Mobility of Humanoid Robots: Stepping over Large Obstacles Dynamically

Humanoid robots are getting increasing attention in the robotics community, not only for the scientific challenge of the complex multibody system issues and mechatronic designs, but also due to their high mobility and versatility. Humanoid robots have the potential to navigate through complex environments such as the standard living surrounding of humans. This is mainly due to the bipedal legged nature of the robotic system, which allows higher mobility than its wheeled counterpart. One of the advantages is that it can negotiate obstacles by stepping over them, which is the topic of the work presented in this paper. The main focus of this research is to investigate stepping over large obstacles. Previous work has reported on algorithms using quasi-static balancing, which resulted in somehow unnatural slow motions. This work however focuses on stepping over larger obstacles in a fluent dynamic motion, using stability criteria on zero moment point instead of center of gravity. All the work is formulated in function of the elaborate HRP-2 humanoid research platform. In this paper a preliminary 2D study on stepping over leg trajectories and their dynamic implications on the overall stability are investigated. The paper discusses the implementation of the stepping over procedure in the overall dynamic motion generator, the implications on the kinematics and dynamics and finally the actual stepping over foot trajectory planner