Human control of an inverted pendulum: is continuous control necessary? Is intermittent control effective? Is intermittent control physiological?

Loram, I. D., Gollee, H. , Lakie, M. and Gawthrop, P. J. (2011) Human control of an inverted pendulum: is continuous control necessary? Is intermittent control effective? Is intermittent control physiological? Journal of Physiology, 589(2), pp. 307-324. (doi: 10.1113/jphysiol.2010.194712)

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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 bandwidth, 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 visual 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 2s-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.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Loram, Dr Ian and Gollee, Dr Henrik and Gawthrop, Professor Peter
Authors: Loram, I. D., Gollee, H., Lakie, M., and Gawthrop, P. J.
College/School:College of Science and Engineering > School of Engineering > Biomedical Engineering
College of Science and Engineering > School of Engineering > Systems Power and Energy
Journal Name:Journal of Physiology
Journal Abbr.:J Physiol
Publisher:Wiley-Blackwell Publishing Ltd.
ISSN (Online):1469-7793
Published Online:22 November 2010

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
476761Intermittent predictive control of man and machineHenrik GolleeEngineering & Physical Sciences Research Council (EPSRC)EP/F069022/1Biomedical Engineering