Browsing by Subject "CEM"

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Collaborative engineering and design management for the Hobby Eberly Telescope tracker upgrade
(2010-07) Mollison, N.T.; Hayes, R.J; Good, J.M; Booth, J.A; Savage, R.D; Jackson, J.R; Rafal, M.D; Beno, J.H.
The engineering and design of systems as complex as the Hobby-Eberly Telescope's* new tracker require that multiple tasks be executed in parallel and overlapping efforts. When the design of individual subsystems is distributed among multiple organizations, teams, and individuals, challenges can arise with respect to managing design productivity and coordinating successful collaborative exchanges. This paper focuses on design management issues and current practices for the tracker design portion of the Hobby-Eberly Telescope Wide Field Upgrade project. The scope of the tracker upgrade requires engineering contributions and input from numerous fields including optics, instrumentation, electromechanics, software controls engineering, and site-operations. Successful system-level integration of tracker subsystems and interfaces is critical to the telescope's ultimate performance in astronomical observation. Software and process controls for design information and workflow management have been implemented to assist the collaborative transfer of tracker design data. The tracker system architecture and selection of subsystem interfaces has also proven to be a determining factor in design task formulation and team communication needs. Interface controls and requirements change controls will be discussed, and critical team interactions are recounted (a group-participation Failure Modes and Effects Analysis [FMEA] is one of special interest). This paper will be of interest to engineers, designers, and managers engaging in multi-disciplinary and parallel engineering projects that require coordination among multiple individuals, teams, and organizations.
Design of an electro-mechanical hexapod for accelerated life testing of optical fiber assemblies
(2010-05) Soukup, Ian Michael; Fahrenthold, Eric P.; Beno, Joseph H.
The quantity and length of optical fibers required for the Hobby-Eberly Telescope Dark Energy eXperiment (HETDEX) create unique fiber handling challenges. More than 33,000 optical fibers will enable the Hobby-Eberly Telescope (HET) to collect data on at least one million galaxies that are 9 billion to 11 billion light-years away, yielding the largest map of the universe ever produced [1,2]. The design advantages made possible by optical fibers also forms challenges to prevent damage to the fragile fibers that can lead to Focal Ratio Degradation (FRD) [3]. Therefore, a life cycle test must be conducted to study fiber behavior and measure FRD as a function of time. This thesis describes the design and design methodology of an electro-mechanical test apparatus for accelerated life testing of optical fiber assemblies. The design methodology summarizes the development of functional requirements and constraints that drove the design. The test apparatus design utilizes six linear actuators to replicate the movement of the fiber system deployed on HETDEX for over 65,000 accelerated cycles, simulating five years of actual operation. The electro-mechanical test apparatus will provide insight into the effects of load history on the performance of optical fibers which published data has thus far been lacking. Performance of the electro-mechanical test apparatus will be demonstrated through simulation, modeling and calculations. The test results that will be generated from the accelerated life test will be of great interest to designers of robotic fiber handling systems for major telescopes.
Design of the fiber optic support system and fiber bundle accelerated life test for VIRUS
(2010-07) Soukup, I.M.; Beno, J.H; Hayes, R.J; Heisler, J.T; Mock, J.R; Mollison, N.T; Good, J.M; Hill, G.J; Vattiat, B.L; Murphy, J.D; Anderson, S.C; Bauer, S.M; et. al.
The quantity and length of optical fibers required for the Hobby-Eberly Telescope* Dark Energy eXperiment (HETDEX) create unique fiber handling challenges. For HETDEX‡, at least 33,600 fibers will transmit light from the focal surface of the telescope to an array of spectrographs making up the Visible Integral-Field Replicable Unit Spectrograph (VIRUS). Up to 96 Integral Field Unit (IFU) bundles, each containing 448 fibers, hang suspended from the telescope's moving tracker located more than 15 meters above the VIRUS instruments. A specialized mechanical system is being developed to support fiber optic assemblies onboard the telescope. The discrete behavior of 448 fibers within a conduit is also of primary concern. A life cycle test must be conducted to study fiber behavior and measure Focal Ratio Degradation (FRD) as a function of time. This paper focuses on the technical requirements and design of the HETDEX fiber optic support system, the electro-mechanical test apparatus for accelerated life testing of optical fiber assemblies. Results generated from the test will be of great interest to designers of robotic fiber handling systems for major telescopes. There is concern that friction, localized contact, entanglement, and excessive tension will be present within each IFU conduit and contribute to FRD. The test apparatus design utilizes six linear actuators to replicate the movement of the telescope over 65,000 accelerated cycles, simulating five years of actual operation.
Design, testing, and installation of a high-precision hexapod for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX)
(2012-07) Zierer, J.J.; Beno, J.H; Weeks, D.A; Soukup, I.M; Good, J.M; Booth, J.A; HIll, G.J; Rafal, M.D.
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.
The Development of high-precision hexapod actuators for the Hobby-Eberly Telescope Wide Field Upgrade
(2010-07) Zierer, J.J.; Mock, J.R; Beno, J.H; Good, J; Booth, J.A; Lazzarini, P; Fumi, P; Anaclerio, E.
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.
Energy Research
(1985) Woodson, H.H.; Evans, J.
Future Trends in Pulsed Power Technology in the Center for Electromechanics, The University of Texas At Austin
(1987-06) Gully, J.H.; Weldon, W.F.
GMTNIRS (Giant Magellan Telescope Near-Infrared Spectrograph): Structural-Mechanical Design
(2012-07) Beets, T.A.; Beno, J.H; Chun, M.Y; Lee, S; Park, C; Rafal, M; Worthington, M.S.
A near-infrared spectrograph (NIRS) has been designed and proposed for utilization as a first-light instrument on the Giant Magellan Telescope (GMT). GMTNIRS includes modular JHK, LM spectrograph units mounted to two sides of a cryogenic optical bench. The optical bench and surrounding, protective radiation (thermal) shield are containerized within a rigid cryostat vessel, which mounts to the GMT instrument platform. A support structure on the secondary side of the optical bench provides multi-dimensional stiffness to the optical bench, to prevent excessive displacements of the optical components during tracking of the telescope. Extensive mechanical simulation and optimization was utilized to arrive at synergistic designs of the optical bench, support structure, cryostat, and thermal isolation system. Additionally, detailed steady-state and transient thermal analyses were conducted to optimize and verify the mechanical designs to maximize thermal efficiency and to size cryogenic coolers and conductors. This paper explains the mechanical and thermal design points stemming from optical component placement and mounting and structural and thermal characteristics needed to achieve instrument science requirements. The thermal and mechanical simulations will be described and the data will be summarized. Sufficient details of the analyses and data will be provided to validate the design decisions.
HETDEX tracker control system design and implementation
(2012-07) Beno, J.H.; Hayes, R.J; Leck, R; Penney, C.E; Soukup, I.M.
To enable the Hobby-Eberly Telescope Dark Energy Experiment, The University of Texas at Austin Center for Electromechanics and McDonald Observatory developed a precision tracker and control system – an 18,000 kg robot to position a 3,100 kg payload within 10 microns of a desired dynamic track. Performance requirements to meet science needs and safety requirements that emerged from detailed Failure Modes and Effects Analysis resulted in a system of 13 precision controlled actuators and 100 additional analog and digital devices (primarily sensors and safety limit switches). Due to this complexity, demanding accuracy requirements, and stringent safety requirements, two independent control systems were developed. First, a versatile and easily configurable centralized control system that links with modeling and simulation tools during the hardware and software design process was deemed essential for normal operation including motion control. A second, parallel, control system, the Hardware Fault Controller (HFC) provides independent monitoring and fault control through a dedicated microcontroller to force a safe, controlled shutdown of the entire system in the event a fault is detected. Motion controls were developed in a Matlab-Simulink simulation environment, and coupled with dSPACE controller hardware. The dSPACE real-time operating system collects sensor information; motor commands are transmitted over a PROFIBUS network to servo amplifiers and drive motor status is received over the same network. To interface the dSPACE controller directly to absolute Heidenhain sensors with EnDat 2.2 protocol, a custom communication board was developed. This paper covers details of operational control software, the HFC, algorithms, tuning, debugging, testing, and lessons learned.
Integration of VIRUS spectrographs for the Hobby-Eberly telescope dark energy experiment
(2010-07) Heisler, J.; Mollison, N; Soukup, I; Hayes, R.J; Hill, G.J; Good, J; Savage, R; Vattiat, B.
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX‡) at the University of Texas McDonald Observatory will deploy the Visible Integral-Field Replicable Unit Spectrograph (VIRUS) to survey large areas of sky. VIRUS consists of up to 192 spectrographs deployed as 96 units. VIRUS units are fiber-fed and are housed in four enclosures making up the VIRUS Support Structure (VSS). Initial design studies established an optimal array size and an upper and lower bound on their placement relative to the existing telescope structure. Tradeoffs considering IFU (optical fiber) length, support structure mass and ease of maintenance have resulted in placement of four 3 x 8 arrays of spectrograph pairs, about mid-point in elevation relative to the fixed HET structure. Because of the desire to minimize impact on the modal performance of the HET, the VSS is required to be an independent, self-supporting structure and will only be coupled at the base of the telescope. Analysis shows that it is possible to utilize the existing azimuth drives of the telescope, through this coupling, which will greatly simplify the design and reduce cost. Each array is contained in an insulated enclosure that will control thermal load by means of heat exchangers and use of facility coolant supply. Access for installation and maintenance on the top, front, and rear of the enclosures must be provided. The design and analysis presented in this paper must provide an optimum balance in meeting the stringent requirements for science and facility constraints such as cost, weight, access, and safety.
Kinematic optimization of upgrade to the Hobby Eberly Telescope through novel use of commercially available three dimensional CAD package
(2010-07) Wedeking, G.A.; Zierer, J.J; Jackson, J.R.
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.
Testing, characterization, and control of a multi-axis high precision drive system for the Hobby-Eberle Telescope Wide Field Upgrade
(2012-07) Soukup, I.M.; Beno, J.H; Hill, G.H; Good, J.M; Penney, C.E; Beets, T.A; Esquerra, J.D; Hayes, R.J; Heisler, J.T; Zierer, J.J; Wedeking, G.A; Worthington, M.S; et. al.
A multi-axis, high precision drive system has been designed and developed for the Wide Field Upgrade to the Hobby-Eberly Telescope at McDonald Observatory. Design, performance and controls details will be of interest to designers of large scale, high precision robotic motion devices. The drive system positions the 20-ton star tracker to a precision of less than 5 microns along each axis and is capable of 4 meters of X/Y travel, 0.3 meters of hexapod actuator travel, and 46 degrees of rho rotation. The positioning accuracy of the new drive system is achieved through the use of high-precision drive hardware in addition to a meticulously tuned high-precision controller. A comprehensive understanding of the drive structure, disturbances, and drive behavior was necessary to develop the high-precision controller. Thorough testing has characterized manufacture defects, structural deflections, sensor error, and other parametric uncertainty. Positioning control through predictive algorithms that analytically compensate for measured disturbances has been developed as a result of drive testing and characterization. The drive structure and drive dynamics are described as well as key results discovered from testing and modeling. Controller techniques and development of the predictive algorithms are discussed. Performance results are included, illustrating recent performance of several axes of the drive system. This paper describes testing that occurred at the Center for Electromechanics in Austin Texas.