Browsing by Subject "Guidance"
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Item ACC 2013, An Airborne Experimental Test Platform: From Theory to Flight Companion Software Package(2014-07-23) Dorobantu, AndreiItem Chondroitin Sulfate And Keratan Sulfate Proteoglycans In Retinal Axon Growth And Guidance(2018-08) McAdams, BrianAxons of retinal ganglion cells grow from the eye to the visual centers of the brain during development. Evidence suggests that adhesive and anti-adhesive interactions between growing axons and the cells and extracellular matrix in their environment guide retinal axons to their central targets. Proteoglycans are a family of extracellular glycoproteins that could contribute to these interactions. The present study investigated the potential interaction and influence of glycosaminoglycans with retinal axons in situ and in vitro. Immunostaining showed both chondroitin sulfate and keratan sulfate proteoglycans throughout the retinotectal pathway during the period of axon growth. Retinal neurites extending from explants in culture were immunopositive for chondroitin sulfate indicating that retinal axons may contribute proteoglycans to the pathway. Retinal neurite behavior was examined in the presence of soluble glycosaminoglycans. High concentrations of chondroitin sulfate promoted retinal neurite growth on normally less adhesive substrates, which suggests that this glycosaminoglycan may promote neurite outgrowth in some conditions. Retinal axon growth was also examined in nanomelic chicks, mutants which do not secrete a large chondroitin sulfate proteoglycan, aggrecan. Aggrecan immunostaining was colocalized with retinal axons in normal embryos. For the parameters studied, retinal axon growth and guidance appeared unaffected in nanomelic mutants, which suggested that aggrecan was not essential for retinal axon growth or guidance. Its spatiotemporal distribution, however, suggests that aggrecan has other developmental roles in this system. Collectively, the data are ambiguous regarding the role of chondroitin sulfate and keratan sulfate proteoglycans relative to retinal axon growth during development. Proteoglycans are capable of influencing retinal axon growth in vitro, but whether they influence growth in vivo and the nature of this influence will require future investigations.Item Design and analysis of optimal ascent trajectories for stratospheric airships(2013-08) Mueller, Joseph BernardStratospheric airships are lighter-than-air vehicles that have the potential to provide a long-duration airborne presence at altitudes of 18-22 km. Designed to operate on solar power in the calm portion of the lower stratosphere and above all regulated air traffic and cloud cover, these vehicles represent an emerging platform that resides between conventional aircraft and satellites. A particular challenge for airship operation is the planning of ascent trajectories, as the slow moving vehicle must traverse the high wind region of the jet stream. Due to large changes in wind speed and direction across altitude and the susceptibility of airship motion to wind, the trajectory must be carefully planned, preferably optimized, in order to ensure that the desired station be reached within acceptable performance bounds of flight time and energy consumption. This thesis develops optimal ascent trajectories for stratospheric airships, examines the structure and sensitivity of these solutions, and presents a strategy for onboard guidance. Optimal ascent trajectories are developed that utilize wind energy to achieve minimum-time and minimum-energy flights. The airship is represented by a three-dimensional point mass model, and the equations of motion include aerodynamic lift and drag, vectored thrust, added mass effects, and accelerations due to mass flow rate, wind rates, and Earth rotation. A representative wind profile is developed based on historical meteorological data and measurements. Trajectory optimization is performed by first defining an optimal control problem with both terminal and path constraints, then using direct transcription to develop an approximate nonlinear parameter optimization problem of finite dimension. Optimal ascent trajectories are determined using SNOPT for a variety of upwind, downwind, and crosswind launch locations. Results of extensive optimization solutions illustrate definitive patterns in the ascent path for minimum time flights across varying launch locations, and show that significant energy savings can be realized with minimum-energy flights, compared to minimum-time time flights, given small increases in flight time. The performance of the optimal trajectories are then studied with respect to solar energy production during ascent, as well as sensitivity of the solutions to small changes in drag coefficient and wind model parameters. Results of solar power model simulations indicate that solar energy is sufficient to power ascent flights, but that significant energy loss can occur for certain types of trajectories. Sensitivity to the drag and wind model is approximated through numerical simulations, showing that optimal solutions change gradually with respect to changing wind and drag parameters and providing deeper insight into the characteristics of optimal airship flights. Finally, alternative methods are developed to generate near-optimal ascent trajectories in a manner suitable for onboard implementation. The structures and characteristics of previously developed minimum-time and minimum-energy ascent trajectories are used to construct simplified trajectory models, which are efficiently solved in a smaller numerical optimization problem. Comparison of these alternative solutions to the original SNOPT solutions show excellent agreement, suggesting the alternate formulations are an effective means to develop near-optimal solutions in an onboard setting.Item FASER Flight 03(2011-12-06) Taylor, BrianItem FASER Flight 04(2011-12-06) Taylor, BrianItem A formal investigation of the organization of guidance behavior: implications for humans and autonomous implications for humans and autonomous(2012-10) Kong, ZhaodanGuidance behavior generated either by artificial agents or humans has been actively studied in the fields of both robotics and cognitive science. The goals of these two fields are different. The former is the automatic generation of appropriate or even optimal behavior, while the latter is the understanding of the underlying mechanism. Their challenges, though, are closely related, the most important one being the lack of a unified, formal and grounded framework where the guidance behavior can be modeled and studied. This dissertation presents such a framework. In this framework, guidance behavior is analyzed as the closed-loop dynamics of the whole agent-environment system. The resulting dynamics give rise to interaction patterns. The central points of this dissertation are that: first of all, these patterns, which can be explained in terms of symmetries that are inherent to the guidance behavior, provide building blocks for the organization of behavior; second, the existence of these patterns and humans' organization of their guidance behavior based on these patterns are the reasons that humans can generate successful behavior in spite of all the complexities involved in the planning and control. This dissertation first gives an overview of the challenges existing in both scientific endeavors, such as human and animal spatial behavior study, and engineering endeavors, such as autonomous guidance system design. It then lays out the foundation for our formal framework, which states that guidance behavior should be interpreted as the collection of the closed-loop dynamics resulting from the agent's interaction with the environment. The following, illustrated by examples of three different UAVs, shows that the study of the closed-loop dynamics should not be done without the consideration of vehicle dynamics, as is the common practice in some of the studies in both autonomous guidance and human behavior analysis. The framework, the core concepts of which are symmetries and interaction patterns, is then elaborated on with the example of Dubins' vehicle's guidance behavior. The dissertation then describes the details of the agile human guidance experiments using miniature helicopters, the technique that is developed for the analysis of the experimental data and the analysis results. The results confirm that human guidance behavior indeed exhibits invariance as defined by interaction patterns. Subsequently, the behavior in each interaction pattern is investigated using piecewise affine model identification. Combined, the results provide a natural and formal decomposition of the behavior that can be unified under a hierarchical hidden Markov model. By employing the languages of dynamical system and control and by adopting algorithms from system identification and machine learning, the framework presented in this dissertation provides a fertile ground where these different disciplines can meet. It also promises multiple potential directions where future research can be headed.Item Investigation of Human Environment Learning in Agile Guidance Tasks(2017-11-20) Verma, Abhishek; Mettler, Berenice; mettler@umn.edu; Mettler, Berenice; University of Minnesota, Department of Aerospace Engineering and Mechanics, Interactive Guidance and Control LabHuman environment learning experiments are done in a simulated environment. The environment is quasi 3-D, made of polygonal obstacles. The simulated environment is displayed to subjects who can navigate in the environment using a joystick. Vehicle motion is restricted to horizontal plane. Subjects start from a specified start state in the obstacle field. Subjects have to learn fastest routes to a specified goal state over multiple runs. The simulation system provides first-person view of the task environment to subjects. The experiment system records trajectory, control, and human gaze location in the displayed environment. Experiments are done with eight subjects.Item Thor Flight 26(2011-10-11) Taylor, BrianItem Thor Flight 27(2011-10-11) Taylor, BrianItem Thor Flight 28(2011-10-11) Taylor, BrianItem Thor Flight 65(2012-08-21) Taylor, BrianItem Thor Flight 66(2012-08-21) Taylor, BrianItem Thor Flight 67(2012-08-21) Taylor, BrianItem Thor Flight 68(2012-08-21) Taylor, BrianItem Thor Flight 79(2014-09-04) Taylor, BrianItem Vision Guidance System for the Robotic Roadway Message Painter(2015-07) Ahmad, WaqasRoads are used as a way of transportation and communication in every part of the world. Road markers are painted on the roads for safety, information and caution purposes. Road markers are mainly used to assist drivers with vital information and caution. The process of painting new and existing roadway markings (turn arrows, STOP messages, railroad crossings, etc.) is an important maintenance task. The Minnesota Department of Transportation (MN/DOT) estimates that over 75% of symbol and message painting is the repainting of existing markings [1]. It would be extremely valuable for an automated painting system to have a vision guidance capability whereby an existing marker could be repainted accurately with little operator input. A vision system capable of identifying existing painted pavement markings and determining their coordinates, dimensions, location, and orientation would be a very useful tool. The information regarding the pavement markings could then be passed to a robotic painting device (currently under development) to enable it to accurately repaint the marking. This would significantly improve the capability of the device to repaint existing pavement markings. Eventual users of a device using this technology could be city, county, state, federal government agencies and private companies or contractors. It will allow improved safety, reduced cost and less time to maintain existing road markers as well as draw new ones.