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Full-Text Articles in Engineering
Satellite Relative Motion Control For Mit's Spheres Program, Samuel P. Barbaro
Satellite Relative Motion Control For Mit's Spheres Program, Samuel P. Barbaro
Theses and Dissertations
Autonomous formation flight concepts and algorithms have great potential to revolutionize spacecraft operations enabling missions to perform autonomous docking, in-space refueling, in-space robotic assembly, and space debris removal. Such tasks require the implementation of speed and path control algorithms to maneuver satellites along relative paths with specified rates along those paths. This thesis uses MATLAB® and SIMULINK® to design and simulate a control algorithm capable of providing relative speed and path control between satellites with a pointing error of less than two degrees, a position error of less than two millimeters, and a millimeter per second of velocity error. The …
Optimal Control Of Electrodynamic Tethers, Robert E. Stevens
Optimal Control Of Electrodynamic Tethers, Robert E. Stevens
Theses and Dissertations
Low thrust propulsion systems such as electrodynamic tethers offer a fuel-efficient means to maneuver satellites to new orbits, however they can only perform such maneuvers when they are continuously operated for a long time. Such long-term maneuvers occur over many orbits often rendering short time scale trajectory optimization methods ineffective. An approach to multi-revolution, long time scale optimal control of an electrodynamic tether is investigated for a tethered satellite system in Low Earth Orbit with atmospheric drag. Control is assumed to be periodic over several orbits since under the assumptions of a nearly circular orbit, periodic control yields the only …
Satellite Formation Control Using Atmospheric Drag, Blake B. Hajovsky
Satellite Formation Control Using Atmospheric Drag, Blake B. Hajovsky
Theses and Dissertations
This study investigates the use of a linear quadratic terminal controller to reconfigure satellite formations using atmospheric drag actuated control while minimizing the loss of energy of the formation. The linearized Clohessy-Wiltshire equations of motion are used to describe the motion of the two-satellite formation about an empty reference position maintained at the formation center. Reconfigurations to final in-plane and elliptical formations are simulated at orbital radii of 6800 km and 7000 km, and the altitude loss and a ?v budget were recorded as performance measures for each reconfiguration. The final states of the spacecraft upon reconfiguration were propagated forward …
Optimal Control Of A Circulare Satellite Formation Subject To Gravitational Perturbations, Jason L. Baldwin
Optimal Control Of A Circulare Satellite Formation Subject To Gravitational Perturbations, Jason L. Baldwin
Theses and Dissertations
Satellite formations, otherwise known in the space community as satellite clusters or distributed satellite systems, have been studied extensively over the last 10 to 15 years. For use in remote sensing applications, formations consisting of smaller, simpler satellites provide numerous advantages over individual satellites. The image resolution capabilities of small-satellite formations constitute a significant technological leap in the ability to synthesize critical information. This research utilizes the nonlinear satellite dynamics, including gravitational perturbations, to search for the optimal fuel cost for maintaining a circular formation. The system dynamics were developed in an earth-centered inertial coordinate frame using the methods of …
The Determination Of Remaining Satellite Propellant Using Measured Moments Of Inertia, Jason W. Geitgey
The Determination Of Remaining Satellite Propellant Using Measured Moments Of Inertia, Jason W. Geitgey
Theses and Dissertations
This research is designed to demonstrate that a change in satellite propellant can be determined using measured moments of inertia (MOI) from a satellite. Because satellites are currently incapable of being refueled in orbit it is important to have multiple methods to determine the remaining fuel onboard. This research can also support satellite operator selection of control-system gains to improve performance or recover the spacecraft. To meet the research objectives, new mathematical models of the Air Force Institute of Technology's Simulated Satellite (SimSat) were developed. These models were created using dynamic response analysis techniques on the reaction wheel and SimSat …
The Effects Of Using Solar Radiation Pressure To Alleviate Fuel Requirements For Orbit Changing And Maintenance Of The Dscs Ii F-13 Satellite, Jody A. Paris
Theses and Dissertations
Orbit disposal and maintenance of aging satellites has become a significant concern over the past few years, as the increasing number of orbiting objects threatens to limit the launching of future satellites. Many of the satellites currently in orbit, however, were not built with disposal considerations. The DSCS II series was launched into orbit beginning in the 1970s, and many satellites are now without the fuel required to conventionally transition to a sanctioned disposal orbit. In GEO orbit the largest non-gravitational perturbation is solar radiation pressure. By adjusting the attitude of a satellite with a controller to maximize the perturbing …
Dynamic Characterization Of Thin Deformable Pvdf Mirror, Eric M. Trad
Dynamic Characterization Of Thin Deformable Pvdf Mirror, Eric M. Trad
Theses and Dissertations
Methodology for the design and fabrication of 5 inch diameter membrane-like mirror structures is explored, resulting in test articles with areal densities as low as 1.57 kg/m2 and a thickness of 1.5 mm. Each optical structure has 7 control patches etched into the PVDF layer, which can be used as actuators. These test articles are utilized to demonstrate the capabilities of an acquisition system to make measurements of static and dynamic actuation of the mirror surface. Static deformations are analyzed statistically and determined to yield maximum deformations in the actuated regions of -2.1 micro with a standard deviation of 0.33 …
Analytical Solution For Low-Thrust Minimum Time Control Of A Satellite Formation, John Sang-Pil Seo
Analytical Solution For Low-Thrust Minimum Time Control Of A Satellite Formation, John Sang-Pil Seo
Theses and Dissertations
Satellite formations or distributed satellite systems provide advantages not feasible with single satellites. Efficient operation of this platform requires the use of optimal control of the entire satellite formation. While the optimal control theory is well established, only a very simple dynamical system affords an analytical solution. Any practical optimal control problem solves the resulting two-point boundary value (TPBV) problem numerically. The relative satellite dynamics using Hill's coordinate system and approximations made by Clohessy and Wiltshire, combined with body-fixed thruster control, result in a linearized dynamic system. This dissertation provides the analysis for the minimum time satellite formation control by …
Data Sorting And Orbit Determination Of Tethered Satellite Systems, Mark J. Faulstich
Data Sorting And Orbit Determination Of Tethered Satellite Systems, Mark J. Faulstich
Theses and Dissertations
Tethered satellite system end masses do not obey the normal laws of motion developed for determining their orbits. In addition, tethered satellite systems cause unique problems for satellite tracking because there are potentially two or more objects which may be tracked. This thesis provides insight into these issues by developing a method of sorting out observation data of tethered satellite systems into their appropriate end mass and providing an estimate on the center of mass orbit of the tethered satellite system. The method used to accomplish both of these tasks is optimization of an estimated simulated orbit. This orbit estimate …
Maneuver Design For Fast Satellite Circumnavigation, Stanley D. Straight
Maneuver Design For Fast Satellite Circumnavigation, Stanley D. Straight
Theses and Dissertations
The feasibility of satellite operations in close proximity to a reference satellite is of interest for both civilian and military applications. One such operation is circular circumnavigation in a time period less than the orbital period of the reference satellite. This thesis investigates a guidance scheme for such maneuvers involving impulsive burns at specific points within a specified toroidal region centered on the circular-orbiting reference satellite. Two analytical methods for determining the magnitude and direction of the impulses are demonstrated. These methods are then used as initial estimates in an optimization scheme to produce the minimum total required impulse.
Geometric Approach To Orbital Formation Mission Design, Matthew J. Press
Geometric Approach To Orbital Formation Mission Design, Matthew J. Press
Theses and Dissertations
For distributed remote sensing architectures to be useful for collecting data, it is essential to have a methodology for relating orbital formation parameters to remote sensing requirements. Utilizing the characteristics of formation parameters, an orbital design approach is developed that establishes a satellite formation from a desired instantaneous spatial distribution as viewed from a target ground site. To maintain a conceptually basic representation, a geometric approach is used to develop the correlating algorithm. This tool will enable mission planning for orbital formations as well as future concept exploration.
Performance Tradeoff Study Of A Gps-Aided Ins For A Rocket Trajectory, Muhittin Istanbulluoglu
Performance Tradeoff Study Of A Gps-Aided Ins For A Rocket Trajectory, Muhittin Istanbulluoglu
Theses and Dissertations
The Turkish Air Force (TuAF) has started a project to launch a satellite using only Turkish resources. Primary motivation behind this research is to assist TuAF's project by keeping up with these innovations in the navigational arena. The basic challenge in navigation system design is to decide which navigation system (or systems) and implementation techniques will be used, depending on accuracy requirements. The two primary navigation systems that will be integrated in this research are the Inertial Navigation System (INS), and the Global Positioning System (GPS). The Kalman filter algorithm is used to integrate INS and GPS. The rocket (Atlas …
Microdot - A Four-Bit Microcontroller Designed For Distributed Low-End Computing In Satellites, Anthony R. Woodcock
Microdot - A Four-Bit Microcontroller Designed For Distributed Low-End Computing In Satellites, Anthony R. Woodcock
Theses and Dissertations
Many satellites are an integrated collection of sensors and actuators that require dedicated real-time control. For single processor systems, additional sensors require an increase in computing power and speed to provide the multi-tasking capability needed to service each sensor. Faster processors cost more and consume more power, which taxes a satellite's power resources and may lead to shorter satellite lifetimes. An alternative design approach is a distributed network of small and low power microcontrollers designed for space that handle the computing requirements of each individual sensor and actuator. The design of microdot, a four-bit microcontroller for distributed low-end computing, is …
Periodic Methods For Controlling A Satellite In Formation, Erin Y. Carraher
Periodic Methods For Controlling A Satellite In Formation, Erin Y. Carraher
Theses and Dissertations
Precise position determination and control is necessary to accomplish proposed satellite formation flying missions of ground movement target indication and synthetic aperture radar. This thesis combines the estimation and control techniques of past AFIT theses with various time-varying and time-invariant LQG control methods. Linear time-invariant control is ideal for on-board satellite estimation and control applications, freeing-up the satellite's limited computational capacity. Using a dynamics frame transformation from the nodal frame to an orbital frame, a higher fidelity, time-periodic model produced nearly identical results for either time-varying or time-invariant control for many scenarios. Scenarios included initial perturbations in the radial, in-track, …
Applications Of Nonlinear Control Using The State-Dependent Riccati Equation, David K. Parrish
Applications Of Nonlinear Control Using The State-Dependent Riccati Equation, David K. Parrish
Theses and Dissertations
This thesis examines the relatively new theory of nonlinear control using state dependent coefficient factorizations to mimic linear state space systems. The control theory is a nonlinear quadratic approach, analogous to linear quadratic regulation. All implementations examined in this thesis are done strictly numerically. This thesis is meant to provide a proof of concept for both satellite control and for an artificial pancreas to regulate blood glucose levels in diabetics by automatic insulin injection. These simulations represent only a first step towards practical use of the NQR method, and do not address noise rejection or robustness issues.