108 Agent-Based Modeling and Simulation with Swarm
FIGURE 4.18: The suboptimal individual and the movement.
FIGURE 4.19: Cross-shaped ro bot.
FIGURE 4.20: Wheel robot.
From the viewpoint of the practical movement method of modular robots,
they can be classified into those that transform like ameba to change a whole
location and those that use leg parts or wheels (Figure 4.20). Although this
result is an option due to a higher velocity than wheels, it requires sufficient
strength and a function to shift directions.
Another exper iment was attempted to ascend stairs via morphogenesis
using GP.
Figure 4.21 shows the “good” individuals that emerged in each gener ation.
The light-colored blocks in the center are normal blocks, and the dark-colored
blocks at the edge are motor blocks.
Figure 4.21(a) shows an individual that emerge d in the third generation.
Because only one motor emerged, which made proceeding straight ahead dif-
ficult, it was not able to achieve a mea ningful task. Figur e 4.21(b) shows
an individual that emerged in the eighth generation, featuring five vertically
aligned blocks.
The robot supported itself using its long vertical part and got on the
gap betwe e n the stairs, but the tilt could not be supported. Afterward, the
robot deviated from the right orbit. The individual that emerged in the 14th
generation, shown in Fig. 4.21(c), ascended the stairs, s upported by the five
central blocks as well. Starting with the eighth generation, there were two
more blocks a t the front. The wider shape co uld avoid deviation from the
orbit caused by the tilting at the time of climbing over the gap in the s tairs.
Figure 4.21(d) shows the best individual during the simulation, which
emerged in the 16th generation. Putting the three blocks o n the right-side
front of the robot upon the next stair, the rob ot could start climbing the
staircase. Compared with Fig. 4.21(c), there were fewer front blocks, thereby
Evolutionary Simulation 109
(a) 3rd generation (b) 8th generation
(c) 14th generation (d) 16th generation
FIGURE 4.21: The bes t evolved individuals.
eliminating the front block obs tacles and allowing the robot to ascend over
the gap in the stairs and shorten the time to realize the ta sk.
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