Robust analysis of biped walking on uneven terrain using output zeroing controls

Limit cycle walkers achieve highly energy-efficient bipedal walking, and the control based on the limit cycle is considered as one of the solution for the energy problem of biped robots. They have, however, the weak robustness on uneven terrains due to their walking properties, thus we need to improve the robustness to make them fit for practical uses. In this paper, we propose a walking control law using output zeroing control with relative degree 3 to improve the robustness for limit cycle walkers on uneven terrains. We show the effectiveness of the proposed method to compare it to output zeroing control with relative degree 2 and evaluate the improvement of the robustness quantitatively using two disturbance rejection measures: Gait Sensitivity Norm and H_∞ norm.