Robots don't want to be pushed around, especially today's robots that can barely walk as it is. Robots need to be tough and stable, and resistant to any bullies who try to push them around.
COMAN, the COmpliant huMANoid robot, is one such bot. In terms of size, it is modeled on a four year-old human child; it's about 95 cm tall and weighs about 31 kg.
Move ahead to 45" to see COMAN's stabilization control, and see how the robot handles being pushed around.
(COMAN, the COmpliant huMANoid robot, video)
It features 25 degrees of freedom (DOF), and a combination of stiff and compliant joints (see diagram below). The compliant joints (14 DOF) rely on series elastic actuators. These actuators—a custom design created by the IIT team—are applied to the the flexion/extension of the arms and legs, and are both small and modular, which makes them ideal for multi-DOF robots like humanoids. The researchers have also built custom torque sensors for each of the elastic joints, including a 6-axis force/torque sensor for the ankle joints. Development of the robot is funded, in part, by the European AMARSI project.
So what exactly does this compliance get you? The elastic actuators literally add a spring to COMAN's step: in walking experiments the robot's hardware naturally absorbed the ground reaction forces of each footstep "without additional control enforcement, which is difficult to be realized by the stiff actuated humanoids if no particular foot mechanism or active control is applied." And when they implemented a stabilization control method, the robot steadied itself on a moving platform and when it was knocked around.
In his 1958 short story Robot Brother, sf author Henry Slesar tells the story of an ardent roboticist who tries to create a robot brother for his own son that can grow and develop over time like his human son.
As time goes on, little Mac, the robot baby, is developing beautifully:
At four months, Fitz is developing along normal lines. His little body has gone from asymmetric postures to symmetric postures, his eyes now converge and fasten on any dangling object held at mid-point.
As for Mac, he is developing even more rapidly. He is beginning to learn control of his limbs: it is apparent that he will walk before his human brother. Before long, he will learn to speak; already I hear the rumbles within the cavity of the soundbox in his chest.
(Read more about Slesar's robot baby)
Philip K. Dick fans recall the robotic boys from his 1953 novel Second Variety.