Balancing stability and maneuverability during rapid gait termination in fast biped robots

Abstract

For fast-moving legged robots, the ability to stop rapidly is essential if they are to move safely through unpredictable environments. There is a trade-off between stability and rapidity however, as the forces that slow the robot down also tend to cause a toppling moment. This paper examines how rapid deceleration motions performed on a bipedal robot are affected if it is forced to maintain zero rate of change in angular momentum (ZRAM) throughout the maneuver. By using trajectory optimization to generate over 4000 gait termination motions from speeds comparable to a sprinting human, it was found that the stopping distance could be reduced by 12% and time by 25% by relaxing the ZRAM condition, with greater reductions possible through the addition of a free stabilizing limb. The ability to moderate the pitch of the robot while decelerating was found to be paramount to achieving a rapid stop and thus, a template incorporating an inertial body and stabilizing appendages is proposed to represent these maneuvers.