Sharif Digital Repository

In recent years, unmanned vehicles have intensively been developed to reduce human dangers for marine applications. Predicting the hydrodynamic coefficients of an autonomous underwater vehicle is important during the vehicle’s design phase. In other words to design an AUV, one must clarify its maneuverability and controllability based on a mathematical model. The mathematical model contains various hydrodynamic forces and moments expressed collectively in terms of hydrodynamic coefficients. Therefore, the correct values of the coefficients must be known to precisely design the controller of AUVs.SUT-2 is an AUV, being developed by Marine Engineering Laboratory of Sharif University of... 

In this thesis, implementing parametric resonance for the purpose of improvement in sensitivity of MEMS gyroscopes is studied. Based on a parametric study on effect of each factor on the sensor’s performance, the desired values for each parameter is determined. Stability of periodic orbits is studied using Floquet Theory. In addition, three expositions are defined and proved in order to make Floquet Theory applicable for stability analysis of origin. Based on this analysis, the relation between stabilities in the system and occurrence of parametric resonance is illustrated. Due to the complexity of dynamics of a parametrically excited MEMS gyroscope, bifurcations are observed in performance... 

Satellite attitude determination means specifying its rotation relative to a known reference. To determine satellite attitude, gyroscope is used to measure angular velocity and attitude sensors such as sun sensor, magnetometer, star tracker and earth horizon scanner are used in order to obtain vector measurements. In kinematic control, satellite angular velocity is determined in a way that its attitude converges to desired attitude. Usually, gyroscope and attitude sensors measurements are contaminated by noise which leads to errors in satellite attitude estimation and control. In the literature, gyroscope and at least two vector meaurements are used to estimate and control the... 

SUVs are susceptible to rollover in high speed due to their shape and high center of mass. This causes numerous limitations for this class of vehicles thus preventing their rollover is a prime issue. In this study, two flywheels with high angular momentum have been used to provide stabilizing momentum on the onset of rollover. However, if these flywheels keep rotating during the normal driving, they will cause maneuvering limitations for the car. The idea of using flywheels is completed by bringing them to speed in a few hundredth of a second when the vehicle is suspicious to rollover.To achieve this, dynamics of the car before and after lift off of one side is investigated. Also the dynamic... 

Cars with high center of gravity, such as SUV-Sport Utility Vehicles- have high tendency to roll over in high speeds and rapid maneuvers. An idea formerly proposed is to use a high speed rotating disc like a gyroscope on the onset of the rollover to exert a high stabilizing moment on the vehicle, and consequently prevent rollovers. Also using two counter rotating discs with opposite nutation will prevent interference with the car other degrees of freedom. To reduce the interference of the spinning discs with the vehicle dynamics, the discs are to be brought to speed by the action of a high accelerating mechanism during the rollover process(similar to the action of an airbag). This project... 

Recently, parametric excitation has been proposed and experimentally proven to provide micro gyroscopes with robustness to parameter variations and enhancement of sensitivity [L.A. Oropeza-Ramos, C.B. Burgner, K.L. Turner, Robust micro-rate sensor actuated by parametric resonance, Sensors and Actuators A: Physical, 152 (2009) 80-87].The first part of this thesis aims at investigating the nonlinear dynamics of MEMS vibratory gyroscopes with parametric excitation which can be represented by a minor variation of nonlinear Mathieu equation coupled to a Duffing oscillator. Our approach is based on analytical frequency response derivation via method of multiple time scales. Stability of responses,... 

Recently, parametric excitation has been proposed and experimentally proven to provide micro gyroscopes with robustness to parameter variations and enhancement of sensitivity. harmonic excitation gyroscopes are very sensitive to response of a resonance at the resonant frequency; therefore it has to be created accurately. However, parametric excitation gyroscopes are not sensitive as a result of wide bound of frequency at drive mode, accordingly it is not necessary to be formed accurately in the same way as harmonic excitation gyroscope.
The produced stress at combs have a significance effect on robustness, sensitivity and calibration curves of parametric excitation gyroscope, as a... 

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... 

Monitoring driving behaviors of drivers, would avoid their dangerous behaviors and remarkably raise the safety. Nowadays real-time supervision is considered as one of the modern methods of controlling driving behaviors. Previously, due to expensive costs of required equipments and other restrictions, this kind of supervision hasn't been considered fairly. Nowadays increasing usage of smart phones, which contain multiple sensors, enables this type of supervision with lower costs. In the present study we would present some models, to assess the driving behavior via smart phone sensors such as accelerometer, gyroscope and rotation vector  

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 thesis deals with the construction of software tools necessary to calculate the position and orientation of the robot. The aim of this project is to use accelerometer, gyroscope, magnetometer and GPS sensors; Determine the position and orientation of the robot where the mobile phone is located. The proposed sensors are used to measure acceleration, angular velocity and magnetic field in 3 axes, respectively. GPS is also a system for calculating the position using signals received from satellites. To do this, an Android application has been designed and written in Java. The sensor information is collected by the software designed in the mobile phone and after proper coding is sent to a...