Sharif Digital Repository

In this thesis a novel non-rotating space tethered configuration is introduced which its relative positions are controlled using electromagnetic forces. The attitude dynamics is controlled by three reaction wheels in the body axes. The nonlinear coupled orbital dynamics of a dumbbell tethered satellite formation flight are derived through a constrained Lagrangian approach. These equations are presented in the leader satellite orbital frame. The advantage of using equations in the Cartesian coordinate system over presenting the equations of satellite formation plane angles is the appearance of gravity gradient and Earth’s magnetic field effects. The tether is assumed to be mass-less and... 

Recent developments in space industry and the great tendency for definition of efficient, precise and low cost missions are the main reasons for the growing interest in satellites formation flight. Regarding the aforementioned, the study of the multiple satellite control methods is the subject of the present project. In this project, the governing equations of motion of satellite formation flight are developed. Based on this development, it is shown that the satellite linear equations of motion like many other linear system presentations, can not sufficiently model the real system. Therefore, some of the most famous uncertainties in space dynamics such as semimajor axis and eccentricity... 

The formation flight of satellites corresponds to a group of small satellites, performing the mission of a presumed larger and more expensive satellite. Usually mission designers tend to put these satellites in such orbital configurations that their trajectories do not intersect. Although a stable configuration in a certain collision-free orbit is desirable for long term purposes, most of the missions including maneuvers like forming or changing a configuration and inserting new satellites need to be planned using a proper path planning algorithm. In this thesis, a path planning algorithm is suggested that acquires the optimal and impact-free trajectories for a group of satellites for... 

According to predictions of big airlines, demand of aerial transportation is rapidly increasing. This jump in aerial traffic is concerning environment activists as well as air traffic control centers. New proposed solutions such as designing new aircrafts and new fuels, require basic infrastructure and take a lot of time. Among these solutions, formation flight is an available answer to the problem as it is consistent with existing infrastructure. In this study, a robust model is proposed in which any kind of aircraft can decide to whether enter or exit a formation, and the formation problem is changed from a static problem to a dynamic one. The runtime is of a scale which can be used as an... 

The increasing demand for air transportation, along with air traffic limitations and environmental pollution concerns, necessitate a comprehensive study in the field of airspace-management. In this regard, one of the promising alternatives is flying smarter via “Formations”. In fact, many works have discussed the benefits of “Commercial Formation Flights”; however, none have discussed a practical way to manage such formations for long-distance cruise. This paper discusses a new approach to manage the “Geometrical Arrangement” of such flights in an efficient manner. In fact, with the help of the so called “Game Theory” and without complex computations we are able to guide each individual... 

Increasing aviation share in air pollution, population growth, scarcity of available resources such as land (airport), airspace and energy along with uncertainties in air transportation demand and energy market, has motivated the industry stakeholders to push researches toward sustainable models in fleet planning and design. In this thesis we have investigated the suitability of a decision-making model for airline fleet management, based on “Game Theory” and the idea of commercial formation flight (COFOFS). We intend to examine the circumstances under which, an airline needs to substitute a wide-body aircraft with number of smaller ones, while employing the approach of formation flight.... 

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... 

The existing trend in air transportation growth, clearly shows that aviation industries need to profoundly look at “formation flights” in a more efficient manner and without complex computations. This work describes a new efficient Logic to accept or reject a possible formation among all available. The approach considers each airplane as an agents that “sees” the current traffic environment and then selects the best “Action” to satisfy its desired objectives. The logic, although simple, considers the location and time to join a formation or to create one; and the position to leave the original formation. Different Mathematical model have been investigated to find-out which one is more... 

Swarm is coordinated group action that usually done with little communication among its members. Using several simple members instead of the complicated ones reduces cost, simplifies system and increases the reliability. On the other hand, the mission can be done faster. This thesis is done in two general sections; theoretical and experimental parts. At first some important missions are simulated in MATLAB/Simulink such as aggregation, dispersion, flocking, obstacle detection, obstacle collision avoidance and orbiting around the obstacle. Orbiting around the obstacle is simulated formation flying and a constellation of satellites (such as GPS systems). The methodology is artificial potential... 

This study explores the trajectory optimization of two aircrafts’ formation flight seeking minimization of fuel consumption and flight duration while considering activation of the Traffic Collision Avoidance System (TCAS) during the flights. In order to model the effects of this system, a set of codes has been developed in the Matlab software environment, which utilizes an estimation model of induced drag for each aircraft by their relative positions. Also, position rotation is allowed, and the number and location of rotations are controllable by the user. The TCAS determines the allowable distances between aircrafts during flights based on relative velocities and relative heading angles.... 

The problem of quadrotors formation flying via optimal approach is investigated using the idea of cooperative and multi-level control. In this respect, a low level optimal control formulation of quadrotors is formulated for stability and tracking where the required tracking commands are generated via the high level controller over a simpler translational dynamics of quads. The idea of multi-level controllers enables one to develop formation keeping controls for complex dynamics systems, where varying agents in terms of dynamics and platform could be utilized. Due to inherent difficulties in implementing acceleration commands emanated out of the high level controller, an inverse dynamic... 

To better facilitate the implementation of the so-called "Formation Flights," this work investigates the possibility of pair-wise switching of the leading aircraft so both aircraft benefit equivalently during a two-aircraft formation flight. The procedure allows all members of a formation group to fly in the wing vortex of one another in turns. A multiple-phase trajectory optimization framework has been developed using GPOPS algorithm, in which the switching point will be found thru minimizing total fuel consumption and flight time. A drag estimation model has been used to approximate the drag reduction factor as a function of lateral and longitudinal distances of two airplanes in an...