Browsing by Subject "Kinematics"
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Item A comparison of extreme wind events as sampled in the 2002 thunderstorm outflow experiment(Texas Tech University, 2003-08) Gast, Kirsten DeannNot availableItem Application of the matrix approach to the kinematic modeling and analysis of spaial mechanisms(Texas Tech University, 1995-05) Suryanarayan, Krishna PrasadThe purpose of this thesis is to apply the homogeneous matrix transformation approach to the design of automotive alignment mechanisms and to briefly review its application to the kinematic analysis of a hyper-redundant manipulator. The homogeneous matrix transformation approach allows the determination of the position, velocity and acceleration of any point on the mechanism, defined in local coordinates, with respect to the world coordinate system, from a knowledge of the joint and link parameters. This homogeneous matrix method presents itself as a unique tool in the analysis of automotive alignment mechanisms as currently, these mechanisms are designed using geometric methods which involve tedious calculations. By the application of this matrix approach to their analysis, the design process is greatly simplified and it enables the design of these mechanisms to be easily implemented by breaking the design into smaller modules which are then solved individually to yield the final solution. Additionally, an investigation is performed to show the use of this matrix approach in the study of the kinematics of a hyper-redundant manipulator which is composed of wedge shaped discs.Item Cenozoic structural evolution of the eastern margin of the Middle Magdalena Valley basin, Colombia : integration of structural restorations, low-temperature thermochronology, and sandstone petrography(2011-08) Sánchez, Carlos Javier, M.S. in geological Sciences; Horton, Brian K., 1970-; Mann, Paul; Ketcham, RichardStructural analysis of surface and subsurface data from the Middle Magdalena Valley basin and Eastern Cordillera fold-thrust belt to construct a kinematic model for its Cenozoic structural and stratigraphic evolution. The La Salina west-vergent thrust system marks the boundary between the Paleogene foreland basin of the Middle Magdalena basin and the Eastern Cordillera fold-thrust belt. New low-temperature thermochonological and sandstone petrographic analyses provide constraints on ages of thrust deformation and sediment dispersal. Apatite fission track (AFT) and U-Th/He thermochronological results show the timing of three structural events along the La Salina fault system: (1) late Eocene-early Oligocene (~43–35 Ma) initial hanging wall exhumation; (2) continued middle Miocene (~15 Ma) exhumation; and (3) continued but more rapid late Miocene (~12–3 Ma) hanging wall exhumation. Vitrinite reflectance results provide estimates of maximum burial depths for the hanging wall of the La Salina fault ranging from 4 to 6 km., this depth of burial estimates constrain the basin geometry during its late Eocene to late Miocene evolution. The eastern hanging wall of the La Salina fault displays a broad anticline-syncline pair affecting Cretaceous to Eocene strata with no significant faulting, whereas the western footwall contains a complex series of tight, thrust-related folds in Eocene-Quaternary strata. For foreland basin province, a proposed triangle zone accommodates a small amount of east-west shortening (< 1000 m) along the frontal thrust system by east-vergent backthrusting within a broader passive-roof duplex. East-west shortening in the Cenozoic stratigraphic section was also accommodated by detachment folding, which produced localized areas of steep dips. In the proposed kinematic restoration, the most recent phase of deformation represents out-of-sequence reactivation of the La Salina fault that is consistent with irregular crosscutting relationships of some footwall structures. Earliest exhumation by ~45–30 Ma in the Eastern Cordillera fold-thrust belt province matches (1) an increased proportion of sedimentary lithic fragments; and (2) a high degree of compositional maturity (Q88F4Lf8). Exhumation since ~15 Ma in the foreland province coincides with (1) the highest accumulation rates observed for the upper Miocene Real Group; and (2) a decrease in compositional maturity (Q55F8Lf36).Item Changes in muscle activity and kinematics of highly trained cyclists during fatigue(2006-12) Joubert, Jason E.G.; Dingwell, Jonathan B.Up to 85% of cyclists experience repetitive strain injuries (RSI's). During long bouts of repetitive tasks, muscle fatigue may cause mal-alignments in kinematics, having cumulative effects, leading to an RSI. Purpose: The study's purpose was to examine how changes in localized muscle fatigue relate to changes in movement kinematics in highly trained cyclists throughout a full fatigue protocol. Methods: Seven highly trained cyclists participated in a 2 session experiment. Session 1 included a VO2 max test and familiarization trial and Session 2 was the fatigue protocol. Kinematic angles measured were trunk lean, hip, knee, ankle, and knee splay angle. Mean angle (MA) and range of motion (ROM) was calculated for each revolution thought the trial. Muscles monitored were the quadriceps, hamstring, gastrocnemius, and tibialis anterior. EMG median frequency (MDF) for each muscle was calculated for each revolution by averaging MDF for the two halves of each revolution. Cross-correlation analysis was done on MDF and MA data and MDF and ROM data. Results: All subjects exhibited increases in trunk lean and decreases in ankle angle. Non-monotonic changes were observed in trunk lean, ankle, knee splay angle, and among ROM results for all 5 angles. A 1-tailed T-tests for all subjects, revealed that HAM (p = 0.020) and GAS (p = 0.018) exhibited significant muscle fatigue. One-tailed T-tests yielded significantly negative cross-correlation time lags [Greek small letter tau] for trunk lean MA, ROM, and hip MA. Conclusions: Non-monotonic changes are present in kinematics and MDF. Therefore pre vs. post experimental designs cannot quantify fatigue processes. Shifts in trunk lean MA, ROM and hip MA are significantly correlated with preceding decreasing shifts of MDF (indicative of onset of fatigue).Item Effects of running with backpack loads during simulated gravitational transitions: improvements in postural control(Texas Tech University, 2003-12) Brewer, Jeffrey DavidThe National Aeronautics and Space Administration is planning for long-duration manned missions to the Moon and Mars. For feasible long-duration space travel, improvements in exercise countermeasures are necessary to maintain cardiovascular fitness, bone mass throughout the body and the ability to perform coordinated movements in a constant gravitational environment that is six orders of magnitude higher than the "near weightlessness" condition experienced during transit to and/or orbit of the Moon, Mars, and Earth. This research provides insight for maintaining the ability of astronauts to perform coordinated, bipedal locomotion activities, following transitions between gravitational acceleration fields. In addition, a unique environmental simulator has been developed which enables further research regarding the complex interactions between humans and the environments in which they move. In order to investigate methods of improving postural control adaptation during these gravitational transitions, a treadmill based precision stepping task was developed to reveal changes in neuromuscular control of locomotion following both simulated partial gravity exposure and post-simulation exercise countermeasures designed to speed lower extremity impedance adjustment mechanisms. The exercise countermeasures included a short period of running with or without backpack loads immediately after partial gravity running. A novel suspension type partial gravity simulator incorporating spring balancers and a motor-driven treadmill was developed to facilitate body weight off-loading and various gait patterns in both simulated partial and full gravitational environments. Studies have provided evidence that suggests: (1) the environmental simulator constructed for this dissertation effort does induce locomotor adaptations following partial gravity running; (2) the precision stepping task is a sensitive test for illuminating aspects of these adaptations; and (3) musculoskeletal loading improves the locomotor adaptation process.Item The kinematics of distributary channels on the Wax Lake Delta, coastal Louisiana, USA(2013-05) Shaw, John Burnham; Mohrig, DavidThe Wax Lake Delta (WLD) is a sandy, modern river delta prograding rapidly into Atchafalaya Bay. This dissertation uses field data to improve the understanding of channel kinematics that dictate river delta geometry and stratigraphy, while providing a framework for coastal restoration efforts. The studies presented here show that the distributary channel network of the WLD is erosional. In the first study, analyses of the feeder channel to the WLD and the channel network within the sub-aerially emergent delta show that the channel bed has incised into the consolidated muds that act as bedrock. The large (>62%) fraction of bedrock exposure found in multi-beam surveys is related to the under-saturation of suspended sand measured during the flood of 2009. The second study concerns the delta front beyond the emergent delta Distributary channels extend 2 – 6 km into the delta front. Four bathymetric surveys of one bifurcating distributary channel – Gadwall Pass – show that the majority of bed aggradation occurs during floods, but the majority of channel extension of each bifurcate channel occurs during low river discharge. In the third study, field measurements of fluid flow during a tidal cycle indicate that tidal augmentation of during periods of low river discharge is responsible for channel extension during low river discharges. Flow direction measured from streaklines present in aerial photomosaics is combined with bathymetric evolution data to quantify spatial velocity changes on the delta front. These data show that flow spreading is insufficient to prevent acceleration at channel margins, providing an explanation for observed erosion. Flow divergence is limited on the delta front by the proximity of neighboring channels, even though they are separated by 10-30 channel widths. The associated convergence of flow in inter-distributary bays occurs along “drainage troughs”. These channel-forms collect flow that has been dispensed from distributary channel network. Finally, ambient currents in Atchafalaya Bay (0.06 – 0.2 m/s) caused by tides and the proximity to the neighboring Atchafalaya Delta appear to alter flow patterns on the delta foreset, and are responsible for channel curvature on the delta front.Item Mathematical modeling and kinematics: a study of emerging themes and their implications for learning mathematics through an inquiry-based approach(2004) Carrejo, David John; Marshall, Jill Ann; Petrosino, Anthony J. (Anthony Joseph), 1961-Item Methodology for creating human-centered robots : design and system integration of a compliant mobile base(2012-05) Wong, Pius Duc-min; Sentis, Luis; Deshpande, AshishRobots have growing potential to enter the daily lives of people at home, at work, and in cities, for a variety of service, care, and entertainment tasks. However, several challenges currently prevent widespread production and use of such human-centered robots. The goal of this thesis was first to help overcome one of these broad challenges: the lack of basic safety in human-robot physical interactions. Whole-body compliant control algorithms had been previously simulated that could allow safer movement of complex robots, such as humanoids, but no such robots had yet been documented to actually implement these algorithms. Therefore a wheeled humanoid robot "Dreamer" was developed to implement the algorithms and explore additional concepts in human-safe robotics. The lower mobile base part of Dreamer, dubbed "Trikey," is the focus of this work. Trikey was iteratively developed, undergoing cycles of concept generation, design, modeling, fabrication, integration, testing, and refinement. Test results showed that Trikey and Dreamer safely performed movements under whole-body compliant control, which is a novel achievement. Dreamer will be a platform for future research and education in new human-friendly traits and behaviors. Finally, this thesis attempts to address a second broad challenge to advancing the field: the lack of standard design methodology for human-centered robots. Based on the experience of building Trikey and Dreamer, a set of consistent design guidelines and metrics for the field are suggested. They account for the complex nature of such systems, which must address safety, performance, user-friendliness, and the capability for intelligent behavior.Item Skid-steer kinematics for dual-arm mobile manipulator system with dynamic center of gravity(2016-12) Ebersole, Benjamin Jarrett; Landsberger, Sheldon; Pryor, Mitchell WayneSkid-steer mobile vehicles bridge an important operational gap in robotics between indoor-only and outdoor-only platforms. Traditionally, skid-steer vehicles have been treated and operated as differential-drive vehicles, which is an adequate approximation with a static center of gravity (CG) coincident with the wheelbase center. With a dual-arm mobile manipulator, such as the Nuclear and Applied Robotics Group's VaultBot platform, the center of gravity's location is dynamic and the differential-drive model is no longer valid. This can result in large errors between desired and actual trajectories over even short periods of time. In this work, the degree to which the platform's behavior changes with a dynamic CG and the intuition behind these effects are discussed. Several different approaches leading to the development of a heuristic model built to improve performance, and the evaluation results of said model, are also discussed.Item Sweep the dust away: infrared kinematics of nearby galaxies(2005) Silge, Julia Dorothea; Gebhardt, Karl