Leg-adjustment strategies for stable running in three dimensions
Leg-adjustment strategies for stable running in three dimensions
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DOI：
10.1088/1748-3182/7/3/036002
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发表时间：
2012-09-01
影响因子：
3.4
通讯作者：
Seyfarth, Andre
中科院分区：
文献类型：
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作者：
Peuker, Frank;Maufroy, Christophe;Seyfarth, Andre
用弹簧倒立摆（SLIP）可以很好地描述人和动物在奔跑过程中矢状面质心的动力学。通过适当的参数，SLIP的运行模式是稳定的，这些模型可以从扰动中恢复，而不需要校正策略，例如施加额外的力。相反，将腿调整到与地面的固定角度就足够了。在这项工作中，我们考虑将SLIP扩展到三维（3D SLIP），并研究在飞行阶段腿部调整的前馈策略。与SLIP模型一样，腿以固定角度放置。我们将可能参考轴的范围从固定的水平和垂直轴扩展到包括CoM速度矢量作为运动相关参考，从而产生六种腿调整策略。只有包含CoM速度矢量的腿调整策略才能产生稳定的运行和大参数域的稳定性。模型从沿运动方向的扰动中恢复的能力（方向稳定性）取决于侧向腿调整的策略。具体而言，基于全局参考轴和速度矢量的策略分别具有渐近和中性方向稳定性。基于速度的腿部调节的其他特征是在任意低速（动能）下运行，以及稳定的3D运行的大区域的出现，这些区域可以顺利地转移到2D SLIP稳定性甚至1D SLIP跳跃。其中一个额外的腿调整策略代表了一个大的凸区域的参数，其中稳定和稳健的跳跃和运行模式存在。因此，这种策略在工程应用（例如机器人）中很有前途。初步对比表明，模型预测结果与实验数据吻合较好，表明三维SLIP模型是一种较为合适的三维人体运动描述模型。基于与运动相关的腿部调节策略的稳定运行预测表明，人类和机器人可能不需要外部目标来指导运动在基于柔性腿部功能的三维空间中运行。这种新的基于运动的参考可以控制3D跑步，因为腿部调整不那么敏感，步态稳定性与方向稳定性分开。
The dynamics of the center of mass (CoM) in the sagittal plane in humans and animals during running is well described by the spring-loaded inverted pendulum (SLIP). With appropriate parameters, SLIP running patterns are stable, and these models can recover from perturbations without the need for corrective strategies, such as the application of additional forces. Rather, it is sufficient to adjust the leg to a fixed angle relative to the ground. In this work, we consider the extension of the SLIP to three dimensions (3D SLIP) and investigate feed-forward strategies for leg adjustment during the flight phase. As in the SLIP model, the leg is placed at a fixed angle. We extend the scope of possible reference axes from only fixed horizontal and vertical axes to include the CoM velocity vector as a movement-related reference, resulting in six leg-adjustment strategies. Only leg-adjustment strategies that include the CoM velocity vector produced stable running and large parameter domains of stability. The ability of the model to recover from perturbations along the direction of motion (directional stability) depended on the strategy for lateral leg adjustment. Specifically, asymptotic and neutral directional stability was observed for strategies based on the global reference axis and the velocity vector, respectively. Additional features of velocity-based leg adjustment are running at arbitrary low speed (kinetic energy) and the emergence of large domains of stable 3D running that are smoothly transferred to 2D SLIP stability and even to 1D SLIP hopping. One of the additional leg-adjustment strategies represented a large convex region of parameters where stable and robust hopping and running patterns exist. Therefore, this strategy is a promising candidate for implementation into engineering applications, such as robots, for instance. In a preliminary comparison, the model predictions were in good agreement with the experimental data, suggesting that the 3D SLIP is an appropriate model to describe human running in three dimensions. The prediction of stable running based on movement-related leg-adjustment strategies indicates that both humans and robots may not require external targets directing the movement to run in three dimensions based on compliant leg function. This new movement-based reference enables the control of 3D running because leg adjustment is less sensitive and gait stability is separated from directional stability.