Biomedical Signal Processing / Medical Signal Processing / Biosignal Processing
Alireza Mirjalili; Vahid Abootalebi; Mohammad Taghi Sadeghi
Volume 8, Issue 4 , February 2015, , Pages 305-323
Abstract
In recent years, Brain-Computer Interface (BCI) has been noted as a new means of communication between the human brain and his surroundings. In order to set up such a system, the collaboration of several blocks, such as data recording, signal processing and user interface are needed. The signal processing ...
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In recent years, Brain-Computer Interface (BCI) has been noted as a new means of communication between the human brain and his surroundings. In order to set up such a system, the collaboration of several blocks, such as data recording, signal processing and user interface are needed. The signal processing block, includes two units of preprocessing and pattern recognition. Pattern recognition block itself involves two phases: feature extraction and classification. In this paper, the sparse representation based classification (SRC) has been used in the classification block. There are two important issues in using the SRC. These are creating an appropriate dictionary matrix and adopting a proper method for finding the sparse solution for an input data. In this research study, the dictionary matrix is formed by extracting an optimal set of features from the training data. Toward this goal, the common spatial patterns algorithm (CSP) is first used. Sensitivity to noise and the over learning phenomena are the main drawbacks of the CSP algorithm. In order to remove these problems, the regularized common spatial patterns algorithm (RCSP) is employed. In previous studies in within the BCI framework, the standard BP algorithm has been used to find a sparse solution. The main disadvantage of the BP algorithm is that the method is computationally expensive. To overcome this weakness, a recently proposed algorithm namely the SL0 approach is used instead. Our experimental results show that when the number of training samples is limited, the RCSP algorithm outperforms the CSP one. Using the features derived from the RCSP, the average detection rate is in average increased by a factor of 7.53%. Our classification results also show that using the SL0 algorithm, the classification process is highly speeded up as compared to the BP algorithm while an almost equivalent accuracy is achieved.
Biomedical Signal Processing / Medical Signal Processing / Biosignal Processing
Sanaz Ahmadzadeh; Hamid Reza Kobravi; Saeed Tosizadeh
Volume 8, Issue 3 , September 2014, , Pages 293-304
Abstract
Multiple muscle groups may be activated simultaneously during the most of activities. So, the appropriate muscle coordination must be emerged during a normal activity. Consequaently, for rehabilitation of movements such as hand writing and paiting in patients for example suffering from carpal channel ...
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Multiple muscle groups may be activated simultaneously during the most of activities. So, the appropriate muscle coordination must be emerged during a normal activity. Consequaently, for rehabilitation of movements such as hand writing and paiting in patients for example suffering from carpal channel syndrom or incomplete spinal cord injury, the correct muscle coordination patterns between the finger muscles and wrist muscles must be reestablished. So, in this paper a prediction methodology based on artificial neural networks (ANN) is proposed to approximate the Thumb fingure extensor and flexor muscles desired activation pattern during the hand writing and Painting. In the presented strategy, A nonlinear auto-regressive neural network (NARX), Recurrent Neural Network (RNN), Radial Basis Function (RBF), Multy Layer Perceptron (MLP) and an Adaptive-network-based fuzzy inference system (ANFIS) are trained to forecast the Extensor pollicis longus and Flexor pollicis brevis muscles activity of one thumb finger of hand using Extensor carpi radialis brevis and Flexor carpi ulnaris muscles activity of forearm. Quantitative evaluations show the promising performance of developed neural networks. Eight healthy volunteers participated in the experiments.
Neuro-Muscular Engineering
Reza Hajian; Farzad Towhidkhah
Volume 8, Issue 1 , March 2014, , Pages 19-29
Abstract
Tremor is one of the most frequent movement disorders which is involuntary and approximately sinusoidal. It affects various body joints such as elbow. Tremor on an elbow is considered as extension, flection, and rotation of the forearm. There are miscellaneous types of treatments for tremor one of which ...
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Tremor is one of the most frequent movement disorders which is involuntary and approximately sinusoidal. It affects various body joints such as elbow. Tremor on an elbow is considered as extension, flection, and rotation of the forearm. There are miscellaneous types of treatments for tremor one of which is electrical stimulation. In this research, we study existing stimulation methods in order to reduce tremor and control stimulation pulses. It should be notified that studying these methods requires 1- an electrical stimulator so that one can run natural experiments and estimate the validity of the model, 2- a skeletal- neuromuscular model in order to study the tremor dynamics and the system simulation, and 3- determining an appropriate stimulation scheme and control method in order that one can control the stimulation parameters to reduce tremor. The antagonist muscle stimulation technique for reducing tremor is in the form of either muscle co-contraction or anti-phase stimulation. In the former method, considering the fact that the time-dependent system has time-delay, disturbance, and non-linearities, a robust controller is needed. Hence, in this study, we take advantage of MPC controller because of its features. The results show that MPC controller is more satisfactory than the PID and fuzzy ones used in previous works and also demonstrate that one can theoretically reduce tremor by applying appropriate electrical stimulation.
Neuro-Muscular Engineering
Sahar Babaei; Ali Maleki
Volume 8, Issue 1 , March 2014, , Pages 57-68
Abstract
Nowadays real time motion tracking have been receiving considerable attention in many applications and research fields such as rehabilitation, medicine and treatment. Recently MEMS accelerometers play an important role to attend desired result for these applications. This paper presents a new design ...
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Nowadays real time motion tracking have been receiving considerable attention in many applications and research fields such as rehabilitation, medicine and treatment. Recently MEMS accelerometers play an important role to attend desired result for these applications. This paper presents a new design for angle measurement device based on accelerometer sensor and Bluetooth module. Using Bluetooth module in addition to providing minimally obtrusive recording, allows you to connect to your personal computer and mobile quicker and easier. This system has made up of 2 complete 3 axis accelerometer ADXL330, which by giving sufficient data in 3D space allows us to investigate joint angle with DCMR method. The mentioned method in dynamic recording remarkably has less error in comparison to CMR method. As one application for this system, determination of elbow joint angle is studied. Eventually experimental recording of elbow joint angle in static and dynamic condition was done by applying CMR method. With reference to electrogoniometer output the maximum static and dynamic error were obtained respectively 3 and 6.1 degrees.
Neuro-Muscular Engineering
Sohrab Barimani; Ali Maleki; Ali Fallah
Volume 8, Issue 1 , March 2014, , Pages 101-111
Abstract
FES based method used for rehabilitation of patients with spinal cord injury (SCI). One of these methods is FES cycling. FES cycling exercise has to be useful among SCI patients because of creating a periodic activity in the muscles of the lower extremities and stability of seating position. The major ...
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FES based method used for rehabilitation of patients with spinal cord injury (SCI). One of these methods is FES cycling. FES cycling exercise has to be useful among SCI patients because of creating a periodic activity in the muscles of the lower extremities and stability of seating position. The major challenge for application of FES in rehabilitation is early fatigue occurrence in electrically stimulated muscles. Motor control system selects a low-cost path among the infinite possible route to the body's movements. High efficiency and the minimum rate of muscle fatigue are main characteristics of the motor control system. This type of control system is called muscle synergy. In this study, the quantification of muscle synergy between the core muscles in cycling has been done by non-negative matrix factorization (NMF) method and considering the kinesiology basis. Four synergies were determined as appropriate and optimal synergies to describe the cycling in different mechanical terms. VAF criteria with regard to the four synergies to describe cycling in speeds of 40, 50 and 60 rpm are 92±4, 92±3 and 91±4% respectively and torques, 5, 7 and 9 Nm are 91±3, 92±5 and 92±4% respectively. Correlation between Synergies extracted at different mechanical terms is 98.4 percent in average.
Gait Analysis
Samane Moeini Sedeh; Navid Arjmand; Mohammad Ali Sanjari; Hamid Reza Mokhtarinia; Morteza Asgari; Mohammad Parnianpour
Volume 7, Issue 4 , June 2013, , Pages 333-340
Abstract
Stability is important to prevent falling during occupational and daily living activities. Control parameters such as direction of motion and external load can affect stability pattern. The purpose of this paper was to evaluate the effect of the mentioned control parameters on stability. Time series ...
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Stability is important to prevent falling during occupational and daily living activities. Control parameters such as direction of motion and external load can affect stability pattern. The purpose of this paper was to evaluate the effect of the mentioned control parameters on stability. Time series of lumbar rotation angle in 19 healthy subjects were investigated. Each subject performed spine flexionextension in two different directions of symmetric (sagittal plane) and asymmetric (between sagittal and transverse planes), with two loading cases of 8 Kg weight and load free. To evaluate dynamic stability of repetitive movement, a nonlinear method of largest Lyapunov exponent has been used. After calculating maximum Lyapunov exponent from each of the experimental cases, results of analysis of variance showed a significant difference between symmetric and asymmetric directions (p=0.016). To interpret this result we can suggest higher recruitment of the internal and external oblique muscle groups and higher mechanical constraints in spine during asymmetric tasks. Mean comparison showed that movement in symmetric direction has more instability than the asymmetric case. Moreover, presence of load and interaction between direction and load did not significantly affect local dynamic stability.
Gait Analysis
Afsaneh Yavari; Mostafa Rostami; Ali Esteki; Ali Tanbakoosaz; Mehdi Yousefi Azar Khanian
Volume 7, Issue 1 , June 2013, , Pages 75-84
Abstract
Most of the recent biomechanical researches have been focused on the stability of people with disabilities and a few researches have been done on the athletes with high balance skill.The methods of elite athletes in keeping the balance can state valuable information about balance strategies and effective ...
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Most of the recent biomechanical researches have been focused on the stability of people with disabilities and a few researches have been done on the athletes with high balance skill.The methods of elite athletes in keeping the balance can state valuable information about balance strategies and effective parameters on balance. In this study we calculate local dynamical stability of musculoskeletal systems during a hard balance motion. Eight non elite athletes and six elite athletes in Wushu participatedin this study. Kinematic parameters for quantitative assessment of postural fluctuations were recorded by VICON ® Motion Analysis System. Using Lyapunov stability theory, stability and preparation of athletes were evaluated and the best model in performing the balance motion was shown to the coaches. Results from this study showed that motion pattern and preparation of athletes are effective in the displacements of center of mass and center of pressure and finally the stability of athletes.
Gait Analysis
Mohammad Iman Mokhlespour Esfahani; Omid Zobeiri; Ali Akbari; Behzad Moshiri; Mohammad Parnianpour
Volume 7, Issue 4 , June 2013, , Pages 361-369
Abstract
Wearable measuring system has major effects onbiomechanics of human movements especially in daily activitiesin order to monitor and analyze the human movements to achievethe most important kinematics parameters. In the recent decade,inertial sensors were utilized by researchers in order todeveloping ...
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Wearable measuring system has major effects onbiomechanics of human movements especially in daily activitiesin order to monitor and analyze the human movements to achievethe most important kinematics parameters. In the recent decade,inertial sensors were utilized by researchers in order todeveloping wearable system for instrumentation of humanmovements. In this study, Sharif-Human MovementInstrumentation System (SHARIF-HMIS) was designed andmanufactured. The system consists of inertial measurement units(IMUs), stretchable clothing and data logger. The IMU sensorsare installed on the human body. The system can be used at homeand also industrial environments. The main features of thissystem are: low cost, low weight, saving data for ten hours andbeing wearable. Furthermore, the software was designed for data acquisition of the IMUs.
Neuro-Muscular Engineering
Rahele Shafaei; Seyed Mohammad Reza Hashemi Golpayegani
Volume 5, Issue 3 , June 2011, , Pages 214-228
Abstract
One of main the issues in achieving to a successful FES control is using an as much as possible accurate model of the under electrical stimulation system so that it can adequately indicate the system behavior. Classical computational models that are commonly used for this purpose have a reductionism ...
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One of main the issues in achieving to a successful FES control is using an as much as possible accurate model of the under electrical stimulation system so that it can adequately indicate the system behavior. Classical computational models that are commonly used for this purpose have a reductionism nature; so they cannot consider the interaction existed in biological systems. Considering these restrictions, recently behavioral black box models are mostly used. These models focus on input/output dynamic, which is certainly the necessary modeling information for control design; thus the system is dealt with as a whole, which has hidden the interactions between components inside. Such a model has notbeen presented for elbow angle movement so far. Therefore in this study, we have been to present and verify a black box model of elbow joint movement in the transverse plane, forreaching movement control in people with C5/C6 SCI using dynamic neural networks, including time-delayed feedforward and recurrent networks. Extreme flexibility of time-delayed feedforward architectures was obtainedin a 2 layer structure including 5 hidden neurons and using 1.25s of history of input with performance indexes of 89.89% & 4.85% for cross correlation coefficient and normalized mean square error respectively. The best recurrent network with NARX architecture and equal history of input & output was also occurred in a 2 layer structure having 12 neurons in the hidden layer and using 0.1s of history, with performance indexes of 89.89% & 4.85% for cross correlation coefficient and normalized mean square error respectively. Comparison between best results of training using feedforward and recurrent networks, clearly illustrates both qualitative and quantitative excellency of the latter one in identification of the under-study system.
Neuro-Muscular Engineering
Abed Khorasani; Abbas Erfanian Omidvar
Volume 5, Issue 3 , June 2011, , Pages 245-255
Abstract
During the last decade, functional neuromuscular stimulation (FNS) has been proposed as a potential technique for restoring motor function in paralyzed limbs. A major challenge to restoring a desired functional limb movement through the use of intramuscular stimulation is the development of a robust ...
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During the last decade, functional neuromuscular stimulation (FNS) has been proposed as a potential technique for restoring motor function in paralyzed limbs. A major challenge to restoring a desired functional limb movement through the use of intramuscular stimulation is the development of a robust control strategy for determining the stimulation patterns. A major impediment to stimulating the paralyzed limbs and determining the stimulation pattern has been the highly non-linear, time-varying properties of electrically stimulated muscle, muscle fatigue, large latency and time constant which limit the utility of pre-specified stimulation pattern and open-loop FES control system. In this paper we present a robust strategy for multi-joint control through intramuscular stimulation in which the system parameters are adapted online and the controller requires no offline training phase. The method is based on the combination of sliding mode control with fuzzy logic and neural control. Extensive experiments on three rats are provided to demonstrate the robustness, stability, and tracking accuracy of the proposed method. The results show that the proposed strategy can provide accurate tracking control with fast convergence.
Neuro-Muscular Engineering
Amir Hosein Eskandari; Ehsan Sedaghat Nejad; Seyed Javad Mousavi; Mohsen Asghari; Mohammad Parnianpour
Volume 5, Issue 3 , June 2011, , Pages 257-273
Abstract
Selection of muscle activation pattern to reach a specific goal by considering the complexities of neuromuscular system and the way it overcomes these complications, is of researchersinterest in motor control. One proposed solutionfor resolving thesecomplexities is the concept of simple module (synergies) ...
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Selection of muscle activation pattern to reach a specific goal by considering the complexities of neuromuscular system and the way it overcomes these complications, is of researchersinterest in motor control. One proposed solutionfor resolving thesecomplexities is the concept of simple module (synergies) that the combination of them leads to more complex activities. In the present work, the existence and arrangement of synergies in the lumbar spine are proved. For this purpose, a model with 18-muscles in level L4-L5 is utilized in the static condition. In order to obtaina muscular and stability synergies, muscle activation, which are obtained by exerting moments in 2D and 3D spaces and angular stiffness to the model,are used. The results show that six muscular synergies suffice to be able to reach any point in the moment space. Also, three stability synergies can reconstruct a part of joint angular stiffness space. In addition, the obtained muscular synergies are robust against changes in the amplitude of exerted moment. In this study, it is shown that one can generates any task involves producing determined moment and angular stiffness in the joint, by combining muscular and stability synergies together.
Biomechanical Motor Control / Motor Control of Human Movement
Hamed Ghomashchi; Ali Esteki; Ali Motie Nasrabadi; Fereydoun Nowshiravan Rahatabad
Volume 4, Issue 3 , June 2010, , Pages 177-185
Abstract
In this study a simple inverted pendulum model with PID controller and delayed feedback is used to model standing-still postural control system for the purpose of achieving useful information about its underlying control structure. Using the Genetic algorithm and an experimental study results, the model ...
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In this study a simple inverted pendulum model with PID controller and delayed feedback is used to model standing-still postural control system for the purpose of achieving useful information about its underlying control structure. Using the Genetic algorithm and an experimental study results, the model and the controller parameters were estimated in a way that the model mimics real experimental sway patterns. The controller parameters found meaningful interpretations and it is shown that degeneration of postural control system affects the values of the parameters. Our findings indicate that although the simple models are not able to describe complexities of postural control system and interactions between its components, they can help us to improve our understanding of postural control system, its performance, its features and the way that the features change.
Neuro-Muscular Engineering
Mehdi Borjkhani; Farzad Towhidkhah
Volume 4, Issue 2 , June 2010, , Pages 109-122
Abstract
Writing is one of the high practiced and complex movement skills of human. Most of the proposed models for writing are bottom-up models, and therefore they could not reflect the biological aspects of movements in this process. Also there is not any model for illustrating the role of different parts of ...
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Writing is one of the high practiced and complex movement skills of human. Most of the proposed models for writing are bottom-up models, and therefore they could not reflect the biological aspects of movements in this process. Also there is not any model for illustrating the role of different parts of the brain in this task. In this paper we are going to describe some neurological and physiological aspects of the brain operation in the writing task. Then some evidence of prediction in writing and existence of internal models for limbs such as hand are presented. According to these, modeling of writing using model predictive control (MPC) is possible. Based on the presented simulations and experimental results it seems that the modeling of writing by MPC is very similar to the real skill, The proposed model has some advantages such as being consistent with the biological evidence, modeling prediction in writing and high correlation of the statical and dynamical features of the generated letters with those written by human.
Biomimetics
Saeed Rashidi; Seyed Mohammad Reza Hashemi Golpayegani; Ali Fallah; Farzad Towhidkhah
Volume 4, Issue 1 , June 2010, , Pages 33-44
Abstract
In drawing movements, the constraints imposed on the trajectory geometry properties and kinematics are known with two laws: 2/3 power law and isochrony phenomenon. In this paper experiments have been designed to study the relation between two empirical laws in straight and curved patterns of drawing ...
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In drawing movements, the constraints imposed on the trajectory geometry properties and kinematics are known with two laws: 2/3 power law and isochrony phenomenon. In this paper experiments have been designed to study the relation between two empirical laws in straight and curved patterns of drawing movements in 16-18 years old subjects. Providing two models of power is indicated that in drawing movements, invariant features can be defining. These features are independent of subject, direction and size of trajectory and together they can simplify the role of the upper motor control system and decrease the degrees of freedom and the computational complexity.
Rehabilitation Engineering
Vahab Nekoukar; Abbas Erfanian Omidvar
Volume 4, Issue 4 , June 2010, , Pages 327-336
Abstract
One major limitation of walker-supported walking using functional electrical stimulation (FES) in paraplegic subjects is the high energy expenditure and the high upper body effort. Paraplegics should exert high amount of hand force to stabilize the body posture and to compensate lack of the sufficient ...
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One major limitation of walker-supported walking using functional electrical stimulation (FES) in paraplegic subjects is the high energy expenditure and the high upper body effort. Paraplegics should exert high amount of hand force to stabilize the body posture and to compensate lack of the sufficient torques at the lower extremity joints. In this paper, we introduce a 2-D musculoskeletal model of walker-assisted FES-supported walking of paraplegics. Using the developed model and an optimal controller, the stimulation patterns are determined such that the tracking errors of lower joint reference trajectories are minimized and the muscle activations and the handle reaction force (HRF) are reduced. Outputs of the optimal controller are stimulation patterns of the lower body muscles and torque acting on the upper body joints. The results show that the HRF and ground reaction force (GRF) generated by simulation are in agreement with the measured HRF and GRF. Moreover, the results indicate that the simulation-generated stimulation patterns of lower body muscles are in consist with the stimulation patterns reported in the literatures.
Rehabilitation Engineering
Robabe Vatanparast; Hossein Karimi; Fariba Bahrami; Roya Narimani
Volume 3, Issue 3 , June 2009, , Pages 171-178
Abstract
CNS applies Anticipatory Postural Adjustments (APA) strategy to reject or minimize perturbation during different voluntary movements. The postural control mechanisms associated with voluntary arm movement (rapid arm rising) in below knee amputees (BKA) was investigated and the results were compared with ...
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CNS applies Anticipatory Postural Adjustments (APA) strategy to reject or minimize perturbation during different voluntary movements. The postural control mechanisms associated with voluntary arm movement (rapid arm rising) in below knee amputees (BKA) was investigated and the results were compared with the normal subjects. Biomechanical variables including ground reaction forces and displacements of the center of pressure were used to investigate the APA in BKA. Six below knee amputees and six control subjects stood on a force plate under three conditions: 1. with both feet on the platform, 2. with right foot (prosthetic foot) and 3. with left foot on the plate. For each condition, the task was repeated 10 times. At the same time, a camera recorded the task performance. The recorded data were used to determine the start moment of the movement. The instant at which, for the first time before starting the movement, any one of the recorded biomechanical variables deviated from its initial value was considered as the beginning of the APA. To increase the validity of the test, efforts were made to match the subjects with regards to their age, gender, cause of amputation and prosthesis types. Our results indicated that the center of pressure in the BKA participants showed greater displacements in medial-lateral and anterior-posterior directions. It was also observed that the vertical components of the ground reaction forces, when the right foot was on the plate, were increased. There were no significant differences in other biomechanical variables between the two groups. We may conclude that the voluntary arm movement perturbs the posture in the BKA participants more than in the control group. The BKA participants shifted their weight to the intact limb by the anticipation of the disturbance to avoid balance loosing. Therefore, in our study the intact limb in below knee amputee subjects played an important role in the balance control. Based on our results, we suggest considering the role of the intact limb in the rehabilitation programs and strengthening the muscles of both limbs as a major part of theses programs.
Gait Analysis
Mohsen Sadeghi Mehr; Davoud Naderi; Nader Farahpour; Saeed Davoud Abadi Farahani
Volume 3, Issue 3 , June 2009, , Pages 179-187
Abstract
The present study was devoted to determine the standing human body reactions to perturbation of a base plate in the frontal plane, in order to preserve its stability. A base plate with sinusoidal fluctuation was designed and built and then markers were mounted on the specified locations on it and the ...
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The present study was devoted to determine the standing human body reactions to perturbation of a base plate in the frontal plane, in order to preserve its stability. A base plate with sinusoidal fluctuation was designed and built and then markers were mounted on the specified locations on it and the skin of subjects before testing. During testing the subjects (N=10) tried to preserve their stability against perturbations. By using Motion Analysis System, the body responses of subjects were analyzed. Using inverse dynamic methods and experimental kinematic results, forces and moments applied to the joints and between feet soles and the base plate were determined. In theoretical study, the kinematic and dynamic equations of motion of a robotic model of human body in frontal plane by using repetitive Newton-Euler method were obtained. Based on the stability of the model and supporting vertical forces criterion an object function was defined, in order to assure the stability of the model. By optimization of the object function, angle of the model joints under perturbation and its first and second derivatives were determined. The good agreement of the theoretical and experimental results states that in similar conditions a robotic model can be used instead of expensive and time-consuming experiments.
Neuro-Muscular Engineering
Davoud Naderi; Mohsen Sadeghi Mehr; Nader Farahpour; Behnam Miripour-Fard
Volume 2, Issue 2 , June 2008, , Pages 85-93
Abstract
Cognition of human postural responses can provide valuable insight on the control of stability. Researchers can use this finding to design rehabilitation exercises to improve the patients, balance. This study was done with the aim of conducting theoretical and experimental investigations on human response ...
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Cognition of human postural responses can provide valuable insight on the control of stability. Researchers can use this finding to design rehabilitation exercises to improve the patients, balance. This study was done with the aim of conducting theoretical and experimental investigations on human response to tilting base plate in the sagittal plane. A four-segment model with three degrees of freedom was used as a biomechanical model of human body and its motion was studied in the sagittal plane. The postures of model were found by optimization technique such that the stability of model to be optimum. Zero moment point stability criterion was applied to find the optimum posture against the tilting base plate. To verify the theoretical results experimentally, the stability measure device was designed and manufactured. In several trials, the responses of ten male healthy persons standing on a tilting platform under perturbations were recorded by using the motion analysis system. Through data analysis, the response of each subject was surveyed and the experimental and theoretical results were compared. Both the experimental and theoretical results showed that the human central nervous system evokes the ankle strategy to keep its balance under tilting base plate conditions. A good coincident between the experimental results and theoretical predictions was observed, indicating that the model basis optimization method can be well relied upon to predict the human joints angle trajectories in response to base plate tilting.
Rehabilitation Engineering
Hamed Ghomashchi; Ali Esteki; Ali Motie Nasrabadi
Volume 2, Issue 2 , June 2008, , Pages 95-107
Abstract
In this study, the underlying dynamics of postural control system during quiet standing were investigated. Single-subject (SS) analysis was used as the statistical technique to compare the results. Center of pressure (COP) trajectories of 21 trials of a standing healthy subject and 24 trials of a cerebrovascular ...
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In this study, the underlying dynamics of postural control system during quiet standing were investigated. Single-subject (SS) analysis was used as the statistical technique to compare the results. Center of pressure (COP) trajectories of 21 trials of a standing healthy subject and 24 trials of a cerebrovascular attacked (CVA) patient were considered in our analysis. Complexity, dimensionality and stability of postural balance control system were evaluated using the first local minimum of auto mutual information (AMI) function, correlation dimension (Dc) and largest lyapunov exponent (LLE), respectively. The results indicated higher time delays (higher determinism), lower correlation dimension (lower active dynamical degrees of freedom) and lower LLE (increase of local stability) in the postural steadiness time series of the CVA patient in compare with the normal subject. The results showed that these measures not only can be used as pathologic measures to distinguish healthy subjects from CVA patient but also provide us new openings to disclose the postural control mechanism during a quiet standing.
Biomechanical Motor Control / Motor Control of Human Movement
Ehsan Rashedi; Mohammad Reza Nassajian; Bahman Nasseroleslami; Mohammad Parnianpour
Volume 2, Issue 2 , June 2008, , Pages 109-122
Abstract
Human motor system is organized for execution of various motor tasks in different and flexible ways. This is mainly achieved by the way that CNS uses the redundancy in musculoskeletal system. The kinetic redundancy in human musculoskeletal systems is a significant property by which CNS achieves many ...
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Human motor system is organized for execution of various motor tasks in different and flexible ways. This is mainly achieved by the way that CNS uses the redundancy in musculoskeletal system. The kinetic redundancy in human musculoskeletal systems is a significant property by which CNS achieves many complementary goals. Following the definition and role of uncontrolled manifold for movement kinematics, the kinetic redundancy concept is explored in mathematical terms. The null space of the kinetically redundant system when certain joint Moment and/or Stiffness are needed is derived and discussed. The mathematical methods have already been developed and applied to a simpler planar model. However in this paper, the aforementioned concepts were illustrated, using a 3-dimensional 3- degree of the freedom biomechanical model of spine with 18 anatomically oriented Hill-type-model muscle fascicles. The results can shed light to the interaction mechanisms in activation patterns of muscles, seen in various tasks and exertions and can provide a significant understanding for future studies and clinical practices related to low back disorders.
Speech processing
Ayoub Daliri; Farzad Towhidkhah; Shahriar Gharibzadeh; Yaser Shekofteh
Volume 2, Issue 2 , June 2008, , Pages 123-129
Abstract
Speech production is one of the most complicated physiological systems including different subsystems. These subsystems must work together in a synchronous manner. One of the important sub-systems is the jaw. Although different models have suggested for jaw, no suitable model has been proposed yet to ...
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Speech production is one of the most complicated physiological systems including different subsystems. These subsystems must work together in a synchronous manner. One of the important sub-systems is the jaw. Although different models have suggested for jaw, no suitable model has been proposed yet to consider the interactions between muscles, bones and nervous system. In this paper, using Spring-Damper-Mass and a nonlinear concept, we introduced a novel model for jaw movement during speech production. Experimental data were used to estimate the model parameters. Computer simulation results showed that the model could generate the jaw movement patterns similar to those observed in physiological behavior. Generality and simplicity of the model are two model features useful for more investigation of the jaw movement in different tasks.
Rehabilitation Engineering
Ali Maleki; Ali Fallah
Volume 2, Issue 2 , June 2008, , Pages 131-140
Abstract
Patients with spinal cord injury in C5/C6 levels are capable of controlling the voluntary movements of the shoulder joints, but some muscles involved in the movement of the elbow joint are paralyzed in these patients. By using FES as well as an appropriate stimulation of the paralyzed muscles, the patients ...
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Patients with spinal cord injury in C5/C6 levels are capable of controlling the voluntary movements of the shoulder joints, but some muscles involved in the movement of the elbow joint are paralyzed in these patients. By using FES as well as an appropriate stimulation of the paralyzed muscles, the patients can be assisted with their essential daily living activities. One of the major problems of using FES for reanimation of the paralyzed arm is to provide voluntary commands for FES control. Kinematic synergy and muscle synergy are two main options in this regard. In this paper, these two command sources were evaluated and compared. Furthermore, a mixed method was proposed, which improves performance. Thus, the EMG and kinematical data during a set of activities of daily living (AOL) were recorded and processed. Precise investigations were carried out in order to determine the appropriate values for high-level neural network controller parameters. Next, six different neural network controller structures were trained by the EMG and/or kinematical data. Using this method, cross correlation between the estimation and measurement for all records was obtained as 94.76% for kinematic synergy and 98.08%, for muscle synergy. In the mixed method, these values were improved to 94.82% and 98.84% respectively. Furthermore, mixed method paved the way to improve the performance of low-level controller with estimating the desired kinematics for the distal joint and desired activity for the paralyzed muscle.
Rehabilitation Engineering
Nima Jamshidi; Mostafa Rostami; Siamak Najarian; Mohammad Bagher Menhaj; Mohammad Saadatnia; Firouz Salami
Volume 2, Issue 1 , June 2008, , Pages 57-64
Abstract
In this research the kinematics parameters derived from ground reaction forces were evaluated to limit the differential diagnoses and measure the degree of disabilities during the walking among neuropathic subjects. 25 neuropathic subjects affected by drop foot and 20 normal subjects were enrolled in ...
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In this research the kinematics parameters derived from ground reaction forces were evaluated to limit the differential diagnoses and measure the degree of disabilities during the walking among neuropathic subjects. 25 neuropathic subjects affected by drop foot and 20 normal subjects were enrolled in the study. There were no differences in the age, weight and height between the patients and normal subjects (p > 0.05). Each subject was tested in average 10±2 times for calculating the kinetic parameters derived from ground reaction forces. Then time parameters and vertical components of force including three extremums of vertical forces, which state various phases in gait, anterior-posterior component of ground reaction force, maximum propulsion force, maximum breaking force during loading stage, maximum propulsion force in the end phase of terminal stance, impact derived from the contact of the patient' foot with floor, loading rate and unloading of vertical forces during the contact' phase of the patient's foot with floor and center of pressure displacement in sole of foot and friction' coefficient between foot and floor were calculated. The results revealed that correlation between the first and second peaks of the anterior-posterior component of ground reaction forces, center of pressure displacement pattern in the sole of foot and time parameters of the vertical forces can be good indexes for differential diagnoses and measuring the degree of disabilities. This research can extend the clinical applications of ground reaction force plate, introduce suitable criteria to limit differential diagnoses and measure the degree of disabilities among the neuropathies. There is a need to replicate this research with more patients and normal subjects to confirm our findings.
Neuro-Muscular Engineering
Hamid Reza Kobravi; Abbas Erfanian Omidvar
Volume 2, Issue 4 , June 2008, , Pages 335-349
Abstract
In this paper an adaptive robust fuzzy controller based on sliding mode control (SMC) approach is proposed to control the knee joint position using quadriceps electrical stimulation and it has been tested on three subjects. The proposed method is based on SMC. The main advantage of SMC derives from the ...
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In this paper an adaptive robust fuzzy controller based on sliding mode control (SMC) approach is proposed to control the knee joint position using quadriceps electrical stimulation and it has been tested on three subjects. The proposed method is based on SMC. The main advantage of SMC derives from the property of robustness to system uncertainties and external disturbances. However, a large value has to be applied to the control gain when the boundary of uncertainties is unknown. Unfortunately, this large control gain may cause chattering on the sliding surface and therefore deteriorate the system performance. In this paper a robust control strategy proposed which is based on the combination of sliding mode, fuzzy logic systems, and an adaptive compensator to reduce the system uncertainties while alleviating the effects of chattering. The fuzzy logic system is used to identify the muscle-joint dynamics. The parameters of this fuzzy system were estimated using another fuzzy system. The controller is evaluated through the simulation studies on a virtual patient and experimental studies on intact subjects. The results show that the adaptive robust controller provides an accurate tracking of desired knee-joint angle for different subjects and different days and can generate control signals to compensate the muscle fatigue and reject the external disturbance.
Biomechanical Motor Control / Motor Control of Human Movement
Saeed Rashidi; Ali Fallah; Farzad Towhidkhah
Volume 1, Issue 4 , June 2007, , Pages 269-280
Abstract
Dynamic signature verification based on temporal features are more precise than the static methods because in addition to position information of the drawing pattern, it uses local and global features extracted from velocity, acceleration, pressure and pen angle signals, while static methods only use ...
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Dynamic signature verification based on temporal features are more precise than the static methods because in addition to position information of the drawing pattern, it uses local and global features extracted from velocity, acceleration, pressure and pen angle signals, while static methods only use image information. In this study, we segmented the signature patterns using the basic role of velocity in the control process of skilled movements and then the function features were extracted. In order to signal the matching evaluation, we applied five generalized functions and five weighting strategies for score level fusion. The results showed that the correlation criterion had the minimum error. The experiments on the database, consisting of persons of Persian, Chinese and English, showed that the skilled forgeries obtained an equal error rate (EER) of 0.87% and 1.24% for the user and universal thresholds, respectively.
