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Possiblity and Implementation of Closed Loop Controller to Control a 2-DOF Electrostatic Torsional Micro-mirror
, M.Sc. Thesis Sharif University of Technology ; Alasti, Aria (Supervisor) ; Salarieh, Hassan (Supervisor)
Abstract
Nowadays, Specific applications of micro-mirrors in MEMS industry as actuartors have been found. In optical networks, these instruments are used to transfer data between optical fibers as an optical switch. According to the high desired precision for the relevant applications, many different aspects should be considered in controlling of these systems. Some of these criteria include: high speed response, overshoot elimination, minimal energy consumption by regulating the system inputs, minimal vibration, consideration of system uncertainities and some unmeasurable state variable, and system rubostness against environmental disturbances. In this research by addressing all of these...
Using Decision Making Tools in Optimum Selection of an Electromechanical System Design Parameters
, M.Sc. Thesis Sharif University of Technology ; Houshmand, Mahmoud (Supervisor)
Abstract
The brushless DC Limited-Angle Torque Motor (LATM) has been widely used in area of aerospace equipment, robot drives, optical scanning systems and any drive systems that require limited motion, ranging from the simple ON-OFF servo valves to the accurate tracking of a reference signal. This paper presents the optimum design procedures of a brushless direct current limited-angle torque motor. According to a request from industry, a two-pole torque motor with a toroidal armature winding was designed based on analysis of magnetic equivalent circuit of motor structure, and using selected ferromagnetic material and rare-earth permanent magnets (PM). To select the best design solution and optimize...
Direct Torque Control of Permanent Magnet Synchronous Machine Using Nonlinear Flux Observer
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
Direct Torque Control (DTC) is one of the vector methods to control Permanent Magnet Synchronous Machines (PMSM). In order to achieve an appropriate control in vector control methods, an accurate estimation of flux is indispensable. Flux estimation should be fulfilled in a wide speed range without considerable dependence on motor parameters. Prevalent flux estimation methods are based on integration of stator voltage which is not feasible in low speed, or performed based on assumption of decoupled equations on d and q axis which is not precise for applications with fast dynamic. Different flux estimation methods are investigated in this thesis with the aim of improving the flux estimation in...
Direct Speed Control of Permenant Magnet Synchronous Machine
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
Accurate and fast position controlling is an important issue in today’s industrial needs. Drives used for position control require fast dynamics on speed control. Cascade linear controllers have sluggish response due to bandwidth limitations on speed and current loop. These structures limit the dynamics above all in high power applications where the switching frequency is low. In this thesis, deadbeat direct speed control is proposed, which overcomes limitations by cascade loops resulting in high-speed control dynamics. This approach uses a model of the plant to generate the control signals. According to measured speed and currents, the controller specifies the best voltage vector in order...
An Analytical Model for No-Load, Slotted, Axial Flux Surface-Mounted PM Machines: Air Gap Flux Density and Cogging Torque
, M.Sc. Thesis Sharif University of Technology ; Oraee Mirzamani, Hashem (Supervisor) ; Taghipour Boroujeni, Samad (Co-Advisor)
Abstract
In the presented dissertation an analytical model is developed for the air gap flux density and the cogging torque in the axial flux surface-mounted PM machines. The slotting effect is taken into account in the magnetic flux distribution.The model is derived from solving the 2D Poisson' equation in the slotted air gap. To simplify the solution process, the concept of the uniqueness theorem is used to replace the slotted air gap by a slotless one and some surface current distribution. In addition, the separation of variables method is applied to the analytical solution of the Poisson equation. However, the proposed 2D analytical model is developed for the quasi 3D model by the well-known...
Dynamic Modeling and Torsional Vibration Analysis of Crankshafts Equipped with DMF & CPVA
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Torque variations caused by intermittent combustion and inertia effects of reciprocating components, exert significant torsional excitation on crankshaft of internal combustion engines. These excitation induces considerable torsional vibration on crankshafts. Therefore, modeling and analysis of crankshaft torsional vibration and absorber systems, especially in automobiles engine that crankshaft tolerate high amplitude excitations coupled with heavy inertia effects has high importance. In this study, ability of centrifugal pendulum vibration absorber and dual mass flywheel which used in rotating machinery for vibration reduction, will be examined. At first, cranktrain will be torsionaly...
Adaptive Compensation of Effect of Slow Dynamic Actuators in Robots Without Output Torque Measurement
, M.Sc. Thesis Sharif University of Technology ; Namvar, Mehrzad (Supervisor)
Abstract
A motion tracking control design of an n-DOF rigid robot by taking into account its actuator dynamics is proposed in this paper using backstepping technique. neglecting actuator dynamics in control of rigid robot manipulators can degrade the performance and loss of stability. However,consideration of actuator dynamics entails joint torque or armature currents measurement. In this study, torque measurement has been avoided using an torque estimator.. Finally, Semi-global convergence for motion tracking error are proven. In addition, A simulation example of a two-link robotic manipulator is also given to clarify the effectiveness of proposed design method. Considering actuator dynamics entails...
Direct Torque Control in Brushless Doubly-Fed Induction Motor
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
Common induction motors are controlled with the stator voltage and so all the power passes throw the converter. In the Brushless Doubly-fed Induction Motor (BDFM) a converter with smaller size and lower cost can be used. Also its brushless operation and cage rotor are advantages in comparison with doubly-fed induction motors with rotor excitation. Direct Torque Control is a method to control induction motors. Its advantages include fast responses to flux and torque commands, not requiring to know machine parameters except winding resistors, and easy implementation. In this thesis application of this method to control the BDFM is studied. At the first, electromagnetic mechanism and coupling...
Optimal Drive for Brushless Doubly Fed Induction Generator
, M.Sc. Thesis Sharif University of Technology ; Oraee Mirzamani, Hashem (Supervisor)
Abstract
In this thesis, losses of steady state operation of brushless doubly-fed induction machines (BDFM) are analyzed and optimized. Since the final objective of engineering systems is economic advantage, after brief introduction to BDFM, economic model of wind farms is presented and BDFM benefits and deficits are studied. Among BDFM’s research topics, power density and efficiency were recognized of most importance, according to the economic model. In absence of analytical model of core loss for BDFM, a maximum torque per ampere optimization for BDFM is presented, including torque equation derivation, optimal current angle extraction and machine design objective function calculation. The...
Improve the Direct Torque Control Method for Brushless Doubly Fed Induction Machines
, M.Sc. Thesis Sharif University of Technology ; Oraee Mirzamani, Hashem (Supervisor) ; Barati, Farhad (Co-Advisor)
Abstract
The Brushless Doubly Fed Induction Machine (BDFIM) has the potential to be used as a generator or motor in adjustable speed variables. But the most important application for the BDFM is to work as a wind generator. Due to this ability it can be considered as a rival for the Doubly Fed Induction Generator (DFIG) that is the most common type of the wind power generators nowadays. Because of problems of relater to brushes in DFIG, the BDFM has more resisted structure compared to the DFIG. Thanks to the special “nested loop” structure of rotor and two different coils on the stator without direct coupling between them, three different operation modes are possible for the BDFM.The synchronous...
Analysis of Brushless Doubly-Fed Motor under Various Operating Modes
, M.Sc. Thesis Sharif University of Technology ; Oraee Mirzamani, Hashem (Supervisor)
Abstract
The Brushless Doubly-Fed Machine (BDFM) is a machine which incorporates the robustness of the squirrel cage induction machine and the speed and power factor control of a synchronous machine. All of these advantages are obtainable from a relatively low rating power electronic converter (e.g. 30% of the machine’s rating). The stator of a BDFM is furnished with two balanced three phase windings of conventional design (power and control winding). These windings differ in pole number and are often excited at different frequencies. Hence, there is no direct magnetic coupling between them. The power winding is connected to a constant-voltage, constant-frequency source and the control winding is...
Direct Torque Control of Brushless Doubly-Fed Induction Machines Using Fuzzy Logic
, M.Sc. Thesis Sharif University of Technology ; Khayyat, Amir (Supervisor)
Abstract
This thesis contributes two separate predictive direct torque control methods; based on hysteresis and fuzzy logic for Brushless Doubly Fed Induction Machine (BDFM). Initially Chapter 1, focuses on BDFM history and concept of this machine and after that a short review about the development of BDFM and the Field Oriented Control will be studied. Chapter 2 introduces the d-q-0 state transformation matrix, dynamic equation of BDFM and represents its steady-state equivalent. Furthermore, in this chapter the bond graph model of BDFM is studied and via distinguishing all energy ports the bond graph model of this motor is introduced and validated, finally the result of this model is compared with...
Development of New Wind Turbine Scheme and Pure DC Wind Farm based on Excitation Controlled Synchronous Generator
, Ph.D. Dissertation Sharif University of Technology ; Parniani, Mostafa (Supervisor)
Abstract
In this thesis, a new wind turbine scheme based on Electrically-Excited Synchronous Generator (EESG) and diode-bridge rectifier is proposed and developed. This new scheme is mainly based on the idea of generator excitation current employment as a means of wind turbine control. That is why the new scheme is called Excitation Controlled Synchronous Generator (ECSG) wind turbine. The most important aspects of the proposed ECSG wind turbine scheme are cost-effectiveness, simplicity and higher reliability, as well as higher efficiency. Considerable cost reduction for the converter unit of ECSG wind turbine is so important since costly converter has been one of the main challenges of the...
Direct Torque Control of Doubly-Fed Induction Motor
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
Conventional induction motors are controlled by stator voltage, so the inverter should pass the full power of the motor. In the doubly-fed rotor wound induction motors, the nominal power of inverter can be reduced. Therefore, these types of machines have been concerned in recent decades and they are able to use as alternative for high power conventional induction machines in the future. Direct torque control is one of the well known methods for controlling the induction motors. Fast torque response and independence of machine parameters (except winding resistance). In this thesis, different sterategies of direct torque control of doubly fed induction motors are presented. In the first...
Robotic Modeling of Paraplegic Locomotion to Improve the Gait Efficiency Using Modified Motion Pattern and Orthotics Design
, M.Sc. Thesis Sharif University of Technology ; Farahmand, Farzam (Supervisor)
Abstract
Walking on legs using orthosis for spinal cord injury patients has many advantages and decreases the physiological and psychological problems comparing with wheelchair application, however high energy consumption and early exhaustion of patients are disadvantages of orthosis usage. The most important group of orthosis for spinal cord injury patients is RGO (Reciprocating Gait Orhtosis) which a reciprocating cable mechanism links two hip joints motion. So swinging of mobile leg gets easier and stability of patient in standing and walking step increases. Regarding to existent reports about high energy consumption in walking by orthosis, this project has been fulfilled to design an improved...
Simulation of Vertical Axis Tidal Turbine and Surrey of the Factors Affecting its Efficiency Applying CFD
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Hassan (Supervisor) ; Abbaspour, Majid (Supervisor)
Abstract
Increasingenergy requirements, limitedfossil resources, environmental pollutioncaused byfossilfuels, global warmingand other factorshaveled tothe approach ofscience and technologyfor renewable energies. One of the renewable energies is the energy relevant to ocean currents that is mainlydue to theinteractionbetween thetidalattraction ofthe moon,sun andearth. In our country,due tothehigh tideon the southern coast, there isgood potentialto use thistype of energy. One of themost favorableareasformarinecurrentpower plantslocated inthe northern part ofthe islandof Qeshmchannel.In this thesis,to exploitthis potential, the newidea ofHunter tidalturbine was investigated,because...
Economic Analysis of Electric Vehicles Based on the Design Parameters of the Motor and Powertrain Systems
, M.Sc. Thesis Sharif University of Technology ; Ahmadian, Mohammad Taghi (Supervisor) ; Assempour, Ahmad (Supervisor)
Abstract
Due to pollution and destructive effects on the environment, while consuming a large amount of fossil fuels that can be converted into high value-added products, gasoline cars are gradually replaced by electric cars. Modern electric vehicles are generally designed and manufactured on the platform of gasoline vehicles. In the present study, it is tried to design three models of electric vehicles based on the SAINA vehicle. Initially, for the first model, an electric motor instead of the SAINA gasoline engine is employed to provide the power required for the vehicle. Then, for the second model, two electric motors are used namely one in the rear axle and one in the front. The third model uses...
A Fabrication Method of Neutrally-buoyant Magnetic Micro-robot to Improve Its Motion Control
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Micro-robotics is one of the currently emerging technologies which has attracted attentions for its probable applications in different fields including biotechnology, diagnosis and treatment in medical engineering as well as general studies in micro-scale science and engineering. Magnetic micro-robotics is considered as the most promising group, primarily due to the biocompatibility of magnetic fields and advances in electronic circuits to produce and control such fields. One critical point in utilizing these robots is their high density in comparison with the working fluid and their tendency to sink. In this thesis, a method to fabricate buoyant magnetic robots has been proposed based on...
Knee Joint Torque Estimation using EMG Signals for Sharif Exoskeleton Control Applications
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor)
Abstract
The human body has more than 600 muscles that cause movement. Disability and motor disorders are some of the problems that people may face due to some factors such as accident, spinal cord injuries, disorders and brain damage, and the presence of a problem in neurological commands due to stroke. One of the proposed methods for solving the problems of people with motor disorder is the use of exoskeletons to generate stimulus. Exoskeletones are electromechanical devices designed to assist human movement, and patients are used to correct their movements using specific motor patterns. Exoskeletones can also be used as an auxiliary device for carrying heavy loads. Many studies have been conducted...
Direct Torque Control of Induction Motor Fed by Reduced Switch Three Phase Inverter
, M.Sc. Thesis Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor)
Abstract
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...