Fig. 1.
Schematic of the 2-link (the right foot and the rest of the body), frontal-plane model of the human body. The right foot is the base of support (BOS) of the model. The ankle joint is modeled as a 1-degree-of-freedom hinge joint, and its angle θ represents the generalized coordinates of the model. The foot and body anthropometric parameters were determined based on a typical male with body height at 1.78m and body mass at 80kg53. The positive X-axis is to the right, and the positive Y-axis is upward. Positive joint rotation is along the positive Z-axis (counterclockwise).