Autonomously generating efficient running of a quadruped robot using delayed feedback control

We report on the design and stability analysis of a simple quadruped running controller that can autonomously generate steady running of a quadruped with good energy efficiency and suppress such disturbances as irregularities of terrain. In this paper, we first consider the fixed point of quasi-passive running based on a sagittal plane model of a quadruped robot. Next, we regard friction and collision as disturbances around the fixed point of quasi-passive running, and propose an original control method to suppress these disturbances. Since it is difficult to accurately measure the total energy of the system in a practical application, we use a delayed feedback control (DFC) method based on the stance phase period measured by contact sensors on the robot's feet with practical accuracy. The DFC method not only stabilizes running around a fixed point, but also results in the transition from standing to steady running and stabilization in running up a small step. The effectiveness of the proposed control method is validated by simulations. MPEG footage of these simulations can be viewed at: http://www.kimura.is.uec.ac.jp/running.