Musculoskeletal Systems Modeling
Hossein Rostami Barooji; Abdolreza Ohadi; Farzad Towhidkhah
Volume 17, Issue 2 , September 2023, , Pages 120-130
Abstract
Despite the extensive progress in the field of biomechanics of human gait, a suitable gait model with the ability to simulate the control system of the human brain has not yet been presented, especially in 3D mode. The importance of the issue increases when the simulation of human walking is one of the ...
Read More
Despite the extensive progress in the field of biomechanics of human gait, a suitable gait model with the ability to simulate the control system of the human brain has not yet been presented, especially in 3D mode. The importance of the issue increases when the simulation of human walking is one of the main requirements of designers of biomechanical equipment such as artificial organs, wearable robots and humanoid robots. Regarding the constraints and complexities of previous studies, in this research, a forward dynamic 3D model of gait based on sliding mode controller (SMC) is presented, which simulates the walking behavior of healthy individual on the ground in different movement phases. One of the strengths of this research is the comprehensive and analytical review of 3D rotation consequences of the joints coordinate systems, which is done with 11 DOF inverse dynamic model. Based on the obtained results, the SMC controller is well able to produce stable 3D human gait. Also, in 3D gait analysis, the Cardan rotation sequence is not suitable and YXZ order should be used. This outcome is a very useful result for 3D motion generation for human like walking pattern. The results of this study can be used in the design of humanoid robots, active and passive prostheses. Also, the presented model can simulate the walking of an amputee with a prosthesis and the role of the controller in the path, which is very important and beneficial in terms of rehabilitation.
Musculoskeletal Systems Modeling
Elham Hazrati; Mahmoud Reza Azghani
Volume 11, Issue 1 , May 2017, , Pages 19-28
Abstract
Pedaling is one of the common physical activities for muscles strengthening. Pedaling performance is affected by various factors. The purpose of this study is investigating the effect of pedaling rate and resistance moment against pedaling in the feasible pedaling places (kinematics view) on the muscles ...
Read More
Pedaling is one of the common physical activities for muscles strengthening. Pedaling performance is affected by various factors. The purpose of this study is investigating the effect of pedaling rate and resistance moment against pedaling in the feasible pedaling places (kinematics view) on the muscles activity and ankle, knee and hip joints forces. For this purpose, the biomechanical model of human movement system presented in AnyBody software, is used. The mechanical power of pedaling is deemed to constant (200 w). The Pedaling rate of 40, 60, 80, 100 and 120 rpm and the resistance moment of 0, 5, 10, 15 and 20 Nm, are considered in the pedaling feasible places. Results indicate that although the range of pedaling feasible places is proper by the kinematics view, however changing the pedaling rate and the applied resistance moment, all of the pedaling places from this range cannot be proper due to the excessive muscles activity (more than 0.95). In the pedaling rate of 80, 100 and 120 rpm by applying the resistance moment of 0 and 5 Nm, approximately all of the feasible places are suitable (muscles activity are less than 0.95). By increasing the pedaling rate in a constant resistance moment, the large part and reversely, by increasing the resistance moment in a constant pedaling rate, the small part of feasible range are appropriate. Joints forces increase with decreasing the pedaling rate and increasing the applied resistance moment.
Musculoskeletal Systems Modeling
Sharareh Kian-Bostanabad; Mahmoud Reza Azghani; Leila Rahnama
Volume 9, Issue 3 , December 2015, , Pages 283-291
Abstract
Cervical multifidus muscle is one of the neck extensor muscles that plays an important role in the neck stability. By observing the different behaviors for this muscle during the six shoulder activities in previous study, it was modeled within the software and the effect of its action on the different ...
Read More
Cervical multifidus muscle is one of the neck extensor muscles that plays an important role in the neck stability. By observing the different behaviors for this muscle during the six shoulder activities in previous study, it was modeled within the software and the effect of its action on the different shoulder activities evaluated as a parametric study. For this end, a biomechanical model of the human locomotion system, which includes muscles of the shoulder, forearm and hand and 3 joints, was considered. After finding the maximum strength in six movement directions of the shoulder joint including flexion, extension, internal rotation, external rotation, abduction and adduction, the strength of 0, 25, 50, 75 and 100 percent of the maximum strength applied to model for each activities separately and the percentage of cervical multifidus and shoulder muscles activities have been saved. Moreover, applied torques by these muscles during different activities have been measured by calculating their effective torque arm. Assesing the relationship between the strength of cervical multifidus muscle with contraction level using the regression models showed a high correlation between these two factors during abduction, external rotation and extension activities (R2= 0.96-0.997). The produced torque by this muscle is more than the main muscles during the abduction and external rotation activities. This study showed that cervical multifidus muscle disfunction in addition to effect on the range of motion of neck, can be effective on the shoulder joint activities that it should be considerd in NIOSH lifting equation for individuals with neck pain.
Rehabilitation Engineering
Ziba Gandomkar; Fariba Bahrami
Volume 7, Issue 1 , June 2013, , Pages 21-37
Abstract
Changes in gait pattern are early symptoms in many disorders such as balance and control problems resulted in fall among elderlies. This paper aims at proposing a new set of features extracted from Gait Frieze Pattern (GFP) in order to classify seniors to fallers and non-fallers. For indicating the effectiveness ...
Read More
Changes in gait pattern are early symptoms in many disorders such as balance and control problems resulted in fall among elderlies. This paper aims at proposing a new set of features extracted from Gait Frieze Pattern (GFP) in order to classify seniors to fallers and non-fallers. For indicating the effectiveness of the presented method, the algorithm is used for recognition of different type of abnormal gaits. The introduced method consists of three main steps: extracting the subject from background, generating GFP and aligning them, and building the proposed image from GFP by thresholding followed by morphological operations. For evaluation of the proposed features, video sequences are collected from 8 elderly fallers, 8 non-fallers, and 8 youth while performing standard Timed Up and Go (TUG) test. In addition to TUG test youths are asked to walk fast and pretend to walk with 6 different types of abnormalities (limping, waddling, anterior- posterior sway, lateral sway, dragging, steppage gait). For finding correct classification rate, each time one data is considered as test and others as train and label of train data with the most similarity with test one on the score of normalized cross correlation is assigned to test data. Comparing to conventional TUG test, correct classification data is improved around 20% for faller detection. In addition, correct classification rate for detecting of different abnormalities in gait is approximately 90%.
Rehabilitation Engineering
Mohammad Salehi Amini; Siavash Kazemirad; Saman Mohammadi; Roya Narimani; Farzam Farahmand
Volume 7, Issue 2 , June 2013, , Pages 121-132
Abstract
The purpose of this study was to design, analyze and evaluate an effective low-cost driving mechanism for gait trainer. The crank-rocker mechanism was favored for reproducing the path of foot during gait cycle, considering the type of motion and design parameters such as adjustability for different anthropometries, ...
Read More
The purpose of this study was to design, analyze and evaluate an effective low-cost driving mechanism for gait trainer. The crank-rocker mechanism was favored for reproducing the path of foot during gait cycle, considering the type of motion and design parameters such as adjustability for different anthropometries, providing sufficient space for interactions with physical therapist, and simplicity of execution. The dimensions of the mechanism were determined using optimization method while applying appropriate constraints so that the normal gait pattern, particularly of stance phase, was obtained. A 2-D model of the lower limb was developed to simulate the gait of a patient when using the mechanism. Results indicated that with appropriate positioning of the patient, the kinematic and kinetic patterns of the normal gait are reconstructed with no risk of injury. However, there is a high risk of injury of the knee articular surfaces and ligaments, if the patient is positioned only 3 cm higher than designed height.
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 ...
Read More
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.
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 ...
Read More
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.
Spinal Biomechanics
Karim Leilnahari; Nasser Fatouraee; Mohammad Saleh Ganjavian
Volume 5, Issue 2 , June 2011, , Pages 161-170
Abstract
Ergonomic factors have a direct influence on the quality of spine support during sleep. Previous studies have shown that a mattress with a homogeneous stiffness can not necessarily maintain the natural spinal alignment. Using mattresses with components of different stiffness could be considered as a ...
Read More
Ergonomic factors have a direct influence on the quality of spine support during sleep. Previous studies have shown that a mattress with a homogeneous stiffness can not necessarily maintain the natural spinal alignment. Using mattresses with components of different stiffness could be considered as a possible solution instead. In this research a new mattress system having elements with different stiffness has been designed. The springs used in this mattress has been combined with a special slice of polyurethane foam, and each of them has its own specific spring constant. After acquiring the anthropometrical data of 25 male volunteers, they were asked to lie in a lateral position on soft and very stiff surfaces according to predefined conditions. Then the coordinates of the markers mounted on their spinous processes were registered through the optical tracking methods. In the next step the arrangement of the foam-spring elements were changed for each subject several times, in order to spinal alignment in a frontal plane was close to his normal alignment corresponding to the upright position. The post-processing of acquired data was considered off line.In order to qualify our experiments the BRG.LifeMod was used to model body position when lying on a mattress. The anthropometrical data of 4 subjects were used for the dimensional indexes of model. Several numerical models were built with several surfaces corresponding to the experimental essays. Once again the spinal alignment extracted. Results of both experimental and numerical modeling showed that the mattress with custom-made arrangement of the elements is an appropriate solution for the optimal support of the spine during sleep. The numerical modeling was able to predict the spinal alignment. The results of this research can be very useful in designing the custom-made sleep systems according to the ergonomic factors.
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) ...
Read More
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.
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 ...
Read More
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
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 ...
Read More
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 ...
Read More
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.
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 ...
Read More
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 ...
Read More
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 ...
Read More
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 ...
Read More
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 ...
Read More
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 ...
Read More
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.
Neuro-Muscular Engineering
Abbas Erfanian Omidvar
Volume -2, Issue 1 , July 2005, , Pages 81-92
Abstract
This paper is concerned with developing a force-generating model of electrically stimulated muscle under non-isometric condition. Hill-based muscle models have been the most popular structure. This type of muscle model was constructed as a combination of different independent blocks (i.e., activation ...
Read More
This paper is concerned with developing a force-generating model of electrically stimulated muscle under non-isometric condition. Hill-based muscle models have been the most popular structure. This type of muscle model was constructed as a combination of different independent blocks (i.e., activation dynamics, force-length and force-velocity relations, and series elastic element). The model assumes that the force-length and the force-velocity relations are uncoupled from the activation dynamics. However, some studies suggest that the shapes of the active force-length and the active force-velocity curves change with the level of the activation. Moreover, the "active state" block of the Hill-type model has no physical interpretation. To overcome the limitation of the Hill-type model, we used the multilayer perceptron (MLP) with back-propagation learning algorithm and Radial Basis Function (RBF) network with stochastic gradient learning rule for muscle modeling, where the stimulation signal, muscle length, velocity of length perturbation, and past measured or predicted force constitute the input of the neural model, and the predicted force is the output. Two modes of network operation are of interest: a time-varying network which allows updating the parameters of network to continue after convergence, and a time-invariant neural network with parameters fixed after convergence. The results show that time-varying and time-invariant neural networks would be able to track the muscle force with accuracy up to 99.5% and 95%, respectively. In addition, the results show that the accuracy of muscle force prediction depends on the structure of neural network. The prediction accuracy of RBF network after 1000 training epochs is higher than that of MLP network after 5000 training epochs.
Neuro-Muscular Engineering
Ali Esteki
Volume -1, Issue 1 , June 2004, , Pages 15-23
Abstract
Computer simulation of a three dimensional model of the thumb and index finger was used to perform a sensitivity analysis of each joint position to individual muscle activation level. The results were used to study the effect of each muscle on hand posture and select specific muscles to get a desired ...
Read More
Computer simulation of a three dimensional model of the thumb and index finger was used to perform a sensitivity analysis of each joint position to individual muscle activation level. The results were used to study the effect of each muscle on hand posture and select specific muscles to get a desired posture of the hand to assist the implementation of FNS systems. The hand was treated as a multi-body system including rigid segments connected by joints. Each joint was subjected to a total moment including muscle active and joint passive components. The forward approach, in which the equilibrium equations are solved for joint positions as a function of muscle moments, was used. The results showed that at the base joint of the index finger, flexion effect of the extrinsic flexor muscles was about two times of that of the intrinsic muscles. It was also shown that each muscle of the extensor system is individually more effective than the extrinsic flexor muscles. At the more distal joints, intrinsic muscles acted as feeble extensors. At the base joint of the thumb, extensor muscles were much more powerful than the flexor and flexor effect of adductor muscles. Also, abductor muscles were much more effective than the adductors. It was revealed that flexor muscles of the more distal joints are as strong as the extensor muscles. The conclusions are that: the minimum required muscles for appropriate positioning of the hand and for grasp and applying force to objects are limited.
