Sharif Digital Repository

In this research a novel intelligent back-stepping control method is developed. This method is robust to sensor noise and external disturbances. In addition, the controller is robust under model uncertainty. This controller does not need precise knowledge of system parameters. This method is based on three methods of: back-stepping control, least squares estimation and a fuzzy compensator. This controller is used to control quadrotor stand witch is like an inverse pendulum. In quadrotor stand modeling, the inverse pendulum effect is considered too, witch is one of the innovations of the research. By doing various simulations, the validity of controller is tested. Also the performance of the... 

In Private Equity funds, the manager (known as general partner) collects funds from the investors (known as limited partners) and invests them over a certain time horizon. Assuming that both parties seek to maximize their interests, a situation arises in which the manager does not consider the best interests of the investors. The manager's compensation package is one of the important parts of corporate governance, which consists of four components: management fee, performance based fees (or carried interest), hurdle rate and proceeds distribution method. In this research, first by conducting a semi-structured interview with 15 experts in the PE ecosystem and publishing a questionnaire, the... 

In this study, I examine the role of board composition and ownership structure and trading days on board compensation of 156 Iranian non-financial public firms. Regarding board composition, I find that board size, CEO-Directorship, and the presence of busy directors positively explain board bonus. Concerning ownership structure, results reveal that outside block-holders and the percentage of individual investors negatively influence on board bonus. Also, trading days is proved to have a positive impact on board bonus. Furthermore, I examine the impact of compensation relating to board composition and ownership structure and trading days (predicted compensation) on the future operating... 

In many industries, including oil and gas industries, power plants, refineries, petrochemicals, steel and cement industries, industrial complexes and consumer industries, there are tanks for storing materials. It is necessary to measure level of products while they are stored in tanks of different sizes. Ultrasonic is one of the non-contact and accurate measurement technologies that can provide a suitable solution for liquid tank monitoring. The purpose of this thesis is to design and build the electronic parts (transmitter and receiver circuits) of an ultrasonic system that is capable of detecting levels at a distance of less than 5 meters with an accuracy of 0.5 % full scale. In this... 

One of the problems in vessels is the marine oscillations that occur due to the collision of sea waves with the vessel. These oscillations in small yachts can cause passengers to seasick upside down and overturn objects in the boat, or in industrial ships can cause problems in the operation of cranes on vessel, and in military vessels can cause errors in targeting weapons and radar systems. The purpose of this research is to design and simulate a robotic compensating table that can actively compensate the vessel fluctuations by using control algorithms in three directions of Roll, Pitch and Heave and create a level that can be used in Medium-sized boats were used to eliminate harmful... 

In this study, a practical approach for robotic beating heart surgery was proposed. This approach eliminates lateral movements of the heart and compensates for normal heart movement by using 1 DOF heart stabilizer and 1 DOF heart compensator simultaneously. It is a compromise between complete fixation of the heart, which damages the heart tissue, on one hand and complex and impractical compensation of the free heart movement on the other. One of the core components of the proposed system is the slave robot, which includes a 1 DOF compensator and a 4 DOF tool holder robot. Based on the selected laparoscopic tool, a modified agile-eye mechanism for activating the wrist was introduced,... 

In cases with excessive anteversion even after adolescence, surgeons have to choose osteotomy surgery to modify this abnormality. This surgery and modifying the anatomical problem does not necessarily lead to modify the patients’ gait cycle abnormalities; the authors’ hypothesis is the probable reason may be the persistence of the implement of the patients’ kinematics compensation mechanism even after the surgery. This mechanism is used to almost correct the gait of those with excessive anteversion. First, by using gait analysis text books, a patient’s gait cycle is analyzed; this analysis is consist of 3DGA with EMG and observational gait. Then, by using OpenSim, the patient’s patterns of... 

Magnetic bearings have been used in industry to achieve an acceptable performance, high precision and vibration suppression of rotating machinery in recent decades.The absence of physical contact between the bearing and rotating components provides access to high rotational speeds which is a problem in conventional bearings.In addition, capabilities such as stiffness and damping adjustment can be used to reduce the harmonic vibrations caused by mass unbalance. The unbalance compensation is one of the main topicswhich has attracted the attention of many researchers in the field of rotordynamics. The aim of this thesis is to design and fabricatea three-pole active magnetic bearing test rig and... 

In last years, many researches are focoused on improving of suspension systems because of their importance in automotive afavourable performance. One of these advanced suspension systems are Magnetorheological suspension with nonlinear dynamic system and complicated behavior like Hysteresis Loops, so their modeling are notable.
In the first chapter as introduction, suspension systems and their aims are expressed briefly. Then Magnetorheological suspension structure and its function are mentioned. After review of researches that has done about its modeling and control , in the third chapter, different types of classic and generalized Prandtl-Ishlinskii models are introduced and... 

Refractory metals (W,Re,Ta,Mo,Nb) and their alloys can exhibit exceptional properties at elevated temperatures. However, refectory metals tend to be relatively heavy and, in some cases, can be relatively difficult to form in complex shapes at low cost. Light composites of refractory metals with high-melting ceramics, which can be fabricated into dense, near net shapes at low temperatures, would be particularly attractive for advanced aerospace applications. In this project, WC powders have been pressed and shaped to cylindrical preforms. Secondly, these performs have been sintered slightly(presintered) into porous, rigid ones with about 50% open porosity. Finally, in order to reach dense... 

In this research, oscillation in control loop caused by control valve stiction, external harmonic disturbance, poor controller tuning or their combination, is recognized and compensated. In control valve stiction based study, flaws in one of the important modeling methods are described and some modifications are proposed. For diagnosis of oscillation source, signal is decomposed to its fundamental modes and oscillation in each mode is investigated. Then, from the existence of harmonics in decomposed modes, stiction is diagnosed. Also, relation between peak differences in autocorrelation functions of other modes, results to external harmonic disturbance or poor controller tuning as... 

By generalizing dictionary learning (DL) algorithms to Multidimensional (MD) mode and using them in applications where signals are inherently multidimensional, such as in three-dimensional (3D) Inverse Synthetic Aperture Radar (ISAR) imaging, it is possible to achieve much higher speed and less computational complexity. In this thesis, the formulation of the Multidimensional Dictionary Learning (MDDL) problem is expressed and six algorithms are proposed to solve it. The first one is based on the method of optimum directions (MOD) algorithm for 1D dictionary learning (1DDL), which uses alternating minimization and gradient projection approach. As the MDDL problem is non-convex, the second... 

Nowadays, with the increasing need of various industries and applications to directly create linear motion, linear resolvers are attracting more attention than ever. Achieving high accuracy as well as measuring absolute position leads to the introduction of a new generation of resolvers, called multi-turn resolvers. Usually, a multi-turn resolver consisted of two individual resolvers in one frame, while using a common core for both resolvers can help to make the multi-turn sensor smaller, cheaper, and lighter. Nevertheless, the studies conducted on linear and multi-turn resolvers are very limited. Therefore, this research proposes an integrated core linear variable reluctance multi-turn... 

With the recent developments in power electronics and electrical drives, there is a need for precise position sensors today more than ever. Having high precision and high reliability in harsh environments, resolvers are the most preferred position sensors among other types of prevalent position detectors. In order to control linear machines, which are widely used in different industries, linear resolvers are employed. This project aims to propose a structure for tubular variable reluctance resolvers, formulate an analytical model for and optimize the proposed structure. In addition to having an acceptable precision, the proposed model should be less time-consuming compared with finite... 

In this research a novel method is proposed which uses the concept of image registration to forecast frames as a new frame up conversion method. This frame rate up conversion method is specially designed for medical videos because of the medical structure of the none rigid image registration used as a field to forecast new frames which causes better results for these kinds of videos. In this method we interpolate new frames in the field of none rigid transformation grid in order to improve video parameters such as blocking, blurriness, etc. which can help doctors to detect abnormalities in such videos much preciously. By analyzing existing methods, we can find that this field is bereft of a... 

One of the subsets of the radar systems is recognition of targets. Radar Target Recognition (RTR) is a process in which a target is distinguished from a set of targets. To recognize radar targets, we need to extract useful information from the returned signal from them. The most important issues in recognizing radar targets are the selection of information that reduces the amount of information needed for the identification process, the ease of extracting information from the moving target, and the ease of decision making to determine the identity of the target. One method is to produce a high resolution range profile, which is the one-dimensional image of the target in the direction of... 

Due to the simplicity and generality, design of feedback control systems in the frequency domain is among the most prominent topics in the control systems engineering. The problem of compensation means properly adjusting the loop frequency response at critical frequencies. Considering the point that the traditional methods usually use trial and error procedures for compensation, analytical design of fixed-structure controllers for exactly adjusting such values has great importance. Benefitting from the capability of fractional-order dynamics, the compensation problem is studied from three aspects in this thesis. At first according to the importance of adjusting the system frequency response... 

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... 

Current transformers (CTs) are the most common current sensors in power system and use with measuring instruments and protective relays. Saturation of the protective CT threatens the proper operation of relays, while, the ratio error in a measuring CT directly reduces the accuracy of power system state estimation. In this dissertation, firstly, a test device has been introduced to identify the parameters of CT low-frequency model. Afterward, a digital compensator has been proposed to suppress the adverse effect of CT saturation. This compensator is capable to reproduce both the saturated inrush current and fault current that distinguishes it from other proposed methods. In addition, this... 

The purpose of carrying out this Master thesis is to detect occurrence of CT saturation which leads to consecutive failures in operation of protective current transformers, as a major component in protection of power systems. The protective relay installed in the secondary side of the protective CT fails to act properly under occurrence of this phenomenon, and it doesn’t reflect proportionally the high value of fault currents passing through CT’s primary winding. As a consequence, faults become undetectable. Meanwhile, the proposed methods for detection of CT saturation must be reliable under a noisy condition, realizing that power systems have some inherent noises always available in the...