Acting together, destabilizing influences can stabilize human balance

John Milton, T. Insperger

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The causes of falling in the elderly are multi-factorial. Three factors that influence balance stability are the time delay, a sensory dead zone and the maximum ankle torque that can be generated by muscular contraction. Here, the effects of these contributions are evaluated in the context of a model of an inverted pendulum stabilized by time-delayed proportional-derivative (PD) feedback. The effect of the sensory dead zone is to produce a hybrid type of control in which the PD feedback is switched ON or OFF depending on whether or not the controlled variable is larger or smaller than the detection threshold, Π. It is shown that, as Π increases, the region in the plane of control parameters where the balance time (BT) is greater than 60 s is increased slightly. However, when maximum ankle torque is also limited, there is a dramatic increase in the parameter region associated with BTs greater than 60 s. This increase is due to the effects of a torque limitation on over-control associated with bang-bang type switching controllers. These observations show that acting together influences, which are typically thought to destabilize balance, can actually stabilize balance.

Original languageEnglish
Article number2018126
JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Volume377
Issue number2153
DOIs
Publication statusPublished - Sep 9 2019

Fingerprint

Torque
Dead Zone
torque
Directly proportional
Derivatives
Feedback
Derivative
Inverted Pendulum
Factorial
Pendulums
Control Parameter
Contraction
Time Delay
Time delay
pendulums
falling
contraction
Controller
controllers
Controllers

Keywords

  • Balance
  • Falling
  • Feedback
  • Hybrid systems
  • Time delay

ASJC Scopus subject areas

  • Mathematics(all)
  • Engineering(all)
  • Physics and Astronomy(all)

Cite this

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