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Showing 71 results for Type of Study: Research

Mr Hamed Nosrati, Dr Mousa Shamsi, Mr Motreza Farhid, Dr Mohammad Hossein Sedaaghi,
Volume 1, Issue 1 (9-2013)
Abstract

Wireless Sensors and wireless sensor networks have been used broadly in academic communities. That is owing to increasingly development of small scale equipment in engineering that prepares enormous applications. Numerous researches have been done in order to using of these sensors as well as establishing them as a network and large variety of solutions have been suggested. One heuristic method to modeling wireless sensor networks is distributed adaptive modeling. Processing is done in fully distributed manner at this way. An adaptive network contains a number of nodes those are capable to learn and adapt. Every node exchanges its data with neighbor nodes so as to the network could finally solve an estimation or interference problem. In this paper, at first, the position of distributed adaptive processing will be explained, then we review some proposed strategies for adaptive modeling and after that simulation results will be compared.
En Mohammad Javad Khosrowjerdi, En Jafar Taheri Kalani,
Volume 1, Issue 1 (9-2013)
Abstract

In this paper, the trajectory tracking problem for a wheeled mobile robot in the presence of kinematic and dynamic uncertainties is considered. A nonlinear control approach based on lyapunove stability theory is proposed for this problem. Uncertainties are modeled as lumped disturbances and are estimated by a generalized disturbance observer using Linear Matrix Inequalities(LMI). These estimates are used for control laws design for compensating disturbances. Simulation results show the effectiveness of the proposed method in the presence of uncertainties generated by sliding velocity.
Behzad Mozaffari Tazehkand,
Volume 1, Issue 1 (9-2013)
Abstract

Abstract— In OFDM systems, it is necessary to estimate the channel to overcome the distortion caused by channel fading’s which can be induced by many phenomena such as: delay spread, mobility and Doppler shift. Most of the channel estimation techniques are proposed in frequency domain using the pilot symbols. One of them that is less complicated is least-squares (LS) method which is widely used in channel estimation but it is more sensitive to noise respected to the other reported techniques. In this paper, a new threshold based method using wavelet decomposition will be proposed which is based on an initial LS estimation technique. The reported simulation results show that the proposed method has better performance compared to the other methods such as Lee Method that has been published recently.
Marziyeh Barootkar, Akbar Ghaffarpour,
Volume 1, Issue 1 (9-2013)
Abstract

Recently, Routing in Vehicular Ad hoc Networks (VANETs) has found significant attention due to its unique characteristics such as lack of energy constraints and high-speed vehicles. In addition, since VANET networks are highly dynamic, design of routing algorithms suitable for an urban environment could be extremely challenging. Appropriate algorithms for urban environments should be opportunistic routing (OR) algorithms in which traffic transmission is performed using the store-carry-forward mechanism. Most of the OR algorithms use the flooding mechanism for increasing delivery ratio without considering the overheads of flooding. In this paper, a new algorithm called Reliability-aware Location and History based Opportunistic Routing (RLHOR) is proposed to reduce overhead of message replication . The RLHOR searches for the most reliable route by evaluating the reliability of intermediate links considering their lifetimes, location and direction of intermediate vehicles, and the history of message delivery by intermediate vehicles. Using the ONE simulator, our performance evaluation results show that the RLHOR can operate better than other conventional OR algorithms under different network scenarios. Under sparse networks, the RLHOR not only increases delivery ratio, but also reduces overhead and traffic loss.
Mr Ardashir Mohammadzadeh, Mr Mohammad Mansuri, Prof Mohammad Teshnehlab, Dr Mehdi Aliyari,
Volume 1, Issue 1 (9-2013)
Abstract

This paper proposes direct adaptive fuzzy control with less restriction on control gain for siso nonlinear systems and is presented a simplified type-2 fuzzy system. Adaptation law is derived based on Lyapunuv stability analysis that assures adaptive parameters and tracking error to be bonded. Since in addition to consequent parameters,width and centers of the membership functions are tuned then the estimation error is very small so as to be negligible.Furthermore, the number of membership functions required is seen to be less than that needed with type-1 fuzzy sets. The simulation results that are conducted on inverted pendulum and magnetic levitation systems confirm the efficacy of the proposed scheme. In the presence of noise the reference input is tracked very well and tracking error is very small.
, ,
Volume 1, Issue 1 (9-2013)
Abstract

Flexible AC Transmission Systems (FACTS) controllers with its ability to directly control the power flow can offer great opportunities in modern power system, allowing better and safer operation of transmission network. In this paper, in order to find type, size and location of FACTS devices to install in power network a Dedicated Improved Particle Swarm Optimization (DIPSO) algorithm is proposed for decreasing the overall costs of power generation. Thyristor-Controlled Series Capacitor (TCSC) and Static VAr compensator (SVC) are two types of FACTS devices that have been considered to install in power network. The purpose of this study is reducing the power generation costs with considering different load levels and the costs of FACTS devices. The main bases of this paper are using of Optimal Power Flow (OPF) and DIPSO algorithm. The Net Present Value (NPV) method is used to economic analysis and power losses and maximum possibility load demand are considered to technical analysis of the results.

Ms Safiye Sheikhalishahi, Mr Sajjad Aghasizade Shaarbaf, Dr Mehdi Mirzaei, Dr Rahim Khoshbakhti Saray,
Volume 1, Issue 2 (1-2014)
Abstract

The control strategy in hybrid electric vehicles (HEV) determines the energy management between an internal combustion (IC) engine and an electric machine to generate the power required to drive the vehicle. In this study, the parameters of an electric assist control strategy of HEV, which is used in ADVISOR software, are optimized by minimizing the fuel consumption while maintaining the engine emissions below the Euro3 standard. In this way, a parallel HEV has been simulated in two drive cycles and the optimal parameters of controller are obtained by the genetic algorithm (GA). The simulation results show that by optimizing the control parameters, the fuel consumption decreases while satisfying the Euro3 standards and other constraints in various drive cycles. Also, different values for optimal parameters have been extracted. This indicates that the optimal parameters of the controller are dependent on the drive cycle.
Mr. Majid Hosseinpour, Dr Mustafa Mohamadian, Dr Ali Yazdian Varjani,
Volume 1, Issue 2 (1-2014)
Abstract

In this paper, the performance of wireless operation of four-leg parallel inverters, at the presence of unbalanced nonlinear loads, is investigated. In order to control the parallel inverters, an inner current and external voltage control loops should be designed. In this paper, a proportional controller for the current internal loop as well as a proportional-resonant one for the voltage external loop are investigated and designed to ensure the proper performance of the system at the presence of unbalanced and nonlinear loads. In this paper, droop control and virtual output impedance loops have formed the power sharing control system for the parallel inverters. The proposed system is able to feed balanced, unbalanced, and nonlinear loads and provides an appropriate sinusoidal voltage waveform for loads by accurately sharing power between the parallel inverters. Simulation results verify the accurate and proper performance of the proposed system.
Mr. Mostafa Rezayi, Dr. Hamid Farrokhi,
Volume 1, Issue 2 (1-2014)
Abstract

A new multiobjective power control algorithm is presented in this paper in which power update is accomplished using local information. The algorithm benefits a multiobjective optimization technique the objectives of which are designed in a way to not only minimize the users’ transmit power but also maintain the users’ SIR at an acceptable level, on one hand, and reduce as much possible the SIR fluctuations, on the other hand. The convergence characteristics of the proposed method are investigated both theoretically and with simulations. The results indicates that, compared to other existing power control algorithms, the proposed algorithm has a higher convergence speed while reducing user’s transmit power. Introducing the practical version of the proposed algorithm, it is then compared with two existing algorithms including B-BPSC (FSPC) and MOTDPC. Simulation results show significant improvements in the convergence speed and average consumed power.
Amir Habibzadeh-Sharif, Mohammad Soleimani,
Volume 1, Issue 2 (1-2014)
Abstract

Optical interconnects as appropriate alternatives for electrical interconnects in the computer chips and boards can be realized by CMOS-based integrated silicon photonics. Dielectric slot waveguide, as one of the newest optical waveguide structures, can form the infrastructure of the passive and active components in these integrated circuits. The passive components have the linear behavior. In order to realize the all-optical active components such as laser, amplifier, and modulator we can use the nonlinear effects in the silicon photonics waveguides. On the other hand, Si-nc:SiO2 as a new material, has a stronger nonlinear property than Si. The results of the full-wave analyzes of the slot waveguide in the linear and nonlinear regimes show that the slot region of this waveguide can be filled with the Si-nc:SiO2 and also realize a high optical intensity. Therefore, this waveguide intensifies the nonlinear behaviors by two factors.
Dr Sehraneh Ghaemi, Miss Farnaz Ghanbarpour,
Volume 1, Issue 2 (1-2014)
Abstract

In this paper, a new approach for controller designing of robust output feedback model reference adaptive control with a function of tracking error for a class of continuous linear systems with multiple uncertain time varying state delays is introduced. Proposed controller is not only robust versus of multiple uncertain time delays and external disturbance with uncertain bound but also improve performance of transient and steady state of closed loop system. The stability of closed loop system and error convergence is shown with an appropriate Lyapunov-Krasovskii function. Simulation results show good performance of proposed controller.
,
Volume 2, Issue 1 (6-2014)
Abstract

Blind source separation is the technique that anyone can separate the original signals from their mixtures without any knowledge about the mixing process, but using some statistical properties of original source signals. Independent component analysis is a statistical method expressed as a set of multidimensional observations that are combinations of unknown variables which are assumed to be statistically independent with respect to each other. In this paper we will use the nonlinear autcorrelation function as an object function to separate the source signals from the noisy mixing signals. Also we apply the wavelet transform in our proposed algorithm. Maximization of the object function in wavelet domain using the LMS algorithm will be obtained the coefficients of a linear filter which separate the source signals with high SNR. To calculate the performance of the proposed algorithm, two parameters of Performance Index and Signal to Noise and Interference Ratio will be used. To test the proposed algorithm, we will use Inovation Gaussian signals, Speech signals and ECG signals. Finally level of wavelet decomposition effects will be consider on the obtained results. It will be shown that the proposed algorithm gives better results than the other methods such as NoisyNA method that has been proposed by Shi.
Dr. Esmaeil Najafi Aghdam, Mr. Mohammad Honarparvar,
Volume 2, Issue 1 (6-2014)
Abstract

Abstract:
Askar Azizi, Sirus Bibak, Hamid Nourisola, Mohammadali Badamchizadeh,
Volume 2, Issue 1 (6-2014)
Abstract

Generally nonlinear modelling of aerospace system has uncertainty in model parameters and also in real situation different disturbances are applied to system. In spite of these uncertainties and disturbances, autopilot control system should be guarantee stability and desired performance of system. The conditions such as fast response, low tracking error, system robustness must be considered in autopilot design. In this paper, a new method is suggested to reduce the tracking error and increase system robustness. The proposed method is based on Backstepping approach. To reduce the tracking error, resulted from the simplification of the missile model, a nonlinear disturbance observer is used to estimate the uncertainty and also update the reference signal. In addition nonlinear disturbance observer is used to eliminate output disturbance. The advantage of the proposed method is its complete flexibility and also it can be employ for linear and nonlinear systems
, ,
Volume 2, Issue 1 (6-2014)
Abstract

One of the serious concern of grid connected distributed resources is islanding problem. This condition should be prevented due to several reasons concerning such as personnel and equipment safety. This paper investigated a passive islanding detection method using wavelet transforms analysis. The proposed method is based on Rate of change of Frequency (RoCoF) measurements and processing of this signal with analysis of a Symlets wavelets transform. The presented studies are based on time-domain simulations using MATLAB, and its feasibility is evaluated with an experimental analysis in comparison with the recently reported method based on Daubechies wavelet transform. The experimental system parameters are the same as those of the simulated system. The results evaluation confirm that the proposed islanding detection method succeeds in detecting islanding mode both in the experimental and simulated systems and is superior to the Daubechies wavelet transform based detection method.
, ,
Volume 2, Issue 1 (6-2014)
Abstract

The equal area criterion method is proposed for the power swing detection. Although this method is good for a single machine system, the method cannot distinguish the stable power swing from the unstable one in a multi machine system. In this paper, a novel method for distinguishing the stable power swing from the unstable one is proposed. In the proposed method the network is separated into the critical and noncritical machines. This method is performed by Digsilent software.
Mostafa Faramin, Mohammad Ataei,
Volume 2, Issue 1 (6-2014)
Abstract

The present paper proves chaos phenomenon for a range of parameters in attitude dynamic of a satellite and designs an appropriate nonlinear controller, while ensuring optimal system performance, the controller guarantees control of a chaotic state. As the dynamic equations of a three-axis satellite are defined as a nonlinear non-autonomous system, a technique is offered for calculating the Lyapunov exponents of such systems that may express the system’s chaotic state. Using the technique, the chaotic behavior of a system is proved within a range of parameters. Then a back-stepping sliding mode controller is proposed based on the desired performance and the closed-loop system stability is proved based on the Lyapunov’s theorem. Moreover, converting the system into a compatible form with the conditions of the Melnikov theorem using this analytical method ensures removing chaos phenomenon in the controlled system. Calculating Lyapunov exponents of the closed system confirms this issue. Finally, the simulation results obtained from the proposed controlling actions for different work fields are presented.
Mr Yashar Hashemi, Dr Khalil Valipour, Mr Babak Hashemi,
Volume 2, Issue 2 (1-2015)
Abstract

An approach for assignment of the optimal location and tap changer adjustment related to Flux-Lock type Superconducting Fault Current Limiter with Tap Changer is used in this paper by debating the reduction of fault current flowing from each device and enhancement of reliability varying with customer type in a distribution network connected with Distribution Generation (DG). Three objective functions based on reliability index, reduction of fault current and number of installed MSFCL is systematized and a Nonlinear Time-Varying Evolution (NTVE) based Multi-Objective Particle Swarm Optimization (MOPSO) style is then formed in searching for best location and tuning of tap changer of MSFCL to meet the fitness requirements. A decision-making procedure based on Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is used for finding best compromise solution from the set of Pareto-solutions obtained through MOPSO-NTVE. In a distribution network as Bus 4 of Roy Billinton Test System (RBTS), comparative analysis of the results obtained from application of the Resistive SFCL (RSFCL) and MSFCL is presented. The results show that optimal placement of MSFCL than RSFCL can improve reliability index and fault current reduction index with less number.
Mr. Reza Mojed, Dr. Mehdi Mirzaei,
Volume 2, Issue 2 (1-2015)
Abstract

Obtaining the optimal control low for nonlinear systems is one of the most active subjects in the control theory. Solutions become more complicate in the presence of physical constraints, especially input constrains. In this paper, a new method has been developed to design a constrained nonlinear controller. In this method, the performance index is developed based on the predictive approach. Then, an optimization problem is solved to obtain the optimal control law in the presence of input constraints. Two constrained optimization methods have been used in this paper. The KKT-based method provides an analytical solution for obtaining the control law. The other method is based on the genetic algorithm (GA) which is considered a numerical optimization technique. These methods are implemented on an example and the results are compared
Mr. Saeid Mansouri, Dr. Hossein Ebrahimnezhad,
Volume 2, Issue 2 (1-2015)
Abstract

3D surface compression is a selected method for reduction of required memory and effective triangular mesh data transfer in networks with low bandwidth. In this paper, an improved technique for compression of triangular surfaces is introduced. It is based on centroidal Voronoi tessellation with density function. By choosing appropriate density function with curvature feature and Lloyd relaxation, vertex density in compressed mesh tends toward details in rough surfaces and prevents vertex redundancy and non-necessary vertex concentration in smoother surface areas. In post-processing step, non-linear Nelder-Mead optimization is applied for better vertex localization and reducing compression error in the simplified mesh. Our proposed method is compared with classic and modern techniques in recent studies. Implementation results show improvements in compression and accuracy of our method compared with available techniques.

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سامانه های غیرخطی در مهندسی برق Journal of Nonlinear Systems in Electrical Engineering
نشریه سامانه‌های غیرخطی در مهندسی برق در خصوص اصول اخلاقی انتشار مقاله، از توصیه‌های «کمیته بین‌المللی اخلاق نشر» موسوم به COPE و «منشور و موازین اخلاق پژوهش» مصوب معاونت پژوهش و فناوری وزارت علوم، تحقیقات و فناوری تبعیت می‌کند.
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