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compensation
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Stability analysis and nonlinear control of a miniature shape memory alloy actuator for precise applications
, Article Mechatronics ; Volume 15, Issue 4 , 2005 , Pages 471-486 ; 09574158 (ISSN) ; Alasty, A ; Salaarieh, H ; Sharif University of Technology
2005
Abstract
This paper presents a new approach for controlling SMA actuators with hysteresis compensation by using two energy based semi active controllers. SMA actuators exhibit severe hysteresis that is often responsible for position inaccuracy in a regulation or tracking system. In this paper, a SMA actuator model is recalled from [Alasty A, Shameli E. Dynamic modeling of a new varying stress SMA actuator for precise applications. In: Proceedings of 2004 IEEE international conference on mechatronics (ICM'04). Istanbul, Turkey, June 3-5, 2004]. Then, a PID and a novel PID-P3 controllers have been suggested to perform a position control. To investigate the stability of controlled system the...
A new technique in passive coherent radar signal processing
, Article EURAD 2005 - 2nd European Radar Conference, Paris, 6 October 2005 through 7 October 2005 ; Volume 2005 , 2005 , Pages 149-151 ; 2960055136 (ISBN); 9782960055139 (ISBN) ; Sedghi, V ; Nayebi, M. M ; Sharif University of Technology
IEEE Computer Society
2005
Abstract
In this paper, we focus on adaptive and wavelet based systems in radar signal processing, and a new algorithm to Doppler compensation is developed. The new wavelet-based method for ambiguity surface smoothing that applies the three dimensions dual tree wavelet transform and adapt constant false alarm rate, is proposed. The model captures the dependence between a wavelet coefficient and its parent. Simulation results show that new approach is better than older algorithms. We have simulated this new method for bistatic FM-based passive coherent receiver
Presentation of a Model and Solving the Problem of Project Portfolio Selection Based on Project Scheduling using Two-Level NSGAII
, M.Sc. Thesis Sharif University of Technology ; Shadrokh, Shahram (Supervisor)
Abstract
This project aims to study a situation in which several projects must be selected. The decision makers should select a subset of these projects taking into account the limitation of resources and scheduling. Project selection models generally do not consider schedule of project activities as part of selection process. On the other hand, except the cases where only one project is under process in each period, prioritizing the selected projects is not optimal not considering their scheduling. Projects scheduling in project activities level may increase the complexity of decision making for portfolio selection and expand the area of search for selection of projects portfolio. Therefore, all the...
VirSense: A novel haptic device with fixed-base motors and a gravity compensation system
, Article Industrial Robot ; Vol. 41, Issue. 1 , 2014 , pp. 37-49 ; ISSN: 0143991X ; Nahvi, A ; Yazdani, M ; Moghadam, M. M ; Arbabtafti, M ; Norouzi, M ; Sharif University of Technology
Abstract
Purpose - This paper aims to present the design and implementation of VirSense, a novel six-DOF haptic interface system, with an emphasis on its gravity compensation and fixed-base motors. Design/methodology/approach - In this paper, the design and manufacture of the VirSense robot and its comparison with the existing haptic devices are presented. The kinematic analysis of the robot, design of the components, and manufacturing of the robot are explained as well. Findings - The proposed system is employed to generate a Virtual Sense (VirSense) with fixed-base motors and a spring compensation system for counterbalancing the torques generated by the weight of the links. The fixed bases of the...
A subsampling-predictor associated approach for fast global motion estimation
, Article Scientia Iranica ; Volume 19, Issue 6 , December , 2012 , Pages 1746-1753 ; 10263098 (ISSN) ; Talebi, S ; Salehinejad, H ; Sharif University of Technology
2012
Abstract
Global Motion Estimation (GME) has many important roles in numerous applications, such as video compression, image stabilization, video-object segmentation, and etc. One well-known GME method is the gradient-based technique. This method uses optimization techniques, like the Levenberg-Marquardt algorithm, to minimize estimation error. Such algorithms require an initial value for the initializing step. In this paper, we propose a simple and reliable GME structure with a new predictor. This structure uses a three-step search and a predictor for the initializing step. It is also incorporated with a fast GME method that uses pixel subsampling. This incorporation reduces the computational...
Digital video stabilization using radon transform
, Article 2012 International Conference on Digital Image Computing Techniques and Applications, DICTA 2012, 3 December 2012 through 5 December 2012 ; December , 2012 ; 9781467321815 (ISBN) ; Bagheri Khaligh, A ; Hassanpour, R ; Sharif University of Technology
2012
Abstract
Digital video stabilization is a category of techniques used to reduce the impact of unintentional camera motion such as jitter, jiggle, and other unsteady motions. These unintentional shakings degrade visual quality of videos and reduce the performance of subsequent processes such as video compression. Digital video stabilization which is performed by post processing the acquired frames, suffers from inaccuracy of motion estimation which is mostly due to the local motions of internal moving objects included in videos, and long processing time which prohibits them from being used in real time applications. In this paper we propose a fast and accurate transform based motion estimation method...
Face recognition under varying illumination based on histogram equalized processed images
, Article ISPA 2011 - 7th International Symposium on Image and Signal Processing and Analysis ; 2011 , Pages 349-354 ; 9789531841597 (ISBN) ; Jamzad, M ; European Association for Signal Processing (EURASIP); IEEE Signal Processing Society; IEEE Region 8; IEEE Croatia Section; IEEE Croatia Section Signal Processing Chapter ; Sharif University of Technology
Abstract
This paper proposes an enhanced illumination compensation algorithm, which can compensate for the uneven illuminations on human faces and reconstruct face images in normal lighting conditions. To detect the illumination category, based on 65 categories in YaleB database, the images processed using Block-based Histogram Equalization (BHE) is compared with the original face image processed using histogram equalization (HE). Based on the identified illumination category, a quadratic model is used to reconstruct an image that will visually be under normal illumination. In order to avoid the effect of light source intensity on face images, we used HE method. Experimental results show that, by...
Current-Transformer Saturation Compensation for Transformer Differential Relays
, Article IEEE Transactions on Power Delivery ; Volume 30, Issue 5 , 2015 , Pages 2293-2302 ; 08858977 (ISSN) ; Vakilian, M ; Sanaye-Pasand, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Current-transformer (CT) saturation threatens accurate discrimination between internal fault current and magnetizing inrush current of a transformer and endangers the proper operation of a differential relay. Thus, compensation of CT saturation could substantially improve the performance and security of transformer differential relays. So far, almost all of the technical literature in this field has focused exclusively on fault current compensation. However, this paper proposes an efficient compensation algorithm to reconstruct the fault and inrush currents which are distorted by CT saturation. Some of the attractive features of the proposed method are its accuracy, fast response time,...
A model-based fuzzy controller using the parallel distributed compensation method for quadrotor attitude stabilization
, Article 2013 21st Iranian Conference on Electrical Engineering, ICEE 2013 ; Pages 1-6 , 2013 , 14-16 May ; 9781467356343 (ISBN) ; Shouraki, S. B ; Sharif University of Technology
Abstract
In this paper, a model-based fuzzy controller for attitude stabilization of a Quadrotor is proposed. To achieve this purpose first a Takagi-Sugeno fuzzy model for Quadrotor which is obtained from dynamic model is presented. Parallel Distributed Compensation (PDC) technique is utilized to design a state feedback controller. The purpose of control is to stabilize the Quadrotor while taking into account performance specifications such as decay rate and constraint on the input. Both of these conditions can be represented in term of linear matrix inequalities (LMIs). By simultaneously solving these LMIs a stabilizing fuzzy controller that achieves desired speed of response and small control...
Approximateml estimator for compensation of timing mismatch and jitter noise in Ti-ADCS
, Article European Signal Processing Conference, 28 August 2016 through 2 September 2016 ; Volume 2016-November , 2016 , Pages 2360-2364 ; 22195491 (ISSN) ; 9780992862657 (ISBN) ; Akhaee, M. A ; Amini, A ; Sharif University of Technology
European Signal Processing Conference, EUSIPCO
2016
Abstract
Time-interleaved analog to digital converters (TI-ADC) offer high sampling rates by passing the input signal through C parallel low-rate ADCs. We can achieve C-times the sampling rate of a single ADC if all the shifts between the channels are identical. In practice, however, it is not possible to avoid mismatch among shifts. Besides, the samples are also subject to jitter noise. In this paper, we propose a blind method to mitigate the joint effects of sampling jitter and shift mismatch in the TI-ADC structure. We assume the input signal to be bandlimited and incorporate the jitter via a stochastic model. Next, we derive an approximate model based on a first-order Taylor series and use an...
Adaptive delay compensator for the robust Wide-Area damping controller design
, Article IEEE Transactions on Power Systems ; Volume 31, Issue 6 , 2016 , Pages 4966-4976 ; 08858950 (ISSN) ; Ranjbar, A. M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
This paper presents an adaptive delay compensator (ADC) on the basis of the latest development in wide-area measurement system (WAMS) to cater to varying latencies. The proposed compensator can effectively reciprocate the phase deviation resulting from varying delays to improve the performance of central wide-area damping controller (WADC). The greatest challenge to continuous delay compensation is the uncertainty regarding the inherent robustness of the central controller. The proposed technique provides an opportunity to epitomize the uncertainty retrieved from phase compensated delay. Next, taking the uncertainty into consideration, the mixed H2H∞ synthesis technique is adopted for the...
Multihypothesis compressed video sensing technique
, Article IEEE Transactions on Circuits and Systems for Video Technology ; Volume 26, Issue 4 , 2016 , Pages 627-635 ; 10518215 (ISSN) ; Karimi, M ; Marvasti, F ; Sharif University of Technology
Abstract
In this paper, we present a compressive sampling and multihypothesis (MH) reconstruction strategy for video sequences that has a rather simple encoder, while the decoding system is not that complex. We introduce a convex cost function that incorporates the MH technique with the sparsity constraint and the Tikhonov regularization. Consequently, we derive a new iterative algorithm based on these criteria. This algorithm surpasses its counterparts (Elasticnet and Tikhonov) in recovery performance. Besides, it is computationally much faster than Elasticnet and comparable with Tikhonov. Our extensive simulation results confirm these claims
Current-Transformer saturation prevention using a controlled voltage-source compensator
, Article IEEE Transactions on Power Delivery ; Volume 32, Issue 2 , 2017 , Pages 1039-1048 ; 08858977 (ISSN) ; Vakilian, M ; Sanaye Pasand, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
Current-transformer (CT) saturation causes severe distortion in the measured current waveform which may lead to maloperation of the protective devices. This paper proposes a low-cost, power-electronic device to prevent the CT from saturation. The proposed compensator is inserted in series with the relay in the CT secondary circuit and acts as a controlled voltage source (CVS). The proposed CVS generates a time-varying voltage to cancel the voltage developed across the CT burden; therefore, the CT magnetic flux remains almost constant and undistorted during the power system transients. It will be shown that this device can precisely compensate fault current, inrush current, and other probable...
Hierarchical Enhancement of Optical Coherence Tomography Images
, Article 24th Iranian Conference on Biomedical Engineering and 2017 2nd International Iranian Conference on Biomedical Engineering, ICBME 2017, 30 November 2017 through 1 December 2017 ; 2018 ; 9781538636091 (ISBN) ; Fatemizadeh, E ; Nasiri Avanaki, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Optical coherence tomography (OCT) is a noninvasive imaging modality that provides cross-sectional images from microstructures of tissues. This optical imaging system works based on Michelson interferometry principle and has intermediate resolution and penetration depth which makes it appropriate for imaging thin tissues such as skin and eye. OCT images suffer from three main artifacts that make images difficult to be analyzed. The first one is small grainy structures called speckle which degrade image quality and decreases axial and lateral resolution. The second one is light intensity attenuation which is a function of depth. It happens because of absorbing and scattering nature of tissue...
Optimal reactive power planning in active distribution systems for steady-state and transient characteristics improvement
, Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 503-508 ; 9781728115085 (ISBN) ; Mirnezhad, H ; Parniani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Numerous operational issues including voltage deviation and instability arise in distribution networks with insufficient reactive support. Static issues have been widely studied for years, and some dynamic ones are recently gaining attention due to the proliferation of distributed generation (DG). In this paper, a two-step reactive compensation planning procedure is proposed to address these challenges. In the first step, passive compensators are optimally sited and sized using a metaheuristic algorithm in order to improve steady-state indices including power efficiency, voltage profile, and static voltage stability. In the second step, a static synchronous compensator (Statcom) is located...
Analysis of degree of polarization as a control signal in PMD compensation systems aided by polarization scrambling
, Article Journal of Lightwave Technology ; Volume 26, Issue 16 , 15 August , 2008 , Pages 2865-2872 ; 07338724 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
2008
Abstract
The performance of degree of polarization (DOP) is investigated as a control signal in polarization-mode dispersion (PMD) compensation systems aided by polarization scrambling. The relation between the input and output polarization states of a signal propagating through a polarization scrambler and a PMD-induced optical fiber is described by a 3 × 3 Stokes transfer matrix. The average DOP of the output signal over a period of polarization scrambling is derived as an alternative to the conventional DOP-based control signal, i.e., minimum DOP. In the presence of first- and all-order PMDs, the performance of the average and minimum DOPs in monitoring of differential group delay (DGD) for...
Spectral subtraction in likelihood-maximizing framework for robust speech recognition
, Article INTERSPEECH 2008 - 9th Annual Conference of the International Speech Communication Association, Brisbane, QLD, 22 September 2008 through 26 September 2008 ; December , 2008 , Pages 980-983 ; 19909772 (ISSN) ; Sameti, H ; Safayani, M ; Sharif University of Technology
2008
Abstract
Spectral Subtraction (SS), as a speech enhancement technique, originally designed for improving quality of speech signal judged by human listeners. it usually improve the quality and intelligibility of speech signals, while the speech recognition systems need compensation techniques capable of reducing the mismatch between the noisy speech features and the clean models. This paper proposes a novel approach for solving this problem by considering the SS and the speech recognizer as two interconnected components, sharing the common goal of improved speech recognition accuracy. The experimental evaluations on a real recorded database and the TIMIT database show that the proposed method can...
Power system stability improvement using self-tuning fuzzy logic controlled STATCOM
, Article EUROCON 2007 - The International Conference on Computer as a Tool, Warsaw, 9 September 2007 through 12 September 2007 ; December , 2007 , Pages 1444-1449 ; 142440813X (ISBN); 9781424408139 (ISBN) ; Zolghadri, M. R ; Ehsan, M ; Sharif University of Technology
2007
Abstract
This paper presents the application of a fuzzy logic controlled Static Compensator (STATCOM) to improve stability of power system. The nonlinear fuzzy logic controller is used to overcome the problems generated by different uncertainties exist in power systems. Different input variables are used to design the controller. Parameters of the proposed controller are adjusted by means of Neural Network techniques to improve performance of the system. Proposed controller is implemented on a single machine infinite bus system to confirm the performance of the controller through simulation results
Reliability Assessment of DSSC devices and Optimal Placement of them with the aim of Enhancing Power System Loadability and Reliability
, M.Sc. Thesis Sharif University of Technology ; Fotuhi-Firuzabad, Mahmoud (Supervisor)
Abstract
One of the important problems in fulfilling the consumers' power demand that has been especially intensified after restructuring is transmission line congestion. To solve this problem, either new transmission lines should be constructed or the existing transmission lines should be better utilized. Construction of new transmission lines is both expensive and time consuming. Therefore, it is usually better to enhance the utilization of the existing transmission assets. FACTS devices have been introduced over the past decades to enhance power systems operation. However, wide scale deployment of them has not occurred yet due to their high initial investment cost and some other problems. In order...
Analysis and Design of a High Speed Embedded SRAM
, M.Sc. Thesis Sharif University of Technology ; Sharifkhani, Mohammad (Supervisor)
Abstract
SRAM has a very wide application in different platforms including Cache Memory in Microcontrollers, etc. also SRAM is the first candidate for memory usage in every application needing High speed or static memory circuits. SRAM Cells are constructed by Minimum size transistors in each technology node and usually the newest technology nodes are used for building SRAM blocks for accommodating maximum number of SRAM Cells in a specific area. Going through smaller technology nodes, Leakage current and Process variations problem, creates serious difficulties in designing Low Power or High speed SRAM Memories and many academic and industrial works are done wishing for improvement in SRAM power...