Feedback Control for a Small-Size Soccer Playing Humanoid Robot

Given the intrinsic instability of walking humanoid robots, the design of controllers assuring robust stabilization of walking gaits is one of the most important goals. Small humanoid robots today available in RoboCup, often lack computing power: they are frequently actuated by microcon- troller based position servos with limited or no feedback. As a consequence it is very difficult to implement feedback control techniques on these platforms in order to guarantee stability. This paper describes a control architecture aiming at decoupling the problem of stable walking in the two relatively simpler problems of legs gait generation and upper body feedback control to guarantee dynamic stability. The presented implementation of the proposed architecture builds on the use of the GCoM point (Ground projection of the Center of Mass) that may be considered a suitable stability index only in quasi static robot states (like when kicking a ball from standing). The presented solution is particularly suited for small size robots having limited onboard computational power and limited sensor suits. The the proposed method has been validated through Matlab simulations and experimental tests performed on a Robovie- MS VStone's platform. Although the performed experiments are rather preliminary, they suggest that the designed architecture is effective.