The design process of unmanned ISR systems has typically driven in the direction of increasing system mass to increase stabilization performance and imagery quality. However, through the use of new sensor and processor technology high performance stabilization feedback is being made available for control on new small and low mass stabilized platforms that can be placed on small UAVs. This project develops and implements a LOS stabilization controller design, typically seen on larger gimbals, onto a new small stabilized gimbal, the Tigereye, and demonstrates the application on several small UAV aircraft. The Tigereye gimbal is a new 2lb, 2-axis, gimbal intended to provided high performance closed loop LOS stabilization through the utilization of inertial rate gyro, electronic video stabilization, and host platform state information. Ground and flight tests results of the LOS stabilization controller on the Tigereye gimbal have shown stabilization performance improvements over legacy systems. However, system characteristics identified in testing still limit stabilization performance, these include: host system vibration, gimbal joint friction and backlash, joint actuation compliance, payload CG asymmetry, and gyro noise and drift. The control system design has been highly modularized in anticipation of future algorithm and hardware upgrades to address the remaining issues and extend the system's capabilities.

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<p> With pressure on the U.S. Defense Acquisition System (DAS) to reduce cost overruns and schedule delays, system engineers&rsquo; performance is only as good as their tools. Recent literature details a need for 1) objective, analytical risk quantification methodologies over traditional subjective qualitative methods &ndash; such as, expert judgment, and 2) mathematically rigorous system-level maturity assessments. The Mahafza, Componation, and Tippett (2005) Technology Performance Risk Index (TPRI) ties the assessment of technical performance to the quantification of risk of unmet performance; however, it is structured for component- level data as input. This study&rsquo;s aim is to establish a modified TPRI with systems-level data as model input, and then validate the modified index with actual system-level data from the Department of Defense&rsquo;s (DoD) Major Defense Acquisition Programs (MDAPs). This work&rsquo;s contribution is the establishment and validation of the System-level Performance Risk Index (SPRI). With the introduction of the SPRI, system-level metrics are better aligned, allowing for better assessment, tradeoff and balance of time, performance and cost constraints. This will allow system engineers and program managers to ultimately make better-informed system-level technical decisions throughout the development phase.</p>

The research described in this report resulted from my participation in the design study for the Phased-Array Imaging Telescope. To maintain high transmission, a practical system should contain a minimum number of components. This consideration leads to the concept of shared symmetries between the subtelescope and final collector. This report presents an approach to the design of such arrays, and examines the implications of including aspheric correction for the telescope array. As expected, the number of elements in this correction design concept seems to work well. Four array systems based on this concept are presented; each uses only one spherical mirror as the beam collector. The effects of changing the primary mirror's relative aperture, and of changing the system length, on the symmetry and order of aberrations arising from the use of an eccentric aspheric, are explained in this report. The subtle limitations of techniques for adding special surfaces for decentered aspheric correction to optical design programs are discussed as well. Two additional design concepts are examined and compared. A preliminary tolerancing analysis is performed, and error budgets developed. An adaptive element is considered for relaxing the alignment and fabrication tolerances.

Photovoltaic cells, appropriately cooled and operating in the combustion-created high radiant-intensity environment of gas-turbine and jet engines, may replace the conventional (gearbox-driven) electrical power generators aboard jet aircraft. This study projects significant improvements not only in aircraft electrical power-generating-system performance, but also in overall aircraft performance. Jet-engine design modifications incorporating this concept not only save weight (and thus fuel), but are--in themselves--favorable to jet-engine performance. The dissertation concentrates on operational, constructional, structural, thermal, optical, radiometrical, thin-film, and solid-state theoretical aspects of the overall project. This new electrical power-generating system offers solid-state reliability with electrical power-output capability comparable to that of existing aircraft electromechanical power-generating systems (alternators and generators). In addition to improvements in aircraft performance, significant aircraft fuel- and weight-saving advantages are projected.

<p>Turbomachinery flow fields are inherently unsteady and complex which makes the related CFD analyses computationally intensive. Physically based preliminary design tools are desirable for parametric studies early in the design stage, and to provide deep physical insight and a good starting point for the later CFD analyses. Four analytical/semi-analytical models are developed in this study: 1) a generalized flat plate cascade model for investigating the unsteady aerodynamics of a blade row with non-uniformly spaced blades; 2) a multistage interaction model for investigating rotor-stator interactions; 3) an analytical solution for quantifying the impeller wake convection and pressure wave propagating between a centrifugal compressor impeller and diffuser vane; and 4) a semi-analytical model based Lifting line theory for unified propeller and horizontal-axis turbine optimization. Each model has been thoroughly validated with existing models. </p><p> With these models, non-uniformly spaced blade rows and vane clocking are investigated in detail for their potential use as a passive control technique to reduce forced response, flutter and aeroacoustic problems in axial compressors. Parametric studies with different impeller blade numbers and back sweep angles are conducted to investigate their effect on impeller wake and pressure wave propagation. Results show that the scattered pressure waves with high circumferential wave numbers may be an important excitation source to the impeller as their amplitude grows much faster as they travel inwardly than the lower order primary pressure waves. Detailed analysis of Lifting line theory reveals the mathematical and physical equivalence of Lifting line models for propellers and horizontal-axis turbines. With a new implementation, the propeller optimization code can be used for horizontal-axis turbine optimization without any modification. The newly developed unified propeller and horizontal-axis turbine optimization code based on lifting line theory and interior point method has been shown to be a very versatile tool with the capability of hub modelling, working with non-uniform inflow and including extra user specified constraints. </p>

<p> This work presents a new automatic differentiation method, Nilpotent Matrix Differentiation (NMD), capable of propagating any order of mixed or univariate derivative through common linear algebra functions&mdash;most notably third-party sparse solvers and decomposition routines, in addition to basic matrix arithmetic operations and power series&mdash;without changing data-type or modifying code line by line; this allows differentiation across sequences of arbitrarily many such functions with minimal implementation effort. NMD works by enlarging the matrices and vectors passed to the routines, replacing each original scalar with a matrix block augmented by derivative data; these blocks are constructed with special sparsity structures, termed &ldquo;stencils,&rdquo; each designed to be isomorphic to a particular multidimensional hypercomplex algebra. The algebras are in turn designed such that Taylor expansions of hypercomplex function evaluations are finite in length and thus exactly track derivatives without approximation error. </p><p> Although this use of the method in the &ldquo;forward mode&rdquo; is unique in its own right, it is also possible to apply it to existing implementations of the (first-order) discrete adjoint method to find high-order derivatives with lowered cost complexity; for example, for a problem with <i>N</i> inputs and an adjoint solver whose cost is independent of <i>N</i>&mdash;i.e., <i><b> O</b></i>(1)&mdash;the <i>N &times; N</i> Hessian can be found in <i><b>O</b></i>(<i>N</i>) time, which is comparable to existing second-order adjoint methods that require far more problem-specific implementation effort. Higher derivatives are likewise less expensive&mdash;e.g., a <i>N &times; N &times; N</i> rank-three tensor can be found in <i><b> O</b></i>(<i>N</i>²). Alternatively, a Hessian-vector product can be found in <i><b>O</b></i>(1) time, which may open up many matrix-based simulations to a range of existing optimization or surrogate modeling approaches. As a final corollary in parallel to the NMD-adjoint hybrid method, the existing complex-step differentiation (CD) technique is also shown to be capable of finding the Hessian-vector product. All variants are implemented on a stochastic diffusion problem and compared in-depth with various cost and accuracy metrics.</p>

<p> The purpose of this qualitative phenomenological study was to examine the phenomenon of enhanced, risk-based Federal Aviation Administration (FAA) oversight of Part 145 repair stations that performed aircraft maintenance for Part 121 air carriers between 2007 and 2014 in Oklahoma. Specifically, this research was utilized to explore what operational changes have occurred in the domestic Part 145 repair station industry such as variations in management or hiring practices, training, recordkeeping and technical data, inventory and aircraft parts supply-chain logistics, equipment, and facilities. After interviewing 12 managers from Part 145 repair stations in Oklahoma, six major theme codes emerged from the data: <i>quality of oversight before 2007, quality of oversight after 2007, advantages of oversight, disadvantages of oversight, status quo of oversight,</i> and <i>process improvement </i>. Of those six major theme codes, 17 subthemes appeared from the data that were used to explain the phenomenon of enhanced oversight in the Part 145 repair station industry. Forty-two percent of the participants indicated a weak FAA oversight system that has hindered the continuous process improvement program in their repair stations. Some of them were financially burdened after hiring additional full-time quality assurance inspectors to specifically manage enhanced FAA oversight. Notwithstanding, the participants of the study indicated that the FAA must apply its surveillance on a more standardized and consistent basis. They want to see this standardization in how FAA inspectors interpret regulations and practice the same quality of oversight for all repair stations, particularly those that are repeat violators and fail to comply with federal aviation regulations. They believed that when the FAA enforces standardization on a consistent basis, repair stations can become more efficient and safer in the performance of their scope of work for the U.S. commercial air transportation industry.</p>

<p> Unmanned aerial vehicles are quickly becoming a significant and permanent feature in today's world of aviation. Amongst the various types of UAVs, a popular type is the quadcopter. Also referred to as a quadrotor, this rotor craft's defining feature is that it has four propellers. While its use is common in the hobbyist community, this aircraft's use within industry is blooming. </p><p> Presented are the efforts to design and implement a controller for a BeagleBone based quadcopter. As part of this effort, characteristics of the quadcopter were experimentally determined. These characteristics consist of physical properties of the quadcopter, such as the moments of inertia, the motor performance characteristics, and variance within its sensors. A model was then created and implemented within a MATLAB environment to simulate the flight of the quadcopter. With a simulated environment created, a controller was designed to control the flight of the quadcopter and a Kalman Filter was implemented to filter a sensor input. These designs were then verified in the simulated environment.</p>