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  • 1
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    Studies on distributed sensing and processing for the control of large flexible spacecraft (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Technology is being developed to process signals from distributed sensors using distributed computations. These distributed sensors provide a new feedback capability for vibration control that has not been exploited. Additionally, the sensors proposed are of an optical and distributed nature and could be employed with known techniques of distributed optical computation (Fourier optics, etc.) to accomplish the control system functions of filtering and regulation in a distributed computer. This paper reviews a procedure for the analytic design of control systems for this application. For illustration, the procedure is applied to the problem of suppressing the vibrations of a simply supported beam. A simulator has been developed to study the effects of sensor and processing errors. An extensive study of the effects of these errors on estimation and regulation performance is presented.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: In: Sensors and sensor integration; Proceedings of the Meeting, Orlando, FL, Apr. 4, 1991 (A93-21961 07-35); p. 126-137.
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  • 2
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    Lumped mass modelling for the dynamic analysis of aircraft structures (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Aircraft structures may be modelled by lumping the masses at particular strategic points and the flexibility or stiffness of the structure is obtained with reference to these points. Equivalent moments of inertia for the section at these positions are determined. The lumped masses are calculated based on the assumption that each point will represent the mass spread on one half of the space on each side. Then these parameters are used in the differential equation of motion and the eigen characteristics are determined. A comparison is made with results obtained by other established methods. The lumped mass approach in the dynamic analysis of complicated structures provides an easier means of predicting the dynamic characteristics of these structures. It involves less computer time and avoids computational errors that are inherent in the numerical solution of complicated systems.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: North Carolina Agricultural and Technical State Univ., The Center for Aerospace Research: A NASA Center of Excellence at North Carolina Agricultural and Technical State University; 10 p
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  • 3
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    Analytic redundancy management for SCOLE (1988)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The objective of this work is to develop a practical sensor analytic redundancy management scheme for flexible spacecraft and to demonstrate it using the SCOLE experimental apparatus. The particular scheme to be used is taken from previous work on the Grid apparatus by Williams and Montgomery.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Proceedings of the 4th Annual SCOLE Workshop; p 329-345
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  • 4
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    Simulator evaluation of system identification with on-line control law update for the controls and astrophysics experiment in space (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A procedure for optimizing the performance of large flexible spacecraft that require active vibration suppression to achieve required performance is presented. The procedure is to conduct on-orbit testing and system identification followed by a control system design. It is applied via simulation to a spacecraft configuration currently being considered for flight test by NASA - the Controls, Astrophysics, and Structures Experiment in Space (CASES). The system simulator is based on a NASTRAN finite element structural model. A finite number of modes is used to represent the structural dynamics. The system simulator also includes models of the electronics, actuators, sensors, the digital controller, and the internal and external disturbances. Nonlinearities caused by quantization are included in the study to examine tolerance of the procedure to modelling errors. Disturbance and sensor noise is modelled as a Gaussian process. For system identification, the system is excited using sinusoidal inputs at the resonant frequencies of the structure using each actuator. Mode shapes, frequencies, and damping ratios are identified from the unforced response sensor data after each excitation. Then, the excitation data is used to identify the actuator influence coefficients. The results of the individual parameter identification analyses are assembled into an aggregate system model. The control design is accomplished based only on the identified model using multi-input/output linear quadratic Gaussian theory. Its performance is evaluated based on time-to-damp as compared with the uncontrolled structure.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Fourth NASA Workshop on Computational Control of Flexible Aerospace Systems, Part 2; p 691-72
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  • 5
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    An overview of controls research on the NASA Langley Research Center grid (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The NASA Langley Research Center has assembled a flexible grid on which control systems research can be accomplished on a two-dimensional structure that has many physically distributed sensors and actuators. The grid is a rectangular planar structure that is suspended by two cables attached to one edge so that out of plane vibrations are normal to gravity. There are six torque wheel actuators mounted to it so that torque is produced in the grid plane. Also, there are six rate gyros mounted to sense angular motion in the grid plane and eight accelerometers that measure linear acceleration normal to the grid plane. All components can be relocated to meet specific control system test requirements. Digital, analog, and hybrid control systems capability is provided in the apparatus. To date, research on this grid has been conducted in the areas of system and parameter identification, model estimation, distributed modal control, hierarchical adaptive control, and advanced redundancy management algorithms. The presentation overviews each technique and presents the most significant results generated for each area.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Marshall Space Flight Center Structural Dynamics and Control Interaction of Flexible Structures; p 435-456
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  • 6
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    Optical processing for distributed sensors in control of flexible spacecraft (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A recent potential of distributed image processing is discussed. Applications in the control of flexible spacecraft are emphasized. Devices are currently being developed at NASA and in universities and industries that allow the real-time processing of holographic images. Within 5 years, it is expected that, in real-time, one may add or subtract holographic images at optical accuracy. Images are stored and processed in crystal mediums. The accuracy of their storage and processing is dictated by the grating level of laser holograms. It is far greater than that achievable using current analog-to-digital, pixel oriented, image digitizing and computing techniques. Processors using image processing algebra can conceptually be designed to mechanize Fourier transforms, least square lattice filters, and other complex control system operations. Thus, actuator command inputs derived from complex control laws involving distributed holographic images can be generated by such an image processor. Plans are revealed for the development of a Conjugate Optics Processor for control of a flexible object.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Proceedings of the Workshop on Computational Aspects in the Control of Flexible Systems, Part 1; p 515-545
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  • 7
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    Evaluation of inertial devices for the control of large, flexible, space-based telerobotic arms (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Inertial devices, including sensors and actuators, offer the potential of improving the tracking of telerobotic commands for space-based robots by smoothing payload motions and suppressing vibrations. In this paper, inertial actuators (specifically, torque-wheels and reaction-masses) are studied for that potential application. Batch simulation studies are presented which show that torque-wheels can reduce the overshoot in abrupt stop commands by 82 percent for a two-link arm. For man-in-the-loop evaluation, a real-time simulator has been developed which samples a hand-controller, solves the nonlinear equations of motion, and graphically displays the resulting motion on a computer workstation. Currently, two manipulator models, a two-link, rigid arm and a single-link, flexible arm, have been studied. Results are presented which show that, for a single-link arm, a reaction-mass/torque-wheel combination at the payload end can yield a settling time of 3 s for disturbances in the first flexible mode as opposed to 10 s using only a hub motor. A hardware apparatus, which consists of a single-link, highly flexible arm with a hub motor and a torque-wheel, has been assembled to evaluate the concept and is described herein.
    Keywords: MECHANICAL ENGINEERING
    Type: The Fifth NASA(DOD Controls-Structures Interaction Technology Conference, Part 1; p 289-301
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  • 8
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    Simulation of the coupled multi-spacecraft control testbed at the Marshall Space Flight Center (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The capture and berthing of a controlled spacecraft using a robotic manipulator is an important technology for future space missions and is presently being considered as a backup option for direct docking of the Space Shuttle to the Space Station during assembly missions. The dynamics and control of spacecraft configurations that are manipulator-coupled with each spacecraft having independent attitude control systems is not well understood and NASA is actively involved in both analytic research on this three dimensional control problem for manipulator coupled active spacecraft and experimental research using a two dimensional ground based facility at the Marshall Space Flight Center (MSFC). This paper first describes the MSFC testbed and then describes a two link arm simulator that has been developed to facilitate control theory development and test planning. The motion of the arms and the payload is controlled by motors located at the shoulder, elbow, and wrist.
    Keywords: CYBERNETICS
    Type: The Role of Computers in Research and Development at Langley Research Center; p 497-517
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  • 9
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    Control of flexible structures with distributed sensing and processing (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Technology is being developed to process signals from distributed sensors using distributed computations. These distributed sensors provide a new feedback capability for vibration control that has not been exploited. Additionally, the sensors proposed are of an optical and distributed nature and could be employed with known techniques of distributed optical computation (Fourier optics, etc.) to accomplish the control system functions of filtering and regulation in a distributed computer. This paper extends the traditional digital, optimal estimation and control theory to include distributed sensing and processing for this application. The design model assumes a finite number of modes which make it amenable to empirical determination of the design model via familiar modal-test techniques. The sensors are assumed to be distributed, but a finite number of point actuators are used. The design process is illustrated by application to a Euler beam. A simulation of the beam is used to design an optimal vibration control system that uses a distributed deflection sensor and nine linear force actuators. Simulations are also used to study the influence of design and processing errors on the performance.
    Keywords: CYBERNETICS
    Type: NASA Workshop on Distributed Parameter Modeling and Control of Flexible Aerospace Systems; p 95-114
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  • 10
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    Real-Time, Holographic, Dynamic Image-Storage Device (1995)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Solid-state device developed for high-speed acquisition, dynamic storage, and amplification of three-dimensional holographic images. Holograms generated via four-wave mixing in two or more photorefractive crystals (or subelements of single crystal) to create single-crystal or multicrystal oscillator. Apparatus provides dynamic storage of holographic image of object after electronic shutter closed to turn off object beam. Provides capability to store, amplify, process, and transmit time-varying, two-dimensional, spatial information. Developments include sensors, actuators, and optical computers operating at speeds on order of speed of light. Potential in applications in which need for high-speed acquisition and storage of three-dimensional holographic images.
    Keywords: PHYSICAL SCIENCES
    Type: LAR-13989 , Laser Tech. Brief.; 1; P. 86
    Format: text
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