A 3D passive dynamic biped with yaw and roll compensation

Autonomous walking bipedal machines, possibly useful for rehabilitation and entertainment purposes, need a high energy efficiency, offered by the conc ept of 'Passive Dynamic Walking' (exploitation of the natural dynamics of t he robot). 2D passive dynamic bipeds have been shown to be inherently stabl e, but in the third dimension two problematic degrees of freedom are introd uced: yaw and roll. We propose a design for a 3D biped with a pelvic body as a passive dynamic compensator, which will compensate for the undesired yaw and roll motion, a nd allow the rest of the robot to move as if it were a 2D machine. To test our design, we perform numerical simulations on a multibody model of the ro bot. With limit cycle analysis we calculate the stability of the robot when walking at its natural speed. The simulation shows that the compensator, indeed, effectively compensates for both the yaw and the roll motion, and that the walker is stable.