Sharif Digital Repository

Nowadays, multi-agent robotic systems are implemented to perform various operations such as military mission, search and rescue operations, etc. One of the most interested robotic platforms for multi-agent systems is quadrotor aerial robot. In this paper, a team of quadrotors is prepared to perform a formation flight toward a specified target in order to catch and transport it on a desired path. Therefore, at first, trajectory tracking control of the quadrotor has been studied and two types of controllers have been introduced: Hierarchical controller and Non-hierarchical controller. Coordinate free structure of the hierarchical controller provides distinctive properties and guarantees... 

Regaining biomechanical function, comfort and quality of every-day life is a prime consideration when designing prosthetic devices for amputees. The magnetorheological (MR) prosthetic knee, which is the subject of this study, is an example of such a device. The study presents a comprehensive and a combined MR device design and MR fluid design approach, aiming to advance the MR prosthetic knee. First, this study focuses on developing a new configuration on magnetorheological (MR) brake damper as prosthetic knee. The new configuration is a rotary damper using MR fluid with a single rotary disc will act as a brake while MR fluid is activated by magnetic field in different walking gait. The main... 

Nowadays, due to expansion of the cities, growth in population and developments in technology, energy demand has increased extremely. Therefore responding this increased demand is a great challenge in political and economical management of all countries. Thus in recent years, cogeneration has become so popular between experts in the energy field because of its great efficiency and performance. The goal of this research is to design a controller based on a model which can predict the behavior of the cogeneration system. This controler is called “Mode Based Predictive Controller”. It utilizes the system in such a manner which has the lowest operation costs. This goal is obtained via modeling... 

Independent robots are equipped with various sound, inertia and visual sensors for decision making. Vision is an attractive sensor due to its non-invasive nature, passivity, and high information content. In natural environments, visual noises such as snow, rain, and dust distort images. in underwater environments, factors such as refraction and absorption of light suspended particles in the water, and color distortion affects the quality of visual data, resulting in noisy and distorted images. As a result, the autonomous underwater vehicles that rely on vision (AUVs) are challenged, resulting in poor performance. To improve the input to the visual algorithm for tracking the pipeline, in... 

Warming the injectable blood is a set of methods used to transfuse blood to the supplier (Accident patients, surgery, dialysis). These methods raise the temperature of the injected blood to body temperature. Blood transfusions are performed directly before World War II, so there is no need to heat the blood, Increased need for blood units caused blood banks. In these banks, to prevent the proliferation of pathogens, the temperature of blood units is reduced to 2-6 degrees Celsius. For indirect injection of these blood units, the injection temperature should be brought to the patient's body temperature before injection to prevent the recipient's body temperature from decreasing.In this... 

The error of the inertial navigation system increases over time due to the cumulative errors of sensors. Inertial navigation system couples with sensors or other systems to prevent navigation system errors growth. One of the systems that can be used to couple with inertial navigation system is visual odometry. Visual odometry can calculate relative position of the camera at any time and estimate the device path through input images from one camera (Monocular) or multiple cameras (Stereo). Visual odometry algorithms improvements in recent decade cause this system used as real time. In this thesis, DSO algorithm, which is a direct method and monocular approach, couples with an inertial system... 

The use of sandwich panels has become very common in recent engineering designs when the weight of the part or structure is important and we are looking to lose weight while maintaining strength. The mechanical properties of this type of structures, including yield stress, fatigue behavior and estimation of their life, failure modes, natural frequencies and resonance phenomena, etc. are affected by various factors, including geometric and environmental factors. Fatigue is one of the most common failures in these structures. Composite materials have complex structures. In these materials, due to the viscoelastic properties, the fatigue behavior changes with changing stress, stress frequency,... 

Now a day measuring dimensions plays an important role in industries. Improving the technology of measuring the dimensions, leads to higher quality of production. It is important for industries to have a rapid and accurate dimensions in short time. In this thesis, we worked on measuring dimensions with 3D laser scanner and in the end, the results related to accuracy and speed and efficiency of the system was shown in the thesis  

Ship maneuverability is so important from different aspects. According to the regulations of International Maritime Organization (IMO), every vessel has to meet the minimum requirements of mentioned rules. Consequently, prediction of ship maneuverability in early stages of the ship design has become to one of the most necessary steps for shipbuilding and design companies. In this research work maneuvering of a high speed ship has been investigated using three different propulsive modes, considering propeller and rudder systems, azipod propeller and waterjet systems. First of all, hydrodynamics equations of each cases while considering different motion modes such as surge, sway, yaw, and roll... 

The collision of moderately large asteroids and comets also referred to as Near-Earth Objects (NEO's) with earth would have catastrophic consequences. Such events have occurred in the past and may occur again in the future. However, for the first time in known history, humanity may have the technology required to counter this threat. Methods studied for mitigation of this hazard are based on deflecting asteroid's trajectory and are normally divided into two basic categories: high energy impulsive methods, and long-duration low-thrust methods. Two parts of mission to be optimized are the trajectory of spacecraft to reach the target and the deflection strategy which could be analyzed by the... 

The minimum cost of energy is the goal of the wind farm layout optimization. This can be achieved by either maximizing the total energy or minimizing the total costs of the farm. This thesis considered the effect of wind speed on the performance and thrust coefficients. We also used two sizes of commercial turbines. First, we started by a single variable objective function (turbine cost to generated power), then, considering cable, foundation and O&M modules, objective function changed to a LCOE function which is non-dimensionalized by dividing all the costs to the cost of one turbine. We modified the simple cost model proposed by Mosetti et al., using cost scaling law, and also included... 

In the late 1980s, the International Maritime Organization started working on reducing air pollution by ships, and the result was the approval of Annex 6 of MARPOL and its mandatory implementation since 2005. Since then, due to the increasing importance of pollutant emissions in the maritime transport industry and the stricter regulations of the International Maritime Organization and the high cost of fuel for ships, ship owners are looking for ways to reduce fuel consumption. For this purpose, various activities related to reducing the fuel consumption of ships were carried out. Among these, the use of energy saving devices can be a solution. Recently, the hull vane, as a fixed underwater... 

In recent years, the area of research on micro flying robots has been developed, because of the development in micro manufacturing technologies. These flying robots can be used in military and Civilian missions such as identifying, espionage, aerial relays, traffic surveillance rescue, help and…because of their advantages. Ability to fly in finite areas, no human injuries, low manufacturing and power cost, easy and fast Application, Easy Maintenance and … are some advantages of these robots. We can control these robots manually by RC remote controllers or by Auto guidance system. On the other hand, these robots are used in research laboratories for testing new control algorithms such as ... 

Magnetic shape memory alloys (MSMAs) are a new kind of smart materials which are great alternatives for energy harvesting systems due to some unmatched characteristics such as reversible large strain, high cycle fatigue and fast time response. In this work, an energy harvesting system using MSMA is studied. For this goal, a 3-D thermodynamic-based MSMA model is applied for predicting magnetomechanical behavior of the MSMA sample which is used in the energy harvester system. Since demagnetization effect, which has a great influence on the model’s outputs, has been neglected in the selected MSMA model, a new approach is presented for inserting demagnetization coefficients, regarding to the... 

Vibration based energy harvesting is the process of trapping and collecting vibrational energy from ambient sources which seem unusable at first sight. The smart materials with the capability of coupling two different fields can be used in converting vibrational energy to electrical one. One of this smart material which has been taken into account recently is the Magnetic Shape Memory Alloy (MSMA) and it can couple the magnetic and mechanical fields. In MSMAs the total magnetization vector changes with the application of stress and make it possible to harvest energy from Faraday law’s of induction. An important phenomena that exist in MSMA is the dependency of magnetization-strain behavior... 

Wide range application of high speed marine crafts in marine industry and other related industries results in attempts to improve the performance of such vessels. The main ideas of using control surfaces in high speed planing crafts are the change of the high speed planing craft‘s resistance due to change of their running attitudes and wave response mitigation of this vessels. Control surfaces produce forces and a pitching moment due to a pressure distribution caused by them, which can be used to alter the running attitude of high speed marine crafts. The present work contains a comprehensive study on trim tab as a control surface for the high speed crafts. The results of this study condense... 

One of the key issues in the design of vessels is their proper stability and performance in waves. Therefore, the use of twin-hull vessel designs such as conventional catamaran and SWATH is suitable for improving stability and seakeeping quality. Although SWATH has a better seakeeping quality than a conventional catamaran, it has been observed that at high forward speeds, especially in head waves, the vertical motions of the vessel is greatly enhanced. Various methods such as correction of the hull form and the use of fin stabilizers can be used to modify SWATH vessel motion behavior. These control surfaces can respond appropriately to the dynamic forces from the waves, reducing the motions... 

Tubular sections and consequently tubular joints in construction of steel structures in the form of space frames is widely used in ground and marine structures, including offshore jacket platforms. The passage of part of the life of the existing offshore platforms has caused cracks in various parts of the joints of these structures due to various reasons, the most important of which is fatigue. In this thesis, by adopting numerous numerical studies and validations with some cited experimental papers, the principles governing the proper buckling behavior of tubular members focusing on the conventional geometries of Persian Gulf platforms as well as the behavior and local flexibility of...