This study aims to estimate the control law employed by the central nervous system (CNS) to keep a person in balance after a sudden disturbance. For this aim, several experiments were carried out, in which the subjects were perturbed sagittally by using a single-axis tilt-platform and their motions were recorded with appropriate sensors. The analysis of the experimental results leads to the contribution of this paper as a conjecture that the CNS commands the muscular actuators of the joints according to an adaptive proportional-derivative (PD) control law such that its gains and set points are updated continuously. This conjecture is accompanied with an assumption that the CNS is able to acquire perfect and almost instantaneous position and velocity feedback by means of a fusion of the signals coming from the proprioceptive, somatosensory, and vestibular systems. In order to verify the conjectured control law, an approximate biomechanical model was developed and several simulations were carried out to imitate the experimentally observed motions. The time variations of the set points and the control gains were estimated out of the experimental data. The simulated motions were observed to be considerably close to the experimental motions. Thus, the conjectured control law is validated. However, the experiments also indicate that the mentioned adaptation scheme is quite variable even for the same subject tested repeatedly with the same perturbation. In other words, this experimental study also leads to the implication that the way the CNS updates the control parameters is not quite predictable.

References

References
1.
Horak
,
F. B.
, and
Nashner
,
L. M.
,
1986
, “
Central Programming of Postural Movements: Adaptation to Altered Support-Surface Configurations
,”
J. Neurophysiol.
,
55
(
6
), pp.
1369
1381
.
2.
McIntyre
,
J.
, and
Bizzi
,
E.
,
1993
, “
Servo Hypotheses for the Biological Control of Movement
,”
J. Motor Behav.
,
25
(
3
), pp.
193
202
.
3.
Kim
,
S.
,
Atkeson
,
C. G.
, and
Park
,
S.
,
2012
, “
Perturbation-Dependent Selection of Postural Feedback Gain and Its Scaling
,”
J. Biomech.
,
45
(
8
), pp.
1379
1386
.
4.
Küng
,
U. M.
,
Horlings
,
C.
,
Honegger
,
F.
,
Duysens
,
J.
, and
Allum
,
J.
,
2009
, “
Control of Roll and Pitch Motion During Multi-Directional Balance Perturbations
,”
Exp. Brain Res.
,
194
(
4
), pp.
631
645
.
5.
Runge
,
C.
,
Shupert
,
C.
,
Horak
,
F.
, and
Zajac
,
F.
,
1999
, “
Ankle and Hip Postural Strategies Defined by Joint Torques
,”
Gait Posture
,
10
(
2
), pp.
161
170
.
6.
Peterka
,
R. J.
,
2003
, “
Simplifying the Complexities of Maintaining Balance
,”
IEEE Eng. Med. Biol. Mag.
,
22
(
2
), pp.
63
68
.
7.
Park
,
S.
,
Horak
,
F. B.
, and
Kuo
,
A. D.
,
2004
, “
Postural Feedback Responses Scale With Biomechanical Constraints in Human Standing
,”
Exp. Brain Res.
,
154
(
4
), pp.
417
427
.
8.
Kuo
,
A. D.
,
2005
, “
An Optimal State Estimation Model of Sensory Integration in Human Postural Balance
,”
J. Neural Eng.
,
2
(
3
), p.
S235
.
9.
Li
,
Y.
,
Levine
,
W. S.
, and
Loeb
,
G. E.
,
2012
, “
A Two-Joint Human Posture Control Model With Realistic Neural Delays
,”
IEEE Trans. Neural Syst. Rehabil. Eng.
,
20
(
5
), pp.
738
748
.
10.
Mussa-Ivaldi
,
F. A.
, and
Solla
,
S. A.
,
2008
, “
Models of Motor Control
,”
The Cambridge Handbook of Computational Psychology
,
R.
Sun
, ed.,
Cambridge University Press, New York
.
11.
Gomi
,
H.
, and
Kawato
,
M.
,
1996
, “
Equilibrium-Point Control Hypothesis Examined by Measured Arm Stiffness During Multijoint Movement
,”
Science
,
272
(
5258
), pp.
117
120
.
12.
Horak
,
F. B.
, 1996, “
Adaptation of Automatic Postural Responses
,”
Proceedings Acquisition of Motor Behavior in Vertebrates
,
J. R.
Bloedel
,
T. J.
Ebner
, and
S. P.
Wise
, eds., MIT Press, Cambridge, MA, pp. 57–85.
13.
Kuo
,
A. D.
, and
Zajac
,
F. E.
,
1993
, “
Human Standing Posture: Multi-Joint Movement Strategies Based on Biomechanical Constraints
,”
Progress in Brain Research
, J. H. J. Allum, D. J. Allum-Mecklenburg, F. P. Harris, R. Probst, eds., Vol. 97,
Elsevier
, Amsterdam, The Netherlands, pp.
349
358
.
14.
Bilgin
,
N.
,
2015
, “
Investigation of Control of Human Balance-Recovery Reactions
,”
Ph.D. thesis
, Middle East Technical University, Ankara, Turkey.http://etd.lib.metu.edu.tr/upload/12619450/index.pdf
15.
Zatsiorsky
,
V. M.
, and
Seluyanov
,
V. N.
,
1983
, “
The Mass and Inertia Characteristics of the Main Segments of the Human Body
,” Biomech.,
V-IIIB
, pp. 1152–1159.
16.
Winter
,
D. A.
,
2009
,
Biomechanics and Motor Control of Human Movement
,
Wiley
, Hoboken, NJ.
17.
van der Kooij
,
H.
,
Jacobs
,
R.
,
Koopman
,
B.
, and
Grootenboer
,
H.
,
1999
, “
A Multisensory Integration Model of Human Stance Control
,”
Biol. Cybern.
,
80
(
5
), pp.
299
308
.
18.
Horak
,
F. B.
,
2009
, “
Postural Control
,”
Encyclopedia of Neuroscience
,
Springer
, Berlin, pp.
3212
3219
.
19.
Jeka
,
J.
, and
Kiemel
,
T.
,
2009
, “
Modeling of Human Postural Control
,”
Encyclopedia of Neuroscience
,
M.
Binder
,
N.
Hirokawa
, and
U.
Windhorst
, eds.,
Springer
,
Berlin
, pp.
2381
2384
.
20.
Jiang
,
J.
, and
Zhang
,
Y.
,
2004
, “
A Revisit to Block and Recursive Least Squares for Parameter Estimation
,”
Comput. Electr. Eng.
,
30
(
5
), pp.
403
416
.
21.
Haugen
,
F.
,
2010
,
Advanced Dynamics and Control
,
TechTeach
, Skien, Norway.
22.
Tang
,
K. S.
,
Honegger
,
F.
, and
Allum
,
J. H. J.
,
2012
, “
Movement Patterns Underlying First Trial Responses in Human Balance Corrections
,”
Neuroscience
,
225
, pp.
140
151
.
You do not currently have access to this content.