Sharif Digital Repository

Outer space mission design utilizing restricted four-body model for spacecrafts equipped with impulsive engines is investigated. Applied researches in the field of space mission design are typically based on two-body models and in some more advanced cases involve application of the restricted three-body models. As the general solution of the two-body problem is known (conic sections), the transfer trajectories are generally designed using simple Hohmann transfers. But, when considering three-body problem, there is no closed-form solution and low-energy transfer trajectories are designed through the use of stable/unstable manifolds of the corresponding halo orbits. In this way, some... 

Using magnetic torquers as the sole actuator for attitude control of small satellite despite its benefits has a drawback that is lack of controllability. Mechanical torques can be created only perpendicular to the instantaneous magnetic field vector, thus at each time instant the satellite can be controlled only around two axes out of its three perpendicular axes.
Fortunately because of the satellite motion, the direction of uncontrollable axis changes by time, therefore the sufficient attitude control can be achieved along time. Almost all of the present magnetic attitude control methods need more than one orbital period to control and cause the attitude to converge to the desired... 

Thus far, there has been a great attraction toward the optimal flight path planning problem. Terrain following/avoidance (TF/TA) flight is one of the most significant applications of this issue. To prevent from detection by the radars, fighter aircrafts, cruise missiles and helicopters often have to fly as close as possible to the surface during the operations. Such types of maneuvers are much more demanding and effortful than to be designed and implemented by human. The optimal TF/TA guidance system design comprises three phases: optimal path planning, closed-loop control system design for trajectory tracking and sensor blending to match the onboard and measured terrain data. So far, the... 

In this dissertation, initial conditions that cause chaotic movement in the relativistic restricted three body problem was obtained by the fast Lyapunov indicator and the time-frequency analysis. With general relativistic model, we can proceed with more accuracy in the design of stable orbit and this chaotic amplification effect could be used as a novel test of general relativity  

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... 

Uncertainty-based Multidisciplinary Design Optimization (UMDO) is a growing approach in design of complex engineering which has been of great interest to many design bureau and research center especially in field of aerospace. The UMDO goal is to achieve a global optimum design using effective disciplines, interdisciplinary relations and appropriate uncertainty modeling. In this regard, choosing main analysis, design discipline, uncertainty modeling and their content fitness, formulating the problem structure, interaction of disciplines, modeling level of fidelity and the optimization method are the most important challenge of the MDO problem so UMDO is a new trend of MDO, and have been the... 

This thesis is focused on flight dynamics modeling and analysis of an articulated Flapping Micro Air Vehicle (FMAV), where the articulating joint is placed near the wing mid chord span. The articulation modeling, its results and verification due to added degrees of freedom are considered the key motivation and novelties of this project. Initial analyses indicated that a simple articulation device such as joint is not appropriate and will not be efficient for flying FMAV. As a corrective action, a spring-damper mechanism was utilized beside the articulation. Subsequently, the kinematics’ equations are developed and verified using the MSC Automated Dynamic Analysis of Mechanical Systems... 

Rapid growth of space traffic and small satellite systems for current and future space missions have generated new enhanced performance requirements for navigation subsystem. As such, the navigation subsystem is considered as a vital part of all active satellite systems that effectively influences their successful missions. In this regard, the present work is dedicated on the subject of autonomous satellite navigation utilizing nonlinear filters, for which some laboratory experimentations have also been implemented. Generally, advanced orbit and attitude estimation algorithms can effectively compensate for the effect of low cost hardware and sensor packs utilized in microsatellites. In... 

Propulsive efficiency of flapping wings is optimized via a combination of flapping and elastic wing behavior. In this thesis, a complex complete model of flapping air vehicles (FAV) is developed in order to simulate the wing aeroelastic behavior. The resulting model is in the form of a complex set of partial differential equations whose solution is only numerically possible. Using the resulting simulation model, the different flapping behavior of the right and left wings can also be evaluated along with the resulting forces and moments that make the FAV flight realizable. One of the key flight conditions considered in many simulations is that of cruise flight. In order to have a... 

The subject of low thrust transfer trajectory design to the Sun-Earth L2 Lagrange point, considering the Moon’s gravitational attraction as the fourth body effect has been investigated. In addition, three body resonance orbits chaotic dynamics are also studied. The problem of transfer trajectory design to Earth-Moon halo orbit is investigated using two approaches for the thrusting phase of flight.In the first approach, a complete Bicircular four body model is utilized to initially insert an Earth bound spacecraft via active low thrust propulsion on a stable manifold (SM) of the Earth-Moon three body system. Subsequently, the spacecraft coasts to its desired Halo orbit with minimum Trajectory... 

In this research, an emotion-based intelligent guidance planning for a flapping vehicle is proposed. It utilizes different sciences including artificial intelligence, neural, fuzzy and psychology accompanied by flight dynamics and modeling. The proposed system enables the robot to make emotion, learn and make decision based on its given personality. The decision making is related to the path planning and how moving from the current position to the designed one. In other words, the robot, at each moment, knows what to do and how to do. Therefore, guidance commands of the flying robot are as outputs of the system. In the present research, the control system is assumed ideal. The introduced... 

This thesis is focused on development, modeling and simulation of a complete 6DOF elastic flapping air vehicle (FAV). In this respect the aerodynamic modeling is performed using a recent experimentally validated generalized modified strip theory (GMST) that considers the unsteady effect of wake and leading edge vortices via the Theodorsen function and Polhamus analogy respectively. The FAV wing structure is modeled using an elastic plate whose dynamic behavior is determined via a modal approach that is also verified with experimentation. The resulting novel integrated aerodynamic and structure (IAS) equations of motion are simulated for case study of FAV flight. Subsequently, since the IAS... 

A complete 6DOF flight dynamic model of an elastic flapping wing (EFW), integrated with unsteady aerodynamic theory is developed. In this respect, initially efficient high fidelity modules for EFW structural dynamics (SD) as well as unsteady aerodynamics loadings (UAL) to be coupled with its flight dynamics are prepared. A modal approach is followed to model structural dynamics of plain and 3D EFWs. This is in contrast with the Euler-Bernoulli beam theory that is mostly utilized for SD in the existing literature. In addition, due to the possibility of large wing deformations as well as the existence of non-linear displacement regime for realistic EFW flights, non-linear modal approaches such... 

Airports are one of the most important elements of the aviation system that provide the ground infrastructure that is required for enabling or flight across the globe. Master Planning is currently the dominant approach to airport strategic planning. However, history shows that this approach can often result in costly mistakes. Because there are many stakeholders with conflicting objectives, deep uncertainty about the future, and many potential strategies, planners often narrow their scope by using a single forecast for the future, leaving out alternative strategies, and excluding stakeholders, resulting in a Master Plan that quickly becomes obsolete and may be opposed by some stakeholders.... 

The goal of this thesis is modeling and simulation of aircraft landing motion in order to evaluate the performance of an optimal anti-skid brake system (ABS) for the main landing gears with friction effects. In this process, the aircraft 6DOF perturbed equations of motion augmented with pertinent friction and brake forces and moments have been utilized. Subsequently, the problem is formulated within the framework of an optimal LQR that has allowed for generation of control brake commands as well as aircraft landing performance at different landing conditions with and without the proposed ABS. The results demonstrate the proposed ABS has been effective in providing admissible landing... 

Flapping Aerial Vehicles (FAVs) are those kinds of aerial vehicles in which the wings are responsible for simultaneous producing of lift and thrust forces. To provide necessary aerodynamic loads, flapping wings employ various unsteady mechanisms. They often fly at relatively high Angle of Attacks (AoA), respective to the relative flow. The aerodynamic modelling of flapping wing has always been a challenging task. The unspecified assumptions in the existing models, make them almost insufficient in flight simulation applications. Therefore, this paper aims to develop a generalized aerodynamic model. To this aim, a comprehensive investigation has been conducted on some of previous aerodynamic... 

The purpose of the current study is to design an optimal trajectory and control for an aircraft to perform a microgravity maneuver automatically. This subject is by itself an important research topic that has not yet been attempted via optimal control formulation and modelling. Space stations are commonly utilized to conduct long-term microgravity research. Unfortunately utility of space stations to perform space based microgravity experiments is expensive and inaccessible for many researchers and scientific institutions. However, since many experiments requiring microgravity conditions can be performed in short time intervals, there is a possibility to meet their demand via optimal... 

The current research is devoted to the design and optimization of a Blended Wing Body aircraft configuration in the conceptual design phase. In this respect, two objective functions with eight design variables have been considered within the optimization process in order to reach to a desired design. The key objective functions include the aerodynamic efficiency as well as the aircraft empty weight alongside the longitudinal stability requirement that are accounted for within the Genetic algorithm optimization loop. In this regard, some analytical and semi-empirical relations are utilized to determine the aerodynamic and structural characteristics of different designs alongside the numerical... 

Experimental determination of aircraft aerodynamic characteristics is of prim importance in evaluation of its trimability and stability requirements. One of the most common tools for experimental identification of aircraft is the wind tunnel equipped with aerodynamic force and moment balance system. Design and development of wind tunnel equipped with such system for measuring aerodynamic forces and moments can affect the accuracy and quality of identifying the aircraft dynamics. However, since procurement of such professional systems is very expensive, the primary goal of this project is focused on initial design of a tabletop wind tunnel with a force and moment balance system. In addition,... 

In this thesis, a method is presented for improving the observability of the heading angle in a UAV when using the Visual-Inertial navigation algorithm MSCKF by adding a magnetometer sensor. The proposed algorithm serves as a complementary extension to the primary algorithm, and efforts have been made to seamlessly integrate the magnetometer sensor into the primary algorithm to allow for easy modifications to the sensor's characteristics and to observe the resulting output in system simulations. Improving the observability of the heading angle will lead to an enhancement in the overall system state estimation. To achieve this, a new update stage is added to the existing algorithm....