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Criteria for Evaluating Bogie Performance For Sustaining Ride Quality
,
Ph.D. Dissertation
Sharif University of Technology
;
Sayyadi, Hassan
(Supervisor)
Abstract
This thesis proposes a dynamic model for studding influences of suspension components behavior on rail vehicle dynamics. As the air springs are very important isolating component in rail vehicles, a new complete nonlinear air spring model, with taking into consideration of thermo–dynamical effects, is developed. The model coefficients are tuned based on the real test data and it can be easily used in dynamic modeling of air springs. The new proposed vehicle model is a complete track–vehicle model with 70 degree of freedoms which is addressed as a modular type. Experimental results from complete rail–vehicle field test, showed remarkable agreement between proposed model and test results....
Control of a Group of Mobile Manipulators for Cooperative object Transportation
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
In this thesis control of wheeled mobile manipulators for cooperative object transportation is investigated. Full dynamic model of a mobile manipulator with a three wheeled mobile base and a three DOF manipulator is derived using Gibbs-Appell method. Input-output linearization technique is used to control individual robots. Transporting the object is divided into two steps, first robots use a decentralized behavior-based method to approach and surround the object. Then virtual structure method is used to control the robots to transport the object cooperatively. Simulation results with three robots handling an object are presented to show the effectiveness of proposed method
Kinematics and Dynamic Analysis of a Compliant Parallel Mechanism with Flexible Links for Micro Applications
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
In this research dynamic modeling of a 3-DOF (degree of freedom) compliant parallel mechanism with flexible intermediate links has been investigated. Unlike conventional rigid mechanisms that gain their mobility from movable joints, the compliant mechanisms transmit or transform through elastic deformation of flexible members (flexible connector and joint), displacement, force, or energy from input into output. Eliminating clearance, friction, wear and demand of lubrication in compliant mechanisms, and having monolithic structure provides high-precision motion with micro/nanometer level resolution for them. Therefore compliant mechanisms play a significant role in modern technologies such as...
Variable Formation & Decentralized Control of Multi-Quadrotor Having Same Dynamic System Using Consensus Algorithm
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Since Formation control have potentail applications in civil and military industries, decenterlized control of formation control is studied in this work using consensus algorithm. A specific robot quadrotor with 3D motion is used in this work. Quadrotor is an underactuated vehicle. First, we derivate twice from dynamical equations of linear positions. Hence, we can obtain appropriate form using linearization of output equations for design a consensus control algorithm. It is needed to design fourth order control algorithm for control of multiagent systems, beacause of twice derivation. Two methods that have been used for formation control in many works are potential function method and...
Design of Distributed Control System for AUV Swarms to Circle Around a Body
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
In this thesis, a new procedure is presented for control and analysis of a group of autonomous underwater vehicle achieving flocking motion by using a fuzzy-logic-based attractive/repulsive function. Two cooperative control laws are proposed for a group of autonomous agents to achieve flocking formations related to two different centers (mass center and geometric center) of the flock. The first one is designed for flocking motion guided at mass center and the other for geometric center. Desired path for AUV’s has been developed using Virtual agents with mass point dynamics. Smooth graph Laplacian is introduced to overcome the difficulties in theoretical analysis. A new fuzzy-logic-based...
Modeling of Energy Harvesting Systems from Shell Structures
,
M.Sc. Thesis
Sharif University of Technology
;
Sayyadi, Hassan
(Supervisor)
Abstract
The electrical voltage, current and power output is calculated due to harmonic forced vibration of shell energy harvester. So five electromechanical equation together with Gauss equation is solved for doubly curve shell harvester in steady state condition in order to derive voltage, current and electric power output. The effect of shell curvature in cylindrical and spherical shells, the harvester series or parallel connection of layers and thickness of substrate and piezoelectric layer, is also considered in order to obtain maximum power output. The results show for small shell curvatures a high frequency load is needed to obtain maximum power and when the shell arc length is three times to...
Configuration Design of Mechanical Structure Coupled with MSMA in Energy Harvesting
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
In recent years, energy harvesting from ambient sources in order to use for low-powered electronics has been considered by many researchers. Wind energy, solar energy, water energy, mechanical energy from vibrations, etc are common sources of ambient energy. In this thesis, optimization of energy harvesting from ambient vibration using magnetic shape memory alloy is presented. To this end, a clamped-clamped beam coupled with MSMA units is considered. A shock load is applied to a proof mass which is attached to the middle of the beam. As a result of beam vibration a longitudinal strain is produced in the MSMA. This strain changes magnetic flux inside the coil connected to MSMA and as a...
Hydrodynamic Modeling of an AUV
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Autonomous underwater vehicles (AUVs) are a type of marine vehicles which are currently being used for exploration, maintenance, repairing of marine structures and military appliances. Unmanned underwater vehicles categorize in two types: ROVs and AUVs, ROVs (remotely operated vehicles) usually are connected to the mother vessel with a cable, conduction signals transfer through this cable and there is an operator in the control loop. The vehicle may be fed up with this cable, AUVs are modern underwater vehicles which the operator on controlling and conducting is removed, there is no connection between the vehicle and mother vessel, energy sources and controlling orders are set up in the...
Modeling and Optimization of Energy Harvesting System by Means of Magnetic Shape Memory Alloy
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Among different mechanisems for ambient energy harvesters, energy harvesting systems by means of magnetic shape memory alloys are noted due to their long life time, large strain amplitudes and the ability to operate at low frequencies. Strain change in these systems, changes the MSMA magnetization resulting change in the magnetic flux leading to inducing voltage by means of pickup coil. in the commercial systems, magnetic flux path is created by inserting an MSMA specimen in the air gap of ferromagnetic core and generation of bias magnetic field by means of the permanent magnet or electromagnet. In this proposed research, a thermodynamic based constitutive model is selected for the mdeling...
A Fuzzy-Behavior Based Approach to “Dynamic and Static Obstacles” Avoidance in an Unknown Space
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
In this article, research has been carried out on the control technique of autonomous mobile robots to navigate in unknown environments, avoiding static and moving obstacles using eight ultrasonic sensors for obstacle recognition.
In this article we used simple three wheeled robots. Each robot has a passive caster wheel and two active fixed wheels which can act independently. In addition robots have holonomic constraints like maximum acceleration, maximum speed and maximum angular velocity, so robot’s speed and orientation change independently and these changes are small in each time step. Each robot has eight ultrasonic sensors, each of them cover 22.5 degree of space from robot‘s...
In this article we used simple three wheeled robots. Each robot has a passive caster wheel and two active fixed wheels which can act independently. In addition robots have holonomic constraints like maximum acceleration, maximum speed and maximum angular velocity, so robot’s speed and orientation change independently and these changes are small in each time step. Each robot has eight ultrasonic sensors, each of them cover 22.5 degree of space from robot‘s...
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...
Dynamics Modeling and Control of Mooring Lines While Cargo Vessels Loading
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
large ships should only make very small horizontal movements at the berth for efficient loading. This is especially a concern in ports facing the open ocean directly, where high swells at sea can cause harbor oscillations and low-frequency surge motions of the ship. A developed mooring unit, the MoorMaster, which replaces conventional mooring lines is addressed here. The hydraulics of the system have a strong reducing effect on the motions of the moored ship. Measurements have shown that the surge motion of container ships was reduced from an amplitude in the order of 1 metre to an amplitude in the order of 5 centimetres, by using MoorMaster units. In here MoorMaster action is divided to two...
Modeling of Strain-Magneticcharacteristic of Magnetic Shape Memory Alloy in Energy Harvester
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Harvesting energy from renewable sources in nature, such as wind energy, solar energy, water energy and vibrations has always attracted researchers. There exist different ways to harvest energy from environmental vibrations. In this thesis, energy harvesting via Magnetic Shape Memory Alloys (MSMAs) has been taken into account due to important advantages of these alloys, such as their long fatigue life and good performance at high amplitudes and low frequencies.In this system, applying strain on alloy changes the magnetization and this change generates voltage in the pick-up coil around the MSMA. On the other hand, since the strain-magnetization relation is nonlinear and hysteresis,...
Harvesting Energy from Magnetic Shape Memory Alloys in Plannar Loading
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Harvesting energy by magnetic shape memory alloy has many advantages against other various methods which harvested from environmental vibrations and has been considered due to high long longevity, large strain amplitude and good performance in low frequencies. These materials can display up to % recoverable strain in response to the application of a magnetic field or compressive mechanical stress. Microstructure of these materials changes under applying mechanical loading and/or magnetic field which cause magnetic vector rotating in magnetic domain. Change in magnetization of these materials, lead to harvesting energy by considering Faraday's law of induction. The model of this...
Design and Fabrication of a Swimmer Robot at Low Reynolds Number
, Ph.D. Dissertation Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Helical swimming robots with a capable propulsion system at low Reynolds numbers have been proposed for many applications. Although linear propulsion characteristics of swimming robots with a single helical flagellum have been extensively studied, the characteristics of maneuverability have not been completely investigated yet. In this thesis two novel mechanisms was proposed. The first mechanism presents a new method for the maneuverability of the helical swimming robot with a single helical flagellum. This mechanism is based on the change in the angle between the helical and body axes. This study shows that a change in the aforementioned angle can enable the swimming robot to have turning...
Control Algorithm of Multi-agent Systems in Special Paths With an Applied Consideration in Biomechanical Engineering to Perform Operations of Interior Treatments
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
In this project Deployment of multi-agent systems was studied. Maximum coverage over a point or curve or area is desired in deployment of multi-agent systems. A facility location optimization function was derived from geometrical concepts such as voronoi, n- geometric median and fermat-weber problem by optimization of which the deployment of multi-agent systems is performed. First, it is assumed that dynamic of agents is first order and second order .Next, it is assumed that agents are in a fluid. In all situations a suitable control algorithm was derived to optimize the facility location function to perform deployment. Next, another facility location function was derived by optimization...
Considering the Ctability of Train Movement Based on Wagons Arrangement
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
The main popuse of this Thesis is investigating of the different wagon arrangement effect on stability of the train set. So to gain this goal, one train with 10 wagons has been simulated. The model of the each wagon is Nonlinear with 40 DOF. 3 of the wagons are heavy and make 3 different kinds of arrangement by putting them at first, middle and the end of the train (HLL, LHL and LLH arrangements). Then these three arrangements have been simulated on two differen tracks and conditions, 1st Accelerating on curved track (320 R) with positive slope and 2nd decelerating on curved track with negative slope.We suppose that the contact is singular point and aslso contact equations have bben solved...
Control of Car-Like Multi Robots for Doing Group Maneuver and Change Formation
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
In recent years formation control of autonomous vehicles has been a well-studied topic, and the attention has shifted from the control of a single mobile robot to the control of multiple mobile robots because of the advantages a team of robots offer, such as increased efficiency, robustness against fault and damaging, and more systematic approaches to tasks like search and rescue operations, automated highways, survey and patrols, military missions, moving large objects and moving a large number of objects. Formation control means the problem of controlling the relative position and orientation of the mobile robots in a group according to some desired pattern for executing a given task. In...
Control Strategies of Swarm Vessels for Circling Mission in Calm Water
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Control of a group of autonomous surface vessels with realistic dynamic for circling mission is distributed with the aid of Lyaponov and graph theory. in this brief, to obtain a cooperative controller, new coordination transfer are presented and graph theory is used to illustrate the communication between the agents. With the aid of Lyaponov theory and graph application, Decentralized and scalable controllers are designed for group of autonomous vessels to converge to desired geometry to circling a specific target. Because of the realistic dynamics, Non-Holonmic dynamics and turning constrains of the vessels are considered in the design process. The advantage of proposed controller is: it...
Hydrodynamics Modeling and Self Orginizing Control of Marine Vehicles
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Dynamic positioning system is a controller system used to maintain the position and heading of a vessel with no use of anchors, jack ups but only using the propellers installed on the vessel. A vessel has six degrees of freedom, including three rotations and three transfer. In dynamic positioning systems, the vessel is controlled only on the horizontal plane such that its position and heading are controlled according to predetermined values. To achieve this, position and heading of the vessel is determined and the controller system computes the direction and required power of each propeller. Preliminary systems utilized PID controllers. As the control science has advanced, model based...