Evolutionary Robotics and Open-Ended Design Automation - Biomimetics: Biologically Inspired Technologies - page 141

Turtle
Bar
Actuator

forward(1)

joint(1), push, joint(1)
forward(1), pop,
clockwise(2)

push, joint(1), forward(1)

pop, clockwise(2)

joint(1), push, joint(1), forward(1),
pop, clockwaise(2)

(b)

(a)

(c)

(d)

Direct Generative

1000 1000

0 0

− 1000

− 1000

− 2000

− 2000

− 3000 − 3000

− 4000

− 4000

5000

− − 5000

1 10 100 1000 10000 1 10 100 1000 10000

Mutation Size

Mutation Size

Figure 4.6 Evolving bodies and brains using generative encodings: (a) Schematic illustration of a construction
sequence and (b) the resulting robot with actuated joints. (c) Three examples of robots produced by evolving
L-systems that produce construction sequences, and (d) their physical instantiations. (e) A comparison of effects of
mutation in the direct encoding versus the generative encoding shows that the generative encoding has trans-
formed the space in a way that makes mutation more effective. (From Hornby, G. S., Lipson, H., Pollack, J. B.
(2003) Generative encodings for the automated design of modular physical robots, IEEE Transactions on Robotics
and Automation, 19(4). With permission.)

oscillates, using integer values from 0 to 5, and the relative phase-offset of the oscillation cycle is
taken from the turtle's state. The commands ''increase-offset'' and ''decrease-offset'' change the
offset value n the turtle's state by + 25% of a total cycle. Command sequences enclosed by ''{}''
are repeated a number of times specified by the brackets' argument.