Stealth walking of 3-link planar underactuated biped

Abstract

This paper discusses a method for generating an underactuated bipedal gait completing in one step in the presence of an upper body that behaves as zero dynamics. First, we introduce a model of a 3-link planar biped robot with an upper body, and develop the equation of motion and holonomic constraint conditions. We also describe a straightforward derivation of the relationship between the angular momentum and whole center of mass. Second, we design two control laws for achieving stable stealth walking. During the single-limb support phase, the stance- and swing-leg angles are strictly controlled to follow the desired trajectories so that the swing foot lands on the ground stealthily at the end of this phase. During the double-limb support phase, the angular position and velocity of the upper body are controlled to follow the desired trajectory for returning them to the initial state. Through numerical simulations, the fundamental gait properties and change tendencies are investigated.