If you ever see ASIMO, a robot created by Honda, you can see the marvelous capacity of walking by this robot. You probably think that this is a recent invention. And with the current state of AI in language and knowledge processing (namely ChatGPT) and advanced generative AI, you probably assume the future imagined in Android Become Human will come true in the coming years. But it is not, the robot was invented in the 80s, and until today there is still no walking robot outside the science festival.
This limitation happen because the system built in Asimo required the cancellation of the natural dynamic existing in the system. This cancellation needs a high amount of torque. If this torque is turned off from the joint, Asimo's attempt to move its feet will be useless.
Underactuated robotics instead use the natural dynamic force as the