Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1988. / Includes bibliographical references. / by Nesbitt Ward Hagood IV. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990. / Includes bibliographical references (leaves 50-52). / by Gail Jeanne Standish. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1993. / Includes bibliographical references (leaf 147). / by William Edward Gorgen. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1999. / Includes bibliographical references (p. 149-151). / The effects of trailing edge blowing on stator unsteady loading were investigated through a set of experiments on a trailing edge blowing fan. Flow field measurements and stator unsteady loading measurements were taken at five radial locations. Reductions in the relative wake harmonics were seen at all spans for the first two multiples of blade passing frequency. The reductions ranged from 59% to 95% for the 1*BPF harmonic and from 19% to 84% for the 2*BPF harmonic. Trailing edge blowing was seen to have significant effects on both the longitudinal and transverse harmonics. The largest reduction (73%) of the 1*BPF transverse harmonic was seen at 37.5% span, while the largest reduction (99%) of the 1*BPF longitudinal harmonic was seen at 75% span. Changes in the stator unsteady loading ranged from -15dB to +7dB at different points along the chord and span. The changes did not correlate well with changes in the wake harmonics. The most notable lack of correlation occurred at 50% span, where the stator unsteady loading increases while the largest overall reductions in wake harmonic amplitude are seen. Two-dimensional steady state analysis of the free stream and wake (maximum velocity deficit) conditions suggests that the effects of the longitudinal and transverse gusts partially cancel each other in the no blowing case at 50% span. Thus, it is likely that trailing edge blowing disturbs the established balance resulting in an unsteady loading increase even though the wake harmonics are reduced. The flow field measurements were used in conjunction with the BBN/PW V072 noise prediction code to obtain stator unsteady loading predictions with and without trailing edge blowing. The predictions correlate to the changes in the wake transverse harmonics and fail to agree with the stator unsteady loading measurements. Because the V072 code only models the effects of transverse gusts and because trailing edge blowing has strong effects on both transverse and longitudinal gusts, the lack of agreement between the predictions and the measurements is understandable. / by Margarita C. Brito. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 157-168). / While creating intelligent agents who can solve stochastic sequential decision making problems through interacting with the environment is the promise of Reinforcement Learning (RL), scaling existing RL methods to realistic domains such as planning for multiple unmanned aerial vehicles (UAVs) has remained a challenge due to three main factors: 1) RL methods often require a plethora of data to find reasonable policies, 2) the agent has limited computation time between interactions, and 3) while exploration is necessary to avoid convergence to the local optima, in sensitive domains visiting all parts of the planning space may lead to catastrophic outcomes. To address the first two challenges, this thesis introduces incremental Feature Dependency Discovery (iFDD) as a representation expansion method with cheap per-timestep computational complexity that can be combined with any online, value-based reinforcement learning using binary features. In addition to convergence and computational complexity guarantees, when coupled with SARSA, iFDD achieves much faster learning (i.e., requires much less data samples) in planning domains including two multi-UAV mission planning scenarios with hundreds of millions of state-action pairs. In particular, in a UAV mission planning domain, iFDD performed more than 12 times better than the best competitor given the same number of samples. The third challenge is addressed through a constructive relationship between a planner and a learner in order to mitigate the learning risk while boosting the asymptotic performance and safety of an agent's behavior. The framework is an instance of the intelligent cooperative control architecture where a learner initially follows a safe policy generated by a planner. The learner incrementally improves this baseline policy through interaction, while avoiding behaviors believed to be risky. The new approach is demonstrated to be superior in two multi-UAV task assignment scenarios. For example in one case, the proposed method reduced the risk by 8%, while improving the performance of the planner up to 30%. / by Alborz Geramifard. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. / Includes bibliographical references (leaves 95-97). / Airlines maximize the use of their resources by minimizing the time between consecutive flight legs in their aircraft and crew schedules. As a result, bad weather or unscheduled aircraft maintenance events can have a significant impact on an airline's operations. The consequences of these disruptions are major costs to airlines, passengers and, ultimately, to the economy itself. In this thesis, the steps taken to implement an airline schedule recovery model in a realistic simulation of the U.S. airspace system are presented. The MIT Extensible Network Simulation (MEANS), an event based queueing model of the U.S. National Airspace System, can be used for tactical decision making, long term decision making and post priori event analysis. Thus, the addition of a recovery model is critical to obtain accurate simulation results. The airline recovery model consists of an optimized aircraft re-scheduling model, a crew re-assigning model and a heuristic passenger itinerary search model. The model was used to simulate airline recovery procedures over the course of a day of operations for different scenarios. / by Fábio Faizi Rahnemay Rabbani. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / "CSDL-T-1503, digital appendix"--CDROM label. Appendix B of thesis text contains an index to the CDROM. / Includes bibliographical references (p. 113-114). / Currently, Draper Laboratory is in the development stages of a gliding autogyro airdrop system. The goal of the project is to design a platform capable of placing small, high value items into urban terrain. Theoretically, autogyros can achieve descent rates and glide slopes similar to current parafoil based systems, but do so with greater precision. Over the past half-century most rotorcraft research has focused on helicopter design, only viewing autorotation as a means of achieving emergency landings. In contrast, this project utilized early rotor theory to develop algorithms which can predict unpowered rotor performance across the entire flight envelope. To validate these predictions, a vertical wind tunnel capable of testing rotors up to 4 feet in diameter at descent rates of up to 25 ft/s was constructed. Emphasis was also placed on developing deployment sequences that would allow the system to achieve stable autorotation autonomously. By varying parameters such as blade pitch angle and rotor solidity, it is shown that in the proper configuration, rotor based systems can match and even surpass parafoils in areas such as descent rate and glide slope. The autogyro also has the added capability of varying its lift-to-drag ratio in flight while maintaining reasonable descent speeds, allowing for more precise control to the target. Possible deployment sequences are displayed, proving that relatively simple configurations can be brought into stable autorotation. The algorithms developed and vertical wind tunnel constructed for this project can be used to gain further knowledge of autogyro performance. / by Michael Oliver. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / Includes bibliographical references (p. 119-124). / The problem of Simultaneous Localization and Mapping (SLAM) has received a great deal of attention within the robotics literature, and the importance of the solutions to this problem has been well documented for successful operation of autonomous agents in a number of environments. Of the numerous solutions that have been developed for solving the SLAM problem many of the most successful approaches continue to either rely on, or stem from, the Extended Kalman Filter method (EKF). However, the new algorithm FastSLAM has attracted attention for many properties not found in EKF based methods. One such property is the ability to deal with unknown data association and its robustness to data association errors. The problem of data association has also received a great deal of attention in the robotics literature in recent years, and various solutions have been proposed. In an effort to both compare the performance of the EKF and FastSLAM under ambiguous data association situations, as well as compare the performance of three different data association methods a comprehensive study of various SLAM filter-data association combinations is performed. This study will consist of pairing the EKF and FastSLAM filtering approaches with the Joint Compatibility, Sequential Compatibility Nearest Neighbor, and Joint Maximum Likelihood data association methods. The comparison will be based on both contrived simulations as well as application to the publicly available Car Park data set. The simulated results will demonstrate a heavy dependence on geometry, particularly landmark separation, for the performance of both filter performance and the data association algorithms used. / (cont.) The real world data set results will demonstrate that the performance of some data association algorithms, when paired with an EKF, can give identical results. At the same time a distinction in mapping performance between those pairings and the EKF paired with Joint Compatibility data association will be shown. These EKF based pairings will be contrasted to the performance obtained for the FastSLAM- Sequential Nearest Neighbor marriage. Finally, the difficulties in applying the Joint Compatibility and Joint Maximum Likelihood data association methods using FastSLAM 1.0 for this data set will be discussed. / by Aron J. Cooper. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991. / Includes bibliographical references (p. 207-208). / by Daniel H. Chang. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1993. / Includes bibliographical references (p. 56). / by David Younghee Oh. / M.S.