Fig. 1.

(a) View of a human leg from the sagittal plane and the definitions of ${\theta }_{th}$ and ${\theta }_f$. (b) The data-driven gait kinematic models of global thigh angles ${\theta }_{th}$, global thigh angular velocities ${\dot{\theta }}_{th}$, and foot angles ${\theta }_f$. Note that each model is multidimensional, depending on $\varphi$, $l$, $r$ (and also $\dot{\varphi }$ for the ${\dot{\theta }}_{th}$ model). For visualization, we plot the models with respect to $\varphi$ and r by fixing l = 1.1 (and $\dot{\varphi }\hspace{0.17em}=\hspace{0.17em}0.8$ for the ${\dot{\theta }}_{th}$ model).