skipping on uneven ground

It is known that humans intentionally choose skipping in special situations (e.g. when descending stairs, reduced gravity). Although those situations involve uneven locomotion, the dynamics of human skipping on uneven terrain has not yet been addressed. To find the reasons that may motivate this choice, we combined experimental data on humans with numerical simulations. Parameters for modeling were obtained from nine subjects skipping across a single drop in ground level. To model and describe the dynamics of skipping, we used a bipedal spring loaded inverted pendulum. We found that regardless of the leg that steps into the perturbation, leg adjustments in humans occur mostly or only on the trailing leg (landing first after flight phase). When transferring the identified strategies to the numerical model, the capacity of the model to cope with sudden-drop perturbations increased. Thus, simplified control, stability, and robustness might be key reasons to adopt skipping.

众所周知，人类会在特定场景下主动选择跳跃步态（skipping）行进，例如下楼梯、低重力环境中。尽管此类场景涉及非平整地形上的移动，但目前学界尚未针对人类在非平整地形上的跳跃步态动力学展开研究。为探寻促使人类做出该选择的潜在原因，本研究将人体实验数据与数值模拟相结合。建模所需的参数取自9名受试者跨越单次地面落差时的跳跃步态数据。为建模并描述跳跃步态的动力学特性，本研究采用了双足弹簧负载倒立摆（bipedal spring loaded inverted pendulum）模型。研究发现，无论哪条腿接触到地面落差扰动，人类的腿部调整大多仅发生在腾空阶段后率先着陆的后随腿（trailing leg，即腾空阶段后率先着陆的腿部）上。将本研究确定的调整策略应用于数值模型后，模型应对突发地面落差扰动的能力得到了提升。由此可见，控制简化、稳定性与鲁棒性或许是人类选择跳跃步态的核心动因。