Sharif Digital Repository

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... 

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... 

Non rigidity of the soil beneath the structure, alters elastic and inelastic response of it. This effect is caused by the soil-structure interaction. The effect of soil-structure interaction is studied in two parts, Kinematic interaction and inertial interaction. Among these, kinematic interaction effects are often assumed to be negligible so that even in existing regulations it has been ignored. While the kinematic part of soil-structure interaction effect could produce a rocking input motion that might be important. In recent years, according to expanding usage of performance based design philosophy, researches on inelastic behavior of the soil-structure systems has been done which is... 

In robotic, Underactuated systems are interesting subject to study. Underactuated system, is a system that have fewer actuator than degrees of freedom. Underactuated systems are composed of active and passive joints. passive joints are existed, in order to decrease the weight, cost, and energy consumption. Usually, control of these systems are difficult. Underactuated systems have acceleration constraint. This property make the control method have fundamental constraint. So that controller dynamic could not be a smooth function of states of system. So most of standard method in control, such as feedback linearization, are not applicable. Local linearizing methods, because of... 

Motorcycle has one of the most complicated geometries and mechanisms and its kinematic, according to the articles surveyed, has always been expressed with approximation and simplification in the degrees of freedom and especially in the magnitude of the angles. Analyzing the dynamic model of bodies, using methods like Kane, Lagrange, Boltzmann-Hamel, Gibbs-Apple, Newton, Hamilton and Ross, lead to mechanism’s equations of motion. While the equations of motions, obtained from alternative methods, lead to the same result, but the number of differential equations and sometimes their order, are different in different methods, and therefore their numerical solving time for the body’s motion, are... 

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... 

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... 

Most elderly and physically disabled people suffer from lack of functionality and dexterity in their elbow or wrist. These disabilities are due to the damages mostly caused by sport surgery, spinal surgery, or stroke. Therefore, design of an assistive exoskeleton robot for upper limb movements seems necessary. The purpose of this study is to design, fabricate and deliver a control algorithm for an assistive wearable robot. The robot has five degrees of freedom in order to help the flexion/extension and abduction/adduction shoulder. Dynamic and kinematic model of elbow, forearm, and wrist is developed to determine the amounts of torques which are required in the joint actuators mounted on the... 

Given the optimum design importance of parallel mechanisms, characteristics such as degree of freedom, decoupled and isotropic in structural synthesis of these mechanisms are considered. Also, due to less attention to the development of 5-DoF parallel manipulators, in this research, the improvement of this types of mechanisms is considered. In this research effort to design 5-DoF cartesian, decoupled and isotropic parallel manipulators leads to represent four numbers of this type of mechanisms with 3T2R and 2T3R degrees of freedom. Represented PMs verified with linear transformation theory. Morever by using Jacobian, they more analyzed for their decoupled and isotropic specifications in... 

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... 

Interceptor is a blade installed on planing hull transom, and it helps the planing performance by making an stagnation point on aft part of the hull thus generating a lift force and reducing the planing trim. In the present study a numerical modeling of a planing hull in still water has been made and the effect of an interceptor in the numerical model has been studied. Then by validating the model with and without the interceptor through experimental model testing, it has been used for modeling a planing hull in waves with an interceptor. The numerical modeling has been made using 2DOF analysis in Ansys-CFX and the experimental model tests have been done in Mechanical department of Sharif... 

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... 

In this thesis, the problem of failure-tolerant control of the satellite in coupled orbital and rotational motion is investigated. All of the actuators of the satellite are thrusters and only the failure of the actuators is considered. At first, the equations of coupled relative translational-rotational motion of the satellite are derived. Then, the required specifications of the approapriate control method for the problem is explored with the conclution that the controller must be able to predict the behavior or planning the future trajectory of the satellite. In the next step, model predictive control, which has the required specifications, is used to control the coupled... 

The purposeof this study isto findthe propertiesof an equivalent linear Multiple Degrees of Freedom (MDOF) system, or so-called substitute structure, that its response is an approximation ofthe target actualnonlinearMDOF structure’s response (Shodja, 2013). In that regard,thestiffness anddampingmatricesofthe substitutestructure are considered as functions ofthe stiffnessand dampingmatrices ofthe actualnonlinear structure. Inthisway,the substitute structurescan be constructedthroughtrial and errorfor structures with different fundamentalperiods, damping ratios and number of floors.Inthat regard, a number of multi-story steel moment resisting frames are considered. The ductilities of these... 

Cable-driven robots are referred to as parallel robots actuated with cables. In fact,in such robots rigid links are replaced by cables, which may be extended to desired lengths without making mechanism much heavy. This robot possesses a number of unique properties that makes it suitable for many industrial applications. The main factor which makes cable robots analysis different from other parallel robots is the incapability of cables to push objects. Hence, obtaining the workspace of a cable robot is one of the most important subjects associated with this type of robot.The goal of this thesis is to design a spatial translational cable driven robot, which may be used for object handling. For... 

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... 

Nowadays, with a constant increase in life expectancy, joints pain and deficiencies have become a major problem and the use of prosthesis is increasing. One of the most important joint in human body is the hip joint which bear a major share of forces in daily activities. Hip joint is a cup-sphere joint with 3 degrees of freedom (DOF). Therefore, design and manufacturing of such prosthesis is very important. The objective of this thesis is to develop the know how for manufacturing of a standard hip prosthesis by hot forging of Ti6Al4V alloy. First a review of kinematics of bones and joints and forces on hip joint is presented, then the proper process for manufacturing of the hip prosthesis... 

In recent years, unmanned vehicles have intensively been developed to reduce human dangers for marine applications. Predicting the dynamic behaviour of an autonomous underwater vehicle is important during the vehicle’s design phase. In other words to design an AUV, one must clarify its maneuverability and controllability based on a mathematical model. The mathematical model contains various hydrodynamic forces and moments expressed collectively in terms of dynamic equations. Therefore, to optimizing the AUV design it is necessary to predict maneuvering abillity and dynamic behaviour of AUV. This can be able by computational simulation. SUT-2 is an AUV, being developed by Marine Engineering... 

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...