Control and Optimization for Aerospace Systems with Stochastic Disturbances, Uncertainties, and Constraints

The topic of this dissertation is the control and optimization of aerospace systems under the influence of stochastic disturbances, uncertainties, and subject to chance constraints. This problem is motivated by the uncertain operating environments of many aerospace systems, and the ever-present push to extract greater performance from these systems while maintaining safety. Explicitly accounting for the stochastic disturbances and uncertainties in the constrained control design confers the ability to assign the probability of constraint satisfaction depending on the level of risk that is deemed acceptable and allows for the possibility of theoretical constraint satisfaction guarantees. Along these lines, this dissertation presents novel contributions addressing four different problems: 1) chance-constrained path planning for small unmanned aerial vehicles in urban environments, 2) chance-constrained spacecraft relative motion planning in low-Earth orbit, 3) stochastic optimization of suborbital launch operations, and 4) nonlinear model predictive control for tracking near rectilinear halo orbits and a proposed stochastic extension. For the first problem, existing dynamic and informed rapidly-expanding random trees algorithms are combined with a novel quadratic programming-based collision detection algorithm to enable computationally efficient, chance-constrained path planning. For the second problem, a previously proposed constrained relative motion approach based on chained positively invariant sets is extended in this dissertation to the case where the spacecraft dynamics are controlled using output feedback on noisy measurements and are subject to stochastic disturbances. Connectivity between nodes is determined through the use of chance-constrained admissible sets, guaranteeing that constraints are met with a specified probability. For the third problem, a novel approach to suborbital launch operations is presented. It utilizes linear covariance propagation and stochastic clustering optimization to create an effective software-only method for decreasing the probability of a dangerous landing with no physical changes to the vehicle and only minimal changes to its flight controls software. For the fourth problem, the use of suboptimal nonlinear model predictive control (NMPC) coupled with low-thrust actuators is considered for station-keeping on near rectilinear halo orbits. The nonlinear optimization problems in NMPC are solved with time-distributed sequential quadratic programming techniques utilizing the FBstab algorithm. A stochastic extension for this problem is also proposed. The results are illustrated using detailed numerical simulations.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/162992/1/awbe_1.pd

Autonomous Spacecraft Control During Close-Proximity Near-Earth Object Operations

A control scheme is proposed for a satellite orbit controller around a small, irregularly shaped near-Earth object (NEO) combining classical control theory and orbital mechanics into a continuous hybrid control system that achieves and maintains a circular orbit in a perturbed environment. NEOs are asteroids and comets that approach Earth\u27s orbit around the Sun. They are currently being studied for resource allocation and threat mitigation, while providing unique opportunities for control systems. The NEO environment consists of a weak and complex gravity field, as well as other perturbations such as solar radiation pressure (SRP) and third-body gravitational disturbances. This project focuses on the gravity field of the NEO and characterizes orbital stability within the NEO\u27s gravity field. A three-term Proportional, Integral, and Derivative (PID) controller is utilized in order to achieve and maintain a circular orbit in close-proximity to the NEO 25143 Itokawa. The proposed control scheme merges a simple controller with orbital mechanics to maximize the effectiveness and efficiency of the thrusters. It uses the PID controller to thrust in the radial direction in order to maintain the proper orbital radius, which is found to be an effective method of correcting perturbed orbits in the NEO environment. This is followed by a change in the orbital velocity of the spacecraft in order to match the specific mechanical energy for the desired circular orbit, which is typically the most efficient method of correcting perturbed orbits. Systems Tool Kit (STK) is used to run the simulation and a MATLAB-STK interface was developed that allows for sophisticated orbit control development. Using the STK simulation software allows for the ability to test multiple orbit parameters for stability. This was applied in studying the interaction between the complex gravity model and its effect on the satellite using a harmonic excitation analysis. It was found that when the ratio of the excitation frequency to the natural frequency (ω/ωn) is greater than seven, the orbit is stable. This thesis provides methods for simulating and predicting satellite orbit control as well as providing guidelines for regions of stability for NEO missions

The Phoenix Pluto Probe

A design proposal for an unmanned probe to Pluto is presented. The topics covered include: (1) scientific instrumentation; (2) mission management, planning, and costing; (3) power and propulsion system; (4) structural subsystem; (5) command, control, and communication; and (6) attitude and articulation control

Design and analysis of lunar lander control system architectures

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 153-157).Although a great deal of separate work exists on the development of spacecraft actuators and control algorithm design, less work exists which examines the connections between the selection of specific actuator types and placements, how this affects control algorithm design, and how these combined factors affect the overall vehicle performance of a lunar lander. This thesis attempts to address these issues by combining a functionality-oriented approach to actuator type/placement with a controls-oriented approach to algorithm design and performance analysis. Three example control system architectures are examined for a generic autonomous 350kg lunar lander during the terminal descent flight phase. Results indicate that stability and control can be achieved using a wide variety of actuator types/placements and algorithms given that a set of 'common sense' subsystem functionality and robustness metrics are met; however, algorithm development was often heavily influenced/restricted by actuator system capabilities. It is therefore recommended that future designers of lunar lander vehicles consider the impact of their control system architectures from both a functionality-oriented and a controls-oriented approach to gain a more complete understanding of the effects of their choices on overall performance.by Joseph M. Morrow.S.M

Using phase space attractors to evaluate system safety constraint enforcement : case study in space shuttle mission control procedure rework

Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2009.Vita. Cataloged from PDF version of thesis.Includes bibliographical references (p. 390-409).As the complexity and influence of engineering systems in modern society increases, so too does their potential to create counterintuitive and catastrophic accidents. Increasingly, the accidents encountered in these systems are defying the linearized notions of accident causality that-though developed for the simpler engineered systems of the past-are prevalently used for accident prevention today. In this dissertation, an alternative approach to accident prevention based on systems theory-the Systems-Theoretic Accident Model and Processes (STAMP) and STAMP-based hazard analysis (STPA)-is augmented with the notion of using phase space attractors to evaluate how well STAMP safety control structures enforce system safety constraints. Phase space attractors are mathematical results that emerge from the behavior of systems with dynamic structures that draw or constrain these systems to specific regions of their phase space in spite of a range of conditions. Accordingly, the goal in using this notion for the evaluation of safety constraint enforcement is to identify and analyze the attractors produced by a safety control structure to determine if it will adequately "attract" the system to safe states in spite of a range of unforeseeable conditions. Support for this approach to evaluating STAMP safety control structures is provided through the study of a safety control structure in an existing complex, socio-technical system. This case study is focused on a safety control process-referred to as Procedure Rework-used in Space Shuttle Mission Control to update procedures during in-flight operations as they are invalidated by changes in the state of the Space Shuttle and its environment.(cont.) Simulation models of procedure rework are developed through physical and human factors principles and calibrated with data from five Space Shuttle missions; producing simulation results with deviations from the historical data that are-as characterized by Theil Inequality Statistics-small and primarily due to cycles and noise that are not relevant to the models' purpose. The models are used to analyze the attractor produced by the Procedure Rework Process across varied conditions, including a notional crewed spacecraft mission to a distant celestial body. A detrimental effect in the process is identified-and shown to be potentially far more severe than light delay on a mission to a distant celestial body-and approaches to mitigating the effect are explored. Finally, the analysis conducted is described as a generalizeable process for using phase space attractors to evaluate system safety constraint enforcement in engineering systems.by Brandon D. Owens.Ph.D

Aeronautical engineering: A continuing bibliography with indexes (supplement 275)

This bibliography lists 379 reports, articles, and other documents introduced into the NASA scientific and technical information system in Jan. 1991

NASA thesaurus. Volume 3: Definitions

Publication of NASA Thesaurus definitions began with Supplement 1 to the 1985 NASA Thesaurus. The definitions given here represent the complete file of over 3,200 definitions, complimented by nearly 1,000 use references. Definitions of more common or general scientific terms are given a NASA slant if one exists. Certain terms are not defined as a matter of policy: common names, chemical elements, specific models of computers, and nontechnical terms. The NASA Thesaurus predates by a number of years the systematic effort to define terms, therefore not all Thesaurus terms have been defined. Nevertheless, definitions of older terms are continually being added. The following data are provided for each entry: term in uppercase/lowercase form, definition, source, and year the term (not the definition) was added to the NASA Thesaurus. The NASA History Office is the authority for capitalization in satellite and spacecraft names. Definitions with no source given were constructed by lexicographers at the NASA Scientific and Technical Information (STI) Facility who rely on the following sources for their information: experts in the field, literature searches from the NASA STI database, and specialized references

Review of NASA Sponsored Research at the Experimental Astronomy Laboratory

Technical details reviewed on NASA sponsored research at Experimental Astronomy Laborator

AAS/GSFC 13th International Symposium on Space Flight Dynamics

This conference proceedings preprint includes papers and abstracts presented at the 13th International Symposium on Space Flight Dynamics. Cosponsored by American Astronautical Society and the Guidance, Navigation and Control Center of the Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to orbit-attitude prediction, determination, and control; attitude sensor calibration; attitude dynamics; and mission design

Advances in Spacecraft Systems and Orbit Determination

"Advances in Spacecraft Systems and Orbit Determinations", discusses the development of new technologies and the limitations of the present technology, used for interplanetary missions. Various experts have contributed to develop the bridge between present limitations and technology growth to overcome the limitations. Key features of this book inform us about the orbit determination techniques based on a smooth research based on astrophysics. The book also provides a detailed overview on Spacecraft Systems including reliability of low-cost AOCS, sliding mode controlling and a new view on attitude controller design based on sliding mode, with thrusters. It also provides a technological roadmap for HVAC optimization. The book also gives an excellent overview of resolving the difficulties for interplanetary missions with the comparison of present technologies and new advancements. Overall, this will be very much interesting book to explore the roadmap of technological growth in spacecraft systems