(Emergent Morphology)
5 The Head
Only one body part is differentiated from the rest - the head - which is the coordinate
where the first body segment starts. This coordinate is used for some experimental
secondary terms in the fitness function, which encourage more realistic behavior
in the animats, similar to a strategy described by Ngo and Marks (93).
All other body parts are free to evolve to function with no constraints.
The secondary fitness terms relating to the head are added to the locomotion
fitness term with varying weights associated with them. They are:
1) reward for the head being held high (proportional to the average height of the head throughout
the animation)
2) penalty for head movement (proportional to the total length of the trajectory traced
by the head throughout the animation - which can be much longer than the total length
of the trajectory traced out by the animat's center of mass)
3) penalty for head collision on the ground (proportional to the accumulation of downward
impact at which the head collides with the ground - if and when it hits).
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