Asymmetric stability property of a sagittal-plane model with a compliant leg and Rolling contact

We report on the stability analysis of the Rolling SLIP (R-SLIP) model, a sagittal-plane and point-mass model with a compliant leg and rolling ground contact. Owing to its asymmetric morphology, it has four different operation modes according to the range of the initial mass speed and leg configuration. Using the return map analysis, the asymmetric stability property of the R-SLIP model was investigated and compared with that of the SLIP model. The analysis results reveal that the R-SLIP model has better but more complicated stability characteristics than the SLIP model. The analysis results also suggest that the R-SLIP model operates better when it has a soft to hard stiffness change. In addition, the effect of the torsion spring position was also investigated.