Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / Includes bibliographical references (p. 107-112). / Model-based diagnosis of devices has largely operated on hardware systems. However, in most complex systems today, such as aerospace vehicles, automobiles and medical devices, hardware is augmented with software functions that influence the system's behavior. As these sophisticated systems are required to perform increasingly ambitious tasks. there is a growing need to ensure their robustness and safety. Prior work introduced probabilistic, hierarchical, constraint automata (PHCA), to allow compact encoding of both hardware and software behavior. The contribution of this thesis is a capability for monitoring and diagnosing software-extended systems in the presence of delayed symptoms, based on the expressive PHCA modeling formalism. Hardware models are extended to include the behavior of associated embedded software, resulting in more comprehensive diagnoses. This work introduces a novel approach that frames diagnosis over a finite time horizon as a soft constraint optimization problem (COP), which is then decomposed into independent subproblems using tree decomposition techniques. There are two advantages to this approach. First, the approach enables finite-horizon diagnosis in the presence of delayed symptoms. Second, the soft COP formulation provides convenient expressivity for encoding the PHCA models and their execution semantics, and enables the use of decomposition-based, efficient optimal constraint solvers. The solutions to the COP correspond to the most likely state trajectories of the software- extended system. / (cont.) These state trajectories are enumerated and tracked within the finite receding horizon, as observations and issued commands become available. The diagnostic capability has been implemented and demonstrated on several scenarios from the aerospace and robotic domains, including vision-based rover navigation, the global metrology subsystem of the MIT SPHERES satellites, and models of the NASA New Millennium Earth Observing One (EO-1) spacecraft. / by Tsoline Mikaelian. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / Includes bibliographical references (p. 127-129). / The information architecture of general aviation cockpits is shifting from one of independent mechanical instruments to one of digital sensors, common databuses, and liquid crystal displays. This integrated architecture presents an opportunity to improve general aviation safety through enhancements to the flight display utilizing the data, computing power, and display capabilities available on a modem integrated cockpit. A study of general aviation accident causes identified takeoff and climbout, stall, and spatial disorientation as potential root causes that could be addressed with enhancements to the Primary Flight Display of an integrated general aviation cockpit. To address these accident causes, four prototype enhancements were designed, implemented on a PFD, and flight tested in a single-engine general aviation aircraft. A Takeoff Performance Monitor prototype demonstrated the usefulness of automating the published takeoff distance calculation required of, but seldom performed by, pilots and also showed that performance deficiencies as small as a 10% reduction in power can be detected within the first few seconds immediately after throttle-up. The prototype was also able to predict takeoff distance in real-time within 200 feet by 55 knots using a simple acceleration model. A Dynamic Stall and V-Speeds prototype calculated stall speeds, best angle of climb speed, best rate of climb speed, and best glide speed given the current flight conditions and marked them on the airspeed indicator. Subject pilots reported the speeds aided in maintaining awareness of stall margin and optimal performance conditions. / (cont.) An Angle of Attack Estimator that used a speed-based method and an angle-based method to compute the angle of attack using only the data available on the PFD without additional sensors was prototyped along with two means of display; a traditional angle of attack gauge and a Pitch Limit Indicator. Both estimator methods were compared to an angle of attack vane during a series of maneuvers. It was shown that a speed-based angle of attack estimator along with the pitch limit indicator is a useful stall avoidance aid. Finally, an Unusual Attitude Alerting prototype provided specific verbal cues over the intercom when pitch or roll limits were exceeded to aid a pilot in recovery from unusual attitudes. Subject pilots preferred alerts that commanded the recovery maneuver over alerts that informed the pilot of the attitude but left the recovery procedure to the pilot, and preferred both to alerts that simply told the pilot to recover without specific information about the attitude. / by Daniel R. Craig. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1989. / Title as it appears in M.I.T. Graduate List, Feb. 1989: A study of IMU transfer alignment. / Includes bibliographical references (leaves 93-94). / by Serge M. Karsenti. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1996. / Includes bibliographical references (p. 97-80). / by D.J. Orr, Jr. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 223-231). / When considering the formation control problem for large number of spacecraft, the advantages of implementing control approaches with a centralized coordination mechanism can be outpaced by the risks associated with having a primary vital control unit. Additionally, in formations with a large number of spacecraft, a centralized approach implies an inherent difficulty in gathering and broadcasting information from/to the overall system. Therefore, there is a need to explore efficient decentralized control approaches. In this thesis a new approach to spacecraft formation control is formulated by exploring and enhancing the recent results on the theory of convergence to geometric patterns and exploring the analysis of this approach using the tools of contracting theory. First, an extensive analysis of the cyclic pursuit dynamics leads to developing control laws useful for spacecraft formation flight which, as opposed to the most common approaches in the literature, do not track fixed relative trajectories and therefore, reduce the global coordination requirements. The proposed approach leads to local control laws that verify global emergent behaviors specified as convergence to a particular manifold. A generalized analysis of such control approach by using tools of partial contraction theory is performed, producing important convergence results. By applying and extending results from the theory of partially contracting systems, an approach to deriving sufficient conditions for convergence is formulated. Its use is demonstrated by analyzing several examples and obtaining global convergence results for nonlinear, time varying and more complex interconnected distributed controllers. Experimental results of the implementation of these algorithms were obtained using the SPHERES testbed on board the International Space Station, validating many of the important properties of this decentralized control approach. They are believed to be the first implementation of decentralized formation flight in space. To complement the results we also consider a short analysis of the advantages of decentralized versus centralized approach by comparing the optimal performance and the effects of complexity and robustness for different architectures and address the issues of implementing decentralized algorithms in a inherently coupled system like the Electromagnetic Formation Flight. / by Jaime Luís Ramírez Riberos. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, February 2002. / Includes bibliographical references (p. 76-79). / by Jessica J. Márquez. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006. / Includes bibliographical references (p. 104-106). / Most modem blade designs in axial-flow compressors diffuse the flow efficiently over 20% to 80% of blade span and it is the endwall regions that set the limits in compressor performance. This thesis addresses the estimation, control and mitigation of three-dimensional separation near the hub corner in axial- flow compressors. A simple method to estimate the onset of hub comer separation in compressor blade passages has been developed. A parameter is defined to quantify the combined effect of adverse pressure gradient and secondary flow which are the two main mechanisms contributing to the formation of three-dimensional flow separation. There is a critical value of the parameter at which the onset of three-dimensional flow separation occurs. Data from existing research and production compressors show the generality of the separation criterion. The new parameter captures the alleviating effect of boundary layer skew on three-dimensional flow separation. Using this concept, a flow control scheme has been developed to mitigate hub comer separation by injecting spanwise momentum from the blade suction surface. A proof of concept flow control experiment demonstrates a reduction in stagnation pressure loss coefficient of 8% with an injection flow of 0.8% of the cascade mass flow. / by Vai-Man Lei. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1994. / Includes bibliographical references (p. 48-51). / by Kathryn A. Fricks. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1995. / Includes bibliographical references (leaves 197-204). / by David Shia. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 263-267). / A stepwise methodology to assist in the development of a model to determine the interlaminar stress fields and the mechanisms that give rise to these stress fields in transversely-loaded grooved composite laminates was developed. The methodology consists of five steps, with each step representing a laminate configuration with an increase in complexity from the previous step. Models for each step were developed in the context of a general formulation proposed in the literature that was previously used to analyze the proposed problem for Step 1. This general formulation is based around an assumed stress approach, where unknown coefficents in the assumed stress shapes are solved via the Principle of Minimum Complementary Energy. Models derived from such an approach were designed to be both accurate in the results as well as more efficient in runtime as compared to other models (e.g. finite element models). Such models are particularly useful for preliminary design, where various laminate configurations need to be analyzed efficiently to find designs for more detailed analysis and further modification. The results from the models for Steps 1 through 3 were found to be in good agreement with results in the literature, when available, or finite element results when analyzing configurations with results not found in literature. Characteristic results were taken from the models for Steps 1 through 3 in order to determine modifications, as well as identifying phenomena in the stress distributions, that require particular attention in the formulation of subsequent models. Key controlling factors in the model for Steps 1 through 3 are identified from the results. Issues encountered in Step 4 with regard to representation of slanted dropoffs prevent further model development. The feasibility of the formulation of the Step 5 model, involving loaded edges, was established assuming a working Step 4 model. Modifications of Steps 4 and 5 of the initially-proposed stepwise methodology were developed such that models for the proposed problems can be developed using the general formulation established for previous steps. These modified steps allow for a closed-form solution within the context of the general formulation as well as identification of the mechanisms and laminate parameters that affect interlaminar stress fields in transversely-loaded grooved laminates. Recommendations for future work are made. / by Alberto Joseph Gayon. / S.M.