http://hdl.handle.net/1903/2737 2013-05-22T01:30:09Z http://hdl.handle.net/1903/13825 Title: AN INVESTIGATION OF CONCENTRATED AND DISTRIBUTED STRAIN INDUCING CONSTRAINTS FOR TRAINING SHAPE MEMORY ALLOYS Authors: Parent, Pauline M. Abstract: This research explores concentrated and distributed strain inducing constraints for Two Way Shape Memory (TWSM) training of cantilevered NiTiNOL shape memory alloy strips via the constrained thermal cycling of deformed Martensite training method. The goal is to evaluate the performance of a tip-moment trained sample actuator, which is characterized by constant strain along the sample length, and compare it with the performance of tip-force trained sample actuators, which have root concentrated strain. The shape and net tip displacement of trained specimens is expected to vary with training constraint type and training load magnitude, rendering it uncertain which sample will have greater work potential. A training structure and systems for introducing thermal and mechanical loads were developed to provide the explored training constraints and induce TWSM. The work performance was evaluated by measuring vertical displacement of tip weights. The experimental results indicate that samples subject to strain distributing constraints during training have higher work potential than samples subject to concentrated strain inducing constraints. 2012-01-01T00:00:00Z http://hdl.handle.net/1903/13564 Title: Evaluation and Improvement of Temperature Sensitive Paint Data Reduction Process through Analysis of Tunnel Data Authors: Bhandari, Pratik Abstract: A data reduction process for a temperature sensitive paint heat transfer measurement system in use at the US Air Force Hypervelocity Wind Tunnel No. 9 has been evaluated using a set of data gathered from tests on a generic hypersonic waverider model. Discrepancies were observed between heat transfer results calculated using temperature sensitive paint based measurements as compared to results calculated using conventional thermocouple measurements at specific locations on the test article. Paint thermophysical property estimates were made and utilized in a series of finite element models to analyze paint behavior. These models were used to perform a sensitivity analysis on system parameters. Key identified parameters were used to perform a non-dimensional analysis of the tunnel data. Based on this analysis, discrepancy areas were identified and a novel two-calibration data reduction process was developed that mitigated the severity of some observed discrepancies and showed the potential for future improvements. 2012-01-01T00:00:00Z http://hdl.handle.net/1903/13555 Title: A Comparative Framework for Maneuverability and Gust Tolerance of Aerial Microsystems Authors: Campbell, Renee Christine Abstract: Aerial microsystems have the potential of navigating low-altitude, cluttered environments such as urban corridors and building interiors. Reliable systems require both agility and tolerance to gusts. While many platform designs are under development, no framework currently exists to quantitatively assess these inherent bare airframe characteristics which are independent of closed loop controllers. This research develops a method to quantify the maneuverability and gust tolerance of vehicles using reachability and disturbance sensitivity sets. The method is applied to a stable flybar helicopter and an unstable flybarless helicopter, whose state space models were formed through system identification. Model-based static H-infinity controllers were also implemented on the vehicles and tested in the lab using fan-generated gusts. It is shown that the flybar restricts the bare airframe's ability to maneuver in translational velocity directions. As such, the flybarless helicopter proved more maneuverable and gust tolerant than the flybar helicopter. This approach was specifically applied here to compare stable and unstable helicopter platforms; however, the framework may be used to assess a broad range of aerial microsystems. 2012-01-01T00:00:00Z http://hdl.handle.net/1903/13546 Title: Automated Kinematic Extraction of Wing and Body Motions of Free Flying Diptera Authors: Kostreski, Nicholas Ivan Abstract: In the quest to understand the forces generated by micro aerial systems powered by oscillating appendages, it is necessary to study the kinematics that generate those forces. Automated and manual tracking techniques were developed to extract the complex wing and body motions of dipteran insects, ideal micro aerial systems, in free flight. Video sequences were captured by three high speed cameras (7500 fps) oriented orthogonally around a clear flight test chamber. Synchronization and image-based triggering were made possible by an automated triggering circuit. A multi-camera calibration was implemented using image-based tracking techniques. Three-dimensional reconstructions of the insect were generated from the 2-D images by shape from silhouette (SFS) methods. An intensity based segmentation of the wings and body was performed using a mixture of Gaussians. In addition to geometric and cost based filtering, spectral clustering was also used to refine the reconstruction and Principal Component Analysis (PCA) was performed to find the body roll axis and wing-span axes. The unobservable roll state of the cylindrically shaped body was successfully estimated by combining observations of the wing kinematics with a wing symmetry assumption. Wing pitch was determined by a ray tracing technique to compute and minimize a point-to-line cost function. Linear estimation with assumed motion models was accomplished by discrete Kalman filtering the measured body states. Generative models were developed for different species of diptera for model based tracking, simulation, and extraction of inertial properties. Manual and automated tracking results were analyzed and insect flight simulation videos were developed to quantify ground truth errors for an assumed model. The results demonstrated the automated tracker to have comparable performance to a human digitizer, though manual techniques displayed superiority during aggressive maneuvers and image blur. Both techniques demonstrated non-intrusive methods for establishing reference flight kinematics, which are being used to develop flight dynamics models in future work. 2012-01-01T00:00:00Z