Human balancing of an inverted pendulum: position control by small, ballistic-like, throw and catch movements
Human balancing of an inverted pendulum: position control by small, ballistic-like, throw and catch movements
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DOI：
10.1113/jphysiol.2001.013077
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发表时间：
2002-05-01
影响因子：
5.5
通讯作者：
Lakie, M
中科院分区：
文献类型：
--
作者：
Loram, ID;Lakie, M
站立时，身体会有微小的摆动。我们的兴趣是使用一个人工任务来阐明摇摆背后的机制，并解释它们大小的变化。受试者使用脚踝肌肉系统来平衡一个大的倒立摆。摆的平衡是不稳定的，观察到了与静止状态类似的准规则摆动。通过全神贯注地减少摆动，受试者可以系统地减少摆动。记录摆位、每个踝关节产生的扭矩以及比目鱼肌和胫骨前肌的肌电。关于人类倒立摆如何平衡的解释通常忽略了这样一个事实，即平衡是在一系列角度上保持的，而不仅仅是在一个角度上。摆的任何静止平衡位置都是不稳定的，实际上是暂时的；运动到不同的静止平衡位置只能通过扭矩的两相“抛接”模式来完成，而不是通过弹性机构。结果表明，平衡是通过不断重复神经产生的弹道状两相扭矩模式实现的，该模式可以控制位置和摇摆大小。分解技术显示，踝关节固有的机械僵硬对扭矩的变化有很大的贡献；然而，这本身不足以维持平衡或控制位置。摇摆尺寸的最小化是由于预期扭矩脉冲的精确度的提高。我们假设，对安静站立的质心和压力中心数据的检查将重复这些结果。
In standing, there are small sways of the body. Our interest is to use an artificial task to illuminate the mechanisms underlying the sways and to account for changes in their size. Using the ankle musculature, subjects balanced a large inverted pendulum. The equilibrium of the pendulum is unstable and quasi-regular sway was observed like that in quiet standing. By giving full attention to minimising sway subjects could systematically reduce pendulum movement. The pendulum position, the torque generated at each ankle and the soleus and tibialis anterior EMGs were recorded. Explanations about how the human inverted pendulum is balanced usually ignore the fact that balance is maintained over a range of angles and not just at one angle. Any resting equilibrium position of the pendulum is unstable and in practice temporary; movement to a different resting equilibrium position can only be accomplished by a biphasic 'throw and catch' pattern of torque and not by an elastic mechanism. Results showed that balance was achieved by the constant repetition of a neurally generated ballistic-like biphasic pattern of torque which can control both position and sway size. A decomposition technique revealed that there was a substantial contribution to changes in torque from intrinsic mechanical ankle stiffness; however, by itself this was insufficient to maintain balance or to control position. Minimisation of sway size was caused by improvement in the accuracy of the anticipatory torque impulses. We hypothesise that examination of centre of mass and centre of pressure data for quiet standing will duplicate these results.