Kangaroos developed bipedal locomotion long before we did.
Increasingly complex prototypes4 show that passive dynamic walking results in a particularly elegant and natural bipedal gait.
These investigations provided important insights into the mechanics of bipedal walking.
Let us mention that many bipedal walking machines have been designed during the last two decades.
The simplest bipedal machines are passive dynamic9,12,13,17,18 and ballistic11,15,19 walking models that have only few degrees of freedom.
Section 2 first describes two bipedal robots whose simulation models are used to validate the control algorithms developed in this research.
