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    A control strategy for reducing the torque ripple in low speed operation of direct torque controlled induction motor

    , Article 2004 IEEE International Symposium on Industrial Electronics, IEEE-ISlE, 4 May 2004 through 7 May 2004 ; Volume 2 , 2004 , Pages 1203-1208 Kaboli, F. S ; Zolghadri, S. M. R ; Haghbin, T. S ; Homaifar, F. A ; Sharif University of Technology
    2004
    Abstract
    A new switching table is proposed for decreasing the torque ripple in DTC especially in low speed. Each sector is divided to two half sector and a proper vector set is defined for each. Through this new switching table, the torque response is smooth even in the beginning of each sector and it leads to the reduction of torque ripple. None of motor parameters are used in this switching strategy and there is no need to shorten the sampling period. Simulation and experimental results confirm the ability of this method in reducing the torque ripple. ©2004 IEEE  

    Torque ripple minimization in DTC of induction motor based on optimized flux value determination

    , Article The 29th Annual Conference of the IEEE Industrial Electronics Society, Roanoke, VA, 2 November 2003 through 6 November 2003 ; Volume 1 , 2003 , Pages 431-435 Kaboli, S ; Zolghadri, M. R ; Haghbin, S ; Emadi, A ; Sharif University of Technology
    2003
    Abstract
    Torque ripple is a major difficulty in direct torque controlled induction motors. The reference value of the motor flux greatly influences the torque ripple. On the other hand, many motors work in an operating cycle, which includes load intervals of less than their nominal power. In these situations, it is not necessary to set their flux value as the nominal value. In this paper, the effect of the reference value of the motor flux on the motor torque ripple is investigated. A new control algorithm is proposed to determine the reference value of the flux according to the value of the motor torque. Simulation and experimental results justify the validity of the proposed method to reduce the... 

    Effects of the flux value on the torque ripple of the direct torque controlled induction motor drives determination

    , Article 5th International Conference on Power Electronics and Drive Systems, PEDS 2003, 17 November 2003 through 20 November 2003 ; Volume 1 , 2003 , Pages 439-444 ; 0780378857 (ISBN) Kaboli, S ; Zolghadri, M. R ; Haghbin, S ; Homaifar, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    Abstract
    Torque ripple is a major difficulty in direct torque control of induction motors. The reference value of the motor flux greatly influences the torque ripple. On the other hand, many motors work in an operating cycle, which includes load intervals of less than their nominal power. In these situations, it is not necessary to set their flux value as the nominal value. In this paper, the effect of the reference value of the motor flux on the motor torque ripple is investigated. The effect of the flux reference variation on the motor power factor as well as torque dynamics is also presented. Simulation results as well as experimental results justify the validity of the proposed method on the... 

    Performance of PI Stator Resistance Compensator on DTC of Induction Motor

    , Article The 29th Annual Conference of the IEEE Industrial Electronics Society, Roanoke, VA, 2 November 2003 through 6 November 2003 ; Volume 1 , 2003 , Pages 425-430 Haghbin, S ; Zolghadri, M. R ; Kaboli, S ; Emadi, A ; Sharif University of Technology
    2003
    Abstract
    Stator resistance PI compensator is one of the simplest methods proposed to estimate stator resistance. This method is based on the real time stator resistance correction regarding the variations of the stator current magnitude, which must be a constant value when the stator flux and motor torque are constant. This reference value can be calculated using the flux and torque commands and motor parameters. In this paper, it is shown that for DTC systems using digital controller with limited sampling frequency, stator current vector amplitude varies as a function of speed, sampling period, and switching strategy. Effects of sampling frequency, motor speed, and switching strategy on this current... 

    Design and implementation of a predictive controller for reducing the torque ripple in direct torque control based high frequency induction motor drives

    , Article 2004 IEEE 35th Annual Power Electronics Specialists Conference, PESC04, Aachen, 20 June 2004 through 25 June 2004 ; Volume 2 , 2004 , Pages 1169-1174 ; 02759306 (ISSN) Kaboli, S ; Zolghadri, M. R ; Roye, D ; Guiraud, J ; Schanen, J. L ; Sharif University of Technology
    2004
    Abstract
    In Direct Torque Control, selection of each voltage vector is based on the measured parameters in the beginning of the sampling period. Due to the fast dynamic of torque, this delay causes an extra torque ripple. In this paper, a new predictive controller is proposed for compensating this delay and reducing the torque ripple. The stator current is measured in the beginning of each sampling period and its expected value in the end of period is predicted according to an extrapolation algorithm. This algorithm is performed by calculating the slope of stator current variation according to the stator flux variation. Thus, there is no need to solve the high order equations of machine. The... 

    Design and implementation of a predictive controller for reducing the torque ripple in direct torque control based induction motor drives

    , Article 2004 IEEE 35th Annual Power Electronics Specialists Conference, PESC04, Aachen, 20 June 2004 through 25 June 2004 ; Volume 1 , 2004 , Pages 476-481 ; 02759306 (ISSN) Kaboli, S ; Zolghadri, M. R ; Roye, D ; Guiraud, J ; Crebier, J. C ; Sharif University of Technology
    2004
    Abstract
    In Direct Torque Control, selection of each voltage vector is based on the measured parameters in the beginning of the sampling period. Due to the fast dynamic of torque, this delay causes an extra torque ripple. In this paper, a new predictive controller is proposed for compensating this delay and reducing the torque ripple. The stator current is measured two times at the beginning of each sampling period and its expected value at the end of period is predicted according to an extrapolation algorithm. Thus, there is no need to machine parameters and the algorithm is quite robust against machine parameters variations. The calculation of the electromagnetic torque is performed using the... 

    Effect of motor speed on the optimum operating point of direct torque controlled induction motor

    , Article 6th International Conference on Electrical Machines and Systems, ICEMS 2003, 9 November 2003 through 11 November 2003 ; Volume 2 , 2003 , Pages 619-622 ; 750626210X (ISBN); 9787506262101 (ISBN) Kaboli, S ; Zolghadri, M. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    Abstract
    The flux and torque hysteresis bands are the only gains to be adjusted in direct torque control (DTC). The torque ripple and harmonic loss of motor and switching loss of inverter are greatly influenced by them. In this paper the effects of flux and torque hysteresis bands on inverter switching loss, harmonic loss and torque ripple of induction motor are investigated through a cost function. Minimizing this cost function leads to the optimum value of the hysteresis bands of torque and flux controllers. The effect of motor speed on cost function is also investigated. © 2003 International Academic Publishers/World Publishing Corporation  

    Reduction of the torque ripple in brushless doubly-fed machine

    , Article Proceedings of the 2011 3rd International Youth Conference on Energetics, IYCE 2011, 7 July 2011 through 9 July 2011 ; July , 2011 , Page(s):1 - 7 ; 9781457714948 (ISBN) Gorginpour, H ; Jandaghi, B ; Oraee, A ; Saket, M. A ; Ahmadian, M ; Oraee, H ; Sharif University of Technology
    2011
    Abstract
    In this paper, a new structure for the rotor of the Brushless Doubly-Fed Machine (BDFM) is introduced to reduce the machine's torque ripple. The ripple has a considerable effect on the machine start up. At the first section of the paper, analytical expressions for the air gap permeance distribution, the air gap MMF distribution, cogging torque and back EMF are presented. Then, the effects of skewing the rotor loops are analyzed. Finally, the relation between non-skewed quantities and their values in skewed coordinate are introduced  

    Efficient design of a torque actuator for lower extremity exoskeleton based on muscle function analysis

    , Article 2011 International Conference on Mechatronics and Materials Processing, ICMMP 2011, Guangzhou, 18 November 2011 through 20 November 2011 ; Volume 328-330 , 2011 , Pages 1041-1044 ; 10226680 (ISSN) ; 9783037852385 (ISBN) Safavi, S ; Selk Ghafari, A ; Meghdari, A ; Guangzhou University ; Sharif University of Technology
    2011
    Abstract
    Several lower extremity exoskeletal systems have been developed for augmentation purpose. Common actuators, have important drawbacks such as complexity, and poor torque capacities. The main scope of this research is to propose a series elastic actuator for lower extremity exoskeletal system which was designed based on muscle functional analysis. For this purpose, a biomechanical framework consisting of a musculoskeletal model with ten degrees-of-freedom actuated by eighteen Hill-type musculotendon actuators per leg is utilized to perform the muscle functional analysis for common daily human activities. The simulation study illustrated functional differences between flexor and extensor... 

    Comprehensive design of a toroidally-wound limited angle torque motor

    , Article International Review of Electrical Engineering ; Volume 6, Issue 1 , 2011 , Pages 198-206 ; 18276660 (ISSN) Zarandi, R. N ; Kelk, H. M ; Toorani, F ; Farahmandzad, H ; Sharif University of Technology
    Abstract
    This paper presents a comprehensive design procedure of a brushless DC limited angle torque motor (LATM) based on magnetic equivalent circuit analysis which predicts its performance and magnetic characteristics. Design of toroidally wounded armature and rotor with two pole tip segments are developed using selected ferromagnetic material and rare earth permanent magnets. Derivation of airgap and other motor dimensions and design parameters with their expressions are given. A finite element analysis verification of designed LATM using a 2D modeling and simulating package is presented. Performance characteristic of analytical model and FEA model of designed LATM is compared which validates the... 

    Direct Torque Control of Brushless Doubly Fed Induction Machine

    , Article SPEEDAM 2010 - International Symposium on Power Electronics, Electrical Drives, Automation and Motion, 14 June 2010 through 16 June 2010 ; June , 2010 , Pages 1744-1747 ; 9781424449873 (ISBN) Fattahi, S. J ; Khayyat, A. A ; Sharif University of Technology
    2010
    Abstract
    This article contributes a torque control based on hysteresis for Brushless Doubly Fed Induction Machine (BDFM) through machine analysis and extracting the d-q parameters that influence on the machine behavior. In this research, a Direct Torque Control (DTC) based on stator flux-oriented vectors and machine's relation and equations with voltage and current of both stators have been introduced. The control for the BDFM is implemented by a voltage source inverter connected to the second stator as a torque controller that uses the classical field-oriented control method widely used in voltage sector selection. Finally BDFM as closed loop model with DTC is simulated and evaluated  

    A loss minimization control strategy for direct torque controlled interior permanent magnet synchronous motors

    , Article Journal of Power Electronics ; Volume 9, Issue 6 , 2009 , Pages 940-948 ; 15982092 (ISSN) Siahbalaee, J ; Vaez Zadeh, S ; Tahami, F ; Sharif University of Technology
    2009
    Abstract
    The main objective of this a paper is to improve the efficiency of permanent magnet synchronous motors (PMSMs) by using an improved direct torque control (DTC) strategy. The basic idea behind the proposed strategy is to predict the impact of a small change in the stator flux amplitude at each sampling period to decrease electrical loss before the change is applied. Accordingly, at every sampling time, a voltage vector is predicted and applied to the machine to fulfill the flux change. The motor drive simulations confirm a significant improvement in efficiency as well as a very fast and smooth response under the proposed strategy  

    Smooth residual generation for robust isolation of faults in manipulators using joint torque sensors

    , Article 58th IEEE Conference on Decision and Control, CDC 2019, 11 December 2019 through 13 December 2019 ; Volume 2019-December , 2019 , Pages 2922-2927 ; 07431546 (ISSN); 9781728113982 (ISBN) Karami, S ; Namvar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    Reliability of model-based failure detection and isolation (FDI) methods depends on the amount of uncertainty in a system model. Recently, it has been shown that the use of joint torque sensing results in a simplified manipulator model that excludes hardly identifiable link dynamics and other nonlinearities. We present a geometric approach to fault detection and isolation (FDI) for robotic manipulators using joint torque sensor in presence of model uncertainty. A systematic procedure is introduced for representing a robotic system model using joint torque sensor being affine with respect to faults and disturbances. The proposed FDI filter has smooth dynamics with freely selectable functions... 

    A new multi-machine control system based on direct torque control algorithm

    , Article 7th Internatonal Conference on Power Electronics, ICPE'07, Daegu, 22 October 2007 through 26 October 2007 ; 2007 , Pages 1103-1108 ; 9781424418725 (ISBN) Mohktari, H ; Alizadeh, A ; Sharif University of Technology
    IEEE Computer Society  2007
    Abstract
    In this paper, a new and simple control method based on Direct Torque Control (DTC) of induction motors is proposed for a multi-machine system. Similar to a conventional DTC, the proposed method has two separate control loops. In the torque control loop, before selection of optimum voltage from the DTC look-up table, the system overall requirement is determined based on requirements of motors torque. Also, Switchable Master-Slave control is used in the flux control loop. The method, which is simulated for a two-parallel induction machine system, can be extended to a multi-machine system. Simulation results are also provided to investigate the performance of the proposed technique. © 2008... 

    Hybrid stepper motor backstepping control in micro-step operation

    , Article 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005, Orlando, 5 November 2005 through 11 November 2005 ; Volume 118 B, Issue 2 , 2005 , Pages 993-997 Ghafari, A. S ; Alasty, A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2005
    Abstract
    A nonlinear position controller based on backstepping control technique is proposed for a hybrid stepper motor in micro-step operation. Backstepping control approach is adapted to derive the control scheme, which is robust to parameter uncertainties and external load disturbance. Simulation results clearly show that the proposed controller can track the position reference signal successfully under parameter uncertainties and load torque disturbance rejection. Copyright © 2005 by ASME  

    How well do the muscular synergies extracted via non-negative matrix factorisation explain the variation of torque at shoulder joint?

    , Article Computer Methods in Biomechanics and Biomedical Engineering ; Volume 16, Issue 3 , 2013 , Pages 291-301 ; 10255842 (ISSN) Moghadam, M. N ; Aminian, K ; Asghari, M ; Parnianpour, M ; Sharif University of Technology
    2013
    Abstract
    The way central nervous system manages the excess degrees of freedom to solve kinetic redundancy of musculoskeletal system remains an open question. In this study, we utilise the concept of synergy formation as a simplifying control strategy to find the muscle recruitment based on summation of identified muscle synergies to balance the biomechanical demands (biaxial external torque) during an isometric shoulder task. A numerical optimisation-based shoulder model was used to obtain muscle activation levels when a biaxial external isometric torque is imposed at the shoulder glenohumeral joint. In the numerical simulations, 12 different shoulder torque vectors in the transverse plane are... 

    A modified DTC for induction motor drive system fed by Indirect Matrix Converter using Active Learning Method

    , Article 2011 2nd Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2011, 16 February 2011 through 17 February 2011 ; February , 2011 , Pages 356-361 ; 9781612844213 (ISBN) Faraji, V ; Aghasi, M ; Khaburi, D. A ; Ghorbani, M. J ; Sharif University of Technology
    2011
    Abstract
    This paper presents a high performance Direct Torque Control (DTC) theme for the induction motor using Indirect Matrix Converter (IMC). To improve the dynamic behavior of motor, Active Learning Method (ALM) is implemented on the DTC. The ALM uses its own modeling technique called the ink drop spread (IDS) method. Functionally the IMC is very similar to the Direct Matrix Converter (DMC) but it has separate line and load bridges. In the inverter stage, the classical DTC method is employed. In the rectifier stage, in order to reduce losses caused by snubber circuit the rectifier four-step commutation method is employed. By suitably selecting switching pattern and using Active Learning Method... 

    Muscle synergies based on a biomechanical biaxial isometric shoulder model minimizing fatigue

    , Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 1 , 2010 , Pages 797-804 ; 9780791849156 (ISBN) Nassajian Moghadam, M ; Aminian, K ; Asghari, M ; Parnianpour, M ; Sharif University of Technology
    Abstract
    In this study we utilize the concept of synergy formation as a simplifying control strategy to manage the high number of degrees of freedom presented in the maintenance of the posture of the shoulder joint. We address how to find the muscle synergy recruitment map to the biomechanical demands (biaxial external torque) during an isometric shoulder task. We use a numerical optimization based shoulder model to obtain muscle activation levels when a biaxial external isometric torque is exposed at the shoulder glenohumeral joint. In the numerical simulations, different shoulder torque vectors parallel to the horizontal plane are considered. For each selected direction for the torque, the... 

    A new loss minimization approach with flux and torque ripples reduction of direct torque controlled permanent magnet synchronous motors

    , Article 2009 13th European Conference on Power Electronics and Applications, EPE '09, 8 September 2009 through 10 September 2009, Barcelona ; 2009 ; 9781424444328 (ISBN) Siahbalaee, J ; Vaez Zadeh, S ; Tahami, F ; Sharif University of Technology
    Abstract
    The main purpose of this paper is to minimize the loss while reducing the flux and torque ripples in permanent magnet synchronous motors (PMSMs) under direct torque control (DTC). Offline method is used to minimize the loss and obtain the optimal flux. To reduce the amount of computation, the optimal flux table is produced according to the conditions in which the machine works. To reduce the flux and torque ripples and to control the switching frequency, SVM-DTC method is applied. Simulation results depict a noticeable increase in efficiency of the motor and a reduction in flux and torque ripples  

    Timoshenko versus Euler-Bernoulli beam theories for high speed two-link manipulator

    , Article Scientia Iranica ; Volume 20, Issue 1 , 2013 , Pages 172-178 ; 10263098 (ISSN) Zohoor, H ; Kakavand, F ; Sharif University of Technology
    2013
    Abstract
    In this paper, a two-link flexible manipulator is considered. For a prescribed motion, Timoshenko and Euler-Bernoulli beam models are considered. Using the Galerkin method, nonlinear equations of motion are solved. The Runge-Kutta method is employed for the time response integration method. A comparative study is made between the Euler-Bernoulli and Timoshenko beam models, with and without foreshortening effects. It is demonstrated that for two-link manipulators, both theories provide good models, and the results for both theories are very similar for all ranges of slenderness ratio. The findings suggest that for two-link manipulators with relatively high slenderness ratios, there is a...