For decades of development of robotics engineers have tested all available technologies for creating manipulators: mechanics, hydraulics , pneumatics. Each of them has its strengths and weaknesses. For example, since 1945, for the creation of robots, cables were used that transmit force to the right place through a system of pulleys. A simple design did not require separate power supplies, but it did not develop due to design constraints.
Hydraulics can transmit a significant effort with excellent feedback and accuracy. However, the technology is rather cumbersome, and requires the pulling of hydraulic hoses.
Pneumatics in itself is not a replacement for hydraulics due to low precision and poor force control. But a group of scientists from Disney Research led by John Whitney succeeded in creating a hybrid of hydraulic and pneumatic systems.
Instead of joints that are opened and closed by a pair of hydraulic lines, the new system uses hydraulics to move the joint in the main direction, while the pneumatics returns it to its original position.
The last demonstration version of the hybrid from Disney Research looks like a robot-humanoid with two hands-manipulators having three degrees of freedom, and a head equipped with stereo cameras. The robot is able to repeat the actions of the operator in real time and to interact with the person. His movements are extremely fast, precise, smooth and allow you to work even with fragile objects.