At first, watching this video of MABEL, a bipedal robot for studying dynamic gaits, we didn’t know if we should be scared or feel sad. By the end, we know that sadness prevailed. Poor MABEL, forced into a grueling routine, is not even allowed to rest when her leg breaks.
To be serious though, MABEL is quite impressive. Instead of using a direct drive on the legs, motors are attached to springs that act like tendons. This helps compensate for variances in the walking surface, hopefully allowing for smoother transitions between gaits as well. As you can see, MABEL handles the height differences quite well, albeit a bit slowly. It is worth noting that there are no visual sensors on MABEL and everything is done through feedback from her gait.