hamid reza kobravi - Academia.edu (original) (raw)

Papers by hamid reza kobravi

The archives of bone and joint surgery, 2020

The purpose of this case report is to present and to assess a new exercise therapy using an intel... more The purpose of this case report is to present and to assess a new exercise therapy using an intelligent robotic system endowed by the functional electrical stimulation (FES) for gait improvement in a person with foot drop due to stroke. The subject was a 30-year-old man who had suffered a hemorrhagic stroke patient 8 years ago. He had gotten all proper conventional physical therapies, yet suffered from right foot drop which affected significantly on the gait quality. The patient wore the FES-robotic system on his impaired ankle and walked about 50 strides in each therapy session. During each gait cycle, the subject voluntarily determined the starting times of the dorsiflexion and plantarflexion of the affected ankle through toughing a sensor. Three clinical tests including Functional Ambulation Category (FAC), Fugl-Meyer Assessment (FMA), and Mini Balance Evaluation System Test (Mini-BESTest) were conducted. All related quantitative indexes increased after four-month exercise therap...

Journal of Medical Signals & Sensors, 2017

Stimulation of spinal sensorimotor circuits can improve motor control in animal models and humans... more Stimulation of spinal sensorimotor circuits can improve motor control in animal models and humans with spinal cord injury (SCI). More recent evidence suggests that the stimulation increases the level of excitability in the spinal circuits, activates central pattern generators, and it is also able to recruit distinctive afferent pathways connected to specific sensorimotor circuits. In addition, the stimulation generates well-defined responses in leg muscles after each pulse. The problem is that in most of the neuromodulation devices, electrical stimulation parameters are regulated manually and stay constant during movement. Such a technique is likely suboptimal to intercede maximum therapeutic effects in patients. Therefore, in this article, a fuzzy controller has been designed to control limb kinematics during locomotion using the afferent control in a neuromechanical model without supraspinal drive simulating post-SCI situation. The proposed controller automatically tunes the weights of group Ia afferent inputs of the spinal cord to reset the phase appropriately during the reaction to an external perturbation. The kinematic motion data and weights of group Ia afferent inputs were the input and output of the controller, respectively. Simulation results showed the acceptable performance of the controller to establish adaptive locomotion against the perturbing forces based on the phase resetting of the walking rhythm.

 Purpose of the study Efficient gait control using FES is yet an open research problem. In this ... more  Purpose of the study Efficient gait control using FES is yet an open research problem. In this research, a new intermittent controller has been designed to control the human shank movement dynamics during the gait.  Method In this approach, at first the three dimensional phase space was constructed using the human shank movement data recorded from the healthy subjects. Then three iterated sine-circle maps were extracted in the mentioned phase space. The three identified one-dimensional maps contained the essential information about the shank movement dynamics during a gait cycle. In the next step, an intermittent fuzzy controller was designed to control the shank angle. According to the adopted intermittent control strategy, the fuzzy controller is activated whenever the shank angle is far enough from the specific. The specific points are described using the identified iterated maps in the constructed phase space. In this manner, the designed controller is activated during a shor...

In this paper, a new control algorithm has been proposed which was designed based on a combinatio... more In this paper, a new control algorithm has been proposed which was designed based on a combination of functional electrical stimulation (FES) and an active mechanical actuator to control the knee joint movement. An adaptive controller and a PD controller have adjusted the motor torque and stimulation intensity, respectively. The FES controller was activated whenever a disturbance observer detected the presence of the external disturbance. In this manner, the occurrence of the muscle fatigue arises from the FES can be postponed. The simulation studies were carried out on a model of muscle-joint system along with a model of a servo-motor. The achieved results prove the ability of the proposed control strategy to not only reject the external disturbance but also compensate the muscle fatigue. In this research, the trajectories envisioned as the knee joint reference trajectory were designed using the recorded human data.

International Clinical Neuroscience Journal

Background: Functional electrical stimulation (FES) applies electrical pulses to paralyzed muscle... more Background: Functional electrical stimulation (FES) applies electrical pulses to paralyzed muscles to restore their function. Closed-loop control of an FES system, incorporating the control strategies, promises to improve the performance of FES systems. Therefore, the purpose of this paper is to design a new control strategy applicable to restoring the upright standing in paraplegic patients through FES. The control strategies proposed in the previous works based on controlling the angular joint position and none of them focused on controlling the center of pressure (CoP) dynamics directly. Since the CoP is representative of posture balance dynamics, in this study, the adopted FES based control strategy designed to control the CoP dynamics directly. Methods: In the proposed control strategy, two controllers determine the stimulation intensity of ankle muscles in a manner to restrict the CoP to a specific zone. According to the proposed strategy, until the CoP confined to the stable ...

Biomedical Signal Processing and Control

Scientia Iranica

A key parameter for analyzing the human balance dynamics during standing is the center of pressur... more A key parameter for analyzing the human balance dynamics during standing is the center of pressure (CoP). But, so far no conclusive idea has been posed with respect to elicited dynamics of the CoP signal during quiet standing. In this paper, a heuristic algorithm has been proposed to prove the chaotic behavior of the CoP signal with high confidence. In the proposed algorithm, at first the deterministic and non-deterministic (may be stochastic or may be chaotic) components of CoP signal are extracted using the empirical mode decomposition (EMD) method. Then the nonlinear features of the extracted components such as fractal dimension, Lyapunov exponent, correlation dimension, and alpha parameter are computed. Then according to the quantitative value of the computed features, the chaotic component is selected among the extracted components. Finally, using the recurrence quantitative analysis (RQA), the selected chaotic component is reanalyzed to give assurance of correct selecting the chaotic component. In this manner, the kind of CoP dynamics can be determined with high confidence. The analyzed CoP signals were recorded through some experiments on 12 healthy subjects being between 20 to 70 years old. The results of this study show that CoP is a chaotic signal whit high confidence.

International Clinical Neuroscience Journal

Background: Spinal cord injury is one of the diseases that, no specific treatment has yet found d... more Background: Spinal cord injury is one of the diseases that, no specific treatment has yet found despite the variety of works that have done in this field. Different approaches to treat such injuries have investigated today. One of them is invasive intra-spinal interventions such as electrical stimulation. Therefore, in this study, the effect of the protocol for intra-spinal variable and fixed electrical stimulation has been investigated in order to recover from spinal cord injury. Methods: In the study, 18 Wistar male rats randomly divided into Three groups, including intraspinal electrical stimulation (IES), IES with variable pattern of stimulation (VP IES) and a sham group. Animals initially subjected to induced spinal cord injury. After one week, the animal movement was recorded on the treadmill during practice using a camera and angles of the ankle joint were measured using the Tracker software. Then, the obtained data were analyzed by nonlinear evaluations in the phase space. R...

International Journal of Developmental Disabilities

International Journal of Developmental Disabilities

Chaos: An Interdisciplinary Journal of Nonlinear Science

In this article, energy-based feedback control is introduced merely as an approach to suppress ch... more In this article, energy-based feedback control is introduced merely as an approach to suppress chaos. We have also shown in this study that an energy-based feedback controller is capable of changing a chaotic dynamic to other chaotic dynamics. In other words, energy feedback can also be used to convert chaos dynamics to another chaos dynamics, and the use of energy feedback should not be limited to suppress chaos. The importance of the issue lies in relating some practical applications of chaos to chaos control. In this short study, we have shown that an energy feedback control can be combined with a fuzzy self-regulating gain system. A short study has been done on Chua's circuit.

Biomedical Physics & Engineering Express

The Open Bioinformatics Journal

Background: Right sitting not only leads to flatness of the lumbar spine and waistline, it also c... more Background: Right sitting not only leads to flatness of the lumbar spine and waistline, it also causes other problems for health. The curved body pushes into lungs and breathing will be problematic. Purpose: The main purpose of this study was investigating changing procedure of lumber muscles patterns and its relationship with the occurrence of fatigue. Methods: Participants were ten male with average age 24 ± 1. Firstly, the process of fatigue during sitting was observed by mid-frequency index. For performing the necessary analysis, the 10-second window of time was used. The 15 minutes of time trial was divided into 3 sub-terms. Each sub-term was investigated separately. The sub-terms contain: The beginning of record until the 90th second, from the 90th second to the 600th second and from the 600th second to the 900th second. Results: Results showed that in each subject there were synergy patterns in both of the first and the second sub-terms. Maximum error between basis vectors in...

Research Journal of Applied Sciences, Engineering and Technology

Journal of medical signals and sensors

Both treadmill training and epidural stimulation can help to reactivate the central pattern gener... more Both treadmill training and epidural stimulation can help to reactivate the central pattern generator (CPG) in the spinal cord after a spinal cord injury. However, designing an appropriate training approach and a stimulation profile is still a controversial issue. Since the spinal afferent signals are the input signals of CPG in the spinal cord, it can be concluded that the number of input afferent signals can affect the quality of movement recovery, such a phenomenon is in accordance with Hebbian theory. Therefore, at first in this paper, through some simulation studies on a model of CPGs, the effective influence of increasing the afferent input weight on activating CPG model was certified. Then, the performance of two different types of treadmill training along with epidural stimulation was compared. The numbers of spinal afferents involved during each designed training approach were different. Experiments were conducted on two groups of spinalized rats. Three quantized integer qu...

Journal of medical signals and sensors

The prediction of the joint angle position, especially during tremor bursts, can be useful for de... more The prediction of the joint angle position, especially during tremor bursts, can be useful for detecting, tracking, and forecasting tremors. Thus, this research proposes a new model for predicting the wrist joint position during rhythmic bursts and inter-burst intervals. Since a tremor is an approximately rhythmic and roughly sinusoidal movement, neural oscillators have been selected to underlie the proposed model. Two neural oscillators were adopted. Electromyogram (EMG) signals were recorded from the extensor carpi radialis and flexor carpi radialis muscles concurrent with the joint angle signals of a stroke subject in an arm constant-posture. The output frequency of each oscillator was equal to the frequency corresponding to the maximum value of power spectrum related to the rhythmic wrist joint angle signals which had been recorded during a postural tremor. The phase shift between the outputs of the two oscillators was equal to the phase shift between the muscle activation of th...

2014 International Congress on Technology, Communication and Knowledge (ICTCK), 2014

Biosystems & Biorobotics, 2013

ABSTRACT The goal of this paper is to control the FES intensity for the disabled tibialis anterio... more ABSTRACT The goal of this paper is to control the FES intensity for the disabled tibialis anterior (TA) muscle in patients with unilateral drop foot, using the existing coordination patterns between the activities of ipsilateral ankle dorsiflexor muscles and contralateral ankle plantarflexor muscles during normal gait. A nonlinear auto- regressive neural network (NARX) and an adaptive-network-based fuzzy inference system (ANFIS) are trained to forecast the TA muscle activity of one foot using gastrocnemius muscle activity of contralateral foot. A two level efficient hybrid training algorithm is employed which consists of a gradient based level (local search) and an evolutionary level (global search). The predicted TA activation then can be used to control the TA muscle FES intensity in real time, using a linear mapping. Eleven healthy volunteers participated in the experiments. Quantitative evaluations show the promising performance of developed neural controllers.

2013 13th Iranian Conference on Fuzzy Systems (IFSC), 2013

ABSTRACT In this paper, a diagnostic approach has been presented for discriminating between patie... more ABSTRACT In this paper, a diagnostic approach has been presented for discriminating between patients with acquired neuropathy called CIDP and congenital neuropathy called Charcot-Marie-Tooth. In the presented approach, nine time-domain and frequency-domain features extracted from the surface EMG signals of tibialis anterior and rectus femoris muscles recorded during walking in patients.All data is the result of 82 human examinations done on the three groups of healthy individuals (34 samples), CIDP patients (25 samples) and Charcot-Marie-Tooth patients (23 samples).70% of the gathered data was used for training and the rest 30% for testing the classifiers. Then, fuzzy KNN classifiers and Adaptive neuro fuzzy inference system(ANFIS) were utilized to detect the discrepancies between two groups of patients. The performance of fuzzy KNN and Anfis were compared. The results show that the accuracies were 98.4% and 96.8% for fuzzy KNN and Anfis classifiers, respectively.

Medical Engineering & Physics, 2012

In this paper, we present a novel decentralized robust methodology for control of quiet upright p... more In this paper, we present a novel decentralized robust methodology for control of quiet upright posture during arm-free paraplegic standing using functional electrical stimulation (FES). Each muscle-joint complex is considered as a subsystem and individual controllers are designed for each one. Each controller operates solely on its associated subsystem, with no exchange of information between them, and the interaction between the subsystems are taken as external disturbances. In order to achieve robustness with respect to external disturbances, unmodeled dynamics, model uncertainty and time-varying properties of muscle-joint dynamics, a robust control framework is proposed. The method is based on the synergistic combination of an adaptive nonlinear compensator with sliding mode control (SMC). Fuzzy logic system is used to represent unknown system dynamics for implementing SMC and an adaptive updating law is designed for online estimating the system parameters such that the global stability and asymptotic convergence to zero of tracking errors is guaranteed. The proposed controller requires no prior knowledge about the dynamics of system to be controlled and no offline learning phase. The results of experiments on three paraplegic subjects show that the proposed control strategy is able to maintain the vertical standing posture using only FES control of ankle dorsiflexion and plantarflexion without using upper limbs for support and to compensate the effect of external disturbances and muscle fatigue.

The archives of bone and joint surgery, 2020

The purpose of this case report is to present and to assess a new exercise therapy using an intel... more The purpose of this case report is to present and to assess a new exercise therapy using an intelligent robotic system endowed by the functional electrical stimulation (FES) for gait improvement in a person with foot drop due to stroke. The subject was a 30-year-old man who had suffered a hemorrhagic stroke patient 8 years ago. He had gotten all proper conventional physical therapies, yet suffered from right foot drop which affected significantly on the gait quality. The patient wore the FES-robotic system on his impaired ankle and walked about 50 strides in each therapy session. During each gait cycle, the subject voluntarily determined the starting times of the dorsiflexion and plantarflexion of the affected ankle through toughing a sensor. Three clinical tests including Functional Ambulation Category (FAC), Fugl-Meyer Assessment (FMA), and Mini Balance Evaluation System Test (Mini-BESTest) were conducted. All related quantitative indexes increased after four-month exercise therap...

Journal of Medical Signals & Sensors, 2017

Stimulation of spinal sensorimotor circuits can improve motor control in animal models and humans... more Stimulation of spinal sensorimotor circuits can improve motor control in animal models and humans with spinal cord injury (SCI). More recent evidence suggests that the stimulation increases the level of excitability in the spinal circuits, activates central pattern generators, and it is also able to recruit distinctive afferent pathways connected to specific sensorimotor circuits. In addition, the stimulation generates well-defined responses in leg muscles after each pulse. The problem is that in most of the neuromodulation devices, electrical stimulation parameters are regulated manually and stay constant during movement. Such a technique is likely suboptimal to intercede maximum therapeutic effects in patients. Therefore, in this article, a fuzzy controller has been designed to control limb kinematics during locomotion using the afferent control in a neuromechanical model without supraspinal drive simulating post-SCI situation. The proposed controller automatically tunes the weights of group Ia afferent inputs of the spinal cord to reset the phase appropriately during the reaction to an external perturbation. The kinematic motion data and weights of group Ia afferent inputs were the input and output of the controller, respectively. Simulation results showed the acceptable performance of the controller to establish adaptive locomotion against the perturbing forces based on the phase resetting of the walking rhythm.

 Purpose of the study Efficient gait control using FES is yet an open research problem. In this ... more  Purpose of the study Efficient gait control using FES is yet an open research problem. In this research, a new intermittent controller has been designed to control the human shank movement dynamics during the gait.  Method In this approach, at first the three dimensional phase space was constructed using the human shank movement data recorded from the healthy subjects. Then three iterated sine-circle maps were extracted in the mentioned phase space. The three identified one-dimensional maps contained the essential information about the shank movement dynamics during a gait cycle. In the next step, an intermittent fuzzy controller was designed to control the shank angle. According to the adopted intermittent control strategy, the fuzzy controller is activated whenever the shank angle is far enough from the specific. The specific points are described using the identified iterated maps in the constructed phase space. In this manner, the designed controller is activated during a shor...

In this paper, a new control algorithm has been proposed which was designed based on a combinatio... more In this paper, a new control algorithm has been proposed which was designed based on a combination of functional electrical stimulation (FES) and an active mechanical actuator to control the knee joint movement. An adaptive controller and a PD controller have adjusted the motor torque and stimulation intensity, respectively. The FES controller was activated whenever a disturbance observer detected the presence of the external disturbance. In this manner, the occurrence of the muscle fatigue arises from the FES can be postponed. The simulation studies were carried out on a model of muscle-joint system along with a model of a servo-motor. The achieved results prove the ability of the proposed control strategy to not only reject the external disturbance but also compensate the muscle fatigue. In this research, the trajectories envisioned as the knee joint reference trajectory were designed using the recorded human data.

International Clinical Neuroscience Journal

Background: Functional electrical stimulation (FES) applies electrical pulses to paralyzed muscle... more Background: Functional electrical stimulation (FES) applies electrical pulses to paralyzed muscles to restore their function. Closed-loop control of an FES system, incorporating the control strategies, promises to improve the performance of FES systems. Therefore, the purpose of this paper is to design a new control strategy applicable to restoring the upright standing in paraplegic patients through FES. The control strategies proposed in the previous works based on controlling the angular joint position and none of them focused on controlling the center of pressure (CoP) dynamics directly. Since the CoP is representative of posture balance dynamics, in this study, the adopted FES based control strategy designed to control the CoP dynamics directly. Methods: In the proposed control strategy, two controllers determine the stimulation intensity of ankle muscles in a manner to restrict the CoP to a specific zone. According to the proposed strategy, until the CoP confined to the stable ...

Biomedical Signal Processing and Control

Scientia Iranica

A key parameter for analyzing the human balance dynamics during standing is the center of pressur... more A key parameter for analyzing the human balance dynamics during standing is the center of pressure (CoP). But, so far no conclusive idea has been posed with respect to elicited dynamics of the CoP signal during quiet standing. In this paper, a heuristic algorithm has been proposed to prove the chaotic behavior of the CoP signal with high confidence. In the proposed algorithm, at first the deterministic and non-deterministic (may be stochastic or may be chaotic) components of CoP signal are extracted using the empirical mode decomposition (EMD) method. Then the nonlinear features of the extracted components such as fractal dimension, Lyapunov exponent, correlation dimension, and alpha parameter are computed. Then according to the quantitative value of the computed features, the chaotic component is selected among the extracted components. Finally, using the recurrence quantitative analysis (RQA), the selected chaotic component is reanalyzed to give assurance of correct selecting the chaotic component. In this manner, the kind of CoP dynamics can be determined with high confidence. The analyzed CoP signals were recorded through some experiments on 12 healthy subjects being between 20 to 70 years old. The results of this study show that CoP is a chaotic signal whit high confidence.

International Clinical Neuroscience Journal

Background: Spinal cord injury is one of the diseases that, no specific treatment has yet found d... more Background: Spinal cord injury is one of the diseases that, no specific treatment has yet found despite the variety of works that have done in this field. Different approaches to treat such injuries have investigated today. One of them is invasive intra-spinal interventions such as electrical stimulation. Therefore, in this study, the effect of the protocol for intra-spinal variable and fixed electrical stimulation has been investigated in order to recover from spinal cord injury. Methods: In the study, 18 Wistar male rats randomly divided into Three groups, including intraspinal electrical stimulation (IES), IES with variable pattern of stimulation (VP IES) and a sham group. Animals initially subjected to induced spinal cord injury. After one week, the animal movement was recorded on the treadmill during practice using a camera and angles of the ankle joint were measured using the Tracker software. Then, the obtained data were analyzed by nonlinear evaluations in the phase space. R...

International Journal of Developmental Disabilities

International Journal of Developmental Disabilities

Chaos: An Interdisciplinary Journal of Nonlinear Science

In this article, energy-based feedback control is introduced merely as an approach to suppress ch... more In this article, energy-based feedback control is introduced merely as an approach to suppress chaos. We have also shown in this study that an energy-based feedback controller is capable of changing a chaotic dynamic to other chaotic dynamics. In other words, energy feedback can also be used to convert chaos dynamics to another chaos dynamics, and the use of energy feedback should not be limited to suppress chaos. The importance of the issue lies in relating some practical applications of chaos to chaos control. In this short study, we have shown that an energy feedback control can be combined with a fuzzy self-regulating gain system. A short study has been done on Chua's circuit.

Biomedical Physics & Engineering Express

The Open Bioinformatics Journal

Background: Right sitting not only leads to flatness of the lumbar spine and waistline, it also c... more Background: Right sitting not only leads to flatness of the lumbar spine and waistline, it also causes other problems for health. The curved body pushes into lungs and breathing will be problematic. Purpose: The main purpose of this study was investigating changing procedure of lumber muscles patterns and its relationship with the occurrence of fatigue. Methods: Participants were ten male with average age 24 ± 1. Firstly, the process of fatigue during sitting was observed by mid-frequency index. For performing the necessary analysis, the 10-second window of time was used. The 15 minutes of time trial was divided into 3 sub-terms. Each sub-term was investigated separately. The sub-terms contain: The beginning of record until the 90th second, from the 90th second to the 600th second and from the 600th second to the 900th second. Results: Results showed that in each subject there were synergy patterns in both of the first and the second sub-terms. Maximum error between basis vectors in...

Research Journal of Applied Sciences, Engineering and Technology

Journal of medical signals and sensors

Both treadmill training and epidural stimulation can help to reactivate the central pattern gener... more Both treadmill training and epidural stimulation can help to reactivate the central pattern generator (CPG) in the spinal cord after a spinal cord injury. However, designing an appropriate training approach and a stimulation profile is still a controversial issue. Since the spinal afferent signals are the input signals of CPG in the spinal cord, it can be concluded that the number of input afferent signals can affect the quality of movement recovery, such a phenomenon is in accordance with Hebbian theory. Therefore, at first in this paper, through some simulation studies on a model of CPGs, the effective influence of increasing the afferent input weight on activating CPG model was certified. Then, the performance of two different types of treadmill training along with epidural stimulation was compared. The numbers of spinal afferents involved during each designed training approach were different. Experiments were conducted on two groups of spinalized rats. Three quantized integer qu...

Journal of medical signals and sensors

The prediction of the joint angle position, especially during tremor bursts, can be useful for de... more The prediction of the joint angle position, especially during tremor bursts, can be useful for detecting, tracking, and forecasting tremors. Thus, this research proposes a new model for predicting the wrist joint position during rhythmic bursts and inter-burst intervals. Since a tremor is an approximately rhythmic and roughly sinusoidal movement, neural oscillators have been selected to underlie the proposed model. Two neural oscillators were adopted. Electromyogram (EMG) signals were recorded from the extensor carpi radialis and flexor carpi radialis muscles concurrent with the joint angle signals of a stroke subject in an arm constant-posture. The output frequency of each oscillator was equal to the frequency corresponding to the maximum value of power spectrum related to the rhythmic wrist joint angle signals which had been recorded during a postural tremor. The phase shift between the outputs of the two oscillators was equal to the phase shift between the muscle activation of th...

2014 International Congress on Technology, Communication and Knowledge (ICTCK), 2014

Biosystems & Biorobotics, 2013

ABSTRACT The goal of this paper is to control the FES intensity for the disabled tibialis anterio... more ABSTRACT The goal of this paper is to control the FES intensity for the disabled tibialis anterior (TA) muscle in patients with unilateral drop foot, using the existing coordination patterns between the activities of ipsilateral ankle dorsiflexor muscles and contralateral ankle plantarflexor muscles during normal gait. A nonlinear auto- regressive neural network (NARX) and an adaptive-network-based fuzzy inference system (ANFIS) are trained to forecast the TA muscle activity of one foot using gastrocnemius muscle activity of contralateral foot. A two level efficient hybrid training algorithm is employed which consists of a gradient based level (local search) and an evolutionary level (global search). The predicted TA activation then can be used to control the TA muscle FES intensity in real time, using a linear mapping. Eleven healthy volunteers participated in the experiments. Quantitative evaluations show the promising performance of developed neural controllers.

2013 13th Iranian Conference on Fuzzy Systems (IFSC), 2013

ABSTRACT In this paper, a diagnostic approach has been presented for discriminating between patie... more ABSTRACT In this paper, a diagnostic approach has been presented for discriminating between patients with acquired neuropathy called CIDP and congenital neuropathy called Charcot-Marie-Tooth. In the presented approach, nine time-domain and frequency-domain features extracted from the surface EMG signals of tibialis anterior and rectus femoris muscles recorded during walking in patients.All data is the result of 82 human examinations done on the three groups of healthy individuals (34 samples), CIDP patients (25 samples) and Charcot-Marie-Tooth patients (23 samples).70% of the gathered data was used for training and the rest 30% for testing the classifiers. Then, fuzzy KNN classifiers and Adaptive neuro fuzzy inference system(ANFIS) were utilized to detect the discrepancies between two groups of patients. The performance of fuzzy KNN and Anfis were compared. The results show that the accuracies were 98.4% and 96.8% for fuzzy KNN and Anfis classifiers, respectively.

Medical Engineering & Physics, 2012

In this paper, we present a novel decentralized robust methodology for control of quiet upright p... more In this paper, we present a novel decentralized robust methodology for control of quiet upright posture during arm-free paraplegic standing using functional electrical stimulation (FES). Each muscle-joint complex is considered as a subsystem and individual controllers are designed for each one. Each controller operates solely on its associated subsystem, with no exchange of information between them, and the interaction between the subsystems are taken as external disturbances. In order to achieve robustness with respect to external disturbances, unmodeled dynamics, model uncertainty and time-varying properties of muscle-joint dynamics, a robust control framework is proposed. The method is based on the synergistic combination of an adaptive nonlinear compensator with sliding mode control (SMC). Fuzzy logic system is used to represent unknown system dynamics for implementing SMC and an adaptive updating law is designed for online estimating the system parameters such that the global stability and asymptotic convergence to zero of tracking errors is guaranteed. The proposed controller requires no prior knowledge about the dynamics of system to be controlled and no offline learning phase. The results of experiments on three paraplegic subjects show that the proposed control strategy is able to maintain the vertical standing posture using only FES control of ankle dorsiflexion and plantarflexion without using upper limbs for support and to compensate the effect of external disturbances and muscle fatigue.