• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1998년도 제13차 학술회의논문집
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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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• 제24권6호
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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.

• 한국정밀공학회지
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• 제22권6호
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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.

• 대한전기학회논문지:전력기술부문A
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• 제48권8호
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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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1471-1472
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• 2013

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.1385-1386
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• 2011

• 대한물리치료과학회지
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• 제4권4호
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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).

• 대한의용생체공학회:의공학회지
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• 제28권1호
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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.

• 대한의용생체공학회:의공학회지
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• 제19권1호
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• pp.69-80
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• 1998

본 연구에서는 엑서사이즈 프로그램이 FES를 이용한 하반신 마비환자의 일어서기 및 보행에 미치는 영향을 고찰하였으며, 또한 주요 다리근육들의 전기자극에 대한 수축특성과 피로특성에 주안점을 두었다. 정상인 10명과 완전 하반신 마비환자 4명의 대퇴사두근에 연속적 혹은 간헐적으로 전기자극을 가하였고, 자극주파수는 20Hz와 80Hz로 하였다. 또 근육의 길이에 따른 피로현상을 살펴보기 위하여 무릎의 각도를 90$^{\circ}$와 150$^{\circ}$로 각각 고정한 뒤 무릎신근 토크를 측정하였다. 그 결과를 바탕으로 남자 하반신 마비환자의 대퇴사두근과 장딴지근에 지난 2년간 FES엑서사이즈를 시행하였다. 무릎신근의 근력이 체중을 지지하기에 충분하다고 판단되었을 때 FES 일어서기를 시작하였으며, 자세교환 연습을 거친 뒤 평행봉 혹은 워커를 잡고 정전압 자극기와 표면전극을 사용한 4 또는 6채널 자극으로 보행하도록 하였다. 마비된 근육은 정상인과는 반대로 최적길이 부근에서 상대적으로 급격한 피로를 나타내었고, 저주와 자극과 간헐 자극이 피로를 지연시키는 것을 확인할 수 있었다. 본 실험에 참가한 환자는 FES 엑서사이즈 프로그램을 실시한 결과, 근력이 초기의 10배 정도로 증가하였고, 피로지수는 초기의 절반 정도로 감소하였으며, 엑서사이즈 횟수를 매주 6일에서 7일로 바꾼 후 근력이 눈에 띄게 향상되었다. 환자 자신의 잔존능력도 향상되어 양쪽 무릎을 10cm정도 들어올릴 수 있게 됨으로써 보행시 스윙 단계에서 이 능력을 최대한 활용할 수 있었다. 현재 환자는 워커를 잡고 스스로 자극기의 스위치를 조작하면서 4채널 자극에 의하여 10m/min의 속도로 최대 약 2분 40초의 보행이 가능하다.

• 대한의용생체공학회:의공학회지
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• 제12권1호
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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.