Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, UK.
J Physiol. 2011 Jan 15;589(Pt 2):307-24. doi: 10.1113/jphysiol.2010.194712. Epub 2010 Nov 22.
Human motor control is often explained in terms of engineering 'servo' theory. Recently, continuous, optimal control using internal models has emerged as a leading paradigm for voluntary movement. However, these engineering paradigms are designed for high band-width, inflexible, consistent systems whereas human control is low bandwidth and flexible using noisy sensors and actuators. By contrast, engineering intermittent control was designed for bandwidth-limited applications. Our general interest is whether intermittent rather than continuous control is generic to human motor control. Currently, it would be assumed that continuous control is the superior and physiologically natural choice for controlling unstable loads, for example as required for maintaining human balance. Using visuo-manual tracking of an unstable load, we show that control using gentle, intermittent taps is entirely natural and effective. The gentle tapping method resulted in slightly superior position control and velocity minimisation, a reduced feedback time delay, greater robustness to changing actuator gain and equal or greater linearity with respect to the external disturbance. Control was possible with a median contact rate of 0.8±0.3 s(-1). However, when optimising position or velocity regulation, a modal contact rate of 2 s(-1) was observed. This modal rate was consistent with insignificant disturbance-joystick coherence beyond 1-2 Hz in both tapping and continuous contact methods. For this load, these results demonstrate a motor control process of serial ballistic trajectories limited to an optimum rate of 2 s(-1). Consistent with theoretical reasoning, our results suggest that intermittent open loop action is a natural consequence of human physiology.
人类运动控制通常可以用工程学的“伺服”理论来解释。最近，基于内部模型的连续最优控制已成为自愿运动的主要范例。然而，这些工程范例是为高带宽、不灵活、一致的系统而设计的，而人类控制则使用噪声传感器和执行器，带宽低且灵活。相比之下，工程间歇控制是为带宽受限的应用而设计的。我们的普遍兴趣是，间歇控制是否比连续控制更普遍适用于人类运动控制。目前，人们可能会认为连续控制是控制不稳定负载的优越和生理自然选择，例如维持人体平衡所需的控制。我们通过对不稳定负载的视觉手动跟踪，表明使用温和的间歇敲击进行控制是完全自然和有效的。温和敲击法导致位置控制略有改善，速度最小化，反馈时间延迟减少，对执行器增益变化的鲁棒性更高，对外部干扰的线性度相等或更高。控制可以在中位数接触率为 0.8±0.3 s(-1)的情况下实现。然而，当优化位置或速度调节时，观察到的模态接触率为 2 s(-1)。这种模态率与敲击和连续接触方法中 1-2 Hz 以外的干扰操纵器相干性无关。对于这种负载，这些结果表明运动控制过程是有限制最佳速率为 2 s(-1)的串行弹道轨迹。与理论推理一致，我们的结果表明，间歇开环作用是人类生理学的自然结果。
