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Showing 6 results for Amiri

M. Alaee, M. Sepahvand, R. Amiri, M. Firoozmand,
Volume 6, Issue 3 (September 2010)

In order to detect targets upon sea surface or near it, marine radars should be capable of distinguishing signals of target reflections from the sea clutter. Our proposed method in this paper relates to detection of dissimilar marine targets in an inhomogeneous environment with clutter and non-stationary noises, and is based on adaptive thresholding determination methods. The variance and the mean values of the noise level have been estimated in this paper, based on non-stationary, statistical methods and thresholding has been carried out using the suggested two-pole recursive filter. Making the rate of false alarm constant, the concerned threshold resolves the hypothesis of existence or absence of the target signal. Performance of the mentioned algorithm has been compared with the well-known conventional method as CA-CFAR in terms of decreasing the losses and increasing calculation speed. The algorithm provided for detection of signal has been implemented as a part of signal-processing algorithms of some practical marine radar. The results obtained from the algorithm performance in a real environment indicate appropriate workability of this method in heterogeneous environment and non-stationary interference.
M. Piry, M. Khanjani Moaf, P. Amiri,
Volume 10, Issue 1 (March 2014)

Class-AB circuits, which are able to deal with currents several orders of magnitude larger than their quiescent current, are good candidates for low-power and high slew-rate analog design. This paper presents a novel topology of a class AB flipped voltage follower (FVF) that has better slew rate and the same power consumption as the conventional class-AB FVF buffer previously presented in literature. It is thus suitable for low-voltage and low-power stages requiring low bias currents. These buffers have been simulated using 0.5µm CMOS Technology models provided by IBM. The buffer consumes 20µA from a 0.9V supply and has a bandwidth of 50MHz with a 18pF load. It has a slew rate of 9.8V/µs and power consumption of 42µw
A. Amiri, S. Mirzakuchaki,
Volume 16, Issue 3 (September 2020)

Watermarking has increased dramatically in recent years in the Internet and digital media. Watermarking is one of the powerful tools to protect copyright. Local image features have been widely used in watermarking techniques based on feature points. In various papers, the invariance feature has been used to obtain the robustness against attacks. The purpose of this research was based on local feature-based stability as the second-generation of watermarking due to invariance feature to achieve robustness against attacks. In the proposed algorithm, initially, the points were identified by the proposed function in the extraction and Harris and Surf algorithms. Then, an optimal selection process, formulated in the form of a Knapsack problem. That the Knapsack problem algorithm selects non-overlapping areas as they are more robust to embed watermark bits. The results are compared with each of the mentioned feature extraction algorithms and finally, we use the OPAP algorithm to increase the amount of PSNR. The evaluation of the results is based on most of the StirMark criterion.

F. Amiri, M. H. Moradi,
Volume 17, Issue 4 (December 2021)

In this paper, a coordinated control method for LFC and SMES systems based on a new robust controller is designed. The proposed controller is used to compensate for frequency deviations related to the power system, to prevent excessive power generation in conventional generators during load disturbances, and to reduce power fluctuations from wind power plants. The new robust controller does not require the measurement of all the power system states and it only uses the output feedback. It also has a higher degree of freedom than the conventional robust controllers (conventional output feedback) and thus it helps improve the system control. The proposed control method is highly robust against load and distributed generation resources (wind turbine) disturbances and it is also robust against the uncertainty of the power system parameters. The proposed method is compared under several scenarios with the coordinated control method for LFC and SMES systems based on Moth Swarm Algorithm-optimized PID controller, the LFC system based on Moth Swarm Algorithm-optimized PID controller with SMES, the coordinated control method for LFC and SMES systems based on Robust Model Predictive Control, and the LFC system based on optimized PID controller without SMES and it puts on satisfactory performance. The simulation was performed in MATLAB.

M. Kamarzarrin, M. H. Refan, P. Amiri, A. Dameshghi,
Volume 18, Issue 2 (June 2022)

One of the major faults in Doubly-Fed Induction Generator (DFIG) is the Inter-Turn Short Circuit (ITSC) fault. This fault leads to an asymmetry between phases and causes problems to the normal state between current lines. Faults diagnosis from non-stationary signals for the Wind Turbine (WT) is difficult. Therefore, the strategy of fault diagnosis must be robust against instability. In this paper, a new intelligent strategy based on multi-level fusion is proposed for diagnosis of DFIG inter-turn stator winding fault. Firstly, to overcome the non-stationary nature of the vibration signals of the WT, empirical mode decomposition (EMD) method is performed in time-frequency domains to extract best fault features from information power sensor and information current sensor. Moreover, a feature evaluation technique is used for the input of the classifier to choose the best subset features. Secondly, Least Squares Wavelet Support Vector Machines (LS-WSVM) classifier is trained to classify fault types based on feature level fusion (FLF) from different sensors. The main parameters of SVM and the kernel function are optimized by Genetic Algorithm (GA). Finally, Dempster-Shafer evidential reasoning (DSER) is used for fusing the GA-LS-WSVM results based on decision level fusion (DLF) of individual classifiers. In order to evaluate the proposed strategy, a DFIG WT test rig is developed. The experimental results show the efficiency of the proposed structure compared to other ITSC fault diagnosis methods. The results show that the classification accuracy of DSER-GA-LS-WSVM is 98.27%.

F. Tootoonchian, M. Amiri,
Volume 19, Issue 1 (March 2023)

Multi-Speed resolvers are desirable position sensors for high performance closed-loop control of inverter driven machines due to their high accuracy. However, developing a winding with high number of poles with limited number of slots is a main challenge in achieving multi-speed function. Therefore, in this paper different winding configuration are proposed to achieve 5-X performance of a disk type wound-rotor resolver. Then, the best winding is chosen for experimental verification. In addition to the accuracy of the sensor, the optimal winding selection index is defined considering copper usage, number of winding layers (overlapping or non-overlapping configurations), the number of turns for each coil of the winding (variable or constant turn configurations), and the amplitude of the fundamental harmonic. An objective function is defined involving all the mentioned indices with different weights determined based on the importance of each index. Finally, a prototype of the sensor with the best winding is built and tested. The experimental measurements verify the results of the simulations that are obtained using 3-D time setting finite element analysis.

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© 2022 by the authors. Licensee IUST, Tehran, Iran. This is an open access journal distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license.