The "Hybrid Hydrostatic Transmission" system uses both fluid- and air-filled lines to control the movements of a telepresence robot. By combining the stiffness of fluid lines with the springiness and responsiveness of air-filled lines, the robot is able to move in a lifelike manner while providing constant, high-quality haptic feedback. "We have developed new rotary actuators using rolling-diaphragm cylinders which provide high torque density," the Disney Research team wrote, "and allow the creation of a new high-performance 10-DOF humanoid robot." While these new actuators are a bit bigger and heavier than conventional valve-based hydraulic systems, they do offer very low impedance. This means that the even bigger and heavier motor doesn't need to be mounted on the limb it's powering, which in turn reduces the amount of power needed to move it.