Sharif Digital Repository

Future mobile networks are expected to not only bring more wireless connectivity and higher data rates, but also to support several high-quality services including low-latency, ultra-reliable, and energy-efficient communications. To support these needs, intelligent reflecting surfaces (IRSs) have recently attracted a lot of attention due to their potential for reconfiguring the wireless channel and are considered as a promising solution for future mobile generations. On the other hand, the exponential growth of network traffic, and its non-uniform distribution result in network congestion during peak-traffic times and network underutilization during off-peak times. Caching or content... 

Experimental determination of aircraft aerodynamic characteristics is of prim importance in evaluation of its trimability and stability requirements. One of the most common tools for experimental identification of aircraft is the wind tunnel equipped with aerodynamic force and moment balance system. Design and development of wind tunnel equipped with such system for measuring aerodynamic forces and moments can affect the accuracy and quality of identifying the aircraft dynamics. However, since procurement of such professional systems is very expensive, the primary goal of this project is focused on initial design of a tabletop wind tunnel with a force and moment balance system. In addition,... 

This paper proposes a novel probabilistic approach to account for soil-structure interaction (SSI) in the seismic design of building structures. In this approach, an SSI response modification factor, RSSI, is introduced to capture SSI effects on the seismic performance of structures. The proposed procedure quantifies RSSI such that the probability distribution of the collapse capacity of the structure designed to account for SSI concurs with that of the structure designed using the default fixed-base provisions. The proposed approach is employed for special steel moment frame buildings with surface foundation. A surrogate single degree of freedom (SDOF) system is developed in this study and... 

It is well known that the most rigorous method to assess the performance and to predict the seismic demands of a structure subjected to earthquake is nonlinear time history analysis. However, this technique is accompanied by complexities and difficulties in evaluating the seismic demands of structures and requires superior knowledge and skill. As a result, in recent years, nonlinear static analysis has been proposed in performance based design procedures. One of the primary assumptions of nonlinear static procedures is that the behavior of a structure with multiple degrees of freedom (MDOF) subjected to seismic ground motion can be estimated from the response of an oscillator with a single... 

This dissertation accounts hydrodynamic coefficients for the hull form of Dolphine Craft using an Experimental-Numerical method. First, a short preface is mentionded about Dolphine craft and its charcterstics. Then, different methods for determining the hydrodynamic coeeficient are reviewed and the method used in this dissertation is introduced. After that, the selected methods will numerically be modeled. For accurate modeling, virtual labarotory is organizing for performing these tests During modeling, six degree freedom equation including the kinematic and Dynamics of body element are extractred and consequently, they are expressed for the rigid body and control volume of fluid. The... 

Human have been thinking to discover all secrets of world, from long time ago. And also the sea exploring and using its resources, including oil and utilization of fish as feed have been the main causes of human interest to ocean. So to access these resources, constructed some equipment to be able to go under water, such as ROV and AUV.
Since the human is concluded that further facts need to synchronize to the world with the natural laws of nature in this area is the best model and teacher; new branch of science called bionic is exploded. For example, look and study of birds in the air movement have produced the fastest aircraft. Same knowledge in the field of marine sciences has... 

In this research, a single degree of freedom (SDOF) system equipped with a telescopic damper is analyzed under earthquake excitations. In order to assess the effectiveness of telescopic damper, some SDOF systems equipped with other types of dampers including viscous damper, friction damper, T-ADAS damper, and Curadelli’s lead damper(CLD) are also analyzed under similar excitations. Inspired by CLD damper, this TLSD damper is primarily introduced, developed and tested at Sharif University of Technology in Tehran by Mr. Pournamazian in 2016. Results shows that the telescopic lead shear damper can increase the CLD damper displacement by 100%. To get better results in terms of damper’s behavior... 

Earthquake motions are among random excitation loads. For that we used random vibration approach to estimate response of multi-degree of freedom base isolated structures under ground excitation. Some models including linear model ,nonlinear Bouc-Wen and BBW models are studied for modeling the superstructure .Several base isolation models including the laminated rubber bearing, high damping laminated rubber bearing ,resilient-friction base isolator with or without sliding upper plate and the Electricity de France system, are studied . El Centro 1940 and Mexico City 1985 earthquake which preserve the nonstationary evolutions of amplitude and frequency content of ground accelerations... 

This thesis is about guiding and controlling the six-degrees of freedom of the reentry vehicle with focus on designing controller by using non-linear dynamic inversion method. Intended reentry vehicle is Apollo which is a reentry capsule without wing and with lifted body and also the proportion of lift to drag is low. Guiding variable instruction, the angle of rolling and constant, are the side slip and attack which reentry vehicle must follow these instructions with the help of controller and with regard to the rotational dynamic of the vehicle. In this thesis more exact six-degrees-freedom model of the vehicle is extracted and the controlling system to
stabilize and to follow guidance... 

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... 

Mono-copter has been considered as a type of drone in recent years. The initial idea for this micro vehicle was to follow the maple seed's motion as it fell from the tree. In this study, using dynamic modeling principles and with the help of aerodynamic relationships of non-permanent blade element as well as momentum theory, we present a dynamic model of forces and moments on this monocopter. Subsequently, using the Newton-Euler approach, the six-degree-of-freedom equations of motion of this are also developed and various simulations are performed on the model using software provided by Simulink Toolkit, which demonstrates the accuracy of the simulation. In addition, we obtain the different... 

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... 

Cable-driven parallel robots (CDPRs) form a class of robotic manipulator in which the actuation end-effector is transmitted through cables. Due to the unique characteristics and advantages of cable transmission, CDPRs have become increasingly studied in recent years. In this thesis, the study of Geometric Analysis and Dynamic Trajectory of a 5-DOF Cable-Suspended Spatial Parallel Robot is investigated. Geometric analysis is corresponds to the workspace on which the robot is designed. The design of cable mechanisms allows the robot to be used with appropriate configuration in various fields such as industry, medicine, etc. The study of CDPR design has been limited due to several reasons.... 

The present research illustrates the Effects of Stiffness Distribution on Demand Reduction in Elastic Multi Degree Freedom Structures. The structural configuration of a structure has an important effect on dynamic performance of it and its nonstructural contents. For equipment, the displacement or acceleration demand is defined in terms of the input motion applied at the appropriate attachment point(s) of the equipment. This demand or input motion is generally represented by an in-structure response spectrum (IRS). The IRS will differ significantly from the design base earthquake (DBE) spectrum because it is essentially filtered and/or amplified through the building. To assess the realistic... 

In this thesis, a fault-tolerant method for controlling the relative position and attitude between two satellites in a leader and follower formation is proposed. The follower satellite is equipped with twelve thrusters which are installed on the satellite in a particular pattern. These thrusters are assumed to be afflicted by faults. The satellites are subject to external disturbances – such as the ellipsoidal gravity of Earth (J2), drag force, solar radiation pressure, and the third body, and a controller is designed to attain the desired formation under these disturbances.For this purpose, six separated neural networks are trained, one for each of the position or attitude channels. Since... 

Motion simulators have been highly sought after by the growth of the aerospace industry. In the meantime, the Stewart mechanism, or the so-called Hexapads, is a robot that, in addition to being used in machining tools, is mainly used to simulate the flight. The Stewart-Gaph mechanism was created and introduced in 1954 and 1965, and since then dynamics and control have been widely addressed in the mechanical engineering literature. The robot is considering the project to test parts and equipment installed in marine vessels under sea movements and waves. Therefore, according to information obtained through relevant organs, the purpose of this project is to design and implement a hexapad... 

Experimental identification (EI) of aircraft static and dynamic characteristics is usually performed for design process verification, its compliance against the existing regulations as well as to extraction of its exact stability and performance characteristics. EI is mostly performed via flight and/or wind tunnel testing of a scaled model of the aircraft under scrutiny. In this regard, the purpose of this thesis is design and development of a 5DoF Table Top Platform (TTP) for Aircraft transfer function identifications as well as some of its key derivatives. The proposed TTP can also function as the motion part of a miniature simulator. The PPT is designed in two parts that is comprised of... 

In recent years, great attention has been devoted to the design of artificial arms. The most crucial problem in such a design is the trajectory of movement. In this paper, a seven degree of freedom arm is modeled and simulated. Also, the optimization method named “Imperialistic Competitive Algorithm” has been modified and better performance of the new version is presented. Energy optimization is performed based on trajectory of the arm with angular velocity, angular acceleration and joint angles using modified imperialistic competitive algorithm (ICA). Considering ICA as a fast optimization algorithm, it would be reasonable to use this algorithm for robotic purposes for online answering. The... 

The robot considered in this project is to test parts and equipment installed in marine vessels under sea movements and waves. After a thorough assessment amongst common solutions to problems of this kind, a Stewart-Gough based manipulator has been chosen so that all the requirements could be satisfied. Therefore, according to the information obtained through relevant organisations, the purpose of this project is to work on dynamics, control, and design of the structure of a 6DOF Stewart platform – based hydraulic motion simulator for heavy payloads for samples weighing up to 2.5 tons which can handle linear accelerations up to 10 m/s2, rotary accelerations up to 150 º/s2 performing at a... 

Control and guidance of a vehicle is vital for it to do its mission correctly. Guidance system and decisional algorithms used in it need exact information of instantaneous position, velocity, and attitude of the guided vehicle to determine and issue proper guiding commands.
Estimation algorithms and navigation sensors are two necessary tools for navigation. In the first section of present study, the reentry head equations of motion are derived and a 6-DOF simulation is done for it. In the second section, measurements of sensors will be simulated using results of the first section and existing reference models for sun position vector and earth magnetic field. The third section appertains...