Sharif Digital Repository

Modeling and Controlling of a satellites fuel slosh is considered a vital problem in the field of satellite attitude control. In this paper modeling and control of the attitude of a satellite carrying a partially filled spherical fuel tank, which uses the diaphragm as a propellant management device (PMD), has been studied. The fuel slosh dynamics is modeled using a spherical pendulum with two degrees of freedom and a rigid arm, which represents the first mode of sloshing. The effects of the diaphragm that surround the fuel surface, are considered as torsional springs and dampers attached to the satellite body. The combined dynamics equations of the satellite rigid motion and the fuel slosh... 

Advanced control techniques are required to achieve a cost-effective and reliable use of the wind power generation. The wind turbines are generally controlled based on two control objectives: the turbine protection and the generation of acceptable power for the utility grid. These objectives are achieved if the control inputs are applied based on appropriate control logics. In this work, a nonlinear multivariable model of the wind turbine with a DFIG generator is considered. The rotor speed and the d-axis rotor current (as the control outputs) are controlled via manipulation of the two generator voltages (as the control inputs) in low wind velocity condition. For high wind velocity, the... 

The purpose of this thesis is to design a controller for a reentry spacecraft to despite the uncertainty in the initial conditions and the aerodynamic characteristics as well as the presence of atmospheric turbulence and the presence of noise in the system. Reentry vehicle that studying in this project is Apollo, a capsule without wings, with a low lift to drag ratio. Earth is modeled as elliptical and Earth's rotation is also considered. The Guidance system produces the bank angle command, and the reentry vehicle must follow the commands with the help of the controller. The controller is designed based on the nonlinear dynamic inversion method. Dynamic and kinematic equations of rotational... 

The problem of spacecraft rendezvous on periodic orbits around the L_1Lagrange point of the Earth-Moon system is investigated. For this purpose, the nonlinear relative equations of motion are drived within the contex of the Circular Restricted Three Body (CRTB) problem. Subsequently, several types of rendezvous missionas well as control teqniques are considered for analysis and simulation. Application of different control approaches allows for partial verification as well as comparison of results achieved with various teqniques. The considered control approaches include optimal closed loop Linear Quadratic Regulator (LQR), nonlinear Feedback Linearazation (FL) as well as the nonlinear... 

In this thesis the problem of spacecrafts formation control for halo orbit around the second libration point (L2) of the Sun-Earth Three Body (TB) system is investigated. Station keeping, reconfiguration and precision formation control of spacecrafts on halo orbits are performed via the use of the nonlinear Integral Sliding Mode (ISM) method, optimal closed loop Linear Quadratic regulator (LQR) approach as well as the Model Prodective Control (MPC). In this regard the nonlinear relative dynamics of deputy-chief spacecrafts are derived within the concept of both circular and elliptical three body problem; as well the perturbation model of the Moon and the linear model of restricted three... 

Subcutaneous needle insertion is one of the key methods of limited invasive surgery in medical diagnosis and treatment. However, errors in needle targeting can reduce the effectiveness of such efforts. One of the main factors of errors is due to the human guidance of the needle, which many researches have approached in recent years, and among the suggested solutions is the use of automatic or semi-automatic assist systems. Considering the treatment of prostate cancer by brachytherapy method, this research has developed a semi-automatic physician assistance system using navigation based on the potential field method and ultrasound images of the needle location, and sliding mode fuzzy... 

Coordinate motion is a considerable phenomenon in biology and very powerful tool for leading and controlling a group of robots. In recent years, robotic becomes a helpful technology for acompilishing in works which is impossiple for human, such as working in toxic environments. In this project, we introduce coordinate motion problems which are applicable in multi-agent systems, and we also present suitable control algorithms for solving this problem. In other word, we use potential field method to model coordinate motion. We propose a three-cycle robot as an agent, such that it has two nonholonomic constraints. Designing an algorithm for solving coordinate motion problems, we propose these... 

A sliding mode nonlinear controller has been developed to control a monohull hard-chine planing vessel. Planing vessels has been used for shoreward marine missions. On the other hand, according to vast shores of our country, offshore applications could be of extra importance for us. Autopilot of a vessel consists of two stages: trajectory design and trajectory control. In this project, trajectory control is being done using sliding-mode nonlinear control method, considering the fact that according to nonlinear dynamics of planing vessels, linear control would not show desirable results. In this dissertation, after description of main information about planing vessels and prior researches,... 

Time delay systems may arise in practice for a variety of reasons, such as autonomous systems (without feedback control), and the delay is the result of an intrinsic property of the system. Sometimes the delay results from feedback control action, instead from the system itself; that is, due to the nature of the system, the feedback is delayed. Another type of delays of similar effects may be incurred due to delayed measurements. In both delayed control and delayed measurement, the delay is usually considered undesirable, which has the tendency to deteriorate the system performance or even destabilize the system.

In this thesis, three types of adaptive controller are proposed for... 

In this study, in order to enhance the accuracy of tracking repetitive maneuvers in Unmanned Aerial Vehicles (UAVs), an educable control scheme is proposed. At the outset, the controller is designed based on the sliding mode control (SMC) technique. In addition, the offline PD-type memory-based iterative learning control (ILC) is used along with SMC. In ILC scheme, the error of states is saved during the maneuvers that will be used in the subsequent iteration. Also, in order to increase flexibility of the new control structure, ILC-SMC, a multilayer perceptron has been developed. This network is designed to extend the control signal, generated by ILC, to similar maneuvers. The presented... 

The aim of this project is decentralized control of a group of robots (swarm robots); such that the aggregation maneuver, leader following, Identification and imaging the target, will be performed so good as to make a three-dimensional model of the target from these images. Swarm robots consist of a number of similar and limited features robots which interaction in a group of robots, will lead to special features for the group. Any agent of group decides what to do only with its local information from the environment. Swarm robots are more applicable for the jobs in which a distributed perception from the environments needed, for example space exploration and military operations.In this... 

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... 

This research has dedicated to study the control of chaos when the system dynamics is unknown and there are some limitations on measuring states. There are many chaotic systems with these features occurring in many biological, economical and mechanical systems. The usual chaos control methods do not have the ability to present a systematic control method for these kinds of systems. To fulfill these strict conditions we have employed Takens embedding theory which guarantees the preservation of topological characteristics of the chaotic attractor under an embedding named "Takens transformation". Takens transformation just needs time series of one of the measurable states. This transformation... 

In this article, guidance and control of reusable launch vehicle at terminal phase has been studied. The goal of this article is increasing the accuracy and safety of the guidance and control system of the launch vehicle in order to successfully land on ground surface. Integrated guidance and control, being a novel method in guidance and control, is used to guide the launch vehicle in the re-entry phase and landing phase on ground surface. The returning object studied is a Falcon 9 rocket for which we find the 6 DOF model. The landing method of this vehicle is vertical. Implementing an integrated guidance and control system is a novel approach in this area. The controller used in this... 

Capsule endoscopy is a minimally invasive diagnostic technology for gastrointestinal diseases providing images from the human’s digestion system. Developing a robust and real-time localization algorithm to determine the orientation and position of the endoscopic capsule is a crucial step toward medical diagnostics. In this thesis, we propose a novel model-aided real-time localization approach to estimate the position and orientation of a magnetic endoscopic capsule swimming inside the stomach. In the proposed method, the governing equations of the motion of an ellipsoidal capsule inside the fluid, considering different hydrodynamics interactions, are derived. Then, based on the dynamic... 

One of the most important processes in the manufacture of mechanical parts in the industry is the machining process. High-speed milling is growing in aerospace, automotive, and many other industries due to advantages such as high material removal rates and better surface finish. However, the instability caused by self-excited vibration (chatter) is not only one of the main limitations for the productivity and quality of the workpiece but also reduces the life of machines and tools. In this research, after introducing the matter of milling flexible parts, the basic concepts of machining are first described, and common terms in machining are explained. Then, a review of past research has been... 

Air-handling unit (AHU) is one of the installations that is responsible to control the temperature and humidity inside a space using the heating, cooling, humidifier and drying air. At present, energy efficiency in building is an important issue to maintain the comfort conditions. One of the most common ways to optimize the performance of industrial installations is the use of control systems, which leads to the reduction in both of the costs and energy consumption. In this research, a multivariable nonlinear dynamic model of the AHU with one zone in the VAV (variable air volume) system for working in summer is considered. At first, introduction, limitations and driving the equations for the... 

The 6DOF modelling and robust attitude control of two tethered satellites using tether tension moments is studied in this thesis. In this regard, the coupled rotational and translational dynamics of two satellites connected by a tether in the presence of Earth’s gravitational perturbation, aerodynamic drag, solar radiation pressure and third body effects (Sun and Moon) and also uncertainties in some of physical parameters of system and sensor’s outputs is modelled. Moreover, the tether attachment point to the satellites is different from their center of mass and its effect on dynamics of the system is taken into consideration. Then, the attitude of both satellites are controlled using robust... 

In the present study, an adaptive sliding mode control method was employed to control a fish robotic system using the method of hardware in the loop. Following the introduction of the nonlinear model for the robot, elongated body theory, suggested by Lighthill, was used to analyze fish movements. Lighthill’s theory inspired from slender body theory in aerodynamics scope could be viable to exercise upon the carangiform mode of swimming. By simplifying Lighthill’s equations in planar motion of fish robot, the number of degrees of freedom exceeds the number of the control variables. In view of the fact that the presented model is an under-actuated model, there exist some parametric and... 

In this research, the main purpose of the controller design is in the second region of operation of a wind turbine, which involves absorbing the maximum energy from the wind. WindPACT 1.5MW turbine has been investigated and the power coefficient of this turbine has been obtained using WT-PERF and FAST softwares. Simulations show that the results of both methods are well matched. Then, using ANFIS, a method for estimating the wind speed is derived from the data obtained by FAST. Inputs to the ANFIS system are the turbine aerodynamic power, rotor speed and blade pitch angle while the output of ANFIS system is the estimated wind speed. The maximum power coefficient of the wind turbine occurs...