Open-loop tracking performance of a limb joint controlled by random, periodic, and abrupt electrical stimulation inputs to the antagonist muscle pair

• Published in: IEEE transactions on biomedical engineering Vol. 45; no. 4; pp. 511 - 519
• Main Authors: Bing-He Zhou, Baratta, R.V., Solomonov, M., Matsushita, N., D'Ambrosia, R.D.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-04-1998; Institute of Electrical and Electronics Engineers
• Subjects: Analysis of Variance; Animals; Ankle Joint - physiology; Biological and medical sciences; Calibration; Cats; Correlation theory; Delay; Electric Stimulation; Electrical stimulation; Electrophysiology; Fatigue; Feedback; Fundamental and applied biological sciences. Psychology; Isometric Contraction - physiology; Joints (anatomy); Muscle; Muscle, Skeletal - physiology; Muscles; Open loop systems; Orthopedic surgery; Periodicity; Peroneal Nerve - physiology; Random Allocation; Recruitment; Recruitment, Neurophysiological; Sciatic Nerve - physiology; Signal processing; Steady-state; Torque; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Fissipedia; Carnivora; Tracking; Input signal; Electrical stimulus; Isometric muscular contraction; Osteoarticular system; Vertebrata; Ankle joint; Mammalia; Animal; Cat; Open loop; Motion study
• ISSN: 0018-9294; 1558-2531
• DOI: 10.1109/10.664207

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.