Sharif Digital Repository

Reliability modeling, analysis and computation of a Thrust Vector Control System (TVC) is investigated. In this respect, first the TVC subsystems including the jet vanes (JVs), sensors and actuators,... are identified and their pertinent Reliability Block Diagram (RBD) is depicted. Subsequently static reliability of a jet vane is calculated considering both structural and thermal loadings via related verified limit state functions. In addition, a sensitivity analysis is performed that identifies the key JVs design parameters from a reliability point of view. Next, knowing the structural and thermal reliability of the JVs, static reliability of the total TVC system is computed via utility of... 

Reduction of power converters’ cost is one of the most important efforts to improve machines control systems. In this way, some new topologies for power electronic converters have been proposed. Among various topologies, four switch three phase inverter (FSTPI) thanks to the simple circuit, low cost, minimized conduction and switching losses and high reliability has attracted much attention recently. In this thesis, direct torque control (DTC) method is utilized to control of four switch inverter fed induction motor. In this way, in order to decrease flux and torque ripple and achieving constant switching frequency, a new Discrete Space Vector Modulation (DSVM) method have been proposed in... 

The goal of the attitude determination is to determine the orientation of a satellite with respect to a reference frame. For this purpose, gyroscopes are used to measure the satellite’s angular velocity. Also, the attitude sensors such as magnetometers, Sun sensors, Earth sensors or star trackers are employed to collect vector measurements. The aim of the attitude control is to calculate the torque which is needed to be applied to the satellite such that its orientation and angular velocity converge to their desired values. It is usual to determine the attitude of satellite first and then use it in the attitude control algorithms. When multiple independent vector measurements are available,... 

converters, the different configurations for matrix converters are proposed. In this thesis, a one-phase to three-phase matrix converter is used to control in three-phase induction motor. Different control methods are proposed to control the induction motor. The novel control methods include close loop speed and converter output current controls of induction motor are proposed based on SPWM. The structure of indirect matrix converter for the mentioned application also investigated. Moreover, three usual method of control of induction motor: DTC (Direct Torque Control), FOC (Field Oriented Control) and Space Vector Modulation are applied to the single to three- phase matrix converter. Each of... 

In this thesis, maneuverability enhancement of a given twin engine fighter aircraft with integrated thrust-vector and conventional aerodynamic control surfaces havebeen studied. For this purpose a nonlinear 6DOF simulation program base on a near exact mathematical model has been prepared for the aircraft, and then a thrust vectoring system for producing moments about three body axes, like that used in F/A-18, has been added to the simulation. The control method that is employed to control the aircraft in simulation environment is based on Nonlinear Dynamic Inversion (NDI). Finally the Velocity Vector Roll (VVR) maneuver has been considered as an example tostudymaneuverability enhacement. It... 

Traffic density estimation is one of the most challenging problems in Intelligent Transportation Systems. One of the important traffic information that is broadcasted to drivers is Traffic Density information. In many traffic control centers; human operators are responsible for estimating traffic density from captured video data. Increasing traffic cameras and constraint number of operators introduce an updating delay to broadcasted information. So it is important to have an automatic traffic density estimation system. In this thesis, machine vision is used to solve this problem. Supervised Image classification is our approach. In supervised Image classification, images are classified to... 

Objective of Secret Sharing is assigning some random variable which will be called shares, generated based on a random variable called secret, to some participant such that only specific subsets of participants could reconstruct the secret by polling their shares together. Constructing shares as small as possible is desired, hence notions like information ratio and average information ratio have been studied and considered to be a measure of efficiency of secret sharing schemes. In this research contribution vectors of access structures with five participants and graph based access structures with six participants have been studied. Small access structures have been considered shortly after... 

Electric motors used in electrical vehicles are varied, but in light electric vehicles such as electric motors and electric bikes, with limited space, permanent magnet motors due to their high power density and efficiency are very useful. These motors are divided into two types: trapezoidal and sinusoidal due to the waveform of the Back EMF voltage. The trapezoidal type, also known as the brushless DC motor , is more commonly used in light electric vehicles due to the simplicity of the control system and the lower cost. The control system of the BLDC motor is very important in its performance. Providing a controller for these engines that at low cost improves their performance is considered... 

The field of microrobotics has seen tremendous advances in recent years. Potential high impact applications of untethered microrobots such as minimally invasive diagnosis and treatment inside the human body, biological studies or bioengineering, microfluidics, desktop micromanufacturing, and mobile sensor networks for environmental and health monitoring are reported. However, There are significant challenges in microrobotic technology, including energy resources, control systems, reliability and safety, design and manufacturing of micromotors and localization. In this work, overall size scale being micron scale is emphasized where mobile robots able to fit in spaces smaller than a millimeter... 

The matrix converter is an array of controlled bidirectional semi-conductor switches that allows direct ac–ac conversion without an intermediate dc link. This converter has several attractive features that have been investigated in the last two decades. Multilevel converter technology has become increasingly popular in recent years due to high power quality,high-voltage capability, low switching losses and low EMI issues.This paper is concerned with applying multilevel techniques to direct ac–ac power converters and concentrates on developing the concepts of space vector modulation for a multilevel matrix converter. The common-mode voltage produced by a modern power converter has been... 

Control of line of sight (LOS) orientation is a fundamental prerequisite for virtually all dynamic applications in which an optical sensor is used to obtain images. In this research, a 3 DOF parallel mechanism is utilized to build a stable platform for high precision satellite photography. The platform may be designed based on the Stewart platform concept. The stability is obtained by controlling the roll, pitch and yaw of the mechanism. To apply linear control techniques and to use roll-pitch and yaw rates and also their absolute values, an active stable platform is designed. Line Of Sight (LOS) is a position vector from origin of a topocentric-horizontal system to the satellite of... 

Brain is the most complicated organ of body which controls the activity of all other organs. Understanding its function and its language could give us a direct communication pathway for connecting injured motor organ and it could be useful for functional repairing. Neurons are atoms of a vast network that generate the brain signals. Processing these signals would help to translate brain’s language and has three main stages: spike detection from signal, spike sorting, and intention extraction from encoded signal.
In this research, we use a dataset of rat’s extracellular recordings during a time interval in which a rat pressed the liver several times to receive water as an award. Since... 

The purpose of this project is to improve current speaker verification techniques with short utterance using phonetic information extraction. I-vector technique is widely used in speaker verification systems. Different speakers span a subspace of universal acoustic space, which is usually modeled by “Universal Background model”. Speaker-specific subspace depends on the voice of speaker. In state-of-the-art speaker verification systems i-vectors are extracted by a factor analysis technique to represent speaker characteristics. Studies demonstrate that voiced phonemes contain more speaker-specific information than unvoiced. In this thesis we have classified voiced frames in order to exploit... 

The spatial diffusion of house prices has been the subject of research for many years. Most of these studies have found a strong relationship between neighboring regions and a weaker relation between nonneighbors. This study uses changes in real house prices within Tehran at the level of municipality zones to illustrate the ripple effect by using quarterly house price data of Tehran’s twenty municipality zones since 1371 to 1391. It also aims to illustrate the heterogeneity in spatial spillovers of house prices development across space and time. We found that a positive shock in house prices diffuse more rapidly that a negative shock; the time shock will diffuse also have a heavier level... 

On the demand of higher directivity, higher throughput and less interference, phased array systems and MIMO have become attractive to reach these goals. The advantages of phased array systems include the ability to perform electronic beam steering and arbitrary pattern synthesis. Phase shifters and variable gain amplifiers are used to reach these advantages. In this thesis, a ‘’ C‘’ band (4.8 GHz-6.2 GHz) vector-sum phase shifter using HMIC technology for realizing a phased array receiver is designed. This phase shifter can change the signal phase and amplitude. The main blocks of this phase shifter are low-insertion phase and low-noise variable gain amplifier, which consists of current... 

Nowadays, stock index forecasting has become an important issue for decision makers as well as investors, and such a forcasting is increasingly difficult thanks to multifarious impact of factors. In this regard, machine learning approaches can be used to analyze and predict the stock index and its influencing factors. Such an approach not only provides decision makers to make more becoming decision associated with the monetary and financial sectors of the country, but also allows investors to chose more appropriate portfolio (lower risk) by forecast long-term stock.In this study, we intend to better predict the stock index based on the necessity by examining the economic factors affecting... 

Monge’s problem was solved by Brenier in 1990. In general, the problem remained unresolved for a long time. some of its cases were solved by assumptions, but the general case and its analytical solution for the first time by Ian Bernier The French mathematician was introduced. He wrote his famous article Solved this nonlinear problem with technical assumptions. With the help of convex analysis and fundamental theorems in functions with vector values, he proved the existence and unity of this nonlinear problem. Monge’s problem, also known as optimal transport, suggests whether a stable­sized mapping can be done by having two probabilistic spaces and one cost function. (Inverted image of any... 

Lameness in dairy cattle is a crucial welfare issue in dairy industry, and over the years scientists are attempting to present a detection method. In recent years it is attracting more attention to make the identification and discrimination of sounds and lames systematic and automatic. Right now, the most hopeful results have been obtained through the measurement of Ground Reaction Forces (GRF) of hooves, and analysis of load distribution between four legs, which seems applicable for wide use in dairy industry. However, the accuracy, validity, and reliability of discrimination is still far from an acceptable point, that is because of a great lack in understanding quantitative effects of the... 

Prediction is an important issue in many areas. Proper planning for the future requires careful forecasting, so providing accurate methods, especially in the financial field, is invaluable. In this study, the main problem is predicting the price of global gold. Factors for gold prices include oil, gas, silver, soybeans, copper, the s & p500 index, the Dow Jones index, the British and Japanese stock market indices, the dollar index, the multi-currency exchange rate (pound-euro-yuan-yen) with the dollar to The title of the influential factors in this research is considered. The time frame of this research is daily, in other words, the data is collected on a daily basis and the goal is to... 

Let G be a simple graph. An eigenvalue of G, is a main eigenvalue if the corresponding eigenspace has a non-orthogonal eigenvector to the all-one vector j. A signed graph is a graph with a sign to each edge. If in the adjacency matrix of background graph change elements that corresponded by -1, set -1 and in the other elements don’t make any change, then we reach the sign matrix of a signed graph. By an eigenvalue of a signed graph, we mean an eigenvalue of its sign matrix. In this research, we study main eigenvalues of graphs and signed graphs. At first, we present the necessary and sufficient conditions for any graph which has exactly m main eigenvalues. Then, by introducing and creating...