Biomechanics of quadrupedal walking: how do four-legged animals achieve inverted pendulum-like movements?
Biomechanics of quadrupedal walking: how do four-legged animals achieve inverted pendulum-like movements?
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DOI：
10.1242/jeb.01177
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发表时间：
2004-09-01
影响因子：
2.8
通讯作者：
Farley, CT
中科院分区：
文献类型：
--
作者：
Griffin, TM;Main, RP;Farley, CT
行走涉及重力势能和质心动能的循环交换。我们的目标是了解行走的四足动物的四肢是如何协调前后四分之一的垂直运动，以产生这些倒金字塔般的运动。我们收集了狗在一定速度范围内行走的运动学和地面反作用力数据。我们发现，狗的前躯和后躯的行为就像两个独立的两足动物，每个人都在各自的支撑肢体上跳跃。质心每一步上下移动两次，就像一个行走的钟摆，通过倒立摆机构回收了提升和加速质心所需的高达70%的机械能。为了理解四肢如何产生这些质心运动，我们创建了一个简单的模型，其中包含两个独立的身体，分别代表前躯和后躯的运动。该模型预测，前和后季度的运动将完全抵消对方，如果前肢落后于后肢的25%的步幅时间和身体质量均匀分布在前和后季度之间。狗不以质心的平坦轨迹行走的主要原因是，每个前肢仅落后于同侧后肢15%的步幅时间，从而产生了前躯和后躯同时向上或向下移动的时间段。第二个原因是前肢支撑了63%的体重。与这些实验结果相一致，两个钟摆模型预测，如果肢体相位小于25%和/或如果总质量不均匀分布在前或后四分之一之间，则每个步幅周期的质心将经历两次波动。
Walking involves a cyclic exchange of gravitational potential energy and kinetic energy of the center of mass. Our goal was to understand how the limbs of walking quadrupeds coordinate the vertical movements of the fore and hind quarters to produce these inverted pendulum-like movements. We collected kinematic and ground reaction force data from dogs walking over a range of speeds. We found that the fore and hind quarters of dogs behaved like two independent bipeds, each vaulting up and over its respective support limb. The center of mass moved up and down twice per stride, like a single walking biped, and up to 70% of the mechanical energy required to lift and accelerate the center of mass was recovered via the inverted pendulum mechanism. To understand how the limbs produce these center of mass movements, we created a simple model of two independent pendulums representing the movements of the fore and hind quarters. The model predicted that the fore and hind quarter movements would completely offset each other if the fore limb lagged the hind limb by 25% of the stride time and body mass was distributed equally between the fore and hind quarters. The primary reason that dogs did not walk with a flat trajectory of the center of mass was that each fore limb lagged its ipsilateral hind limb by only 15% of the stride time and thereby produced time periods when the fore and hind quarters moved up or down simultaneously. The secondary reason was that the fore limbs supported 63% of body mass. Consistent with these experimental results, the two-pendulum model predicts that the center of mass will undergo two fluctuations per stride cycle if limb phase is less than 25% and/or if the total mass is not distributed evenly between the fore or hind quarters.