Document Detail

Open-loop tracking performance of a limb joint controlled by random, periodic, and abrupt electrical stimulation inputs to the antagonist muscle pair.
MedLine Citation:
PMID:  9556968     Owner:  NLM     Status:  MEDLINE    
The ability of the cat's ankle joint to track various input signals when controlled by electrically elicited motor unit recruitment, firing rate and antagonist muscle coactivation was examined. Pseudo-random, sinusoidal and staircase signals were used to control the soleus and tibialis anterior muscles isometrically and with a 250-g pendulum. Tracking was evaluated through cross correlation for pseudo-random and sinusoidal signals, and by rise time and steady-state error in step signals. Better tracking was obtained in isometric conditions than in load-moving conditions. Pseudo-random signals resulted in 250-ms delay between input and isometric torque output. For load-moving conditions, 340-ms and 400-ms delay in torque and angle were obtained. For sinusoids, delays decreased from 240 ms at 0.5 Hz, to 140 ms at 2 Hz in isometric conditions. Time delays for angle were between 300 and 400 ms, decreasing as frequency increased. Poor cross correlation was found for torque in load-moving conditions, because of pendulum nonlinear dynamics. Step size was not uniform in staircase trials, with steady-state errors between 9% and 39%, and rise times between 200 and 1000 ms. It is concluded that open-loop joint control results in poor tracking, presumably because it is devoid of feedback mechanisms.
B H Zhou; R V Baratta; M Solomonow; N Matsushita; R D D'Ambrosia
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  IEEE transactions on bio-medical engineering     Volume:  45     ISSN:  0018-9294     ISO Abbreviation:  IEEE Trans Biomed Eng     Publication Date:  1998 Apr 
Date Detail:
Created Date:  1998-04-30     Completed Date:  1998-04-30     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0012737     Medline TA:  IEEE Trans Biomed Eng     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  511-9     Citation Subset:  IM    
Louisiana State University Medical Center, Department of Orthopaedic Surgery, New Orleans 70112, USA.
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MeSH Terms
Analysis of Variance
Ankle Joint / physiology*
Electric Stimulation*
Isometric Contraction / physiology
Muscle, Skeletal / physiology*
Peroneal Nerve / physiology
Random Allocation
Recruitment, Neurophysiological
Sciatic Nerve / physiology

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