Stable walking and running robots without feedback

In this paper we give an overview of our previous work on open-loop stable walking and running robots. The concept of open-loop control implies that all actuators of a robot receive purely periodic pre-calculated torque or force inputs that are never altered by any feedback interference. Passive-dynamic robots call be considered as a special case with zero actuation for which a stabilization is much easier due to the possibility of time shifts. We have developed a numerical method that optimizes the open-loop stability of solutions of periodic optimal control problems with discontinuities. Using this method, we were able to find a number of open-loop stable one- and two-legged robot configurations and motions.