Balance of biped robots: special double-inverted pendulum

This paper deals with dynamic equilibrium of biped robots. We focus our attention on balance of a planar biped standing upon one small foot. The trunk and leg on contact can be seen as a double-inverted pendulum without actuators at the contact point but with a controlled counterweight corresponding to the free leg. We identify all the singular points of this structure before making a linearization and deriving a state feedback control law. A description of the prototype is then described