Joseph J. Zierer

Current status of the Hobby-Eberly Telescope wide-field upgrade

The Hobby-Eberly Telescope (HET) is an innovative large telescope of 9.2 meter aperture, located in West Texas at the McDonald Observatory (MDO). The HET operates with a fixed segmented primary and has a tracker which moves the four-mirror corrector and prime focus instrument package to track the sidereal and non-sidereal motions of objects. A major upgrade of the HET is in progress that will increase the pupil size to 10 meters and the field of view to 22′ by replacing the corrector, tracker and prime focus instrument package. In addition to supporting the existing suite of instruments, this wide field upgrade will feed a revolutionary new integral field spectrograph called VIRUS, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEXχ). This paper discusses the current status of this upgrade.

Performance Testing of a Vehicular Flywheel Energy System

The University of Texas at Austin Center for Electromechanics has designed and integrated a 40,000 rpm, 150 kW, 1.93 kWh flywheel energy storage system into a hybrid electric transit bus as a demonstration of the technology. The flywheel stores energy recovered during braking and returns it to the power train during acceleration, reducing the peak power requirements and size for the prime power unit. Additionally, the system provides a longer life energy storage alternative to the more traditional chemical battery bank. While the flywheel system was demonstrated on a transit bus, similar improvements are possible on other terrestrial or marine mobile applications. This paper presents the results and information learned during several multi-thousand-cycle duration tests, composite flywheel tests, terrain-simulating shaker tests, and on-bus road tests.

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 theWide 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.

Lightweight 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.

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.

End-of-life design for composite rotors [flywheel systems]

The University of Texas Center for Electromechanics (UT-GEM) is developing flywheel energy storage systems for combat and commercial vehicles and also leads the major US Flywheel Safety and Containment Program, a consortium effort of several leading flywheel developers. Safety for high performance composite flywheel systems on combat vehicles presents special challenges that impact the design of all flywheel components, especially the composite rotor and the bearings. This paper presents an overview of the issues and discuss design strategies and solutions applicable to the combat vehicle environment, using the flywheel energy storage system design recently completed under the Defense Advanced Research Projects Agency (DARPA) Combat Hybrid Power System (CHPS) Program as a case study. In particular, the paper will trace basic design and safety strategy, fatigue cycle development, lifetime design approach, and the resulting design margins.

Design and Performance Testing of an Advanced Integrated Power System with Flywheel Energy Storage

The University of Texas Center for Electromechanics (UT-CEM) has completed the successful design, integration and testing of a hybrid electric power and propulsion system incorporating a flywheel energy storage device. During testing, the improved drive train was shown to double acceleration rates while simultaneously reducing prime power usage in excess of 25% when compared to the same vehicle without the flywheel energy storage system. While the system was designed for and demonstrated on a transit bus, the technology described herein is applicable to a wide variety of applications, including additional mobile and marine power and propulsion systems. This paper (1) describes the drive train design with an overview of the critical components and (2) presents results from system-level testing of the transit bus with the integrated drive train.

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.

Use of failure modes and effects analysis in design of the tracker system for the HET wide-field upgrade

In support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), the Center for Electromechanics at The University of Texas at Austin was tasked with developing the new Tracker and control system to support the HETDEX Wide-Field Upgrade. The tracker carries the 3,100 kg Prime Focus Instrument Package and Wide Field Corrector approximately 13 m above the 10 m diameter primary mirror. Its safe and reliable operation by a sophisticated control system, over a 20 year life time is a paramount requirement for the project. To account for all potential failures and potential hazards, to both the equipment and personnel involved, an extensive Failure Modes and Effects Analysis (FMEA) was completed early in the project. This task required participation of all the stakeholders over a multi-day meeting with numerous follow up exchanges. The event drove a number of significant design decisions and requirements that might not have been identified this early in the project without this process. The result is a system that has multiple layers of active and passive safety systems to protect the tens of millions of dollars of hardware involved and the people who operate it. This paper will describe the background of the FMEA process, how it was utilized on HETDEX, the critical outcomes, how the required safety systems were implemented, and how they have worked in operation. It should be of interest to engineers, designers, and managers engaging in complex multi-disciplinary and parallel engineering projects that involve automated hardware and control systems with potentially hazardous operating scenarios.

Design and Proof Testing of a Composite Containment System for Mobile Applications

As the need for energy storage increases on future hybrid electric vehicles, the desire for increased performance, energy/power densities, and component life increases proportionally. Flywheel batteries have demonstrated power density and life superiority over conventional chemical batteries; however, fears of unexpected and uncontained failures may prevent their widespread acceptance in the United States marketplace. The University of Texas at Austin Center for Electromechanics (UT-CEM) has designed, built, and tested a full-scale composite flywheel containment system for use in mobile applications. The flywheel containment system that will be described stems from an in-depth investigation into the type of faults that are most likely to occur in mobile applications. In all cases, the worst-case scenario results in a challenge to flywheel integrity; therefore, a comprehensive flywheel containment system is considered the “last line of defense” in protecting personnel and equipment. The containment system described is an energy absorption device used in parallel with a UT-CEM flywheel on the hybrid electric Advanced Technology Transit Bus (ATTB). The most important aspect of the containment device is the free-rotating composite liner intended to absorb the energy of a flywheel failure. The current containment design has been developed over a six-year period during the participation of UT-CEM in the DARPA/DOT Flywheel Containment Program. A comparison between a previous full scale containment test (November 1999) and the current configuration is made, illustrating how “lessons learned” from the previous test are integrated into the latest design. The test was conducted in August 2002 and a detailed description of the mounting configuration, test setup, and data acquisition is presented along with results. Of particular interest to the design team was torque on the aluminum containment housing, axial and hoop stresses in the housing, and acceleration. The test was successful in that the composite debris was contained and all metallic structures remained fully intact. INTRODUCTION In May 1996, Argonne National Laboratory (ANL) was contracted to perform a flywheel battery (FWB) safety assessment for a transit bus [1]. All of the key components of the UT-CEM flywheel battery (energy stored, composite flywheel, speed, magnetic bearings, etc.) had been determined and were used as input into the safety assessment model. ANL recommended a “defense in depth” approach to flywheel safety that included: • engineering to avoid accidental initiation of events • incorporating a safety system for the detection of problems • instituting a mitigation system to minimize the risk of low probability events that could result in a significant energy release In their study, ANL engineers identified the five most likely modes of failure: slow loss of vacuum (a leak), rapid loss of vacuum (a failed hose or pump), failure of magnetic bearings, inadvertent flywheel over speed, and startup without vacuum. In all five of the failure modes described above, the worst-case scenario would result in a challenge to the containment system. After a careful review of the report, UT-CEM made the decision to implement the threephase “defense in depth” approach to prevent the onset of flywheel failure initiators. The first step was to apply good engineering principles in the design phase of the project. Secondly, adequate instrumentation (vacuum, magnetic bearing displacement, and speed sensors) combined with a friendly user interface was designed so that a fault in the system would be indicated and easily recognized. As a third line of defense, a lightweight, rotatable composite liner was designed, tested, and built in the unlikely event of a flywheel burst. J.J. Zierer, J.H. Beno, R.J. Hayes, J.L. Strubhar, R.C. Thompson and T. Pak 2004-01-0005 THIS DOCUMENT IS PROTECTED BY U.S. AND INTERNATIONAL COPYRIGHT It may not be reproduced, stored in a retrieval system, distributed or transmitted, in whole or in part, in any form or by any means. Downloaded from SAE International by Brought to you by the University of Texas Libraries, Wednesday, October 02, 2013 11:06:59 AM