The robotics lab at the Institute for Human Machine Cognition in Florida is one of the top research centres in the world for bipedal walking and humanoid robotics. IHMC are developing their own humanoid robot, Nadia, which incorporates a mixture of electric and hydraulic actuators. The robot has a range-of-motion close to that of a human and will be used to explore motions such as crawling, climbing and gymnastics.
The legs and torso shown were already designed before I started working with IHMC. Instead, I have been working on a pair of arms for the Nadia robot. The arm actuators use BLDC motors and a custom cycloidal transmission. The idea is that these transmissions are sufficiently backdrivable for open-loop torque control without a dedicated torque sensor, yet still have a high enough gear ratio that we can achieve high torques without a very heavy motor.
Images and video courtesy of IHMC