Sharif Digital Repository

In this thesis, kinematic, dynamic modeling and simulation, and control of SQ15-06N industrial robot have been presented. This robot is mostly used in the painting industry. Studying the robot requires familiarity with the robot programming and the hardware used in the robot. In this research, robot characteristics such as repeatability, load carrying capacity and accessibility have been investigated. The principles of industrial robot programming and robot programming language have been studied. The use of simulation software is common due to cost savings, reduced time, no need for robots and controllers, and the ability to test programs in a virtual environment. For this purpose, the... 

Nowadays, industrial companies deal with a wide range of serious problems in the field of power transmission maintenance and also fault detection. A large amount of money and time is spent on these issues in order to solve them; consequently, there is an essential need for this subject. In this thesis, in order to tackle those major issues which were referred above, an artificial neural network is trained with only one hidden layer. Also, a suitable database for training an efficient neural network is needed. Thus, a one-stage gearbox system with appropriate degrees of freedom is used to set up referred database. In this system, a crack is imposed to a tooth of spur gear with different sizes... 

In this thesis, a dynamic model of the biomimetic robotic fish with a flexible tail is developed. In this model, the oscillating frequency of the tail controls the forward velocity, and the body spline offset parameter controls the heading angle. The robotic fish were divided to two parts: a rigid body, and a flexible tail. The rigid body includes the head and the electrical and mechanical equipment. The bond graph model was developed and the numerical values were extracted from constructed robotic fish have also been hydrodynamically analyzed. Simulation results were quantitatively compared and verified with Matlab Simmechanics simulations. These simulations described the lateral movement... 

Cooperative systems have been widely studied in literature. The Dual-Arm Cam-Locked (DACL) robot manipulators are reconfigurable arms formed by two parallel cooperative manipulators which operate redundantly but they may lock into each other in specific joints to increase structural stiffness in the cost of losing some degrees of freedom. Obtaining the optimal configuration demands lots of computational time and is not practical in real-time applications. In the present work, considering the kinematics of the manipulator, the optimal control problem of redundancy is formulated in the framework of tasks with the order of priority. The optimal control formulation is derived by using the... 

Due to high cost and ineffectiveness of molecular models a new method for coupling continuum models with molecular models is used. In this method, the continuum and molecular domains are overlapped. Comparing the results obtained from the concurrent simulations and molecular dynamic simulations proves the accuracy of the method used. The method is used for modeling single layered graphene sheets, stress contours are presented for multiscale and both static and dynamic simulations of concurrent. For multiscale simulations two different carbon nano tubes are investigated and strees-bond angle and strees-bond length are also presented  

In the present thesis, the movement of the clusters of fullerenes and nanocars are separately investigated on graphene surface, using molecular dynamics simulations. Investigating the fullerene clusters with different populations, it is concluded that, as the number of molecules inside the cluster increases, the displacement range of the motion decreases. In fact, some parts of the energy of the fullerene cluster are wasted through the intermolecular interactions, and as a result, the mobility of the cluster diminishes. During the investigation of the three-dimensional structures of fullerene, the wetting property of the clusters is revealed relative to the graphene surface. The decrease of... 

In this dissertation, Hydrogen storage in the solids based was investigated. The carbon-based structure used is the graphene that decorated with metal atoms to increase intermolecular interactions and increase the adsorption weight capacity. The structure of graphene has been considered due to its properties such as low density, high heat transfer coefficient and high specific surface area. Initially, the structure of pure graphene was investigated using the molecular dynamics method for hydrogen storage and it was shown that the interaction between hydrogen molecules and pure graphene is very weak and it can’t be a good option for use in cars. Then, the structures of graphene reinforced... 

Both resources have shaped the development of societies during the course of history. The increase in population, the growthe of middle-class societies, climate changes, economic development, health and environmental concerns, all play roles in magnifying or reducing the growing stresses on the vital resources of water and energy. Projections for water availability and quality, food and enrgy availability, soil and air quality are alarming. These alarms point to a major conclusion:’business as usual’ is no longer viable. Indeed, they call for a fundamental shift in the manner in which we understand and manage resources: a shift away from traditional approaches toward more integrative,... 

Isolated electric energy systems are often needed to supply 3 kind of electric loads. This could be caused due to geographic isolation, the necessity of load mobility, demanded values of voltage and current that are not compatible with the local networks. This makes the design and construction of stand-alone energy systems a must. Because of sustainability concerns and enviromental pollution avoidance, Modern designs are being pushed towards cleaner energies and technologies. Polymer electrolyte membrane type fuel cells are among the new technologies that are being considered as a good alternative to the traditional power sources used for stand-alone energy systems. Although the basic... 

Space debris have increasing importance for space missions. The towing removal scheme is one of the most promising ways for active removal of these debris from LEO orbits. In this approach, an active propelled satellite captures the debris via a space tether and a tethered net which by producing a force opposite to its velocity, it will cause deorbiting and burning the debris in the dense atmosphere. One of the issues with this technique is the danger of tether rupture which for solving that two tethers instead of one can be used. In this research study of active removal of flexible space debris via double tethered towing system has been done. Dynamic modeling has been done with Newton’s and... 

There is a class of small vertical take-off and landing flying vehicles that only have a dual coaxial engine on top and move based on the thrust vector control method. In this project in order to have better insight about the physical mechanism we are dealing with, a conceptual design of a prototype vehicle is first carried out. It is then followed by extraction of two and three dimensional dynamic models of the vehicle. By computer simulation and a simple dynamic analysis, the equations are verified and the movement of the aircraft is discussed for different flight phases  

In this research, the dynamic model of a quadrotor-cable airborne wind energy system is presented. These systems have received a lot of attention in recent years and many examples of them have been designed and built. In addition to comprehensive system modeling, cables and quadrotor in the quasi-stable autorotation phase are modeled separately. These models can be used in other fields in addition to wind energy systems. One of the applications of this thick cable model is in the marine industry.In this research, Newton-Euler method has been used for modeling. The cable model is considered and developed as rigid elements with joints with rotary springs and dampers. The quadrotor model is... 

Auxiliary Power Unit (APU) is a single spool turboshaft engine aimed to start the main gas turbine engine on the ground as well as to supply the necessary power to the auxiliary and electrical equipment during an engine emergency shut down. Similar to the main gas turbine engine, the performance of APU depends on the altitude. Hence, a control system with an appropriate logic is required for a dual function APU which provides electrical power as well as pressurized air through a generator and load compressor, respectively. It should be emphasized that while the output of the generator remains almost not affected with the altitude, the performance of the load compressor is altered by this.... 

In order to observe natural gas turbine phenomena and predicting engine behavior, we need to have a comprehensive simulator in every engine phase of design and analysis. Because of the high cost of manufacturing and prototype experimental tests, it's beneficial to access a gas turbine engine simulator. As well it's hard to make change in a manufactured engine, while we can change a simulator easily.Gas turbine is simulating in zero, one, two and three dimensions. In this project, we have studied previous researches and according to problem, among all simulations, we have studied the ATEC simulation and its assumptions in this thesis. Of these, zero and one dimensional simulations are simpler... 

For the VTOL aircraft mission profiles, terminal phases are considered the most crucial and convoluted due to the interrelated aspects involved in transition from level flight into vertical motion. Flight safety is the trivial, yet essential requisite that should be satisfied during all flight phases. This paper aims to present a comprehensive model for determining a safe distance for urban VTOL air taxies during the landing phase through predicting possible conflictions and reducing this possibility by performing a conflict resolution maneuver while maintaining the flight safety requirements.The safe distance during landing is calculated based on a Monte-Carlo simulation which employs the... 

In present research, a new system of energy extraction from water flow has been studied and optimized. This semi-active energy harvesting system consists of an airfoil that is connected to the generator by an arm. The passage of water causes the airfoil to move, so the hydrodynamic forces on the airfoil will cause the arm to move and finally the generator. In this research, complete dynamic modeling of this energy extraction system including generator, airfoil, controller and actuator modeling is presented and the governing dynamic equations are extracted using this modeling for dynamic simulation. Two dimensional fluid simulations have also been performed using fluent software. Finally, in... 

In this Thesis, an unmanned multicopter with a new structure is modeled and a nonlinear controller is designed for it to track the trajectories precisely. The multicopter in this thesis, has six propellers with a hybrid propulsion system (a combination of fuel and electric propulsion system) that has the ability to carry more payload and maintain more flight duration compared to electric multicopters. In the beginning, the performance characteristics and technical specifications of the hexacopter are presented. For modeling, first the equations of six degrees of freedom movement of the hexacopter are derived by the Newton-Euler method. In the next step, the forces and torques applied to the... 

A complete 6DOF flight dynamic model of an elastic flapping wing (EFW), integrated with unsteady aerodynamic theory is developed. In this respect, initially efficient high fidelity modules for EFW structural dynamics (SD) as well as unsteady aerodynamics loadings (UAL) to be coupled with its flight dynamics are prepared. A modal approach is followed to model structural dynamics of plain and 3D EFWs. This is in contrast with the Euler-Bernoulli beam theory that is mostly utilized for SD in the existing literature. In addition, due to the possibility of large wing deformations as well as the existence of non-linear displacement regime for realistic EFW flights, non-linear modal approaches such... 

Quadrotors are one of the most popular unmanned aerial vehicle (UAVs) that has been subject of extensive research in recent years. One of the most important applications of these aerial vehicles is transporting a cable-suspended payload from one point to another. The major challenge in modeling of this system is dynamic coupling which exist between all components of the system i.e. payload, cable and quadrotor. The purpose of this research is mathematical modeling and dynamic analysis of the system in presence of this dynamic coupling and considering the effects of cable's flexibility. In this regard, it is assumed that the payload has variable mass. In this thesis, in the first step, by... 

Using unmanned aerial vehicles in aerial payload carrying leads many changes requiring significant study and research. In recent years, there has been considerable maturation in Micro Aerial Vehicles (MAV) developement especially quadcopters. In addition to the endurance restriction, considerations on volume and weight that can be carried, and safety issues are also obstacles to the development of unmanned aerial payload carrying in urban environments. One of the ways to make a quadcopter more agile while carrying a load is to hang the cargo from the quadcopter via a cable. In this way, it is possible that quadcopters carry the cargo in a cooperative way, which if properly arranged,...