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    On dynamic stiffness of spacecraft flexible appendages in deployment phase

    , Article Aerospace Science and Technology ; Volume 47 , 2015 , Pages 1-9 ; 12709638 (ISSN) Bagheri Ghaleh, P ; Malaek, S. M ; Sharif University of Technology
    Deployment inertial effects of a spacecraft appendage on its flexible dynamics are investigated. The Euler-Bernoulli beam theory and the actual deployment profile, in which appendage axial motion accelerates from static state and then decelerates to end at zero velocity and acceleration, are employed. The study is concentrated on the arm dynamic stiffness introduced by inertial effects of the arm deployment, and the resultant effects on the arm flexible motions. Lagrange's equations and some appropriate shape functions in the series approximation method are employed to study the arm lateral elastic displacements. Finally a system of ordinary differential equations with time varying... 

    Optimal configuration of dual-arm cam-lock robot based on task-space manipulability

    , Article Robotica ; Volume 27, Issue 1 , 2009 , Pages 13-18 ; 02635747 (ISSN) Ghaemi Osgouie , K ; Meghdari, A ; Sohrabpour, S ; Sharif University of Technology
    In this paper obtaining the optimal configuration of the dual-arm cam-lock (DACL) robot at a specific point is addressed. The objective is to optimize the applicable task-space force in a desired direction. The DACL robot is a reconfigurable manipulator formed by two parallel cooperative arms. The arms normally operate redundantly but when needed, they can lock into each other in certain joints in order to achieve a higher stiffness, while losing some degrees of freedom. Furthermore, the dynamics of the DACL robot is discussed and parametrically formulated. Considering the geometrical constraints at a given point in the robot's workspace, the optimum configuration for maximizing the... 

    Design of mixed fuzzy-GA controller for SCARA type robot

    , Article 2006 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2006, Beijing, 9 October 2006 through 15 October 2006 ; 2006 , Pages 2173-2178 ; 142440259X (ISBN); 9781424402595 (ISBN) Eftekharian, A. A ; Sayyaadi, H ; Sharif University of Technology
    This paper presents a Mixed Fuzzy-GA Controller (MFGAC) for trajectory tracking of an industrial Selective Compliance Assembly Robot Arm (SCARA), which is one of the most employed manipulators in industrial environments. In this robot nonlinear effects due to centrifugal, coriolis and internal forces are more important than friction and gravity forces, unlike most industrial robots. The control procedure of MFGAC is consisting of a mixed fuzzy controller which is optimized by genetic algorithm. In this work we first design a Traditional Fuzzy Controller (TFC) from the viewpoint of a Single-Input Single-Output (SISO) system for controlling each degree of freedom of the robot. Then, an... 

    Control of Two-Arm Flexible Robot Carrying Fluid Tank With Constraint on the Elevation of the Liquid Free-Surface

    , M.Sc. Thesis Sharif University of Technology Bagheri, Pedram (Author) ; Haddadpour, Hassan (Supervisor) ; Kouchakzadeh, Mohammad Ali (Supervisor)
    Control of two-arm flexible robot is studied in this research. The goal is to control the robot in order to carry a fluid tank installed in the top of the last arm, while the vibration of fluid must be damped. The equations governing the system are extracted by the energy method while Euler-Bernoulli beam is selected to model the elastic members. In order to develop the equations, all of the potential and kinematic energies due to rigid and elastic motions are calculated, then a proper controller is designed for the system to accomplish the considered missions. Since the system is classified as an under-actuated system, the exact feedback linearization method is not practical to control the... 

    Thompson Algorithm and Multi-armed Bandit Problem

    , M.Sc. Thesis Sharif University of Technology Farazmand, Siavash (Author) ; Haji Mirsadeghi, Miromid (Supervisor) ; Alishahi, Kasra (Co-Supervisor) ; Zamani, Sadegh (Co-Supervisor)
    The multi-armed bandit problem is a popular model for studying exploration/exploitation trade-off in sequential decision problems. Many algorithms are now available for this well-studied problem. One of the earliest algorithms, given by W. R. Thompson, dates back to 1933. This algorithm,referred to as Thompson Sampling, is a natural Bayesian algorithm. The basic idea is to choose an arm to play according to its probability of being the best arm. Thompson Sampling algorithm has experimentally been shown to be close to optimal. In this dissertation several papers are being reviewed. In these papers it has been shown that Thompson Sampling algorithm achieves logarithmic expected regret for the... 

    Optimal control of multiple-arm robotic systems using gradient method

    , Article 2004 IEEE Conference on Robotics, Automation and Mechatronics, 1 December 2004 through 3 December 2004 ; 2004 , Pages 312-317 ; 0780386469 (ISBN); 9780780386464 (ISBN) Babazadeh, A ; Sadati, N ; Sharif University of Technology
    Optimal control frameworks are very important in optimization of multiple-arm robotic systems, although complexity, non-linearity and having large scales usually cause some computational problems in the capacity and time needed. In this paper, coordination of multiple-arm robotic systems in order to carry a rigid object is considered and the state space equations for the overall system are developed. Coordination of the robot arms is done through minimizing a related cost function based on the gradient method. This method is simple and easy to be used  

    Investigation on the Effect of Cooling Rate on the Solidification Behavior and Microstructure of Al 713 alloy using Thermal Analysis Technique

    , M.Sc. Thesis Sharif University of Technology Abbasi, Mohammad Hossein (Author) ; Varahram, Nasser (Supervisor)
    Considering the limited number of works on investigation of solidification characteristics of Al-Zn-Mg-Cu cast alloys as well as the applications of this alloy system in aerospace industries, the solidification conditions of Al 713 alloy were investigated in this study. In order to achieve this goal, a number of experiments were designed and conducted including quantometry, thermal analysis, metallography and hardness measurements. In this thesis, effects of cooling rate on secondary dendritic arms spacing as well as solidification parameters including nucleation temperature, solidification time and temperature range, dendrite coherency point and formation temperature of intermetallic... 

    3D Dynamic analysis of a flexible deploying arm subjected to base angular motions

    , Article International Journal of Structural Stability and Dynamics ; Volume 13, Issue 2 , March , 2013 ; 02194554 (ISSN) Ghaleh, P. B ; Malaek, S. M ; Sharif University of Technology
    Problems related to the three-dimensional (3D) dynamics of the deploying flexible arms subjected to base angular motions are studied with simulated tip payloads and actual deployment trajectories. To facilitate the solution, an equivalent dynamical system is developed by introducing the inertial reaction forces on the arm, while the equations of motion are derived in the non-Newtonian reference frame attached to the arm. The dynamic behavior of the arm is investigated both by the finite element and assumed Modes methods for the purpose of verification. This study reveals that base angular motions lead to considerable couplings between the two lateral displacements and axial motions.... 

    Silicon morphology modelling during solidification process of A356 al alloy

    , Article International Journal of Cast Metals Research ; Volume 25, Issue 1 , 2012 , Pages 53-58 ; 13640461 (ISSN) Shabani, M. O ; Mazahery, A ; Davami, P ; Razavi, M ; Sharif University of Technology
    In this paper, an introduction of the finite element approach to microstructure based modelling is provided, and the primary and secondary dendrite arm spacings of A356 alloy in the solidification process are simulated. The simulated results of dendrite morphology and the experimental measurements are presented and compared with the investigations of other researchers, which confirmed the accuracy of this model in its ability to predict the dendrite arm spacing. Each of the length scales, including silicon rod diameter and spacing, is discussed in detail. Analytical equations are generated for the length scales and incorporated in the Sharif University Technology academic software for the... 

    Design and development of an omnidirectional mobile manipulator for indoor environment

    , Article 6th RSI International Conference on Robotics and Mechatronics, IcRoM 2018, 23 October 2018 through 25 October 2018 ; 2019 , Pages 152-158 ; 9781728101279 (ISBN) Kebritchi, A ; Hosseiniakram, P ; Havashinezhadian, S ; Rostami, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    In this paper, a mobile manipulator is developed and studied in order to manipulate the complicated objects and navigate in an indoor environment. The arm consists of an actuator that makes the first linkage to move in two degrees of freedom in the first step of the task. In the next mode of the task, another actuator causes the second linkage to move in the third degree of freedom. In addition, the arm contains a gripper that grabs a variety of objects such as a screw. Therefore, the robotic arm can manipulate objects, and the mobile robot connected to the arm can detect, classify and track targets in its surrounding. Results carried out that the manufactured robot is able to manipulate and... 

    Toward calibration of low-precision MEMS IMU using a nonlinear model and TUKF

    , Article IEEE Sensors Journal ; Volume 20, Issue 8 , 2020 , Pages 4131-4138 Ghanipoor, F ; Hashemi, M ; Salarieh, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    MEMS-IMUs have an extensive application in multifarious studies, as well as industrial and commercial areas. It is crucial to diminish their intrinsic errors in a suitable calibration procedure. In this paper, a novel calibration procedure was proposed for Inertial Measurement Units (IMUs) on a turntable. A general nonlinear model of the IMU output including the effects of bias, scale factor, misalignment, and lever arm was derived. Transformed Unscented Kalman Filter (TUKF) was utilized to perform the estimation of error parameters for gyroscopes and accelerometers. The calibration maneuvers were applied using a tri-axis turntable to create input signals. In addition, assuming the sensors... 

    Dynamic Analysis of Deploying Elastic Arms In Interaction With Spacecraft Dynamics

    , M.Sc. Thesis Sharif University of Technology Bagheri Ghaleh, Parisa (Author) ; Malaek, Mohammad Bagher (Supervisor) ; Abedian, Ali (Supervisor)
    Dynamic analysis of deploying elastic arms of spacecrafts carrying tip mass has been presented. The research concentrates on the precise analytical simulation to reveal the phenomena which are usually eliminated in estimations. One of the most important factors which affect the dynamic response of such arms is rigid body dynamics of spacecraft. Considering this aspect of the problem the evolutionary analytical simulation has been developed through three steps. The first step focuses on the minute simulation of the arm deployment, in which a new mathematical approach called "elastic profile" has been developed which leads to semi-analytical solutions for the arm carrying tip mass.... 

    Online Recommender System and Exploration-Exploitation Trade-Off

    , M.Sc. Thesis Sharif University of Technology Goshtasbpour, Shirin (Author) ; Hossein Khalaj, Babak (Supervisor)
    The recent data explosion phenomena and numerous data consumer services over the world have made recommender systems a crucial component for online platforms.Recommender systems are filtering systems that prune the large volume of information to make the small prefered quota easily and readily accessible to the users. In social networks and news sites, due to the dynamic nature and constantly changing items and user preferences, reinforcement learning in recommender systems has become a hot research topic in the last decade. Our focus of attention,Multi-Armed Bandit, a tool of reinforcement learning, is a sequential decision making problem that illustrates the trade-off between exploring the... 

    Separating Linkages in 3-Space

    , M.Sc. Thesis Sharif University of Technology Kouhestani, Bahram (Author) ; Mahdavi Amiri, Nezamoddin (Supervisor)
    Here, the properties of separability of linkages are studied. In general, a linkage is a simple polygonal chain embedded in 3-space with disjoint, straight-line edges, which are fixed-length bars. The internal vertices are called joints. If the two end points are connected then the linkage is a closed linkage, otherwise it is an open linkage. By imposing restrictions on the way the bars in joints can move, three kinds of linkages as rigid, revolute and flexible can be introduced. A motion in a linkage is the motion of its vertices that preserves the length of the bars, and adheres the restrictions on joints. A collection of linkages are said to be separatable if for any distance d, there is... 

    Value-Aware low-power register file architecture

    , Article CADS 2012 - 16th CSI International Symposium on Computer Architecture and Digital Systems ; 2012 , Pages 44-49 ; 9781467314824 (ISBN) Ahmadian, S. N ; Fazeli, M ; Ghalaty, N. F ; Miremadi, S. G ; Sharif University of Technology
    In this paper, we propose a low power register file architecture for embedded processors. The proposed architecture, "Value-Aware Partitioned Register File (VAP-RF)", employs a partitioning technique that divides the register file into two partitions such that the most frequently accessed registers are stored in the smaller register partition. In our partitioning algorithm, we introduce an aggressive clock-gating scheme based on narrow-value registers to furthermore reduce power. Experimental results on an ARM processor for selected MiBench workloads show that the proposed architecture has an average power saving of 70% over generic register file structure  

    Synthesis of a compensated kick pattern for humanoid robots using conservation laws

    , Article 2006 ASME International Design Engineering Technical Conferences and Computers and Information In Engineering Conference, DETC2006, Philadelphia, PA, 10 September 2006 through 13 September 2006 ; Volume 2006 , 2006 ; 079183784X (ISBN); 9780791837849 (ISBN) Meghdari, A ; Tamaddoni, S. H ; Jafari, F ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    The motivation of this work is to synthesize a kicking pattern for a humanoid robot with consideration of various objectives such as retaining its balance even after the kick is done and reducing the undesired angular momentum using both hands and torso. This kick pattern is designed so that a desirable ball velocity is achieved. In this paper, the law of conservation of angular momentum is used to generate a less energy consuming trajectory. Effectiveness of the proposed method is verified using computer simulation and is tested on Sharif CEDRA humanoid robot. Copyright © 2006 by ASME  

    On the dynamics of the flexible robot arm in a real deployment profile

    , Article 2010 IEEE International Conference on Robotics, Automation and Mechatronics, RAM 2010, Singapore, 28 June 2010 through 30 June 2010 ; 2010 , Pages 112-117 ; 9781424465033 (ISBN) Bagheri Ghaleh, P ; Malaek, S. M ; Sharif University of Technology
    The dynamics of the flexible robot arm subjected to tip mass during an actual deployment is studied. The Euler-Bernoulli beam theory and the real deployment are considered in the simulation. A new real axial velocity profile is developed. This new suggested profile simulates the actual deployment such that the arm movement starts from immovability and after attaining the final required length comes back again to the static state. Using Lagrange's equation, the equations of motion of the system are derived to study the system dynamics in this suggested deployment profile. A series approximation is used to represent the lateral elastic displacements. Using variables separation and also some... 

    A SystemC Transaction Level Modeling of an ARM Processor

    , M.Sc. Thesis Sharif University of Technology Kouchaki, Mohammad Reza (Author) ; Vosughi Vahdat, Bijan (Supervisor) ; Ghorshi, Mohammad Ali (Supervisor)
    Advanced RISC Machines (ARM) are an example of a simple processor used to accomplish simple processing tasks in many applications. They can be found in PDA’s, mp3 players, and other portable electronic devices. ARM processors have small instruction sets and basic processor architecture, and they can be modeled in transaction level by SystemC. SystemC is one of many high level programming languages used to write hardware descriptive codes. We have chosen TLM in SystemC so that abstract data types can be used for higher level modeling and faster simulation. System architects and embedded software developers are accepting transaction level modeling into their design flow because it addresses... 

    Synthesis of Azacrown Macrocyclic Ligand with Pendant Arms and Study of Their Complexation with [60] Fullerene and Cu(II) Cation

    , M.Sc. Thesis Sharif University of Technology Kazemi, Ameneh (Author) ; Ghanbari, Bahram (Supervisor)
    In this research, four N2O2–azacrown macrocyclic ligands with naphthalene pendant arms (L1-L4) were synthesized using direct synthesis. The products were characterized applying 1H and 13C {1H} NMR spectroscopy, IR and Mass spectrometry. Interaction of these ligands with [60]fullerene and Cu(II) were monitored respectively by fluorescent as well as UV-vis spectroscopy and applying Benesi-Hildebrand equation. These intercations were compared with N2O2 macrocyclic ligands in previous experiments in terms of their calculated association constants (Ka). According to our results, the presence of naphthalene pendant arm groups led to increase the interaction with [60]fullerene compared to the... 

    A Mathematical Model to Prediction of the Formation of Microporsities in Aluminium Alloy Cast Parts

    , M.Sc. Thesis Sharif University of Technology Bahmani, Ahmad (Author) ; Varahram, Naser (Supervisor) ; Davami, Parviz (Supervisor)
    Today, application of aluminium alloys in industries is developing. And this is because of some specification of these alloys like high proportion of the Strength per weight. One of the most useful alloys of this alloy group is A356 alloy that contain 7 % Silicon and 0.4 Percent of magnesium, this alloy because of cast ability, heat treat ability specification is use developing in air and automotive industries. But usage of this alloys combined with some difficulties like low fluidity and formation of shrinkage and gas porosities in this alloys. In present work with programmer software Visual Fortran, based on Finite difference method, a simulation model has been developed, can solve heat...