Scrivens J E, Deweerth S P, Ting L H
Department of Mechanical Engineering, Interdisciplinary Bioengineering Program, Georgia Institute of Technology, 313 Ferst Drive, Atlanta, GA 30332-0535, USA.
Bioinspir Biomim. 2008 Jun;3(2):026002. doi: 10.1088/1748-3182/3/2/026002. Epub 2008 Apr 25.
Postural stability in standing balance results from the mechanics of body dynamics as well as active neural feedback control processes. Even when an animal or human has multiple legs on the ground, active neural regulation of balance is required. When the postural configuration, or stance, changes, such as when the feet are placed further apart, the mechanical stability of the organism changes, but the degree to which this alters the demands on neural feedback control for postural stability is unknown. We developed a robotic system that mimics the neuromechanical postural control system of a cat in response to lateral perturbations. This simple robotic system allows us to study the interactions between various parameters that contribute to postural stability and cannot be independently varied in biological systems. The robot is a 'planar', two-legged device that maintains compliant balance control in a variety of stance widths when subject to perturbations of the support surface, and in this sense reveals principles of lateral balance control that are also applicable to bipeds. Here we demonstrate that independent variations in either stance width or delayed neural feedback gains can have profound and often surprisingly detrimental effects on the postural stability of the system. Moreover, we show through experimentation and analysis that changing stance width alters fundamental mechanical relationships important in standing balance control and requires a coordinated adjustment of delayed feedback control to maintain postural stability.
站立平衡中的姿势稳定性源于身体动力学机制以及主动神经反馈控制过程。即使动物或人类有多条腿着地，也需要对平衡进行主动神经调节。当姿势构型或 stance（姿势）发生变化时，例如双脚分得更开时，机体的机械稳定性会改变，但这在多大程度上改变了对姿势稳定性神经反馈控制的需求尚不清楚。我们开发了一种机器人系统，它能模拟猫在受到侧向扰动时的神经机械姿势控制系统。这个简单的机器人系统使我们能够研究各种有助于姿势稳定性的参数之间的相互作用，而这些参数在生物系统中无法独立变化。该机器人是一个“平面”双足装置，在支撑面受到扰动时，能在各种 stance（姿势）宽度下保持柔顺平衡控制，从这个意义上说，它揭示了也适用于两足动物的侧向平衡控制原理。在这里，我们证明 stance（姿势）宽度或延迟神经反馈增益的独立变化可能对系统的姿势稳定性产生深远且常常令人惊讶的有害影响。此外，我们通过实验和分析表明，改变 stance（姿势）宽度会改变站立平衡控制中重要的基本力学关系，并且需要对延迟反馈控制进行协调调整以维持姿势稳定性。
