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  • 1
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    Actuators for actively controlled space structures (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A free-flying platform of about 4 x 17 m overall dimensions, carrying a variety of imaging and sounding payloads, calls for an intelligent structure with active dynamic control of structural resonances. The actuators for such a structure must be lightweight, require low power, and allow integration into the structure without degradation of its integrity; the dc-to-100 Hz dynamic range required may entail several types of actuators, as is presently emphasized. Broadband damping of higher-order modes requires modeling of the structure with a distributed array of sensors and actuators.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    High speed reaction wheels for satellite attitude control and energy storage (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The combination of spacecraft attitude control and energy storage (ACES) functions in common hardware, to synergistically maintain three-axis attitude control while supplying electrical power during earth orbital eclipses, allows the generation of control torques by high rotating speed wheels that react against the spacecraft structure via a high efficiency bidirectional energy conversion motor/generator. An ACES system encompasses a minimum of four wheels, controlling power and the three torque vectors. Attention is given to the realization of such a system with composite flywheel rotors that yield high energy density, magnetic suspension technology yielding low losses at high rotational speeds, and an ironless armature permanent magnet motor/generator yielding high energy conversion efficiency.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    The impact of rare earth cobalt permanent magnets on electromechanical device design (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Specific motor designs which employ rare earth cobalt magnets are discussed with special emphasis on their unique properties and magnetic field geometry. In addition to performance improvements and power savings, high reliability devices are attainable. Both the mechanism and systems engineering should be aware of the new performance levels which are currently becoming available as a result of the rare earth cobalt magnets.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 195-206
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Modified independent modal space control method for active control of flexible systems (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A modified independent modal space control (MIMSC) method is developed for designing active vibration control systems for large flexible structures. The method accounts for the interaction between the controlled and residual modes. It incorporates also optimal placement procedures for selecting the optimal locations of the actuators in the structure in order to minimize the structural vibrations as well as the actuation energy. The MIMSC method relies on an important feature which is based on time sharing of a small number of actuators, in the modal space, to control effectively a large number of modes. Numerical examples are presented to illustrate the application of the method to generic flexible systems. The results obtained suggest the potential of the devised method in designing efficient active control systems for large flexible structures.
    Keywords: STRUCTURAL MECHANICS
    Type: Institution of Mechanical Engineers, Proceedings, Part C - Journal of Mechanical Engineering Science (ISSN 0954-4062); 203; C2 1; 103-112
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Optimum vibration control of flexible beams by piezo-electric actuators (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The utilization of piezoelectric actuators in controlling the structural vibrations of flexible beams is examined. A Modified Independent Modal Space Control (MIMSC) method is devised to enable the selection of the optimal location, control gains and excitation voltage of the piezoelectric actuators in a way that would minimize the amplitudes of vibrations of beams to which these actuators are bonded, as well as the input control energy necessary to suppress these vibrations. The developed method accounts for the effects that the piezoelectric actuators have on changing the elastic and inertial properties of the flexible beams. Numerical examples are presented to illustrate the application of the developed MIMSC method in minimizing the structural vibrations of beams of different materials when subjected to different loading and end conditions using ceramic or polymeric piezoelectric actuators. The obtained results emphasize the importance of the devised method in designing more realistic active control systems for flexible beams, in particular, and large flexible structures in general.
    Keywords: STRUCTURAL MECHANICS
    Type: VPI&SU/AIAA Symposium; Jun 29, 1987 - Jul 01, 1987; Blacksburg, VA; United States
    Format: text
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    NASA TECHNICAL REPORTS
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