Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 7 of 7
Full-Text Articles in Entire DC Network
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 …
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 …
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.
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.