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  • 1
    Electronic Resource
    Electronic Resource
    Finite element design of manipulator-coupled spacecraft for a research testbed (1995)
    Springer
    Journal of intelligent and robotic systems 13 (1995), S. 75-91 
    Details
    ISSN: 1573-0409
    Keywords: Harmonic drives ; Manipulator-Coupled Spacecraft ; Control Moment Gyro ; Finite Element Analysis ; Lagrangian Equations of Motion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper describes the design and analysis of a research testbed developed to study the control of manipulator-coupled spacecraft with independent attitude control systems. This scenario could present itself in the assembly of Space Station Freedom (SSF). SSF assembly calls for a rendezvous of the Space Shuttle (SS) with SSF. Part of the assembly process requires that both spacecraft be coupled via the Space Shuttle Remote Manipulator System. An additional criterion that poses increased complexity is that the Space Shuttle controls and Space Station controls can not communicate. The technical issue involved is unwanted vibrations of the coupled-configuration that occur retraction and the complications due to non-interacting control systems. To understand these vibrations and possible complications, a research testbed has been built at the Marshall Space Flight Center in Huntsville, AL. To build the testbed, the manipulator links joints, and vehicles that represent the Space Shuttle and Space Station had to be designed. Pre-design simulation studies using ANSYS [1] (a Finite Element Computer Code) is used to size and design the manipulator links for the experimental facility. The ANSYS results were verified by the development of the Lagrangian Equations of motion. The Harmonic drives used as joints for the two link, three joint manipulator have been dissected into free body diagrams to ensure proper load paths in the ANSYS models. Accurate simulation of manipulator-coupled spacecraft is an important technology for NASA to understand. This paper outlines the methodology behind the preliminary design of a research testbed developed to help NASA gain knowledge in this area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01664756
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  • 2
    Electronic Resource
    Electronic Resource
    Deflection characteristics of some special configurations of snake-type robots (1995)
    Springer
    Journal of intelligent and robotic systems 12 (1995), S. 145-153 
    Details
    ISSN: 1573-0409
    Keywords: Redundant robot ; critical manipulation ; backbone curve ; end-point deflection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The redundant robots analyzed here have large numbers of degrees of freedom. Such robots are analogous to snake or tentacles and are useful for operation in highly constrained environments and novel forms of locomotion — here it has been defined as critical manipulation. In this paper the end-point deflection of hyper-redundant robots have been studied by parameterization of the flexible links of the robot manipulator. A number of planar configurations of the redundant manipulator were taken into consideration for the present study and the configuration which gives minimum end-point deflection has been recommended for the critical manipulation. This work is significant for some of the research activities recently going on in NASA's Kennedy Space Center towards the application of hyper-redundant robots for manipulation inside the space Shuttle Cargo Bay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01258383
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Cardiac Involvement in Limited Systemic Sclerosis: Non-invasive Assessment in Asymptomatic Patients (1999)
    Springer
    Clinical rheumatology 18 (1999), S. 136-139 
    Details
    ISSN: 1434-9949
    Keywords: Key words:Cardiac involvement – Echocardiography – Limited cutaneous systemic sclerosis – Radionuclide ventriculography – Systemic sclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: Nineteen patients with limited systemic sclerosis (SSc) and without any cardiac symptoms were evaluated non-invasively for silent cardiac involvement using electrocardiography; M-mode, two-dimensional and Doppler echocardiography, and resting and post exercise radionuclide ventriculography. Left anterior hemiblock and mild pericardial effusion were seen in two patients. The interventricular septal thickness and left ventricular posterior wall thickness were greater in patients compared with controls. Patients with limited SSc also exhibited low early diastolic filling velocities and a low early diastolic atrial filling ratio. However, these values did not correlate with the age of the patient or disease duration. Eight patients (42.1%) were found to have cardiac dysfunction, of which four had combined systolic and diastolic dysfunction. Isolated systolic and diastolic dysfunction was seen in three patients and one patient, respectively. The age and disease duration in patients with cardiac dysfunction did not differ from patients without cardiac dysfunction. Functional cardiac involvement occurs in a large proportion (42.1%) of patients with limited SSc, and can be easily picked up by non-invasive methods such as echocardiography and radionuclide ventriculography. The prognostic significance of these findings requires further long term studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100670050071
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Visioplasticity solution of deformation problems: Data handling procedures (1983)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 19 (1983), S. 257-269 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Procedures for smoothing experimentally determined displacement fields are presented such that dynamic, non-steady-state metalworking processes can be analysed using the visioplasticity method. The procedure establishes a rectangular grid in which strain, strain rate and stress values may optionally be obtained at all points on the grid. The condition of material continuity is automatically satisfied by constraints during polynomial smoothing in position and time, using the Gram-Schmidt orthogonalization technique. Examples are given of quasi-static and dynamic plane strain upsetting operations.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620190207
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    Paper (German National Licenses)
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