• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.352-355
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• 1998

A musculotendon model is investigated to show muscle fatigue under the repeated functional electrical stimulation (FES). The normalized Hill-type model can predict the decline in muscle force. It consists of nonlinear activation and contraction dynamics including physiological concepts of muscle fatigue. A muscle fatigue as a function of the intracellular acidification, pHi is inserted into contraction dynamics to estimate the force decline. The computer simulation shows that muscle force declines in stimulation time and the change in the estimate of the optimal fiber length has an effect only on muscle time constant not on the steady-state tetanic force.

• The Journal of Korean Physical Therapy
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• v.24 no.6
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• pp.409-413
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• 2012

Purpose: Rehabilitative devices are used to enhance sensorimotor training protocols, for improvement of motor function in the hemiplegic limb of patients who have suffered a stroke. Sensorimotor integration feedback systems, included with these devices, are very good therapeutic frameworks. We applied this approach using electrical stimulation in stroke patients and examined whether a functional electric stimulation-assisted biofeedback therapy system could improve function of the upper extremity in chronic hemiplegia. Methods: A prototype biofeedback system was used by six subjects to perform a set of tasks with their affected upper extremity during a 30-minute session for 20 consecutive working days. When needed for a grasping or releasing movement of objects, the functional electrical stimulation (FES) stimulated the wrist and finger flexor or extensor and assisted the patients in grasping or releasing the objects. Kinematic data provided by the biofeedback system were acquired. In addition, clinical performance scales and activity of daily living skills were evaluated before and after application of a prototype biofeedback system. Results: Our findings revealed statistically significant gradual improvement in patients with stroke, in terms of kinematic and clinical performance during the treatment sessions, in terms of manual function test and the Purdue pegboard. However, no significant difference of the motor activity log was found. Conclusion: Hemiplegic upper extremity function of a small group of patients with chronic hemiparesis was improved through two weeks of training using the FES-assisted biofeedback system. Further research into the use of biofeedback systems for long-term clinical improvement will be needed.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.6 s.171
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• pp.207-212
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• 2005

The purpose of this work is to develop the FES controller that can cope with the muscle fatigue which is one of the most important problems of current FES (Functional Electrical Stimulation). The feasibility of the proposed FES controller was evaluated by simulation. We used a fitness function to describe the effect of muscle fatigue and recovery process. The FES control system was developed based on the biological neuronal system. Specifically, we used PD (Proportional and Derivative) and GC (Gravity Compensation) control, which was described by the neuronal feedback structure. It was possible to control of multiple joints and muscles by using the phase-based PD and GC control method and the static optimization. As a result, the proposed FES control system could maintain the cycling motion in spite of the muscle fatigue. It is expected that the proposed FES controller will play an important role in the rehabilitation of SCI patient.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.8
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• pp.1046-1053
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• 1999

The musculotendon model is presented to show the declines in muscle force and shortening velocity during muscle fatigue due to the repeated functional electrical stimulation (FES). It consists of the nonlinear activation and contraction dynamics including physiological concepts of muscle fatigue. The activation dynamics represents $Ca^{2+}$ binding and unbinding mechanism with troponins of cross-bridges in sarcoplasm. It has the constant binding rate or activation time constant and two step nonlinear unbinding rate or inactivation time constant. The contraction dynamics is the modified Hill type model to represent muscle force - length and muscle force - velocity relations. A muscle fatigue profile as a function of the intracellular acidification, pH is applied into the contraction dynamics to represent the force decline. The computer simulation shows that muscle force and shortening velocity decline in stimulation time. And we validate the model. The model can predicts the proper muscle force without changing its parameters even when existing the estimation errors of the optimal fiber length. The change in the estimate of the optimal fiber length has an effect only on muscle time constant in transient period not on the tetanic force in the steady-state and relaxation periods.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1471-1472
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• 2013

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1385-1386
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• 2011

• Journal of Korean Physical Therapy Science
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• v.4 no.4
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• pp.539-548
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• 1997

The purpose of this study was to determine the effects of FES on the clinical test patients who had disturbance gait due to cereberal vascular accident. The subjects for study were 16 hemiplegic patients (9 Male and 7 Female) who can gait with or without device. Their average age was 55 and they received average of 20.19 month of treatment collected data analysis was completed by using one-way analysis variable(ANOVA), Pearson ($-1{\leq}r{\geq}1$). The results were as follows : 1) There was difference in four variable (stride length,gait speed,gait cadence) between at the biginning and at the end of the treatment of FES (p<0.01). 2) There was relationship in capacity of activity between MAS and stride length (r = 0.751), gait speed (r = 0.689) but no relationship gait cadence (r = 0.236). 3) Age revealed relationship of stride length (r = -0.727), gait speed (r = -0.725), gait cadenc (r = -0.362). 4) There was no relationship in months post-CVA with MAS (r = 0.171), stride length (r = -0.110), gait speed (r = -0.096), gait cacedce (r = -0.154).

• Journal of Biomedical Engineering Research
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• v.28 no.1
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• pp.29-35
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• 2007

This study was designed to investigate the feasibility to utilize the electromyogram (EMG) for estimating the muscle torque. The muscle torque estimation plays an important role in functional electrical stimulation because electrical stimulation causes muscles to fatigue much faster than voluntary contraction, and the stimulation intensity should then be modified to keep the muscle torque within the desired range. We employed the neural network method which was trained using the major EMG parameters and the corresponding knee extensor torque measured and extracted during isometric contractions. The experimental results suggested that (1) our neural network algorithm and protocol was feasible to be adopted in a real-time feedback control of the stimulation intensity, (2) the training data needed to cover the entire range of the measured value, (3) different amplitudes and frequencies made little difference to the estimation quality, and (4) a single input to the neural network led to a better estimation rather than a combination of two or three. Since this study was done under a limited contraction condition, the results need more experiments under many different contraction conditions, such as during walking, for justification.

• Journal of Biomedical Engineering Research
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• v.19 no.1
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• pp.69-80
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• 1998

This research was designed to investigate how the exercise program affects paraplegic standing and walking employing functional electrical stimulation(FES). Emphasis was also given to fatigue of major lower extremity muscles induced by different types of electrical stimulation. We applied continuous and intermittent rectangular pulse trains to quadriceps of 10 normal subjects and 4 complete paraplegic patients. The frequencies were 20Hz and 80Hz, and the knee angle was fixed at 90$^{\circ}$and 150$^{\circ}$to investigate how muscle fatigue is related to muscle length. The knee extensor torque was measured and monitored. We have been training quadriceps and gastrocnemius of a male paraplegic patient by means of electrical stimulation for the past two year. FES standing was initiated when the knee extensors became strong enough to support the body weight, and then the patient started FES walking utilizing parallel bars and a walker. We used an 8-channel constant-voltage stimulator and surface electrodes. The experimental results indicated that paralyzed muscles fatigued rapidly around the optimal length contrary to normal muscles and confirmed that low frequency and intermittent stimulation delayed fatigue. Our exercise program increased muscle force by approximately 10 folds and decreased the fatigue index to half of the initial value. In addition, the exercise enabled the patient to voluntarily lift each leg up to 10cm, which was of great help to the swing phase of FES walking. Both muscle force and resistance to fatigue were significantly enhanced right after the exercise was applied every day instead of 6 days a week. Up to date, the patient can walk for more than two and half minutes at 10m/min while controlling the on/off time of the stimulator by pushing the toggle switch attached to the walker handle.

• Journal of Biomedical Engineering Research
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• v.12 no.1
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• pp.1-7
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• 1991

This paper describes and discusses the employment of HMG pattern analysis to provide upper-motor-neuron paraplegics with patient-responsive control of FES ( functional electrical stimulation) for the purpose of walker-supported walking. The use of above-lesion EMG signals as a solution to the control problem is considered. The AR(autoregressive)parameters are identified by time-varying nonstationary Kalman filler algorithm using DSP chip and classified by fuzzy theory. The control and stimuli part of the below-lesion are based on micro-processor(8031). The designed stimulator is a 4-channel version. The experiments described above have only attempted to discriminate between standing function and sit-down function A further advantge of the this system Is applied for motor rehabilitation of social readaption of paralyzed humans.