Sharif Digital Repository

Laser ultrasonic is a novel method for measuring sheet parameters. In this technique an intense pulse is irradiated to the target which instantaneously vaporizes the surface layer into the high temperature and high pressure plasma. Expansion of plasma produces shock wave that propagates through the surface. Mechanical properties of target can be calculated by measuring and analyzing produced shock wave. In this project wave propagation is simulated using finite element and numerical-computation methods. The numerical-computation simulation was performed using lamb wave equations. ANSYS software was employed for finite element simulation. The results corroborate each other. Next, simulation... 

Nowadays, autonomous underwater vehicles (AUVs) are implemented to carry out various activities under water. Amongst applications of these vehicles we can mention monitoring of marine creatures, mine installation and neutralization, and many military applications. The objective of this research is designing a control algorithm for underwater vehicles such that an under actuated vehicle can reckon a moving target as a reference and whilst chasing it, vehicle can keep a fixed distance from this target. First the dynamics of underwater vehicles are modeled and in this modeling different effects due to under water motion such as drag force, buoyancy force, and also added mass are included... 

In this paper, the general research of impedance control is addressed for a robotic manipulator with a moving flexible base. Impedance control imposes a relation between force and displacement at the contact point with the environment. The concept of impedance control of flexible base moving manipulators (FBMM) is rather new and is being considered. The dynamic of manipulator is decomposed into slow and fast dynamics using singular perturbation method. New sliding mode impedance control method (SMIC), using an element on the end effector is proposed for high precision impedance control of FBMM. The sliding mode impedance control method as a robust impedance control law is derived for the... 

The reflective optical rotary encoders are used greatly in automation systems for speed and position measurements. Their approach of reading code as pulses which results in position and speed information is very similar to what a CD-ROM driver performs to read the saved data as pits and lands on the compact disc data layer. Moreover, the micron size of pits and lands in compact disc promise a high-resolution, and low cost rotary encoder based on CD-ROM technology. In this thesis, two concepts of length coding and hybrid incremental-absolute coded discs are proposed. To verify the implementation of these concepts, the rotary encoder set based on CD-ROM technology is designed and tested. It... 

The main objective of this project is to investigate modeling for a robotic swarm with suitable sensors and to analyze effect of sensory noise on the control and unity of the swarm. This project is an extension of analytical study done by S. Etemadi, A. Alasty and G. Vossoughi in Sharif University of technology. The flocking frame assumed to have a leader robot that controls over all behavior of the swarm made of agents’ robots with limited equipments and low intelligence that only obey some basic attraction and repulsion laws that will be explained. As an initial step of the analysis, we investigate proper physical model, sensors and navigation systems suitable to the model. Next, the... 

Modeling and Control are fundamental issues for fish robots, which can play basic roles in design, optimization, fabrication, and eventually utilization of them. A review on the literature reveals the shortage of an analytical closed form model with little simplifications and high precision, and also control works based on such models. Studying LAEBT theory, it is shown that this theory is suitable for determining the forces produced due to the tail movements considered in the present work, and then it is used to determine the forces. Experimental investigations by means of the setup made for this purpose showed that the obtained equations for the forces have got acceptable precision.... 

Temperature noise phenomenon in nuclear reactors results to the vital information about the system. This phenomenon may originate from coolant inlet temperature fluctuations, coolant fluid velocity fluctuations or the reactor power fluctuations in PWR reactors. Diagnosis of such temperature noise sources shall improve the reactor control and protection.The present research aims to develop a software to model the temperature noise in the axial direction of a single channel comprises of fuel rod and the associated coolant to recognize the type of temperature noise sources. In this regard, research stages are as follows: first the temperature noise caused by three conventional noise sources in... 

The Very-High Temperature Reactor (VHTR) design is one of the six candidates for the Generation IV nuclear reactors. The reactor core type of the VHTR design is either prismatic or pebble-bed. In pebble bed reactors, the core is filled of thousands of graphite and fuel pebbles. Fuel pebbles in these reactors consist of TRISO particles, which are embedded in a graphite matrix stochastically. The reactor core is also stochastically filled up of fuel and dummy pebbles with an unequal ratio. These two stochastic geometries are the so-called double heterogeneous of this type of reactors. In the current study, a... 

This research focuses on the robust mobile robot localization exploiting motion information acquired from an optical mouse operating based on optical flow technology. Most techniques of visual motion measurement are based on the well research discipline called “optical flow”. Theoretically, optical flow as a method of localization can be highly accurate, but it is sensitive to the noise and surface texture/optical characteristics and distance variations between the CCD detector and surface. As one could not achieve acceptable results in practical situations, to handle these problems, we propose to attach an acceleration – gyro (INS) sensor on the CCD detector (optical mouse) to improve the... 

Robot navigation and guidance is an important issue in robotic. Navigation by itself includes localization, path planning and guidance. For having a successful navigation it is necessary to succeed in all of those parts. The localization precision as basic part of localization is important and having more accurate information of robot position is important. Recently, sensors which use optical flow technic and are widely used in optical mouses are so common and they are able to measure displacement with resolution of 3 to 63 micron. In this research, a localization method for micro robot localization based on optical flow and INS sensor data fusion is presented.
Two data fusion method... 

Noise phenomena, which is considered as a nuisance factor, always acts as a barrier to achieve optimal performance in all systems. In Nuclear power reactors, noise can occur due to mechanical problems such as fluctuation in control rods, failure in placing Fuel assembly in their locations properly or other factors such as creation of small bubbles in moderator. Regardless of its cause, noise leaves its impact on cross section area of material within the reactor core. Change in material cross section area shows its effect in neutron flux. Although noise is a small disturbance and may not have much impact on the reactor momentarily performance itself, in case of continuity, it can leave... 

• Brachiation robot is a kind of under-actuated robots. A brachiating robot is a type of a mobile arm that is capable of moving from branch to branch similar to a long-armed ape. The purpose of this thesis is control of a two link Brachiation robot. The purpose of this thesis is control of a two link Brachiation robot using neural network and geometry control. For this purpose a genetic algorithm based training Neural Network is used to produce a suitable path for the second link of the robot and then using input-output linearization method, the second link is controlled to follow the path. The simulations shows that the Nero Controller designed in this thesis is suitable. The controller can... 

One of the subjects that have been title for many research proposals in recent years is application of Nano Zero Valent Iron (NZVI) particles in contaminant removal from groundwater sources. Despite many studies being done, field application of this particles in a practical scale is not widespread yet which is due to many challenges like rapid settlement of particles or their unclear behavior through field application. The main purpose of this thesis in the first place is to find a practical and productive method for stabilization of particles and enhancement of their transport properties. To reach this goal, application of a natural polymer like starch has been studied as a solution. To... 

Microrobots are generally suitable for implementation of certain works in miniature dimensions such as micro assembly, microsurgery, adaption with small animals and so on. In this way, there is special position for mobile microrobots capable of moving in the range of more than theirs dimensions. Achivieng to high resolution and high speed locomotion are the challenging issues in the microrobot’s development in which much effort has been done.The goal of this project is dynamic modeling and velocity control of an A-shaped microrobot with with nanometric locomotion. During this project, first the dynamic modeling of microrobot is investigated and simplified based on the previous studies.... 

The present study deals with designing controller for Therapeutic Exercise Robots which belongs to larger group namely Rehabilitation robots. Therapeutic exercise robots are often realized in shape of exoskeleton robots. The main line of present research is involved with, designing controller for lower limb therapeutic exercise robots and offering and implementing technical rehabilitation ideas. Firstly, in order to have a reliable position-control, considering practical limitations (e.g. system uncertainties), a robust adaptive control has been designed. Adaptive control can deals with parameters uncertainties and covering unstructured uncertainties (e.g. disturbance and noise) can be... 

There are several methods for identifying unknown elements of an unknown compound. One of the common methods for this purpose, using neutron activation analysis. In conjunction with this method, different computer codes and softwares have been developed and used. One of these methods is K0 method that is a single comparator method. The code that based on this method is K0-IAEA code that is written by the International Atomic Energy Agency and access to it is free. Foremost objective of this study is to determine how to work with this code. In order to evaluate the accuracy of the results of the code, examples have taken into consideration the amount of time previously unknown elements by... 

Nowadays exoskeltons are developed because of improvements carried out in mechatronic technologies, to use in applications such as human rehabilitation and power augmentation. By reason of interaction between exoskeleton robot and human, an appropriate control strategy should be considered to implement regulated interaction force between them. As an example there are situations that a person wants to carry heavy load with this robot without suffering from weight of the load, so control of robot movements is of great importance. The aim of this thesis is dedicated to develop and implement a control strategy achieving minimum ineraction force in a 2 degree of freedom lower limb exoskeleton.... 

The main goal of this thesis is to develop and implement a variable Impedance control method with the ability to refine the desired gait in an online manner. For this purpose, a dataset consisting of 89 healthy gaits was utilized. Then, “Basic shapes” were driven using principal component analysis and their meaningfulness was investigated. Regarding the meaningfulness of coefficients of basic shapes, a normality metric was defined to evaluate the human gaits. Furthermore, as a reference gait refinement in Impedance control, an outer loop was added to change the desired gait, according to traversed gait. Kalman filter was used to estimate the coefficients of basic shapes in this loop. In... 

One of the methods to enhance the economic performance and safety factor of nuclear power plants is to determine a suitable fuel loading strategy in a reactor core. Different methods have been already elaborated to choose the proper fuel loading pattern. Selection of the best pattern for fuel loading ensures the best use of fissile material and more safety during reactor operation. Perturbation theory method is one the methods which could be used to solve this kind of problems. The effect of non-uniform perturbations on the reactor operation can be evaluated by multigroup calculations and using proper space dependent group constants. In this study, a C# based program is developed to find the...