Harnessing the robot's body dynamics: a global dynamics approach

While bipedal walking robots developed recently are based on high-gain servo to planned trajectory, our purpose is to make a robot's behavior more natural: exploiting the useful feature of the dynamics of the body itself. A new concept for controlling humanoid robots, the global dynamics approach is proposed. This is to harness the robot body by applying control input intensively around critical points of the planned motion and for the rest of period, rely on passive stability of its own dynamics. As the first step, we numerically studied motion and stability of an elastic body in standing position. A robot with three joints is used and linear springs are adopted for each joints. We show that the body is more stable for small oscillation, if the body is more elastic (i.e., movable joints are many, each spring is soft). Next, we show a way to change the body's dynamical state by changing its dynamical parameters. Combining these two results, the global dynamics method is being developed.