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  • Other Sources  (1,345)
  • MECHANICAL ENGINEERING  (1,345)
  • 1990-1994  (1,345)
  • 1
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    Evolving directions in NASA's planetary rover requirements and technology (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The evolution of NASA's planning for planetary rovers (that is robotic vehicles which may be deployed on planetary bodies for exploration, science analysis, and construction) and some of the technology that was developed to achieve the desired capabilities is reviewed. The program is comprised of a variety of vehicle sizes and types in order to accommodate a range of potential user needs. This includes vehicles whose weight spans a few kilograms to several thousand kilograms; whose locomotion is implemented using wheels, tracks, and legs; and whose payloads vary from microinstruments to large scale assemblies for construction. Robotic vehicles and their associated control systems, developed in the late 1980's as part of a proposed Mars Rover Sample Return (MRSR) mission, are described. Goals suggested at the time for such a MRSR mission included navigating for one to two years across hundreds of kilometers of Martian surface; traversing a diversity of rugged, unknown terrain; collecting and analyzing a variety of samples; and bringing back selected samples to the lander for return to Earth. Current plans (considerably more modest) which have evolved both from technological 'lessons learned' in the previous period, and modified aspirations of NASA missions are presented. Some of the demonstrated capabilities of the developed machines and the technologies which made these capabilities possible are described.
    Keywords: MECHANICAL ENGINEERING
    Type: CNES, Missions, Technologies, and Design of Planetary Mobile Vehicles; p 443-454
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  • 2
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    A parameter identification method for the rotordynamic coefficients of a high Reynolds number hydrostatic bearing (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: In identifying the rotordynamic coefficients of a high-Reynolds-number hydrostatic bearing, fluid-flow induced forces present a unique problem, in that they provide an unmeasureable and uncontrollable excitation to the bearing. An analysis method is developed that effectively eliminates the effects of fluid-flow induced excitation on the estimation of the bearing rotordynamic coefficients, by using power spectral densities. In addition to the theoretical development, the method is verified experimentally by single-frequency testing, and repeatability tests. Results obtained for a bearing are the twelve rotordynamic coefficients (stiffness, damping, and inertia coefficients) as functions of eccentricity ratio, speed, and supply pressure.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME, Transactions, Journal of Vibration and Acoustics (ISSN 0739-3717); 115; 3; p. 264-270.
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  • 3
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    Gripper for truss structure assembly (1991)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The CIRSSE two-finger gripper is designed to be used with a 6-axis wrist-mounted force-torque sensor as part of an experimental testbed for cooperative robotic manipulation. The gripper system consists of a dedicated controller and a pneumatic powered gripper that is servoed in position or grasping force. The gripper also has a between fingertip light beam sensor. The major features of this new design are: high grasping force to weight ratio (25::1) and compactness (14 cm base-fingertip, 0.8 kilograms); low cost dedicated slave controller; and simple host-controller communications protocol to minimize command interpretation delay. Shared software functions between the host and the controller processor permit the host to select servo mode, servo gain-parameter values, and calibration offsets. Hidden primitive self-test, calibration and servo confidence functions are included.
    Keywords: MECHANICAL ENGINEERING
    Type: Cooperative Intelligent Robotics in Space; Nov 06, 1990 - Nov 07, 1990; Boston, MA; United States
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  • 4
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    A walking prescription for statically-stable walkers based on walker/terrain interaction (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The walker/terrain interaction phenomena for the control of a statically stable walking machine are described. The algorithms, measures, and knowledge of walker/terrain interaction phenomena are then combined to form a prescription for how to walk on general terrain. This prescription consists of two parts: nominal control and reactive control. The function of nominal control is the evaluation and execution of planned motions, based on predicted foot force redistributions, to achieve reliable locomotion. The function of reactive control is the monitoring of walker/terrain interaction in real-time to detect anomalous conditions and then respond with the appropriate reflexive actions. Simulations and experiments have been used to test and verify various aspects of the walking prescription.
    Keywords: MECHANICAL ENGINEERING
    Type: In: 1992 IEEE International Conference on Robotics and Automation, 8th, Nice, France, May 12-14, 1992, Proceedings. Vol. 1 (A93-35501 13-63); p. 149-156.
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  • 5
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    Active damping with a reaction mass actuator (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: This paper presents analytical and experimental results in actively damping flexible structures with reaction mass actuators. A two degree of freedom spring-mass model of a flexible structure is analyzed and the key parameters of actuator mass participation and pole-zero separation are related to the maximum damping achievable from rate feedback control. The main conclusion of the paper is that the larger the pole-zero separation the larger the amount of damping that can be imparted to a structural mode. Laboratory experiments conducted on an 8-foot truss structure support the analytical predictions.
    Keywords: MECHANICAL ENGINEERING
    Type: In: Controls for optical systems; Proceedings of the Meeting, Orlando, FL, Apr. 21, 22, 1992 (A93-34276 13-74); p. 182-192.
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  • 6
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    Dynamics of rotating multicomponent turbomachinery systems (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The ultimate objective of turbomachinery vibration analysis is to predict both the overall, as well as component dynamic response. To accomplish this objective requires complete engine structural models, including multistages of bladed disk assemblies, flexible rotor shafts and bearings, and engine support structures and casings. In the present approach each component is analyzed as a separate structure and boundary information is exchanged at the inter-component connections. The advantage of this tactic is that even though readily available detailed component models are utilized, accurate and comprehensive system response information may be obtained. Sample problems, which include a fixed base rotating blade and a blade on a flexible rotor, are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA PAPER 93-1629 , In: AIAA(ASME)ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 34th and AIAA/ASME Adaptive Structures Forum, La Jolla, CA, Apr. 19-22, 1993, Technical Papers. Pt. 5 (A93-33876 1; p. 2836-2847.
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  • 7
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    Magnetic bearings for free-piston Stirling engines (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The feasibility and efficiency of applying magnetic bearings to free-piston Stirling-cycle power conversion machinery currently being developed for long-term space missions are assessed. The study was performed for a 50-kWe Reference Stirling Space Power Converter (RSSPC) which currently uses hydrostatic gas bearings to support the reciprocating displacer and power piston assemblies. Active magnetic bearings of the attractive electromagnetic type are feasible for the RSSPC power piston. Magnetic support of the displacer assembly would require unacceptable changes to the design of the current RSSPC. However, magnetic suspension of both displacer and power piston is feasible for a relative-displacer version of the RSSPC. Magnetic suspension of the RSSPC power piston can potentially increase overall efficiency by 0.5 to 1 percent (0.1 to 0.3 efficieny points). Magnetic bearings will also overcome several operational concerns associated with hydrostatic gas bearing systems. These advantages, however, are accompanied by a 5 percent increase in specific mass of the RSSPC.
    Keywords: MECHANICAL ENGINEERING
    Type: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 5 (A93-25851 09-44); p. 5.381-5.386.
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  • 8
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    Development of advanced seals for space propulsion turbomachinery (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Current activities in seals for space propulsion turbomachinery that NASA sponsors are surveyed. The overall objective is to provide the designer and researcher with the concepts and data to control seal dynamics and leakage. Included in the program are low-leakage seals, such as the brush seal, the 'ceramic rope' seal, low-leakage seals for liquid oxygen turbopumps, face seals for two phase flow, and swirl brakes for stability. Two major efforts are summarized: a seal dynamics in rotating machinery, and an effort in seal code development.
    Keywords: MECHANICAL ENGINEERING
    Type: SAE PAPER 921028 , ; 14 p.|SAE, Aerospace Atlantic Conference; Apr 07, 1992 - Apr 10, 1992; Dayton, OH; United States
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  • 9
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    Laminar flow in a recess of a hydrostatic bearing (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The flow in a recess of a hydrostatic journal bearing is studied in detail. The Navier-Stokes equations for the laminar flow of an incompressible liquid are solved numerically in a two-dimensional plane of a typical bearing recess. Pressure- and shear-induced flows, as well as a combination of these two flow conditions, are analyzed. Recess friction, pressure-ram effects at discontinuities in the flow region, and film entrance pressure loss effects are calculated. Entrance pressure loss coefficients over a forward-facing step are presented as functions of the mean flow Reynolds number for pure-pressure and shear-induced laminar flows.
    Keywords: MECHANICAL ENGINEERING
    Type: STLE Tribology Transactions (ISSN 0569-8197); 35; 4; p. 738-743; Discussi
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  • 10
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    Robotics technology discipline (1990)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: Viewgraphs on robotics technology discipline for Space Station Freedom are presented. Topics covered include: mechanisms; sensors; systems engineering processes for integrated robotics; man/machine cooperative control; 3D-real-time machine perception; multiple arm redundancy control; manipulator control from a movable base; multi-agent reasoning; and surfacing evolution technologies.
    Keywords: MECHANICAL ENGINEERING
    Type: Technology for Space Station Evolution. Executive Summary and Overview; p 197-233
    Format: application/pdf
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