TY  - JOUR
PY  - 2019//
TI  - Acting together, destabilizing influences can stabilize human balance
JO  - Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
A1  - Milton, John
A1  - Insperger, Tamas
SP  - e20180126
EP  - e20180126
VL  - 377
IS  - 2153
N2  - 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. This article is part of the theme issue 'Nonlinear dynamics of delay systems'.<p />  <p>Language: en</p>
LA  - en
SN  - 1364-503X
UR  - http://dx.doi.org/10.1098/rsta.2018.0126
ID  - ref1
ER  -