  Legged robots promise higher versatility and the ability to traverse much
more difficult terrains than their wheeled counterparts. Even though the use of
legged robots have increased drastically in the last few years, they are still
not close to the performance seen from legged animals in nature. Robotic legs
are typically fairly simple mechanically, and few feature an ankle joint, even
though most land mammals have one. The ankle could be a key to better
performance and stability for legged robots, and in this paper we investigate
how the use of an ankle in a bipedal robot could improve its performance when
combined with evolutionary techniques for gait optimization. Our study shows,
both in simulation and physical experiments, that the addition of an ankle
joint results in greater walking speeds for a supported bipedal robot.
