Modeling and control of a one-legged hopping mechanism

This paper deals with one-legged jumping motion with a model of 3-DoF leg with foot. Equations of motion are derived through the Lagrange method and a soft contact model is used in computation of the contact forces between the foot and ground. Flight and stance phases of jumping motion are separately investigated and specific controllers are proposed for each phase. Flight phase control is considered as a servo positioning problem while stance phase control is considered as a force control problem. In controller design, total mass of the articulated leg is assumed to be concentrated at the hip level and a fictitious spring is assumed to operate between the hip and ankle joints. The approach is evaluated by taking into account dynamic balance with Zero Moment Point.