Asymmetry in Skipping Enhances Viability Against Control Input Noise

Quadruped animals use the galloping gait at the highest speeds, which exhibits distinctive left–right asymmetry in gait parameters, such as touchdown angles and the relative phases of limb movements. The underlying reasons for this asymmetric behavior, as well as the functional advantages of asymmetric gait in robotic applications, remain unclear. In this study, we hypothesized that such asymmetry enhances robust control. To investigate this, we employ a simple two‐legged spring‐loaded inverted pendulum model that introduces asymmetry in the touchdown angles of the left and right legs to generate skipping. By applying viability theory, we quantified the viability regions within the state‐control space to evaluate the robustness against control input noise. The results show that introducing asymmetry broadens the viability region, thereby improving the system's robustness. This asymmetry helps maintain stable locomotion without falling, even in the presence of larger control input disturbances. Specifically, the maximum affordable noise of skipping with a specific touchdown angle difference is more than twice as large as that of the symmetrical case.