Research Publication
Professor of Biology John Milton
Professor of Biology John Milton is collaborating with theoretical mechanical engineers at the Budapest University of Technology and Economics (Tamás Inpserger and Gábor Stépán) to use human balance tasks to identify how the nervous system uses sensory perceptions to control motor actions. Stabilizing unstable states is often expedient above controlling stable ones, especially from the viewpoint of required control energy. This might be the key to the success of how the human brain controls complex body motions in the three dimensional space such as balancing and movement. Since these motions are governed by the Newtonian laws, the mechanism of the neural control system can be explored by the combination of mechanics and neural sciences. Human balancing includes all the important elements of the complex system: (1) neural effects such as reflex delay or intermittent activation of the muscles; (2) a mechanical system at an unstable equilibrium. The understanding of balancing provides a keyhole through which it is possible to gain insights into the complex cooperation between the visual, auditory and the tactile sensory systems and motor control. A model for human postural balance is considered in which the time-delayed feedback depends on position, velocity and acceleration (proportional– derivative–acceleration (PDA) feedback). It is shown that a PDA controller is equivalent to a predictive controller, in which the prediction is based on the most recent information of the state, but the control input is not involved into the prediction. In an article to appear in the Journal of the Royal Society Interface, these investigators show that balance control is more effective if it combines P, D and A information, i.e. a PDA controller.  


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