AUT Journal of Electrical Engineering
https://eej.aut.ac.ir/
AUT Journal of Electrical Engineeringendaily1Wed, 01 Mar 2023 00:00:00 +0330Wed, 01 Mar 2023 00:00:00 +0330A Wideband Transmitarray Antenna Design Based on the Transmission Characteristic of the UnitCell
https://eej.aut.ac.ir/article_4987.html
In this paper, a procedure is proposed to design a wideband transmitarray upon a specified frequency band. In this way, the phase control parameter of a unit cell is adjusted in a suggested range, ensuring linear phase change and low transmission loss over the band. The unit cell is designed for a range of phase control parameters (e.g., slot length in a CSRR), in which a 360&deg; phase variation is provided. Part of this range is applied for the central elements of TA, in which the maximum overlapped passband (for different values of phase control parameter) around the desired frequency is to be achieved. In this way, a scenario for the phase specification of the array elements would be obtained. This range is specially applied for the central elements of the array, which are in exposure to feed peak power. As a proof of this concept, a 14&times;14 element transmitarray is designed and fabricated based on a back-to[1]back square Complementary Split-Ring Resonator (CSRR). Measurement results indicate maximum gain, 1-dB bandwidth, and aperture efficiency of 24.6 dB, 18.4%, and 53% respectively, at the center frequency of 11.5GHz. At the end of the paper, a comparison between the proposed TA and the previous ones is provided.Gradient-Controlled Gaussian Kernel for Image Inpainting
https://eej.aut.ac.ir/article_4873.html
Image inpainting is the process of filling in damaged or missing regions in an image by using information from known regions or known pixels of the image. One of the most important techniques for inpainting is convolution-based methods, in which a kernel is convolved with the damaged image iteratively. Convolution based algorithms are very quick, but they don&rsquo;t have good results in structures and textural regions and result in blurring. The kernel size in the convolution-based algorithm is a critical parameter. The large size results in edge blurring, and if the kernel size is small, the information may not be sufficient for reconstruction. In this paper, a novel convolution-based algorithm is proposed that uses known gradient of the pixels to construct a convolution mask. In this algorithm, the kernel size is controlled by the gradient of the image in the known regions. The algorithm computes the weighted sum of the known pixels in a neighborhood around a damaged pixel and replaces the value in the place of that damaged pixel. The proposed algorithm is fast and results in good edges and smooth regions reconstruction. It is an iterative algorithm and its implementation is very simple. Experimental results show the effectiveness of our algorithm.Retracted Article: "A Multi-Stage TIA based on Cascoded-Inverter Structures for Low-power Applications"
https://eej.aut.ac.ir/article_4724.html
This article discusses a multi-stage transimpedance amplifier (known as TIA), which is based on three stages of a modified inverter structure. The traditional inverter structures&rsquo; performances are improved adding two cascoded transistors. This new structure benefits from elimination of the Miller-capacitances in comparison with the traditional inverters, which can provide higher speed and wider frequency bandwidth. Manipulating the trade-offs among bandwidth, gain and power consumption beside using Gm/ID technique, this paper introduces a low-power transimpedance amplifier for high-bit rates in optical communication receiver systems. Moreover, active types of inductors are also used to lesson the occupied area and increase the frequency bandwidth. Transferring poles of the improved circuit to higher frequencies means less required DC current for a fixed bandwidth range, which results in low-power characteristic. The proposed circuit is simulated using 90nm CMOS technology parameters. Results for frequency response show the transimpedance gain of 42.3 dBâ„¦ and the bandwidth of 3.47 GHz. Moreover, the circuit consumes 2.7mW using 1V supply, which is relatively close to the targeted 2.5mW power, using gm/ID. Other required simulations such as eye diagram, Monte Carlo, temperature and VDD variations, post layout simulation beside its mathematical equations are also added to manuscript to justify ts performance.Design Procedure for a Novel LMDS Base Station Reflectarray Antenna
https://eej.aut.ac.ir/article_4903.html
A Reflectarray Antenna is designed to operate at X-band as a Local Multipoint Distribution Service (LMDS) base station antenna. It is a center-fed single layer reflectarray consisting of 23&times;27 elements. The unit cell of the reflectarray has linear polarization with more than 400&deg; linear phase shift and its geometrical parameters have been optimized to achieve wide bandwidth and low cross polarization (XP) level for the reflectarray. An iterative design procedure, that is valid for obtaining any arbitrary pattern, has been implemented to achieve the specified radiation pattern over a desired frequency range. The method has been successfully applied to a LMDS base station antenna, characterized by a sectorial cosecant squared beam in the frequency range of 9.3 GHz - 11.5 GHz. The simulation results are in a good agreement with the design requirements. The antenna has cosecant squared pattern over the bandwidth of 21%, XP level better than -30 dB, and SLL less than -20 dB in both elevation and azimuth planes. The total size of the 23&times;27-element array is 246&times;289 mm2 , and its 1dB gain bandwidth is wider than 19%. The proposed antenna performs significantly better than similar structures and has all the features and standards required for LMDS base station antennaA Fast Fault Location Based on a New Proposed Modern Metaheuristic Optimization Algorithm
https://eej.aut.ac.ir/article_4912.html
Double-circuit power systems are one of the main types of modern transmission lines due to their reliability. Fault location in these transmission lines has always been a potential problem due to the mutual coupling between lines. Accordingly, this paper presents a novel objective function for the fault location using synchronous post-fault measurements of currents and voltages captured by distance protective relays. Moreover, a fast and accurate modern metaheuristic optimization algorithm for this cost function is proposed, which are key parameters to estimate the fault location methods based on optimization algorithms. In this regard, first, the input data (current and voltage signals) were refined using some auxiliary functions such as Fast Fourier transformation (FFT), Decaying Dc Elimination (DDE), and frequency tracking algorithm to accurately extract the fundamental component of the voltage and current signals. Afterwards, the proposed fault location based on the proposed metaheuristic optimization algorithm estimates the fault location using these input signals. The main advantage of the presented algorithm is the parallel estimation processing to improve the convergence speed and the accuracy of the objective function of the fault location, and was applied to various fault types and various operating conditions to validate the performance of the proposed approach. In addition, the performance of the proposed method was compared with different fault location methods. The simulation was implemented in the PSCAD and MATLAB&reg; software. The simulation results show that the novel proposed approach outperforms other fault locations in estimating the fault location.Classifying the Clarity of Questions in CQA Networks: A Topic based Approach
https://eej.aut.ac.ir/article_4927.html
Today, there are various sources of information in different fields that users can refer to. Generally, the presence of a question in users&rsquo; minds leads to reference to these sources of information. Users can search for the answer by entering a few keywords in search engines. They can also ask their questions in more detail in the Community Question Answering (CQA) networks so that experts can give a more comprehensive answer to their questions. To get the proper answer, it is necessary to address all the required details in the question. The questions posted in these networks can be divided into clear and unclear. In this study, an attempt has been made to extract unique features from the questions through various machine learning approaches, which can be used to classify questions. To extract these features, the word vector of each question was created, and then using unsupervised algorithms, the questions with similar word vectors were placed in the same group. Afterwards, repetitive concepts were extracted from each group, and their repetition rate in each question makes its feature vector. Finally, the questions were classified based on the extracted feature vector, using ensemble classification models. The achievement of this study is an efficient classification model along with efficient high-resolution feature extraction for classifying clear and unclear questions in CQA networks. Compared to other baselines and transformer[1]based models on different datasets, the proposed method makes high accuracy results.Control Strategy for Power Sharing in Input-Parallel and Output-Parallel Connected DC-DC Converters
https://eej.aut.ac.ir/article_4932.html
Input-Parallel Output-Parallel DC-DC converters are convenient for high voltage and high current applications. One important goal of this type connection is to power-share and reduce circulating current between the converters. Therefore, control methods for power-sharing between converters should be used when the parameters mismatch. In this paper, a configuration comprising two DC-DC common grounded Z-source converters with Input-Parallel Output-Parallel connections is presented, which common grounded Z-source converter have advantages over similar converters. This study proposes two control strategies: (1) a decentralized inverse-droop control, (2) a general control strategy. Inverse-droop control is a simple method and does not need any communication between parallel converters. In the general control strategy, each converter is self-contained, and no external controller is required for achieving input/ Output Current Sharing, and a few wires are needed to create the entire system. The simulation results of an Input-Parallel Output-Parallel system comprising two common grounded Z-source converters are evaluated for investigating effectiveness of general control and inverse-droop control. It reported performance of the general control method to be better than the decentralized inverse-droop control method, which enhances the stability and dynamic characteristics of the system. The validity of the two control strategies has been studied through MATLAB simulation and the results were satisfactory.The Effectiveness of Non-Ionizing Radiation Protective Clothing: A Computational Study
https://eej.aut.ac.ir/article_4950.html
Exposure protective clothing has been suggested as a protection against RF and microwave electromagnetic fields, especially for pregnant women. These clothings are usually made of metal-woven fabrics. In this article, we use computer simulation methods with a homogeneous human model and plane wave exposure at different polarizations and wave incidence angles over a wide range of frequencies to inspect if a typical anti-exposure clothing model might fail to reduce the fields inside the body under certain exposure conditions and/or at some frequencies. Indeed, as far as our model and computational study can represent actual conditions, it is found that for waves incident along the body axis (as arises e.g. in the sleeping status against a cell-phone tower) the clothing might not only fail to reduce the penetration of EM fields, but can rather increase the electric field intensity in certain body areas, including the abdominal parts which were intended to be protected during pregnancy. We conclude that more physics-aware designs should be employed for such clothing.Maximizing Economic Host Capacity Related to Distributed Generation, and Improving the Power System Performance
https://eej.aut.ac.ir/article_5040.html
There are numbers of technical limitations that must to be satisfied for the operation of the power systems, and these limitations are related to the power flow of the power system, thus the solar panels cannot inject any unlimited amount of power into the power system. Therefore, the maximum injection power of solar panels is limited to the specific value. This issue is also true for the reactive power produced or consumed by SVCs and solar panels, so the maximum injected power of photovoltaic panels must be obtained in such a way that the technical limitations of the power system are maintained. In the current research, a 33 bus radial distribution network has been considered and the goal is to maximize the injection power of photovoltaic panels, minimize the network power losses, by reconfiguring in this type of the network and establishing effective coordination between the control devices, including the output reactive power of photovoltaic panels and the fire angle of the SVC and graph of the power system. The bus voltage should be within the allowed range, and the cost of purchasing electricity from the upstream network should be minimized. The results of the simulation on the 33 bus radial network confirm the validity of the above claims.Assistive Control of a Hip Exoskeleton Robot, using a DQN-Adjusted Delayed Output Feedback Method
https://eej.aut.ac.ir/article_4969.html
A major challenge in the development of an assistive exoskeleton robot is to design appropriate control algorithms. These algorithms should be trajectory-independent and require a minimum number of sensors to work in any intended motion and to be easily implementable. As a simple assistive strategy with all promising features, Delayed Output Feedback Control (DOFC) is shown to be effective in assisting the wearers in different types of motion. In this method, the assistive torques are defined in proportion to delayed feedback from the angle difference between the two legs. The authors have recently suggested an intelligent version of DOFC, in which a Deep Q-Network (DQN) was used to adjust the feedback delay according to the speed of the motion. Simulation studies were used to investigate the idea. By conducting some real-world experiments, the present paper extends the results to practical conditions. The provided results clearly verify that if the time delay is adjusted according to the walking speed, the DOFC method can effectively help the users in their motions of any speed. The results also indicated that a fixed or an inappropriate value of the delay may result in resistance against the user motion.GPR of Multiple Vertical Rods under Lightning Strokes Considering Ionization, Dispersion, and Non-Homogeneity of Lossy Soils
https://eej.aut.ac.ir/article_4978.html
In this paper, the effects of ionization and dispersion of a lossy soil on the Grounding Potential Rise (GPR) of buried multiple vertical rods under lightning return strokes are simultaneously studied. In all studies, an efficient modeling method, called improved Multiconductor Transmission Line, is adopted. In the case of a single rod, it is shown that the simultaneous occurrence of soil ionization and dispersion causes further reduction in the value of GPR as compared to the case where each phenomenon takes place separately. The amount of reduction is further accentuated when treating highly resistive soils and fast-fronted lightning currents. In the case of multiple rods, however, the value of GPR in both ionized and dispersed soil lies between those of the only-ionized and only-dispersive soils. Besides, the sensitivity analysis of the non-homogeneity effect in ionized and dispersive soils provides a comprehensive platform to study the soil dependence of the GPR of buried rods in a multi[1]layer soil. Finally, closed-form expressions are proposed that can accurately predict the value of GPR for both single and multiple rods buried in a dispersive and ionized lossy soil when subjected to a lightning current waveform.Reactive Power Management of PV Systems by Distributed Cooperative Control in Low Voltage Distribution Networks
https://eej.aut.ac.ir/article_4992.html
A distributed control strategy is proposed to enhance voltage regulation and reactive power sharing in Low Voltage (LV) distribution networks with high penetration of Photovoltaic (PV) systems. This paper investigates the disadvantages of the available methods that their aims are modifying the voltage profile levels of buses and managing the reactive power of PV inverters. Next, through the proposed method, PV systems reduce the deviation of voltage profile by absorbing or injecting reactive power. This paper eliminates the disadvantages of the available control method by the combination of distributed and local control approaches. Indeed, a local droop characteristic determines the reactive power ratio of the worst bus voltage deviation at a critical bus. Afterwards, the distributed control coordinates all PV systems to operate according to the PV system that locates at the critical bus. In addition, the proposed technique prevents PV systems from active power curtailment and manages reactive power sharing among PVs based on their reactive power ratings. A radial LV distribution system with seven PV systems is presented to analyze the proposed procedure. Simulation consequences are demonstrated to confirm the effectiveness of the control method for decreasing voltage deviation and precise reactive power sharing in the distribution network with PV systems.Dense Stereo Matching Based on the Directional Local Binary Pattern
https://eej.aut.ac.ir/article_5012.html
New applications such as 3D graphics, 3D displays, and image-based modeling have made stereo vision an active research area in recent years. In dense disparity map estimation, which is a basic problem in stereo vision, using two left and right images taken from a scene from two different positions, the disparity of each pixel of the reference image is determined (meaning determining each pixel with how displacement is appeared in the other image). Based on the disparity value, the depth of each pixel in scene is simply determined. For dense disparity map estimation, local stereo matching methods are simpler and faster than global methods, and therefore suitable for real time applications. In these methods, defining proper window which aggregate intensity pattern as well as keeping disparity consistency in all the window area, is an important challenge. To overcome this challenge, the idea of directional multiple window has been proposed in the previous researches. On the other hand, local binary patterns have considerable success in pattern recognition applications, while computationally simple. Therefore, the idea of using local binary pattern in a directional multiple window arrangement is proposed for dense stereo matching in this paper. Experimental results on standard stereo images show the better performance of the proposed method with respect to other proposed binary descriptorsHigh-Resolution Rotor Fault Diagnosis of Wound Rotor Induction Machine Based on Stator Current Signature analyse
https://eej.aut.ac.ir/article_5067.html
Wound rotor induction machine (WRIM) has been extensively used in different applications such as medium-power wind turbine and traction systems. Since, these machines works under harsh and difficult conditions, condition monitoring of such system are crucial. Different electrical and mechanical signatures of machines were used for electrical and mechanical fault detection in electrical machines such as vibration, acoustic emission, stray flux and stator current signature. In recent years, stator current signature analysis due to simplicity, cost-effectiveness and availability has been considered for fault detection process in comparison with pervious conventional methods such as acoustic and vibration. In this paper, high-resolution technique based on chirp-Z transform is used for rotor asymmetry fault (RAF) detection in induction machines through stator current signature analysis. In this regard, Teager-Kaiser energy operator (TKEO) technique for demodulation fault characteristic frequency is used as pre-processing stage to avoid leakage of supply frequency. The method has better accuracy due to better spectral resolution and resolvability. Furthermore, computational complexity in the proposed method will be reduced in compare to the pervious conventional ones which have used Fast Fourier transform (FFT). The proposed technique is tested through synthetic and experimental stator current of WRIM in healthy and faulty conditions with different rotational speeds and fault severities. The results show the validity of proposed method in rotor asymmetry fault detection through stator current signature of WRIM.Underwater acoustic signal acquisition based on optical interferometry in shallow water
https://eej.aut.ac.ir/article_5068.html
Here, it is investigated the results of implementation of interferometric optical fiber acoustic sensor based on fiber Bragg grating (FBG). It is investigated the importance of different types of interferometers configurations as Michelson or Mach-Zehnder interferometers on the signal to noise ratio. It is also considered the role of polymer coating on the increasing of signal to noise ratio. The results show, the Michelson interferometer setup using polymer packaging causes increasing signal to noise ratio. This latter configuration is used in a field setup in shallow water for acoustic signal detection in range of 0.5-5 kHz. The goal of this paper is extracting acoustical signal using optical signal via optical sensors and demodulation methods.
Here, it is investigated the results of implementation of interferometric optical fiber acoustic sensor based on fiber Bragg grating (FBG). It is investigated the importance of different types of interferometers configurations as Michelson or Mach-Zehnder interferometers on the signal to noise ratio. It is also considered the role of polymer coating on the increasing of signal to noise ratio. The results show, the Michelson interferometer setup using polymer packaging causes increasing signal to noise ratio. This latter configuration is used in a field setup in shallow water for acoustic signal detection in range of 0.5-5 kHz. The goal of this paper is extracting acoustical signal using optical signal via optical sensors and demodulation methods.Proposing a THz refractive index sensor based on the excitation of SPPs with InSb cylinder
https://eej.aut.ac.ir/article_5076.html
A novel metamaterial absorber sensor has been proposed for refractive index measurement in the range of [1-2] for the THz frequency band. This structure is based on using a plasmonic coaxial resonator which is excited by an InSb cylinder. Surface Plasmon Polaritons (SPPs) are excited on the surface of the InSb cylinder due to an inward plane wave and propagate downward toward the cavity and thru it. Based on the radius and height of the InSb cylinder, the &ldquo;high-absorption&rdquo; and &ldquo;high-quality factor&rdquo; sensing performance is introduced and analyzed. It is shown that nearly 98% absorption can be achieved for all the range of refractive index [1-2] at f = 1.8622 THz and in the case of &ldquo;high-quality factor&rdquo;, absorption reaches nearly 100% for the refractive index range of [1.5-2]. Also, by changing the radius and height of the cavity, absorption can be changed. Furthermore, sensitivity (S), quality factor (Q-factor), and figure of merit (FoM) in the range of 166-672 GHz per refractive index unit (GHz/RIU), 69.1-118.7 and 10.2- 29.7 is achievable, respectively. A wide range of refractive index measurements besides superior sensing performance made this structure a good candidate for sensing applications such as medical and biological or environmental applications.DS4NN: Direct training of deep spiking neural networks with single spike-based temporal coding
https://eej.aut.ac.ir/article_5080.html
Backpropagation is the foremost prevalent and common algorithm for training conventional neural networks with deep construction. Here we propose DS4NN, temporal backpropagation for deep spiking neural networks with one spike per neuron. We consider a convolutional spiking neural network consisting of simple non-leaky integrate-and-fire (IF) neurons, and a form of coding named time-to-first-spike temporal coding in which, neurons are allowed to fire at most once in a specific time interval, which corresponds to simulation duration here. These features together improve the cost and the speed of network computation. We use a surrogate gradient at firing times to solve the non-differentiability of spike times with respect to the membrane potential of spiking neurons, and to prevent the emergence of dead neurons in deep layers, we propose a relative encoding scheme for determining desired firing times. Evaluations on two classification tasks of MNIST and Fashion-MNIST datasets confirm the capability of DS4NN on the deep structure of SNNs. It achieves the accuracy of 99.3% (99.8%) and 91.6% (95.3%) on testing samples (training samples) of respectively MNIST and Fashion-MNIST datasets with the mean required number of 1126 and 1863 spikes in the whole network. This shows that the proposed approach can make fast decisions with low-cost computation and high accuracy.Probabilistic Optimal Planning of Passive Harmonic Filters in Distributed Networks Considering Possible Network Configurations with High Penetration of Non-linear Loads
https://eej.aut.ac.ir/article_5107.html
Nowadays, non-linear loads are being used in distribution systems increasingly. Despite the good features such as low initial construction cost, high efficiency, and controllability, these loads cause harmonic distortions. In previous studies, passive harmonic filters have been proposed to decrease the produced harmonics, and to do so, various techniques have been suggested. However, the probability of daily load change, possible arrangements of distribution grid taking into consideration the filter design requirements and the impact of temperature change in harmonic filter parameters have been neglected in these studies. Therefore, in the current paper, a comprehensive model based on the probabilistic rearrangement of the distribution grid has been presented for the probabilistic planning of passive harmonic filters. In the proposed method, a two-level probabilistic optimization problem has been introduced with the objective of reducing harmonic distortions, voltage profile improvement, and loss, and investment cost reduction. As a result, the optimum placement of filters, the most optimal number and type of filters, and filter design parameters have been determined. The proposed procedure has been applied on the modified 33-bus IEEE network. The simulation results indicate that neglecting grid rearrangement may lead to a violation of power quality limits during some hours of the day. On the other hand, the combination of various network topologies in planning studies, ensures that the total harmonic distortion (THD) level is maintained within the standard range, guaranteeing loss, line density, and filter investment cost reduction.Online Non-Intrusive Efficiency Monitoring of Pumping Systems
https://eej.aut.ac.ir/article_5110.html
Moving toward a sustainable energy future requires improving efficiency of energy systems. The fact that about 22% of the industrial electricity is consumed by induction-motor-driven centrifugal pumps, highlights the importance of continuous monitoring of such systems to assure they are operating at their best-efficiency points. This results in overall reduction of energy consumption and consequently lowers carbon footprint of pumping systems. This paper presents a non-intrusive approach towards estimating the efficiency of the whole motor-pump chain. The motor efficiency is calculated using only motor electrical signals along with the nameplate information. To estimate the pump efficiency, a hybrid method is adopted which uses the pump characteristic curve, impeller speed and affinity laws. Both estimation algorithms are based on electrical signature analysis (ESA) which requires only motor terminal quantities i.e. current and voltage. The proposed methods are tested on laboratory setups and the experimental results show their accuracy in estimating the efficiency of induction-motor-driven pumps. Given the non-intrusive nature of the proposed method, a simple data acquisition system to acquire motor current and voltage signals along with a microprocessor to implement the algorithms discussed here can be integrated into a single affordable board to be used in utilities for continuous efficiency monitoring purposes.A blade-pitch controller for a large wind turbine generator in the presence of time-varying delay and polytopic uncertainty
https://eej.aut.ac.ir/article_5112.html
A pitch-regulated wind turbine has an exclusive pitch activator for every single blade, and it is possible to send various pitch angle demands to each blade. They possess a controller to perform this task, and the problem of delay-dependent robust stability with polytopic type uncertainties of these time-varying delay systems must be resolved. This paper deals with the dynamic output feedback robust stabilization of the large wind turbine generator in the presence of time-varying delay and polytopic uncertainty. Two critical assumptions are considered for the turbine model involving model&#039;s parameters are uncertain, and the blade-pitch control input actuates by a time-varying unknown delay parameter. A set of intervals are considered for the uncertain and delay parameters, which are assumed to be given and known. Then, a novel algorithm is proposed to design a proper controller for this system based on the Lyapunov Krasovskii functional approach. The proposed controller simultaneously compensates for the effects of both delay parameters and uncertain parameters. To validate the results in this study, two simulation examples are proposed considering different turbines to compare the performance of the designed controller with previously designed controllers. The results reveal the superiority of the proposed controller compared to the existing controller.Optimal Energy Management of Microgrids using Quantum Teaching Learning Based Algorithm
https://eej.aut.ac.ir/article_5121.html
The most important challenge in microgrids is the coordination of distributed energy resources (DERs), due to the existence of several DERs with fugacious characteristics. In this paper, a robust frame associated with a quantum version of the Teaching-Learning-Based Optimization (quantum TLBO) algorithm is proposed for the first time to the microgrid optimal energy management problem. Uncertainties in the load and in the output power of renewable energy sources are modeled using robust optimization (RO). The operation cost of the microgrid is considered as an objective function. The problem is formulated as a bi-level minimum-maximum optimization problem and is solved in two levels iteratively. First, by maximizing the operation cost of the microgrid, the worst case for the uncertain parameters is determined using Particle Swarm Optimization (PSO). Then, according to the results obtained in the first level, by minimizing the operation cost of the microgrid, the final optimal solution is obtained using the Quantum TLBO (QTLBO). This approach is applied to a grid-connected microgrid consisting of renewable energy sources, microturbine, fuel cell, and battery system. The obtained simulation results demonstrate that the QTLBO is significantly superior to the TLBO, Differential Evolution, and Real-Coded Genetic Algorithm in terms of both achieving the final optimal solution and convergence speed.Experimental Validation of Adaptive Sliding Mode Fuzzy Controller for an Inertially Stabilized Platform
https://eej.aut.ac.ir/article_5128.html
The adaptive fuzzy control algorithm using the novel membership function was designed to suppress chattering phenomena in the performance of the three-axis Inertially Stabilized Platform (ISP) applied to the stabilization and tracking of the line of sight in optical cameras mounted on a moving boat. The stability of the nonlinear controller was proven through the Lyapunov method. For the theoretical evaluation of the controller performance, a series of numerical simulations were performed. The nonlinear kinematic and dynamic equations of the ISP were derived for this purpose. Due to the coupling between ISP frames, direct implementation of the suggested controller was not feasible. To this end, four simplified assumptions were applied to the ISP design. To evaluate the performance of the proposed control algorithm, both numerical simulation and experimental methods were used on the three-axis ISP, and the results of both methods were compared and validated. Further, the results of the proposed nonlinear control algorithm were compared with the optimal PID linear algorithm. Besides, experimentally obtained angular velocities of a boat were used for the base motion of the ISP in the numerical simulations. Despite the existence of uncertainties in dynamic system modeling, the outcomes of the implementation of the control algorithm and experimental tests indicated that the adaptive fuzzy sliding mode algorithm stabilized the line of sight with acceptable accuracy and improved its performance in suppressing chattering phenomena.Implementation of N-inputs Ternary to Binary Converter with Multipart division technique Based on CNTFET
https://eej.aut.ac.ir/article_5132.html
In this paper, the new structure N&times;M (N-Ternary inputs and M-Binary outputs) Ternary to Binary Converter based on Carbone Nanao Tube Field Effect Transistor is presented. The Carbone Nanao Tube Field Effect Transistor (CNTFET) has especial properties as controlled threshold voltage. The aforementioned advantages related to the multi-level (more specifically Ternary) circuits and systems based on CNTFET technology have encouraged researchers to put more effort on their design and realization in recent years. The Encoder (one input- five outputs), 3&times;1 multiplexer (one input &ndash; one selector-three outputs) and especial Adder blocks (Full Adder and Half Adder) are base blocks that are implemented by transistor level using especial properties of CNTFET transistor. In general, to implement a N-input ternary-to-binary converter, the number of inputs can be divided into two small converters, and also a ternary-to-binary converter can be designed for each input. In this paper, 2&times;4, 3&times;5, 4&times;7 and 5&times;8 Ternary to Binary converters are designed and simulated by Hospice and 32 nano meter technology. The result of simulation is shown that 5&times;8 Ternary to Binary converter has 1.89 &micro;W DC-Power and 52 ps propagation delay. The proposed 5&times;8 TTBC converter is implemented by 365 CNTFET transistors and divided two ternary to binary converters.Well-being Approach of the Power Systems Integrated to the Central Receiver Power Plants
https://eej.aut.ac.ir/article_5133.html
The solar power tower (central receiver power plant) as one type of concentrated solar thermal power systems can be used to generate the electricity in a way similar to the thermal power plants and so, numerous large-scale central receiver power plants have been constructed and connected to the bulk power system to transfer their generated power to the power network. The variation in the solar radiation leads the generated power of these power plants changes, too. Thus, the integration of these large-scale solar power towers to the power system results in the some challenges that must be addressed. To study the effect of solar power towers on the power system, new techniques must be developed to consider the uncertainty nature of these plants. For this purpose, in this paper, to investigate the impact of central receiver power plants on the operation studies of the power system, the well-being approach is proposed. To consider the solar power towers in the operation studies of the power system, a multi-state model is developed for these plants that both variation in the generated power and failure of composed components are taken into account. To evaluate the effectiveness of the proposed technique, the well-being models of two reliability test system including RBTS and IEEE-RTS are determined and the effect of central receiver power plant on the operation indices such as health state probability, risk, spinning reserve, peak load carrying capability and increase in peak load carrying capability is investigated.A Plasmonic Refractive Index Sensor Using a Water-Based Metamaterial Absorber
https://eej.aut.ac.ir/article_5145.html
A structure for refractive index sensing application in THz band is proposed and analyzed in this paper. This structure is comprised of a golden plasmonic metamaterial absorber in which water is used as a dielectric and a thin topas layer-which does not have a significant effect on the performance of the sensor- is used for the separation of analyte and water. This structure has an absorption of 99.2% at resonance frequency 2.8725 THz. Lateral absorption frequency shift occurs due to variation in the refractive index (RI) of the analyte. This structure can be used for refractive index measurement in the range of 1-1.4 with full-width half maximum (FWHM), sensitivity (S), the figure of merit (FoM), and quality factor (Q-factor) in the ranges of 0.01647 THz, 427-644 GHz per refractive index unit (RIU), 6.3-26.5 and 26.23-175.5, respectively. It is worth mentioning that for a limited refractive index range 1.1 to 1.15, the values of FWHM, Q-factor, and FoM enhance to 0.0053327 THz, 516 and 90, respectively. The simplicity, compactness, ease of fabrication Due to the use of water as a dielectric along with appropriate refractive index sensitivity and FoM help this structure to use in biological , medical and environment sensing applications.Design Optimization of the Multi-layer Switched Reluctance Motor to Minimize Torque Ripple and Maximize Average Torque
https://eej.aut.ac.ir/article_5159.html
Because of high torque ripple of the switched reluctance motor (SRM), a novel design optimization method is introduced in the present paper for the multi-layer switched reluctance motor. Using this design optimization method, torque ripple is reduced significantly and average torque is increased as well. In the proposed method, the significant reduction of torque ripple is derived from variation of both the motor geometric structure and the design/control parameters. The most important design parameters of the SRM that have significant effect on the torque ripple and average torque of the motor are stator/rotor poles arcs. The optimal values of these parameters are determined here using the design of experiments (DOE) algorithm. Having the instantaneous torque waveform of the motor is necessary for accurate calculation of torque ripple. In the present paper, this waveform is predicted using analysis of the motor based on finite element method (FEM). Applying the introduced design optimization method to a typical 8/6 multi-layer SRM, simulation results are presented and effectiveness of the proposed design optimization method is demonstrated. Since the produced average torque of the multi-layer SRM is higher than the conventional type of the SRM (one-layer), the proposed design optimization procedure could be utilized appropriately for construction of a high-power SRM with minimum torque ripple.