Sharif Digital Repository

Autonomous underwater vehicles (AUVs) are a type of marine vehicles which are currently being used for exploration, maintenance, repairing of marine structures and military appliances. Unmanned underwater vehicles categorize in two types: ROVs and AUVs, ROVs (remotely operated vehicles) usually are connected to the mother vessel with a cable, conduction signals transfer through this cable and there is an operator in the control loop. The vehicle may be fed up with this cable, AUVs are modern underwater vehicles which the operator on controlling and conducting is removed, there is no connection between the vehicle and mother vessel, energy sources and controlling orders are set up in the... 

In this project Deployment of multi-agent systems was studied. Maximum coverage over a point or curve or area is desired in deployment of multi-agent systems. A facility location optimization function was derived from geometrical concepts such as voronoi, n- geometric median and fermat-weber problem by optimization of which the deployment of multi-agent systems is performed. First, it is assumed that dynamic of agents is first order and second order .Next, it is assumed that agents are in a fluid. In all situations a suitable control algorithm was derived to optimize the facility location function to perform deployment. Next, another facility location function was derived by optimization... 

In this thesis control of wheeled mobile manipulators for cooperative object transportation is investigated. Full dynamic model of a mobile manipulator with a three wheeled mobile base and a three DOF manipulator is derived using Gibbs-Appell method. Input-output linearization technique is used to control individual robots. Transporting the object is divided into two steps, first robots use a decentralized behavior-based method to approach and surround the object. Then virtual structure method is used to control the robots to transport the object cooperatively. Simulation results with three robots handling an object are presented to show the effectiveness of proposed method  

Since Formation control have potentail applications in civil and military industries, decenterlized control of formation control is studied in this work using consensus algorithm. A specific robot quadrotor with 3D motion is used in this work. Quadrotor is an underactuated vehicle. First, we derivate twice from dynamical equations of linear positions. Hence, we can obtain appropriate form using linearization of output equations for design a consensus control algorithm. It is needed to design fourth order control algorithm for control of multiagent systems, beacause of twice derivation. Two methods that have been used for formation control in many works are potential function method and... 

In this research dynamic modeling of a 3-DOF (degree of freedom) compliant parallel mechanism with flexible intermediate links has been investigated. Unlike conventional rigid mechanisms that gain their mobility from movable joints, the compliant mechanisms transmit or transform through elastic deformation of flexible members (flexible connector and joint), displacement, force, or energy from input into output. Eliminating clearance, friction, wear and demand of lubrication in compliant mechanisms, and having monolithic structure provides high-precision motion with micro/nanometer level resolution for them. Therefore compliant mechanisms play a significant role in modern technologies such as... 

In this thesis, a new procedure is presented for control and analysis of a group of autonomous underwater vehicle achieving flocking motion by using a fuzzy-logic-based attractive/repulsive function. Two cooperative control laws are proposed for a group of autonomous agents to achieve flocking formations related to two different centers (mass center and geometric center) of the flock. The first one is designed for flocking motion guided at mass center and the other for geometric center. Desired path for AUV’s has been developed using Virtual agents with mass point dynamics. Smooth graph Laplacian is introduced to overcome the difficulties in theoretical analysis. A new fuzzy-logic-based... 

The electrical voltage, current and power output is calculated due to harmonic forced vibration of shell energy harvester. So five electromechanical equation together with Gauss equation is solved for doubly curve shell harvester in steady state condition in order to derive voltage, current and electric power output. The effect of shell curvature in cylindrical and spherical shells, the harvester series or parallel connection of layers and thickness of substrate and piezoelectric layer, is also considered in order to obtain maximum power output. The results show for small shell curvatures a high frequency load is needed to obtain maximum power and when the shell arc length is three times to... 

Torque variations caused by intermittent combustion and inertia effects of reciprocating components, exert significant torsional excitation on crankshaft of internal combustion engines. These excitation induces considerable torsional vibration on crankshafts. Therefore, modeling and analysis of crankshaft torsional vibration and absorber systems, especially in automobiles engine that crankshaft tolerate high amplitude excitations coupled with heavy inertia effects has high importance. In this study, ability of centrifugal pendulum vibration absorber and dual mass flywheel which used in rotating machinery for vibration reduction, will be examined. At first, cranktrain will be torsionaly... 

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, 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... 

large ships should only make very small horizontal movements at the berth for efficient loading. This is especially a concern in ports facing the open ocean directly, where high swells at sea can cause harbor oscillations and low-frequency surge motions of the ship. A developed mooring unit, the MoorMaster, which replaces conventional mooring lines is addressed here. The hydraulics of the system have a strong reducing effect on the motions of the moored ship. Measurements have shown that the surge motion of container ships was reduced from an amplitude in the order of 1 metre to an amplitude in the order of 5 centimetres, by using MoorMaster units. In here MoorMaster action is divided to two... 

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... 

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... 

In recent years formation control of autonomous vehicles has been a well-studied topic, and the attention has shifted from the control of a single mobile robot to the control of multiple mobile robots because of the advantages a team of robots offer, such as increased efficiency, robustness against fault and damaging, and more systematic approaches to tasks like search and rescue operations, automated highways, survey and patrols, military missions, moving large objects and moving a large number of objects. Formation control means the problem of controlling the relative position and orientation of the mobile robots in a group according to some desired pattern for executing a given task. In... 

Harvesting energy from renewable sources in nature, such as wind energy, solar energy, water energy and vibrations has always attracted researchers. There exist different ways to harvest energy from environmental vibrations. In this thesis, energy harvesting via Magnetic Shape Memory Alloys (MSMAs) has been taken into account due to important advantages of these alloys, such as their long fatigue life and good performance at high amplitudes and low frequencies.In this system, applying strain on alloy changes the magnetization and this change generates voltage in the pick-up coil around the MSMA. On the other hand, since the strain-magnetization relation is nonlinear and hysteresis,... 

Helical swimming robots with a capable propulsion system at low Reynolds numbers have been proposed for many applications. Although linear propulsion characteristics of swimming robots with a single helical flagellum have been extensively studied, the characteristics of maneuverability have not been completely investigated yet. In this thesis two novel mechanisms was proposed. The first mechanism presents a new method for the maneuverability of the helical swimming robot with a single helical flagellum. This mechanism is based on the change in the angle between the helical and body axes. This study shows that a change in the aforementioned angle can enable the swimming robot to have turning... 

The main popuse of this Thesis is investigating of the different wagon arrangement effect on stability of the train set. So to gain this goal, one train with 10 wagons has been simulated. The model of the each wagon is Nonlinear with 40 DOF. 3 of the wagons are heavy and make 3 different kinds of arrangement by putting them at first, middle and the end of the train (HLL, LHL and LLH arrangements). Then these three arrangements have been simulated on two differen tracks and conditions, 1st Accelerating on curved track (320 R) with positive slope and 2nd decelerating on curved track with negative slope.We suppose that the contact is singular point and aslso contact equations have bben solved... 

In this article, research has been carried out on the control technique of autonomous mobile robots to navigate in unknown environments, avoiding static and moving obstacles using eight ultrasonic sensors for obstacle recognition.
In this article we used simple three wheeled robots. Each robot has a passive caster wheel and two active fixed wheels which can act independently. In addition robots have holonomic constraints like maximum acceleration, maximum speed and maximum angular velocity, so robot’s speed and orientation change independently and these changes are small in each time step. Each robot has eight ultrasonic sensors, each of them cover 22.5 degree of space from robot‘s... 

Dynamic positioning system is a controller system used to maintain the position and heading of a vessel with no use of anchors, jack ups but only using the propellers installed on the vessel. A vessel has six degrees of freedom, including three rotations and three transfer. In dynamic positioning systems, the vessel is controlled only on the horizontal plane such that its position and heading are controlled according to predetermined values. To achieve this, position and heading of the vessel is determined and the controller system computes the direction and required power of each propeller. Preliminary systems utilized PID controllers. As the control science has advanced, model based... 

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...