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  • 1
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    Robust control of an active precision truss structure (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A description is given of the efforts in control of an active precision truss structure experiment. The control objective is to provide vibration suppression to selected modes of the structure subject to a bandlimited disturbance and modeling errors. Based on performance requirements and an uncertainty description, several control laws using the H-infinity optimization method are synthesized. The controllers are implemented on the experimental facility. Preliminary experimental results are presented.
    Keywords: CYBERNETICS
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  • 2
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    High temperature superconductors for magnetic suspension applications (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: High temperature superconductors (HTS) hold the promise for applications in magnetic levitation bearings, vibration damping, and torque coupling. Traditional magnetic suspension systems require active feedback and vibration controls in which power consumption and low frequency vibration are among the major engineering concerns. HTS materials have been demonstrated to be an enabling approach towards such problems due to their flux trapping properties. In our laboratory at TCSUH, we have been conducting a series of experiments to explore various mechanical applications using HTS. We have constructed a 30 lb. model flywheel levitated by a hybrid superconducting magnetic bearing (HSMB). We are also developing a levitated and vibration-dampled platform for high precision instrumentation. These applications would be ideal for space usages where ambient temperature is adequate for HTS to operate properly under greatly reduced cryogenic requirements. We will give a general overview of these potential applications and discuss the operating principles of the HTS devices we have developed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA. Langley Research Center, Second International Symposium on Magnetic Suspension Technology, Part 1; p 111-118
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  • 3
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    Recent results on structural control of an active precision structure (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This paper describes recent results in structural control of an active precision truss structure at JPL. The goal is to develop practical control methodology and to apply to active truss structures intended for high precision space-based optics applications. The active structure considered incorporates piezoelectric active members which apply control forces internal to the structure and thereby improve the structure's dimensional stability. Two approaches to structural control system design were investigated. The first approach uses only noncollocated measurements of acceleration at the location of a simulated optical component to achieve structural stabilization. The second approach is essentially the same as the first one except that a viscous damper was used in place of a truss member on the structure to improve the dampings of selected flexible modes. The corresponding experimental closed-loop results are presented in this paper.
    Keywords: CYBERNETICS
    Type: AIAA PAPER 91-2693
    Format: text
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  • 4
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    Integrated control-structure design of the JPL phase B testbed (1992)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Structure and damper optimization problems driven by control objective metrics are developed for the optimal design of a testbed structure emulating a spaceborne interferometer. The structure optimization problem uses a multiobjective criterion to generate a family of optimized design that allows trades to be made between the competing objectives of minimizing structural mass and maximizing disturbance attenuation. The damper optimization problems focus on the placement and tuning of viscous elements to maximally damp selected modes of the testbed structure. The optimization techniques are verified on a large model of the testbed.
    Keywords: CYBERNETICS
    Type: AIAA PAPER 92-1151
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  • 5
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    Development and fabrication of improved power transistor switches (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A new class of high-voltage power transistors has been achieved by adapting present interdigitated thyristor processing techniques to the fabrication of NPN Si transistors. Present devices are 2.3 cm in diameter. The electrical performance obtained is consistent with the predictions of an optimum design theory specifically developed for power switching transistors. The forward safe operating area of the experimental transistors shows a significant improvement over commercially available devices. The report describes device design, wafer processing, and various measurements which include dc characteristics, forward and reverse second breakdown limits, and switching times.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA-CR-135013
    Format: application/pdf
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  • 6
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    Active member control of a precision structure with an H(infinity) performance objective (1990)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper addresses the noncollocated control of active structures using active structural elements. A top level architecture for active structures is presented, and issues pertaining to robust control of structures are discussed. Controllers optimized for an H sub inf performance specification are implemented on a test structure and the results are compared with analytical predictions. Directions for further research are identified.
    Keywords: CYBERNETICS
    Type: AIAA PAPER 90-1224 , AIAA Dynamics Specialists Conference; Apr 05, 1990 - Apr 06, 1990; Long Beach, Ca; United States
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  • 7
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    Development and fabrication of improved power transistor switches (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A new class of high-voltage power transistors was achieved by adapting present interdigitated thyristor processing techniques to the fabrication of npn Si transistors. Present devices are 2.3 cm in diameter and have V sub CEO (sus) in the range of 400 to 600V. V sub CEO (sus) = 450V devices were made with an (h sub FE)(I sub C) product of 900A at V sub CE = 2.5V. The electrical performance obtained was consistent with the predictions of an optimum design theory specifically developed for power switching transistors. The device design, wafer processing, and assembly techniques are described. Experimental measurements of the dc characteristics, forward SOA, and switching times are included. A new method of characterizing the switching performance of power transistors is proposed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA-CR-159524
    Format: application/pdf
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  • 8
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    Uncertainty modelling for the control of an active structure (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Two approaches to uncertainty modeling of a precision active truss structure for control design are presented. The first approach is based on the H(infinity) optimal control theory, which is used for robust control design with an additive uncertainty model. It is designed to provide vibration suppression to selected modes of the structure at the accelerometer locations. The uncertainty model can be used as an adjustable design parameter which will enable a study of the trade-offs between performance and robust stability. The second approach is based on mu-synthesis. Although the structured singular value can be used to analyze the robustness of any type of uncertainty, there exist difficulties in synthesis if the uncertainty block contains both real and complex variations. Mu-synthesis techniques do not allow for real-parameter variations in the synthesis procedure. The use of a complex variation description enclosing the real variation is suggested.
    Keywords: CYBERNETICS
    Type: ASME Winter Annual Meeting; Dec 10, 1989 - Dec 15, 1989; San Francisco, CA; United States
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  • 9
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    Optimization methods for passive damper placement and tuning (1992)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The effectiveness of viscous elements in introducing damping in a structure is a function of several variables, including their number, their location in the structure, and their physical properties. In this paper several optimization problems are posed to optimize these variables. The paper investigates various metrics to define the optimization problem, and compares the damping profiles that are obtained. Both discrete and continuous optimization problems are formulated and solved, corresponding, respectively, to the problems of placement of damping elements and to the tuning of their parameters. The paper particularly emphasizes techniques to make feasible the large scale problems resulting from the optimization formulations. Numerical results involving a lightly damped tested structure are presented.
    Keywords: CYBERNETICS
    Type: AIAA PAPER 92-4608 , AIAA Guidance, Navigation and Control Conference; Aug 10, 1992 - Aug 12, 1992; Hilton Head Island, SC; United States
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  • 10
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    System identification and control of the JPL active structure (1991)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper describes recent advances in structural quieting technology as applied to active truss structures intended for high precision space based optics applications. Collocated active damping control loops are designed in order to impedance match piezoelectric active members to the structure. Noncollocated control loops are also studied in relation to controlling lightly damped structures.
    Keywords: CYBERNETICS
    Type: AIAA PAPER 91-1231 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference; Apr 08, 1991 - Apr 10, 1991; Baltimore, MD; United States
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