• Journal of the Korean Society for Precision Engineering
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• v.21 no.8
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• pp.171-179
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• 2004

The purpose of this study is to generate cycling motion for FES (functional electrical stimulation) using knee muscles only. We investigated the possibility by simulation. The musculoskeletal model used in this simulation was simplified as 5-rigid links and 2 muscles (knee extensor and flexor). For the improvement of the present feedforward control in FES, we included feedback path in the control system. The control system was developed based on the biological neuronal system and was represented by three sub-systems. The first is a higher neuronal system that generates the motion command for each joint. The second is the lower neuronal system that divides the motion command to each muscle. And the third is a sensory feedback system corresponding to the somatic sensory system. Control system parameters were adjusted by a genetic algorithm (GA) based on the natural selection theory. GA searched the better parameters in terms of the cost function where the energy consumption, muscle force smoothness, and the cycling speed of each parameter set (individual) are evaluated. As a result, cycling was implemented using knee muscles only. The proposed control system based on the nervous system model worked well even with disturbances.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.981-982
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• 2013

• 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.

• 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 Biomedical Engineering Research
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• v.34 no.2
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• pp.63-68
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• 2013

Activeness of exercise is critical for stroke rehabilitation so that application of stimulation in response to patient's intention would be effective in FES cycling. The purpose of this study was to investigate the relationship between muscle reaction force (MRF) and electromyogram (EMG) during cycling exercise, for the future usage of MRF as patients' intention signal. Seven young men ($24{\pm}1.63$ yrs) participated in this study. Cycling speed was set to 20 RPM and 60 RPM. MRF and EMG were measured in the vastus lateralis muscle of right leg. Active cycling was performed at the maximal load (16 Nm) of an ergometer. Angle dependent artifact in MRF was measured from passive cycling and was subtracted from the MRF of active cycling. The delay of MRF with respect to EMG envelope and their correlation coefficients were derived from the best of cross correlation. MRF was significantly correlated with EMG amplitude in all subjects (p<0.01). Their mean correlations were 0.84 and 0.91 for 20 RPM and 60 RPM, respectively. Mean delay in MRF was 59.14 ms and 53.14 ms for 20 RPM and 60 RPM, respectively. The result suggests that MRF can be used to assess patient's intention for exercise as a substitute to EMG. The method may be applied to FES cycling to encourage patient's effort which is critical for stroke rehabilitation.