Studies of modular robot motion are usually focused on locomotion
generation. Widely-used locomotion generators are based on
Central Pattern Generators (CPGs), which produce periodical signals
for the actuators [13]. Locomotion generators can provide an
efficient way to move a robot in a desired manner or in a given direction. However, a single locomotion generator is not sufficient
to reach a distant goal in a complex environment. Similarly, a single
locomotion generator may become useless if the environment
changes, e.g. if the terrain changes from gravel to sand. In such
cases, the robot should be equipped with several locomotion generators,
which are switched by a high-level algorithm to achieve
the desired goal. For example, a robot equipped with ‘walk’ and
‘rotate-left’ actions can visit many places in an environment, but
these actions need to be combined to reach a goal and to avoid obstacles.
This can be achieved by using motion planning.