Sharif Digital Repository

Using fractional order calculus to model complex phenomena with combined behavior (i.e., dissipative, capacitive and inertia behavior) is one of the most recent research fields in the world. These accurate models lead to better understanding of the phenomena. For example, consider viscoelastic materials. In early models, dissipative behavior is separated from capacitive behavior but by using fractional order models, these two behaviors are considered simultaneously thus the complexity of the model would be reduced. To use fractional order models in real-life engineering applications, it is important to investigate the dynamics of these systems. Unfortunately, there are a few proper... 

In this study, by INS and auxiliary acoustic sensors data fusion, underwater navigation algorithm is implemented and validated by computer simulations. Extended Kalman Filter based on perturbation analysis is used as combination algorithm. The outputs of the INS forms equations of mechanism. The variational variables are state variables estimated in the Kalman filter. Because of the weakness of the GPS signals due to electromagnetic signals Attenuation in water, acoustic sensors are used as auxiliary sensors in underwater navigation. Here those acoustic sensors that implementing them in this country is impossible or very costly would not be examined.In this research the output of Doppler... 

Synchronization means to control the response system to follow the drive system. It first began in 1990 in a paper by Pecora and after that it is used in many applications like secure communication. Another application for synchronization which is introduced here is identification of chaotic systems. According to the research done, this application hasn’t been in the literature as it is known to us. Synchronization papers usually devide into two parts. In one of them the parameters of the systems are unknown, so adaptive laws are used to estimate the parameters. In the other part, the parameters are taken known. It is not mentioned in the first group that the estimation would converge to the... 

The PID controller has been used for a long history in control engineering and is acceptable for many real applications due to its simplicity in architecture. Hence, in many real industrial applications, the PID controller is still widely used even though lots of new control techniques have been proposed. In recent years, by developing fractional calculus in control applications, using fractional order PID controller —which is simply called — was proposed by Podlubny. Up to now, several methods of tuning fractional order PID controller has been established for time invariant systems, but dynamics of real systems are mostly time varying. Because of this fact, using adaptive control and... 

Despite the advancement of technology in the world still some parts of the work are done by human hands. Gloves that increase fingers force can cause less fatigue, greater accuracy and efficiency in carrying out their duties in person.Also patients with muscle weakness due to M.S. or apoplexy, or elderly people are unable to do the simplest tasks. A wearable robotic glove that can restore hand function can increase the quality of life for people with mobility problems. The aim of this research is to design, build and control a conceptual prototype of a flexible wearable robot to increase fingers force by cable mechanism; and in this glove, force and position control concurrently is done by... 

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,... 

The purpose of this thesis is to design haptic control system for vehicle steering mechanism in a tele-driving system. Thus the subject is a developed subject in comparison with a steer by wire system. The difference is that in the steer by wire system, due to the lack of delay in sending and receiving data, possibility of instability is very low. This subject makes haptic control more difficult in vehicle tele-driving. Control of vehicle tele-driving steering system has been done by different bilateral control structures available in the literature. simulation results of the case that there is no delay in the transmission block suggest that used different control structures in order to... 

Navigation is the science of determining the velocity and attitude of a moving object in every given moment. There have been many methods for navigation. Nowadays with the advancement of technology, advanced navigation systems have been developed. Although each of these navigation systems have their pros and cons, in order to improve the overall performance of the system and to solve their problems, these systems are integrated.The goal of this project is to present an integrated cascade method to decrease error and also decrease dependence on GPS. In this project, INS, DVL & GPS are integrated with the cascade method.To achieve this, INS-GPS and INS-DVL integration are first performed. 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 thesis, the problem of trajectory planning for a high speed planing boat under nonlinear equality and inequality constraints is addressed. First, a nonlinear mathematical model of the craft’s dynamics is derived. To solve a trajectory optimization problem, we can utilize the indirect or direct methods. In the indirect methods, maximum principle of Pontryagin is used to transform the optimal control problem into Euler Lagrange equations, on the other hand, in the direct methods it is necessary to transcribe the optimal control problem into a nonlinear programming problem (NLP) by discretization of states and controls. The resulted NLP can be solved by well-developed algorithms such as... 

In this work dynamic behavior of a two body TSS with main satellite as rigid body is studied and effects of tether elasticity and tension on the satellite dynamic are indicated in station keeping phase and circular orbit. Also a simplified modeling is introduced which could be used in nonlinear controller design. Lagrange and extended Lagrange method is used to derive equations of motion. It is shown that longitudinal vibration of tether has small effect on satellite attitude and angular velocity and because of high frequency it can be decoupled from satellite dynamic. In the simplified model, orbital motion is decoupled from equations of TSS and main satellite dynamic. Effect of decoupling... 

There are challenges in controlling and guidance of vehicles which makes it necessary to have true information about the position, velocity, and orientation of the system. This issue is severe to some extent when a UAV is the object to be controlled. The navigation system is responsible for supplying the mentioned information which is usually accompanied with some errors. Therefore, threre are a wide range of algorithms developed for omitting these errors leading to a well-calibrated navigation system. One of the precise and reliable calibration method is based on the data fusion of intertial navigation sensors and magnetometer measurements. As the obtained data via magnetometers are usually... 

Because of importance of knowing angular velocity in a lot of engineering problems, Rate gyroscopes is widely used in different engineering fields. Among all kinds of gyroscopes, proof mems MEMS gyroscopes are mostly used because of their low cost and light weight. Improvement of the accuracy of the MEMS gyroscopes and their based inertial navigation systems is intended in this thesis considering some undesirable conditions on the gyro and trying to solve the gyro’s equations in that conditions. Existing linear or angular acceleration on the structure that the gyro is installed on is one of these undesirable conditions; Quadrature error in the gyroscope is the other one. In this thesis, the... 

As a subset of hybrid systems, piecewise affine (PWA) systems are capable of approximating the behavior of a wide range of nonlinear systems. Considering the preliminaries regarding these systems and the vast literature gathered around them, the main contributions of the current study are presented in two separate sections. In the first section a class of uncertain piecewise affine systems subject to additive noise are studied. The problem of minimizing the bound on the variance of the steady response of these systems, by means of a piecewise affine observer-controller, is formulated as an optimization problem subject to a number of constraints in the form of matrix inequalities. Then the... 

According to high nominal pressure and controllable flow, variable displacement axial piston pumps are used widely in hydraulic industry. However, there still exist many problems and limitations in the areas of design, controllers and performance. To solve the problems without wasting time and money in making prototypes, an accurate dynamic model of the pump is required which predicts pump behavior under various control signals and loads. The lack of simple and practical methods of measuring describing parameters of pump dynamics, makes investigation and verification of such a model very challenging. In this thesis, literature review is presented in a wide range. After investigating of... 

Control and guidance of a vehicle is vital for it to do its mission correctly. Guidance system and decisional algorithms used in it need exact information of instantaneous position, velocity, and attitude of the guided vehicle to determine and issue proper guiding commands.
Estimation algorithms and navigation sensors are two necessary tools for navigation. In the first section of present study, the reentry head equations of motion are derived and a 6-DOF simulation is done for it. In the second section, measurements of sensors will be simulated using results of the first section and existing reference models for sun position vector and earth magnetic field. The third section appertains... 

Control and guidance of a vehicle is vital for it to do its mission correctly. Guidance system and decisional algorithms used in it need exact information of instantaneous position, velocity, and attitude of the guided vehicle to determine and issue proper guiding commands.
Estimation algorithms and navigation sensors are two necessary tools for navigation. In the first section of present study, the satellite equations of motion are derived and a 6-DOF simulation is done for it. In the second section, measurements of star tracker will be simulated using results of the first section. The third section appertains to development of navigation equations, attitude determination using UKF... 

In this work inspiring from the nature a control method is proposed for a stable rhythmic walking in a seven-link underactuated biped robot. Stable walking is a very important issue in biped robots and proposing a dynamically stable pattern of motion with the capability of acceleration and learning is our main purpose. It is tried that the presented method make the robot have a human like motion. This method controls dynamically the hybrid model of robot’s movement and stabilizes it by converging the time-invariant constraints considered to make this movement. Moreover, in addition to providing a suitable gait for the bipod robot, a robust control method is designed to improve the ability of... 

Systems that are electrostatically actuated have found a vast role in MEMS application. This technology is used in optical systems, sensors, micro switches, and deformable mirrors. Raising the use of these systems in fields that needs better performance highlighted the need to accurate study of dynamics and control of electrostatic actuated systems in micro scale. This work is dedicated to design of an estimation and control system for a micro-beam that is actuated by electrostatic. After a comprehensive survey on pervious works that are done on dynamic, applications, fabrication and control of these systems dynamic of the system is fully derived. The environmental factors like fringing... 

Walking-robots have received much attention because of the variety of motion maneuvers they can produce and the many applications they have in various areas including rehabilitation. One of these maneuvers is running. In this study, a time-invariant controller is designed to dynamically stabilize a five-link and a seven-link running-robots in two dimensions. In the simulation of the seven-link model, an attempt has been made to measure the impact of the circular foot on the stepping pattern. Also, it is tried to present a dynamically simple model similar to the geometry of the human body. Simulations are performed in MATLAB software. The running is modeled with three phases of stance, flight...