Theses and Dissertations from UMD
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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 give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Pneumatic Artificial Muscle Driven Trailing Edge Flaps For Active Rotors(2011) Woods, Benjamin King Sutton; Wereley, Norman M; Kothera, Curt S; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research focuses on the development of an active rotor system capable of primary control and vibration reduction for rotorcraft. The objective is to investigate the feasibility of a novel Trailing Edge Flap (TEF) actuation system driven by Pneumatic Artificial Muscles (PAMs). A significant design effort led to a series of experimental apparatuses which tested various aspects of the performance of the actuators themselves and of TEF systems driven by them. Analytical models were developed in parallel to predict the quasistatic and dynamic behavior of these systems. Initial testing of a prototype blade section with an integrated PAM driven TEF proved the viability of the concept through successful benchtop testing under simulated M = 0.3 loading and open jet wind tunnel tests under airspeeds up to M = 0.13. This prototype showed the ability of PAM actuators to generate significant flap deflections over the bandwidth of interest for primary control and vibration reduction on a rotorcraft. It also identified the importance of high pneumatic system mass flow rate for maintaining performance at higher operating frequencies. Research into the development and improvement of PAM actuators centered around a new manufacturing technique which was invented to directly address the weaknesses of previous designs. Detailed finite element model (FEM) analysis of the design allowed for the mitigation of stress concentrations, leading to increased strength. Tensile testing of the swaged actuators showed a factor of safety over 5, and burst pressure testing showed a factor of safety of 3. Over 120,000,000 load cycles were applied to the actuators without failure. Characterization testing before, during, and after the fatigue tests showed no reduction in PAM performance. Wind tunnel testing of a full scale Bell 407 blade retrofitted with a PAM TEF system showed excellent control authority. At the maximum wind tunnel test speed of M = 0.3 and a derated PAM operating pressure of 28 psi, 18.8° half-peak-to-peak flap deflections were achieved at 1/rev (7 Hz), and 17.1° of half-peak-to-peak flap deflection was still available at 5/rev (35 Hz). A quasistatic system model was developed which combined PAM forces, kinematics and flap aerodynamics to predict flap deflection amplitudes. This model agreed well with experimental data. Whirl testing of a sub-span whirl rig under full scale loading conditions showed the ability of PAM TEF systems to operate under full scale levels of centrifugal (CF), aerodynamic, and inertia loading. A commercial pneumatic rotary union was used to provide air in the rotating frame. Extrapolation of the results to 100% of CF acceleration predicts 15.4° of half-peak-to-peak flap deflection at 1/rev (7 Hz), and 7.7° of half-peak-to-peak flap deflection at 5/rev (35 Hz). A dynamic model was developed which successfully predicted the time domain behavior of the PAM actuators and PAM TEF system. This model includes control valve dynamics, frictional tubing losses, pressure dynamics, PAM forces, mechanism kinematics, aerodynamic hinge moments, system stiffness, damping, and inertia to solve for the rotational dynamics of the flap. Control system development led to a closed loop control system for PAM TEF systems capable of tracking complex, multi-sinusoid flap deflections representative of a combined primary control and vibration reduction flap actuation scheme. This research shows the promise that PAM actuators have as drivers for trailing edge flaps on active helicopter rotors. The robustness, ease of integration, control authority and tracking accuracy of these actuators have been established, thereby motivating further research.Item Insulin-like Growth Factor 1 Genotype Influences Muscle Strength Response to Sterngth Training in Older Adults(2004-11-03) kostek, matt; Hurley, Ben F; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Strength training (ST) is considered an intervention of choice for the prevention and treatment of sarcopenia. The insulin-like growth factor 1 protein (IGF-I) plays a major role in ST-induced skeletal muscle hypertrophy and strength improvements. A microsatellite repeat in the promoter region of the IGF1 gene has been associated with IGF-I blood levels and phenotypes related to IGF-I in adult men and women. To examine the influence of this polymorphism on muscle hypertrophic and strength responses to strength training (ST), we studied 67 Caucasian men and women before and after a 10-week single leg knee extension ST program. One repetition maximum (1RM) strength, muscle volume (MV) via computed tomography (CT), and muscle quality (MQ) were assessed at baseline and after 10 weeks of training. The IGF1 repeat promoter polymorphism and three single nucleotide polymorphisms (SNP) were genotyped. For the promoter polymorphism, subjects were grouped as homozygous for the 192 allele, heterozygous, or non-carriers of the 192 allele. After 10 weeks of training, 1RM, MV, and MQ increased significantly for all groups combined (P < 0.001). However, carriers of the 192 allele gained significantly more strength with ST than non-carriers of the 192 allele (P = 0.02). There was also a non-significant trend for a greater increase in MV in 192 carriers than non-carriers (P = 0.08). No significant associations were observed for the other polymorphisms studied. Thus, these data suggest that the IGF1 promoter polymorphism may influence the strength response to ST. Larger sample sizes should be used in future studies to verify these results