Does a crouched leg posture enhance running stability and robustness?
Does a crouched leg posture enhance running stability and robustness?
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DOI：
10.1016/j.jtbi.2011.04.029
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发表时间：
2011-07-21
影响因子：
2
通讯作者：
Seyfarth, Andre
中科院分区：
文献类型：
--
作者：
Blum, Yvonne;Birn-Jeffery, Aleksandra;Seyfarth, Andre
人类和鸟类都用顺从的腿行走和奔跑。然而，根据观察到的步态模式，腿部结构的差异可能会导致特定物种的腿部控制策略。在这项工作中，基于概念模型推导了稳定运行的控制策略，并与奔跑的人和野鸡(Phasianus Colchicus)的实验数据进行了比较。从模型的角度来看，用柔顺的腿跑步可以用平面弹簧质量模型来表示，并通过应用摆动腿控制来稳定。这里假设了摆动后期腿角度、腿长度和腿刚度这三个腿参数的线性自适应。对实验观察到的人类和鸟类跑步的运动学控制参数(腿旋转和腿长度变化)进行了比较，并在该模型的背景下进行了解释，重点讨论了稳定性和鲁棒性特性。这些结果表明，人类和鸟类跑步的稳定性特征和应用的控制策略不同，这可能与腿部姿势(人类的直腿姿势和鸟类的蹲腿姿势)的不同有关。有研究表明，蹲腿姿势可能会提高稳定性。然而，由于控制策略系统被过度确定，我们的模型研究结果表明，蹲腿姿势并不一定能增强跑步稳定性。该模型还预测了人类和鸟类跑步时不同的腿部僵硬适应率，并建议蹲着的鸟类腿部姿势既能缩短腿部也能延长腿部，允许在不调整腿部僵硬的情况下稳定地跑步。相比之下，在直腿人类跑步中，地面接触的准备似乎更关键，需要调整腿部僵硬才能保持稳定。最后，对一个简单的稳健性指标--归一化最大落差的分析表明，蹲腿姿势可能对地形高度的变化提供更强的稳健性。(C)2011爱思唯尔有限公司。保留所有权利。
Humans and birds both walk and run bipedally on compliant legs. However, differences in leg architecture may result in species-specific leg control strategies as indicated by the observed gait patterns. In this work, control strategies for stable running are derived based on a conceptual model and compared with experimental data on running humans and pheasants (Phasianus colchicus). From a model perspective, running with compliant legs can be represented by the planar spring mass model and stabilized by applying swing leg control. Here, linear adaptations of the three leg parameters, leg angle, leg length and leg stiffness during late swing phase are assumed. Experimentally observed kinematic control parameters (leg rotation and leg length change) of human and avian running are compared, and interpreted within the context of this model, with specific focus on stability and robustness characteristics. The results suggest differences in stability characteristics and applied control strategies of human and avian running, which may relate to differences in leg posture (straight leg posture in humans, and crouched leg posture in birds). It has been suggested that crouched leg postures may improve stability. However, as the system of control strategies is overdetermined, our model findings suggest that a crouched leg posture does not necessarily enhance running stability. The model also predicts different leg stiffness adaptation rates for human and avian running, and suggests that a crouched avian leg posture, which is capable of both leg shortening and lengthening, allows for stable running without adjusting leg stiffness. In contrast, in straight-legged human running, the preparation of the ground contact seems to be more critical, requiring leg stiffness adjustment to remain stable. Finally, analysis of a simple robustness measure, the normalized maximum drop, suggests that the crouched leg posture may provide greater robustness to changes in terrain height. (C) 2011 Elsevier Ltd. All rights reserved.