Light-Weight Containment for High Energy, Rotating Machines

Developed a lightweight containment system for high-speed composite rotors. The containment device, consisting of a rotatable, composite structure, has been demonstrated to contain the high-energy release from a rotor burst event and is applicable to composite rotors for pulsed power applications. The most important aspect of this design is that the free-floating containment structure dissipates the major loads (radial, torque, and axial) encountered during the burst event, greatly reducing the loads that pass through the stator structure to its attachments. The design results in significant system-level weight savings for the entire rotating machine when compared to a system with an all-metallic containment. Of equal interest to the containment design, the experimental design and instrumentation was very challenging and resulted in significant lessons learned. This paper describes the containment system design, rotor burst test setup, instrumentation for measuring loads induced by the burst event, and a detailed explanation of the successful containment test results and conclusions.Center for Electromechanic

Design and analysis of the tracker bridge for the Hobby-Eberly Telescope wide field upgrade

A large structural weldment has been designed to serve as the new star tracker bridge for the Wide Field Upgrade to the Hobby-Eberly Telescope at McDonald Observatory in support of the Hobby-Eberly Telescope Dark Energy Experiment‡. The modeling approach, analysis techniques and design details will be of interest to designers of large structures where stiffness is the primary design driver. The design includes detailed structural analysis using finite element models to maximize natural frequency response and limit deflections and light obscuration. Considerable fabrication challenges are overcome to allow integration of precision hardware required for positioning the corrector optics to a precision of less than 5 microns along the 4-meter travel range. Detailed descriptions of the bridge geometry, analysis results and challenging fabrication issues are discussed.Center for Electromechanic

The Development of high-precision hexapod actuators for the Hobby-Eberly Telescope Wide Field Upgrade

Hexapods are finding increased use in telescope applications for positioning large payloads. Engineers from The University of Texas at Austin have been working with engineers from ADS International to develop large, high force, highly precise and controllable hexapod actuators for use on the Wide Field Upgrade (WFU) as part of the Hobby Eberly Telescope Dark Energy Experiment (HETDEX)‡. These actuators are installed in a hexapod arrangement, supporting the 3000+ kg instrument payload which includes the Wide Field Corrector (WFC), support structure, and other optical/electronic components. In addition to force capability, the actuators need to meet the tracking speed (pointing) requirements for accuracy and the slewing speed (rewind) requirements, allowing as many observations in one night as possible. The hexapod actuator stroke (retraction and extension) was very closely monitored during the design phase to make sure all of the science requirements could be met, while minimizing the risk of damaging the WFC optical hardware in the unlikely event of a hexapod actuator or controller failure. This paper discusses the design trade-offs between stiffness, safety, back-drivability, accuracy, and leading to selection of the motor, high ratio worm gear, roller screw, coupling, end mounts, and other key components.Center for Electromechanic

Design, testing, and installation of a high-precision hexapod for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX)

Engineers from The University of Texas at Austin Center for Electromechanics and McDonald Observatory have designed, built, and laboratory tested a high payload capacity, precision hexapod for use on the Hobby-Eberly telescope as part of the HETDEX Wide Field Upgrade (WFU). The hexapod supports the 4200 kg payload which includes the wide field corrector, support structure, and other optical/electronic components. This paper provides a recap of the hexapod actuator mechanical and electrical design including a discussion on the methods used to help determine the actuator travel to prevent the hexapod payload from hitting any adjacent, stationary hardware. The paper describes in detail the tooling and methods used to assemble the full hexapod, including many of the structures and components which are supported on the upper hexapod frame. Additionally, details are provided on the installation of the hexapod onto the new tracker bridge, including design decisions that were made to accommodate the lift capacity of the Hobby-Eberly Telescope dome crane. Laboratory testing results will be presented verifying that the performance goals for the hexapod, including positioning, actuator travel, and speeds have all been achieved. This paper may be of interest to mechanical and electrical engineers responsible for the design and operations of precision hardware on large, ground based telescopes. In summary, the hexapod development cycle from the initial hexapod actuator performance requirements and design, to the deployment and testing on the newly designed HET tracker system is all discussed, including lessons learned through the process.Center for Electromechanic

Design and analysis of a 20 MW propulsion power train

The electric ship research program at the University of Texas at Austin focuses on the development of power system technology for future electric ships. The main goal of the on-going research activity is to identify critical, high pay-off technology development needed to enable major improvement, in size and functionality, of navy ships power systems. Initial efforts were directed towards the establishment of a baseline power train which highlights various constraints and provides a basis for later optimization efforts. A 20 MW power train system was chosen for such a baseline, and all components, from fuel to propulsion motor, were considered and their impact on the whole power system assessed. The baseline design consists of a 25 MVA/3600 rpm radial flux permanent magnet generator, a 22 MVA PWM converter, and a 20 MW/150 rpm radial flux permanent magnet motor, along with the amount of fuel sized for an assumed mission profile, and the widely used LM2500 gas turbine. The analysis shows that fuel is by far the dominant component contributing to weight and volume and, consequently, overall efficiency of power train components is the most relevant parameter to reduce weight and volume. The 3600 rpm generator is the smallest component. The 150 rpm motor is the heaviest component, other than fuel, weighing close to 100 tonnes.Center for Electromechanic

Kinematic optimization of upgrade to the Hobby Eberly Telescope through novel use of commercially available three dimensional CAD package

The University of Texas, Center for Electromechanics (UT-CEM) is making a major upgrade to the robotic tracking system on the Hobby Eberly Telescope (HET) as part of the Wide Field Upgrade (WFU). The upgrade focuses on a seven-fold increase in payload and necessitated a complete redesign of all tracker supporting structure and motion control systems, including the tracker bridge, ten drive systems, carriage frames, a hexapod, and many other subsystems. The cost and sensitivity of the scientific payload, coupled with the tracker system mass increase, necessitated major upgrades to personnel and hardware safety systems. To optimize kinematic design of the entire tracker, UT-CEM developed novel uses of constraints and drivers to interface with a commercially available CAD package (SolidWorks). For example, to optimize volume usage and minimize obscuration, the CAD software was exercised to accurately determine tracker/hexapod operational space needed to meet science requirements. To verify hexapod controller models, actuator travel requirements were graphically measured and compared to well defined equations of motion for Stewart platforms. To ensure critical hardware safety during various failure modes, UT-CEM engineers developed Visual Basic drivers to interface with the CAD software and quickly tabulate distance measurements between critical pieces of optical hardware and adjacent components for thousands of possible hexapod configurations. These advances and techniques, applicable to any challenging robotic system design, are documented and describe new ways to use commercially available software tools to more clearly define hardware requirements and help insure safe operation.Center for Electromechanic

Optimization of gas turbine generator-sets for improved power density

Many future U.S. Navy ships will employ all-electric propulsion systems instead of mechanical drives. To help optimize performance of these systems, studies are under way at The University of Texas at Austin Center for Electromechanics (UT-CEM) to minimize the size of power generation components. These studies focus on increasing the power density of directly coupled gas turbines and generators (gen-sets). The approach adopted in this paper uses scaling laws of gas turbines and synchronous electrical generators to examine the possibility of increasing power density by operating at higher shaft speeds. Included is consideration of inlet and exhaust turbine ducts and issues involving power electronics. Study results indicate that if inlet and exhaust duct volumes are neglected, the power density of directly coupled gas turbine-generator sets can be significantly improved by scaling to higher operating speeds. However, the advantages of scaling to higher speeds are largely negated when duct volumes typically encountered on modern ships are included. This suggests locating power generation equipment near the ambient terminus of inlet and exhaust ducts, so that duct lengths are minimized and fully exploiting the power density advantages of scaling to higher shaft speeds becomes possible.Center for Electromechanic

Wind loading analysis and strategy for deflection reduction on HET wide field upgrade

Wind loading can be a detrimental source of vibration and deflection for any large terrestrial optical telescope. The Hobby-Eberly Telescope* (HET) in the Davis Mountains of West Texas is undergoing a Wide Field Upgrade (WFU) in support of the Dark Energy Experiment‡ (HETDEX) that will greatly increase the size of the instrumentation subjected to operating wind speeds of up to 20.1 m/s (45 mph). A non-trivial consideration for this telescope (or others) is to quantify the wind loads and resulting deflections of telescope structures induced under normal operating conditions so that appropriate design changes can be made. A quasi-static computational fluid dynamics (CFD) model was generated using wind speeds collected on-site as inputs to characterize dynamic wind forces on telescope structures under various conditions. The CFD model was refined until predicted wind speed and direction inside the dome agreed with experimental data. The dynamic wind forces were then used in static loading analysis to determine maximum deflections under typical operating conditions. This approach also allows for exploration of operating parameters without impact to the observation schedule of the telescope. With optimum combinations of parameters (i.e. dome orientation, tracker position, and louver deployment), deflections due to current wind conditions can be significantly reduced. Furthermore, the upper limit for operating wind speed could be increased, provided these parameters are monitored closely. This translates into increased image quality and observing time.Center for Electromechanic

Job strain-associated inflammatory burden and long-term risk of coronary events: Findings from the MONICA/KORA Augsburg case-cohort study.

Background We examined the association between job strain and coronary heart disease (CHD) and investigated the role of markers of inflammation and endothelial dysfunction as possible mediators of job strain-associated CHD risk. Methods The sample (n = 1027) included employed participants (35-64 years old, 68% male) from the population-based MONICA/KORA (Monitoring of Trends and Determinants in Cardiovascular Disease/Kooperative Gesundheitsforschung in der Region Augsburg) studies. At baseline Karasek's Job Strain Index was assessed during standardized personal interviews, and nine biological markers were measured (1984-1995). Participants were followed (average, 12 years) to assess incident events (sudden cardiac death or fatal and nonfatal myocardial infarction). In this case-cohort design, the final sample contained 114 cases and 913 noncases. Results Baseline distributions of cardiometabolic risk factors were significantly different between cases and noncases, with no detectable job strain-specific differences. However, cases with high job strain had higher monocyte chemoattractant protein-1, interleukin (IL)-8, and IL-18 compared with noncases with high job strain. High-sensitivity C-reactive protein, IL-6, and soluble intercellular adhesion molecule-1 were increased in cases versus noncases, regardless of work stress. Job strain was associated with incident coronary events in Cox proportional hazards models adjusted for age, sex, and survey (hazard ratio = 2.57, 95% confidence interval = 1.09-6.07) and after adjustment for CHD risk factors (2.35, 1.003-5.49). Adjustment for monocyte chemoattractant protein-1 or IL-8 increased this risk estimate by 14.5% or 9.4%, respectively, whereas adjustment for C-reactive protein and soluble intercellular adhesion molecule-1 led to decreased hazard ratios (-9.9% and -5.5%, respectively). Conclusions Job strain increased CHD risk in healthy workers; the associated inflammatory burden may contribute to stress-related coronary pathogenesis

Job strain associated CRP is mediated by leisure time physical activity: Results from the MONICA/KORA study.

Background: Psychological stress at work is considered a cardiac risk factor, yet whether it acts directly through neuroimmune processes, or indirectly by increasing behavioral risk factors, is uncertain. Cross-sectional associations between job strain and serum biomarkers of inflammation and endothelial dysfunction were investigated. Secondary analyses explored the role of psychosocial/cardiometabolic risk factors as mediators of job stress associated inflammation in healthy workers. Methods: Information on risk factors was obtained in standardized personal interviews of a subcohort of working participants in the MONICA/KORA population (n = 951). Work stress was measured by the Karasek job strain index. Biomarkers were measured from non-fasting venous blood. Multivariate regression analyses were used to examine the association of job strain with inflammatory biomarkers. Mediation analysis (Sobel test) was used to determine the effect of psychosocial risk factors on the association between job strain and C-reactive protein (CRP). Results: High job strain was reported by half (n = 482, 50.7%) of the study participants. While workers with high job strain were more likely to have adverse workplace conditions (competition with coworkers, job dissatisfaction and insecurity), sleeping problems, depressive symptoms, a Type A personality, and be physically inactive, no differences in cardiometabolic risk factors were detected. A strong and robust association between job strain and CRP was observed in age and sex adjusted models, as well as models adjusted for classic coronary heart disease risk factors (beta = 0.39, p = 0.006 and beta = 0.27, p = 0.03, respectively). Adjustment for physical activity abrogated this effect (beta = 0.23, p = 0.07), and a mediating effect of physical activity on stress-associated inflammation was demonstrated (p = 0.04). Conclusions: The analyses provide evidence for both a direct and an indirect effect of job strain on inflammation