A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Analysis of Helicopter Flight Dynamics through Modeling and Simulation of Primary Flight Control Actuation System(2015) Nelson, Hunter Barton; Celi, Robertro; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A simplified second-order transfer function actuator model used in most flight dynamics applications cannot easily capture the effects of different actuator parameters. The present work integrates a nonlinear actuator model into a nonlinear state space rotorcraft model to determine the effect of actuator parameters on key flight dynamics. The completed actuator model was integrated with a swashplate kinematics where step responses were generated over a range of key hydraulic parameters. The actuator-swashplate system was then introduced into a nonlinear state space rotorcraft simulation where flight dynamics quantities such as bandwidth and phase delay analyzed. Frequency sweeps were simulated for unique actuator configurations using the coupled nonlinear actuator-rotorcraft system. The software package CIFER was used for system identification and compared directly to the linearized models. As the actuator became rate saturated, the effects on bandwidth and phase delay were apparent on the predicted handling qualities specifications.Item EXTREME VERTICAL DISPLACEMENT, HIGH FORCE, SILICON MICROSTAGE ZIPPER ACTUATORS(2013) Felder, Jason; DeVoe, Don L; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Large vertical deflection, high force microactuators are desired in MEMS for a variety of applications. This thesis details a novel large-displacement electrostatic "zipper" microactuator capable of achieving hundreds of microns of out-of-plane deflection and delivering high forces, fabricated entirely from SOI (silicon-on-insulator). This technology is novel in its use of SiO2 as both a high quality dielectric and the stressed layer of the bimorph. Geometries are explored analytically, numerically and experimentally to provide the greatest electromechanical output while constraining the device footprint to 1mm2. Device performance was benchmarked against previously established out-of-plane microactuators. We report the first instance of zipper-inspired electrostatic "microstage" actuators whose flat center stage and vertical actuation mode is ideal for carrying and moving a load. Fabricated microstages are capable of achieving out-of-plane deflections up to 1.2 mm, force outputs up to 1 mN, pull-in voltage as low as 20 V, and switching times of 1 ms.Item Towards the Use of Dielectric Elastomer Actuators as Locomotive Devices for Millimeter-Scale Robots(2012) Pearse, Justin Daminabo; Smela, Elisabeth; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Dielectric elastomer actuators (DEAs) are electromechanical transducers that are promising for small scale applications. The work presented in this thesis seeks to develop DEAs as an actuation technology that would serve the purpose of ambulating millimeter-scale robots in a robust and predictable manner. To begin, the "planar" DEA configuration was characterized and the performances of various elastomers were investigated. Then, based on the requirements of a proposed robot walking gait, two principles were examined as means of converting in-plane actuation strain to bending actuation. Bending DEAs were fabricated and tested, and a maximum end displacement of 1.5 mm was achieved for a 10 mm long sample. Bending actuator design was optimized by maximizing both speed and payload capabilities. Finally, some challenges facing the design of robots ambulated by DEAs were outlined; of particular note is the DEAs' electrostatic interaction with each other and their surroundings.