Underactuated
When the walking robot Asimo was unveiled in 1996 by Honda, it was the absolute pinnacle for a certain type of robot. It could walk, climb the stairs, etc., move comfortably.
But look closely it seems that Asimo is planning each move, each move is very deliberate and controlled. “It is not making use of the dynamics” chimed in Prof. Tedrake (in the video above). In robotics there is the dynamics of the system, robot, the environment which define what can happen. Then there is the control, the actuator that guides the system to a certain direction.
In many ways Asimo is overly controlled. Humans and many species in nature evolved to be underactuated, that is guiding their system with minimal control, making use (based on our prediction of) the larger dynamics. It is more energy efficient that way; when we walk we don’t baby sit all our actions, what we actually perform is controlled falling.
In a way, we are like surfers. The outcomes a surfer achieves are in obscene proportion compared to the control input s/he applies. With one turn of the hip, with certain stance, you are at the top of a wave, compared to the middle of the cusp shooting through right before it closes on you. This is underactuated control. Less energy, more outcome. Asimo requires 20 times more energy to achieve what a human does.
Look at this this passive walker, it requires no external energy, it completely “rides the wave of gravity” to walk.
Life is full of control actions. We apply control to economics, in international relations. The optimal thing is not controlling everything, but riding a wave, making use of the larger energy that is the outside dynamics.