Delay effects in the human sensory system during balancing

Abstract

Mechanical models of human self-balancing often use the Newtonian equations of inverted pendula. While these mathematical models are precise enough on the mechanical side, the ways humans balance themselves are still quite unexplored on the control side. Time delays in the sensory and motoric neural pathways give essential limitations to the stabilization of the human body as a multiple inverted pendulum. The sensory systems supporting each other provide the necessary signals for these control tasks; but the more complicated the system is, the larger delay is introduced. Human ageing as well as our actual physical and mental state affects the time delays in the neural system, and the mechanical structure of the human body also changes in a large range during our lives. The human balancing organ, the labyrinth, and the vision system essentially adapted to these relatively large time delays and parameter regions occurring during balancing. The analytical study of the simplified large-scale time-delayed models of balancing provides a Newtonian insight into the functioning of these organs that may also serve as a basis to support theories and hypotheses on balancing and vision.

Changes in balance coordination and transfer to an unlearned balance task after slackline training: a self-organizing map analysis

“…However, while these approaches constitute useful first approximations, they ignore the complex interactions between the large numbers of degrees of freedom of the human body. Every degree of freedom in its turn can be studied at multiple levels (joint angle, velocity, acceleration, frequency domain) and each level provides important information because the sensorimotor subsystems (proprioception, vestibular, visual) rely on these different types of kinematic information, although it is not exactly known how these inputs are weighted and integrated (Stepan and Kollar 2000;Peterka 2002;Stepan 2009). …”

Balancing on tightropes and slacklines

“…However, it is worth noting that our results are robust to different choices of sensory input; for example, the same qualitative behaviour is observed if we assume that _ a and _ f are measured separately by the proprioceptive system, or even in the ideal case when the whole state can be measured. For the control action, we assume that balancing around the upright position is achievable using the torque F a [8] that is assumed to be bounded, i.e. jF a ðtÞj F a max (see appendix C for a simple derivation of an upper bound on the scaled torque F a max ≃ 0:3).…”

“…R is a parameter that identifies the position of the body along the rope. The inverted pendulum is assumed to have length l and a concentrated mass m on top, and its deviation from the radial direction is the angle a [8,16]. The cart is assumed to have mass M, with an angular position along the track given by the angle f. We will initially consider R and M þ m as independent parameters by assuming, for example, that the rope pretension, and thus the sag, can be set at will, but will relax it eventually and in §5, we discuss the effects of a possible linear dependence between them induced by the elasticity of the rope.…”

“…Thus, vestibular feedback sensors are thought to be more relevant on moving platforms, whereas proprioceptive and visual systems are the primary feedback sensors during quiet standing [13]. Furthermore, the presence of delay in the feedback loop has a non-negligible impact on the overall performance [8,14].…”

“…A variety of models have been proposed to describe the dynamics of body sway motion during balancing on a fixed or moving platform [8,9]. Most of them reduce to the dynamics of a single degree-of-freedom system where the body is represented as an inverted pendulum; this simplification allows researchers to easily analyse the dynamics and control issues that arise for obtaining insight into postural balance strategies implemented by neural controllers [1, [9][10][11][12]].…”