Intermittent control with ankle, hip, and mixed strategies during quiet standing: A theoretical proposal based on a double inverted pendulum model
Intermittent control with ankle, hip, and mixed strategies during quiet standing: A theoretical proposal based on a double inverted pendulum model
复制标题
DOI：
10.1016/j.jtbi.2012.06.019
复制
发表时间：
2012-10-07
影响因子：
2
通讯作者：
Morasso, Pietro
中科院分区：
文献类型：
--
作者：
Suzuki, Yasuyuki;Nomura, Taishin;Morasso, Pietro
人的直立姿势作为一个机械系统，具有鞍型失稳的特点，既有稳定的动力模式，也有不稳定的动力模式。根据延时神经反馈控制，大脑通过产生主动关节力矩来稳定这种系统。尚待解决的是对中枢神经系统使用的控制策略和控制机制的清楚了解，以便在保持灵活性的同时以稳健的方式稳定不稳定的姿势。这方面的研究大多局限于单级倒立摆模型，该模型对于形式化基本力学方面是有用的，但不足以解决与神经控制策略有关的更一般的问题。在这里，我们考虑在矢状面上的二级倒立摆模型，在脚踝和髋关节处具有小的被动粘弹性。尽管在存在大反馈延迟的情况下稳定二级倒立摆模型存在困难，但我们证明了通过在二级倒立摆状态空间的不同部分的不同控制器之间切换的“分而治之”的间歇控制机制来实现对直立摆姿态的鲁棒且灵活的镇定，从而达到稳定身体姿态的目的。值得注意的是，研究表明，即使单个控制器是不稳定的，用于从一个控制器切换到另一个控制器的信息被严重延迟，也可以获得全局鲁棒稳定性，就像在生物现实中所发生的那样。此外，间歇控制器可以自动解决与肌肉协同作用相关的多个主动力矩之间的协调，导致根据髋关节的被动弹性，在安静站立期间出现不同的时间协调主动力矩模式，称为间歇脚踝、髋关节和混合策略。(C)2012爱思唯尔有限公司。保留所有权利。
Human upright posture, as a mechanical system, is characterized by an instability of saddle type, involving both stable and unstable dynamic modes. The brain stabilizes such system by generating active joint torques, according to a time-delayed neural feedback control. What is still unsolved is a clear understanding of the control strategies and the control mechanisms that are used by the central nervous system in order to stabilize the unstable posture in a robust way while maintaining flexibility. Most studies in this direction have been limited to the single inverted pendulum model, which is useful for formalizing fundamental mechanical aspects but insufficient for addressing more general issues concerning neural control strategies. Here we consider a double inverted pendulum model in the sagittal plane with small passive viscoelasticity at the ankle and hip joints. Despite difficulties in stabilizing the double pendulum model in the presence of the large feedback delay, we show that robust and flexible stabilization of the upright posture can be established by an intermittent control mechanism that achieves the goal of stabilizing the body posture according to a "divide and conquer strategy", which switches among different controllers in different parts of the state space of the double inverted pendulum. Remarkably, it is shown that a global, robust stability is achieved even if the individual controllers are unstable and the information exploited for switching from one controller to another is severely delayed, as it happens in biological reality. Moreover, the intermittent controller can automatically resolve coordination among multiple active torques associated with the muscle synergy, leading to the emergence of distinct temporally coordinated active torque patterns, referred to as the intermittent ankle, hip, and mixed strategies during quiet standing, depending on the passive elasticity at the hip joint. (c) 2012 Elsevier Ltd. All rights reserved.