Search for: motor-control
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    Application of actor-critic reinforcement learning method for control of a sagittal arm during oscillatory movement

    , Article Biomedical Engineering - Applications, Basis and Communications ; Volume 16, Issue 6 , 2004 , Pages 305-312 ; 10162372 (ISSN) Golkhou, V ; Lucas, C ; Parnianpour, M ; Sharif University of Technology
    Institute of Biomedical Engineering  2004
    Numerous disciplines are engaged in studies involving motor control. In this study, we have used a single link system with a pair of muscles that are excited with alpha and gamma signals to achieve an oscillatory movement with variable amplitude and frequency. The system is highly nonlinear in all its physical and physiological attributes. The major physiological characteristics of this system are simultaneous activation of a pair of nonlinear muscle-like-actuators for control purposes, existence of nonlinear spindle-like sensors and Golgi tendon organ-like sensor, actions of gravity and external loading. Transmission delays are included in the afferent and efferent neural paths to account... 

    Neuromuscular control of sagittal ARM during repetitive movement by actor-critic reinforcement learning method

    , Article Intelligent Automation and Control Trends, Principles, and Applications - International Symposium on Intelligent Automation and Control, ISIAC - Sixth Biannual World Automation Congress, WAC 2004, Seville, 28 June 2004 through 1 July 2004 ; 2004 , Pages 371-376 ; 1889335223 (ISBN) Golkhou, V ; Lucas, C ; Parnianpour, M ; Sharif University of Technology
    In this study, we have used a single link system with a pair of muscles that are excited with alpha and gamma signals to achieve an oscillatory movement with variable amplitude and frequency. This paper proposes a reinforcement learning method with an Actor-Critic architecture instead of middle and low level of central nervous system (CNS). The Actor in this structure is a two layer feedforward neural network and the Critic is a model of the cerebellum. The Critic is trained by State-Action-Reward-State-Action (SARSA) method. The system showed excellent tracking capability and after 280 epochs the RMS error for position and velocity profiles were 0.02, 0.04 radian and radian/sec,... 

    Direct yaw moment control for motorized wheel electric vehicles

    , Article 18th Biennial Conference on Mechanical Vibration and Noise, Pittsburgh, PA, 9 September 2001 through 12 September 2001 ; Volume 6 A , 2001 , Pages 215-222 Goodarzi, A ; Esmailzadeh, E ; Vossoughi, G. R ; Sharif University of Technology
    A new control law for direct yaw moment control of an electric vehicle is developed. Although this study is considered as part of a global control system for the traction control of a four motorized wheel electric vehicle, but the results of this study is quite general and can be applied to other types of vehicles. The dynamic model of the system has been analyzed and, in accordance with the optimal control theory, an optimal controller is designed. Two different versions of the control law have been considered and the performance of each version has been separately studied and compared with each other. Finally, the numerical simulation of the vehicle-handling model with and without the use... 

    The effect of chronic low back pain on trunk accuracy in a multidirectional isometric tracking task

    , Article Spine ; Vol. 39, Issue. 26 , 2014 , pp. E1608-E1615 ; ISSN: 1362-2436 Hadizadeh, M ; Mousavi, S. J ; Sedaghatnejad, E ; Talebian, S ; Parnianpour, M ; Sharif University of Technology
    Study Design. A cross-sectional study to quantify trunk motor control during multidirectional isometric tracking tasks.Objective. To investigate the effect of chronic low back pain (LBP) on trunk neuromuscular performance while participants performed isometric exertions of trunk muscles to track targets in different angles with various magnitudes.Summary of Background Data. Tracking tasks especially in multidirectional activities are among the common research methods to quantify human motor control in different conditions. However, little information is available on trunk motor control during these tasks. There is no study investigating trunk accuracy during multidirectional isometric... 

    Energy optimization of field oriented six-phase induction motor drive

    , Article Advances in Electrical and Computer Engineering ; Volume 11, Issue 2 , 2011 , Pages 107-112 ; 15827445 (ISSN) Taheri, A ; Rahmati, A ; Kaboli, S ; Sharif University of Technology
    This paper deals with the efficiency optimization of Field Oriented Control (FOC) of a six-Phase Induction Motor (6PIM) by adaptive flux search control. The six-phase induction motor is supplied by Space Vector PWM (SVPWM) and voltage source inverter. Adaptive flux search controller is fast than ordinary search control technique and easy to implement. Adaptive flux Search Control (SC) technique decreases the convergence time by proper change of flux variation steps and increases accuracy of the SC technique. A proper loss model of 6PIM in conjunction with the proposed method is used. The six-phase induction machine has large zero sequence harmonic currents that can be reduced by SVPWM... 

    A comprehensive evaluation of spine kinematics, kinetics, and trunk muscle activities during fatigue-induced repetitive lifting

    , Article Human Factors ; 2021 ; 00187208 (ISSN) Kazemi, Z ; Mazloumi, A ; Arjmand, N ; Keihani, A ; Karimi, Z ; Ghasemi, M. S ; Kordi, R ; Sharif University of Technology
    SAGE Publications Inc  2021
    Objective: Spine kinematics, kinetics, and trunk muscle activities were evaluated during different stages of a fatigue-induced symmetric lifting task over time. Background: Due to neuromuscular adaptations, postural behaviors of workers during lifting tasks are affected by fatigue. Comprehensive aspects of these adaptations remain to be investigated. Method: Eighteen volunteers repeatedly lifted a box until perceived exhaustion. Body center of mass (CoM), trunk and box kinematics, and feet center of pressure (CoP) were estimated by a motion capture system and force-plate. Electromyographic (EMG) signals of trunk/abdominal muscles were assessed using linear and nonlinear approaches. The L5-S1... 

    The role of multisensor data fusion in neuromuscular control of a sagittal arm with a pair of muscles using actor-critic reinforcement learning method

    , Article Technology and Health Care ; Volume 12, Issue 6 , 2004 , Pages 425-438 ; 09287329 (ISSN) Golkhou, V ; Parnianpour, M ; Lucas, C ; Sharif University of Technology
    IOS Press  2004
    In this study, we consider the role of multisensor data fusion in neuromuscular control using an actor-critic reinforcement learning method. The model we use is a single link system actuated by a pair of muscles that are excited with alpha and gamma signals. Various physiological sensor information such as proprioception, spindle sensors, and Golgi tendon organs have been integrated to achieve an oscillatory movement with variable amplitude and frequency, while achieving a stable movement with minimum metabolic cost and coactivation. The system is highly nonlinear in all its physical and physiological attributes. Transmission delays are included in the afferent and efferent neural paths to... 

    Design and Construction of an Artificial Thumb Controlled by Command from the Index Finger

    , M.Sc. Thesis Sharif University of Technology Loghmani, Javad (Author) ; Salak Ghafari, Ali (Supervisor)
    This study provides preliminary work on the development of manual rehabilitation device for wearable and robotic manual applications. This work examines the motion of the fingers using the sensors. The developed mechanism is based on a combination of strain gauge sensors and a stepper motor, which forms the motion of the artificial thumb. In this thesis, the creation of an artificial thumb has been done with one degree of freedom, the movement and grabbing of lightweight objects. For grabbing objects, the command of controlling and keeping objects is performed through the IAR software and labVIEW software which is given to the stepper motor.This study describes the details of the work done... 

    Investigation of the micro-step control positioning system performance affected by random input signals

    , Article Mechatronics ; Volume 15, Issue 10 , 2005 , Pages 1175-1189 ; 09574158 (ISSN) Selk Ghafari, A ; Behzad, M ; Sharif University of Technology
    This paper gives the results of simulation and experimental investigation on the effects of random signals on the accuracy of micro-stepping control positioning. For studying and simulation of the effect of random noise signals on performance of the accurate position control systems, such as Hybrid Stepper Motors (HSMs), a micro-step driver and controlling unit using PID controller has been designed and constructed. Several parametric studies have been carried out including different white noise power and micro-step per revolution. Tracking problem for a HSM model has been simulated, and the experimental study for similar cases has been carried out by implementing the designed controller in... 

    Flexion and Extension of Spine in Sagittal Plane with Muscles Under the Control of Central Pattern Generators

    , M.Sc. Thesis Sharif University of Technology Seddighi, Alireza (Author) ; Parnianpour, Mohamad (Supervisor) ; Sadati, Nasser (Supervisor) ; Narimani, Roya (Supervisor)
    Low back pain is a widespread disorder in industrialized countries. Based on epidemiological reports, 80% of the population faces this activity limitation at least once in their lifetime which places tremendous human and economic costs to individuals and societies. Handling heavy loads, with fast trunk motions, repetitive movements, and awkward postures are some of the risk factors related to low back injuries. Hence, better understanding of the neuro-musculo-skeletal system performance would help us to recognize various abnormalities in spine behavior and assist us in a way to design the workplace to reduce the risk of injuries. For this purpose, we can use biomechanicals model to... 

    A predictive loss minimisation direct torque control of permanent magnet synchronous motors

    , Article Australian Journal of Electrical and Electronics Engineering ; Volume 9, Issue 1 , 2012 , Pages 89-98 ; 1448837X (ISSN) Siahbalaee, J ; Vaez Zadeh, S ; Tahami, F ; Sharif University of Technology
    Although permanent magnet synchronous motors (PMSMs) are inherently of high efficiency, their efficiency is enormously dependent on their control strategy. The purpose of this paper is to improve the efficiency of PMSMs under a direct torque control (DTC) method. The main idea behind the proposed method is to predict a required small change of the statorflux amplitude at each sampling period to reduce the machine electrical loss before the change is applied. Accordingly, at every sampling time, a voltage vector is predicted and applied to the machine to change the flux amplitude in a xvay that the electrical loss decreases. The results of simulation show significant improvement in the... 

    A biologically plausible learning method for neurorobotic systems

    , Article 2009 4th International IEEE/EMBS Conference on Neural Engineering, NER '09, Antalya, 29 April 2009 through 2 May 2009 ; 2009 , Pages 128-131 ; 9781424420735 (ISBN) Davoudi, H ; Vosoughi Vahdat, B ; National Institutes of Health, NIH; National Institute of Neurological Disorders and Stroke, NINDS; National Science Foundation, NSF ; Sharif University of Technology
    This paper introduces an incremental local learning algorithm inspired by learning in neurobiological systems. This algorithm has no training phase and learns the world during operation, in a lifetime manner. It is a semi-supervised algorithm which combines soft competitive learning in input space and linear regression with recursive update in output space. This method is also robust to negative interference and compromises bias-variance dilemma. These qualities make the learning method a good nonlinear function approximator having possible applications in neuro-robotic systems. Some simulations illustrate the effectiveness of the proposed algorithm in function approximation, time-series... 

    Adjustable primitive pattern generator: A novel cerebellar model for reaching movements

    , Article Neuroscience Letters ; Volume 406, Issue 3 , 2006 , Pages 232-234 ; 03043940 (ISSN) Vahdat, S ; Maghsoudi, A ; Haji Hasani, M ; Towhidkhah, F ; Gharibzadeh, S ; Jahed, M ; Sharif University of Technology
    Cerebellum has been assumed as an array of adjustable pattern generators (APGs). In recent years, electrophysiological researches have suggested the existence of modular structures in spinal cord called motor primitives. In our proposed model, each "adjustable primitive pattern generator" (APPG) module in the cerebellum is consisted of a large number of parallel APGs, the output of each module being the weighted sum of the outputs of these APGs. Each spinal field is tuned by a coefficient, representing a descending supraspinal command, which is modulated by ith APPG correspondingly. According to this model, motor control can be interpreted in terms of the modification of these coefficients.... 

    Normal postural responses preceding shoulder flexion: Co-activation or asymmetric activation of transverse abdominis?

    , Article Journal of Back and Musculoskeletal Rehabilitation ; Vol. 27, issue. 4 , 2014 , p. 545-551 Davarian, S ; Maroufi, N ; Ebrahimi, E ; Parnianpour, M ; Farahmand, F ; Sharif University of Technology
    BACKGROUND AND OBJECTIVES: It is suggested that activation of the transverse abdominis muscle has a stabilizing effect on the lumbar spine by raising intra-abdominal pressure without added disc compression. However, its feedforward activity has remained a controversial issue. In addition, research regarding bilateral activation of trunk muscles during a unilateral arm movement is limited. The aim of this study was to evaluate bilateral anticipatory activity of trunk muscles during unilateral arm flexion.MATERIALS AND METHODS: Eighteen healthy subjects (aged 25 ± 3.96 years) participated in this study and performed 10 trials of rapid arm flexion in response to a visual stimulus. The... 

    Control of lumbar spine flexion-extension movement by PD controller and feedback linearization method

    , Article ICCAS 2010 - International Conference on Control, Automation and Systems, 27 October 2010 through 30 October 2010 ; 2010 , Pages 2024-2029 ; 9781424474530 (ISBN) Abedi, M ; Vossughi, G. R ; Parnianpour, M ; Sharif University of Technology
    The role of motor control in development of low back pain is subject of many researches both in theoretical and experimental fields. In this work flexion-extension movement of lumbar spine have been controlled by three different methods, including feedback linearization (FBL), PD control and their combinations. The model involves 7 links: 1 link for pelvis, 5 links for lumbar vertebrae and 1 link for trunk. Torque actuators have been used on each joint to make them follow desired trajectory. In linear control method, equations of motion have been linearized with respect to upright position and then control signals have been applied in the direction of eigenvectors. Robustness of each method... 

    Non-linear dynamical features of center of pressure extracted by recurrence quantification analysis in people with unilateral anterior cruciate ligament injury

    , Article Gait and Posture ; Volume 31, Issue 4 , 2010 , Pages 450-455 ; 09666362 (ISSN) Negahban, H ; Salavati, M ; Mazaheri, M ; Sanjari, M. A ; Hadian, M. R ; Parnianpour, M ; Sharif University of Technology
    Knowledge about the non-linear dynamical pattern of postural sway may provide important insights into the adaptability (flexibility) of human postural control in response to everyday stresses imposed on the body. A commonly used non-linear tool, i.e. recurrence quantification analysis, was chosen to investigate the effect of prior anterior cruciate ligament injury on the deterministic pattern of postural sway under different conditions of postural and cognitive difficulty. In double leg stance, as postural difficulty increased from open-eyes to closed-eyes and rigid-surface to foam-surface, the centre of pressure regularity (%determinism) increased as well. In comparison to healthy... 

    Comparison of spinal stability following motor control and general exercises in nonspecific chronic low back pain patients

    , Article Clinical Biomechanics ; Volume 48 , 2017 , Pages 42-48 ; 02680033 (ISSN) Shamsi, M ; Sarrafzadeh, J ; Jamshidi, A ; Arjmand, N ; Ghezelbash, F ; Sharif University of Technology
    Background Motor control exercise was claimed to improve spinal stability in patients with chronic non-specific back pain, but to investigate the effectiveness of this exercise, other outcome measures have been used rather than spinal stability itself. The aim of our study is to assess motor control exercise effects on spinal stability using a biomechanical model. Methods Fifty-one patients were assigned to either motor control or general exercises. Before and after trainings, participants were tested for spinal stability at seven isometric tasks. Electromyography signals were recorded from ten superficial muscles, and a hybrid EMG-driven musculoskeletal model estimated spinal stability... 

    Comparison of the trunk-pelvis and lower extremities sagittal plane inter-segmental coordination and variability during walking in persons with and without chronic low back pain

    , Article Human Movement Science ; Volume 52 , 2017 , Pages 55-66 ; 01679457 (ISSN) Ebrahimi, S ; Kamali, F ; Razeghi, M ; Haghpanah, S. A ; Sharif University of Technology
    Elsevier B.V  2017
    Inter-segmental coordination can be influenced by chronic low back pain (CLBP). The sagittal plane lower extremities inter-segmental coordination pattern and variability, in conjunction with the pelvis and trunk, were assessed in subjects with and without non-specific CLBP during free-speed walking. Kinematic data were collected from 10 non-specific CLBP and 10 non-CLBP control volunteers while the subjects were walking at their preferred speed. Sagittal plane time-normalized segmental angles and velocities were used to calculate continuous relative phase for each data point. Mean absolute relative phase (MARP) and deviation phase (DP) were derived to quantify the trunk-pelvis and bilateral... 

    Shared and specific synchronous muscle synergies arisen from optimal feedback control theory

    , Article 2009 4th International IEEE/EMBS Conference on Neural Engineering, NER '09, Antalya, 29 April 2009 through 2 May 2009 ; 2009 , Pages 155-158 ; 9781424420735 (ISBN) Bayati, H. R ; Vahdat, S ; Vosoughi Vahdat, B ; National Institutes of Health, NIH; National Institute of Neurological Disorders and Stroke, NINDS; National Science Foundation, NSF ; Sharif University of Technology
    In this study the properties of muscle synergies, arising from optimal feedback control are investigated. Three different tasks namely reaching, via-point, and hitting are performed using optimization of corresponding cost functions. Then by applying non-negative matrix factorization method to a dataset of muscle tensions, synchronous muscle synergies are obtained. In this way, different muscle patterns can be generated by linear combination of these basis vectors with non-negative time-varying scaling coefficients. According to our simulations some of obtained muscle synergies are shared between tasks and some of them are specific for one task. This finding is also in agreement with the... 

    Effects of lumbosacral orthosis on dynamical structure of center of pressure fluctuations in patients with non-specific chronic low back pain: A randomized controlled trial

    , Article Journal of Bodywork and Movement Therapies ; Volume 23, Issue 4 , 2019 , Pages 930-936 ; 13608592 (ISSN) Azadinia, F ; Ebrahimi Takamjani, I ; Kamyab, M ; Asgari, M ; Parnianpour, M ; Sharif University of Technology
    Churchill Livingstone  2019
    Background: A few clinical trials have examined the effect of treatment interventions on postural control in patients with chronic low back pain, all of which have exclusively evaluated postural stability using traditional linear measures of postural sway. However, postural control improvement cannot be determined by exclusively relying on linear measurements, because these parameters provide no information on underlying motor control mechanisms. Objective: This study aimed to compare the effect of using lumbosacral orthoses (LSO) together with routine physical therapy, compared to routine physical therapy alone on postural control, using nonlinear analysis techniques. Methods: Forty-four...