Step Adjustment for a Robust Humanoid Walk

A stable and fast walk for humanoid robots is a challenging problem. In particular for multiple robots with different degrees of wear, it is necessary to tune several control parameters, which consumes a lot of time and wears down the hardware even more. In this paper, we present the latest improvements of our current walk, which enable a significant boost in the walking speed and stability, basically independent of the robot's hardware state. Based on a linear inverted pendulum model and thresholds determined statistically, the feet positions are adapted to follow the center of mass' direction of movement and let the robot walk in the direction of a potential fall if necessary. In addition, we ensure that the movement of the swing foot is parallel to the ground with a closed-loop feedback controller over the measured rotation errors of the support foot, without the direct use of the inertial measurement unit. The approaches presented allow for a up to 40% faster walk on different robots of the same type, without the need for a manual calibration.