UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
6 results
Search Results
Item IMPROVED PREDICTION OF FLAPPING WING AERIAL VEHICLE PERFORMANCE THROUGH COMPONENT INTERACTION MODELING(2018) Gerdes, John William; Gupta, Satyandra K; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Flapping wing aerial vehicles offer the promise of versatile performance, however prediction of flapping wing aerial vehicle performance is a challenging task because of complex interconnectedness in vehicle functionality. To address this challenge, performance is estimated by using component-level modeling as a foundation. Experimental characterization of the drive motors, battery, and wings is performed to identify important functional characteristics and enable selection of appropriate modeling techniques. Component-level models are then generated that capture the performance of each vehicle component. Validation of each component-level model shows where errors are eliminated by capturing important dynamic functionality. System-level modeling is then performed by creating linkages between component-level models that have already been individually validated through experimental testing, leading to real-world functional constraints that are realized and correctly modeled at the system level. The result of this methodology is a system-level performance prediction that offers the ability to explore the effects of changing vehicle components as well as changing functional properties, while maintaining computational tractability. Simulated results are compared to experimental flight test data collected with an instrumented flapping wing aerial vehicle, and are shown to offer good accuracy in estimation of system-level performance properties.Item DESIGN, ANALYSIS, AND TESTING OF A FLAPPING WING MINIATURE AIR VEHICLE(2010) Gerdes, John William; Gupta, Satyandra K; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Flapping wing miniature air vehicles (MAVs) offer several advantageous performance benefits, relative to fixed-wing and rotary-wing MAVs. The goal of this thesis is to design a flapping wing MAV that achieves improved performance by focusing on the flapping mechanism and the spar arrangement in the wings. Two variations of the flapping mechanism are designed and tested, both using compliance as a technique for improved functionality. In the design of these mechanisms, kinematics and dynamics simulation is used to evaluate how forces encountered during wing flapping affect the mechanism. Finite element analysis is used to evaluate the stress and deformation of the mechanism, such that a lightweight yet functional design can be realized. The wings are tested using experimental techniques. These techniques include high speed photography, stiffness measurement, and lift and thrust measurements. Experimentally measured force results are validated with a series of flight tests. A framework for iterative improvement of the MAV is described, that uses the results of physical testing and simulations to investigate the underlying causes of MAV performance aspects; and seeks to capture those beneficial aspects that will allow for performance improvements. Wings and flapping mechanisms designed in this thesis are used to realize a bird-inspired flapping wing miniature air vehicle. This vehicle is capable of radio controlled flights indoors and outdoors in winds up to 6.7m/s with controlled steering, ascent, and descent, as well as payload carrying abilities.Item THE VEHICLE ROUTING PROBLEM WITH DEMAND RANGES(2009) Cornick, Namrata Uppal; Golden, Bruce; Applied Mathematics and Scientific Computation; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The classic Capacitated Vehicle Routing Problem (CVRP) has been studied in the Operations Research field for over 5 decades. This thesis formulates the vehicle routing problem with a variation that has not been studied in detail. It is called the Vehicle Routing Problem with Demand Ranges (VRPDR). With increasing competition, corporations are looking to minimize costs. This problem aims to reduce the cost of distributing goods by allowing flexibility in the delivered or dropped off quantity. This benefits the customer as well, by reducing storage and other inventory costs. We solve the VRPDR problem where the customer gives the distributor a demand range. The distributor is rewarded for delivering more. A metaheuristic, record-to-record travel with demand range (RTRDR), is developed which is capable of solving large problem instances. The metaheuristic is a modification of a successful CVRP metaheuristic used in the past. In this thesis, we report results on problems ranging in size from 560 to 1200 customers. The developed metaheuristic uses the Clarke-Wright procedure to get initial solutions and then applies record-to-record travel in conjunction with two-opt moves, one point moves, and two point moves. Since the problem has not been studied yet from a computational point of view, we have developed a comparison algorithm, which takes advantage of the demand range flexibility of this problem only after the algorithm has optimized for distance alone. We use the results from this algorithm as a benchmark to compare with our proposed metaheuristic RTRDR.Item An Analysis of Vehicle Fires and Potential Methods to Reduce Their Severity Through More Stringent Material Standards(2008-06-17) Patronik, Evan; Mowrer, Frederick; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the United States, more than 1 in every 12 fire fatalities occurs in a passenger road vehicle; vehicle fires claim roughly 1200 injuries, $1.3 billion in property loss, and 490 lives annually. Very little progress has been made over the last several decades to confront the hazards of vehicle fires, but recently researchers and standards organizations have begun addressing these challenges. A literature review of the progress made and methods of reducing fire severity through technologies and standards was conducted. NFPA 556 is one proposed standard aimed at mitigating the hazards to occupants of vehicle fires; it was used to analyze the fire retardancy of a new, fire-resistant acoustic insulation material through small, bench, and large-scale testing. The feasibility of the use of this material in new vehicles for the reduction of losses was assessed through a cost-benefit analysis. Upon review of the results, it was determined that the new insulation did not pass all the requirements of NFPA 556. However, the standard does include stringent requirements, so the improved performance of the material should not be underappreciated. Based on the literature search and experiments, this standard, in combination with other fire protection technologies, provides a basis for improved vehicle fire safety.Item Transformation Plans for Optimizing Military Vehicle Testing(2007-05-15) Hoy, Timothy W; Herrmann, Jeffrey W; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The U.S. Army Aberdeen Test Center is a leading Department of Defense developmental test center and test range. A majority of the testing conducted at the Aberdeen Test Center is automotive in nature. Due to recent conflicts around the world, the U.S. Armed Services need to field new armored systems rapidly. The rapid deployment of automotive systems has caused the Department of Defense test community and the Aberdeen Test Center in particular to reevaluate and redefine traditional test plans and practices in order to maximize the amount of valid and pertinent data obtained from shortened test schedules. As a result, this thesis studies new transformation plans to provide ways to optimize military test plans. These transformation plans take into account existing military vehicle data from multiple sources including the Aberdeen Test Center's automotive road courses. These transformation plans are not only useful for shortened military tests, but can also be easily employed in developing test plans for private industry customers as well as long term test projects. The benefits in all cases are the same: an optimized test plan for automotive endurance operations.Item Vehicle Shaping for Mine Blast Damage Reduction(2006-07-28) Genson, Kevin William; Fourney, William; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)When a buried explosive is detonated beneath a target (such as a vehicle), the target is rapidly loaded by flying ejecta, high pressure gas, and shock waves. This paper explores how changes in the shape of the underside of a target affect the total impulse captured from the detonation of a buried charge. The effects of changes in target height and charge burial depth are also examined. Testing was conducted on dihedral target plates using 0.636 gram charges. These were buried in saturated sand at three depths, and shaped targets were placed at four heights above the surface. The impulse applied to the plate by the exploding charge was determined through analysis of high speed digital video recordings. Changing the geometry of the target reduced the impulse by up to 45%. Increasing standoff distance reduced impulse by up to 70%.