites) the proportion of C0, C1 and C2 remained constant: respectively 40%, 45% and 15% (C3 are negligible).
Figure 3. Some examples of final patterns of aggregation.
Figure 4. Classification of aggregation patterns.
|Swarm-bots project started
on October 1,2001
|The project terminated
on March 31, 2005.
Sat, 21 Aug 2010 19:46:15 +0200