Galaxy evolution explorer PI-mode implementation experience
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GALEX↗
Engineering topics
Fanson, James L.
Publications and source records attributed to Fanson, James L..
Multilayer Active Control For Structural Damping And Optical-Path Regulation
Two active-control concepts incorporated into system for suppression of vibrations in truss structure and regulation of length of optical path on structure to nanometer level. Optical-path-length-control subsystem contains two feedback control loops to obtain active damping in wide amplitude-and-frequency range. Concept described in more detail in number of previous articles, including "Stabilizing Optical-Path Length on a Vibrating Structure" (NPO-19040), "Controllable Optical Delay Line for Stellar Interferometry" (NPO-18686), "Test Bed for Control of Optical-Path Lengths" (NPO-18487).
Rahman, Zahidul H.↗
Technology for Space Optical Interferometry
The Micro-Precision Control/Structure Interaction (CSI) program at JPL is chartered to develop the structures and control technology needed for sub-micron level stabilization of future optical space systems. The extreme dimensional stability required for such systems derives from the need to maintain the alignment and figure of critical optical elements to a small fraction (typically 1/20th to 1/50th) of the wavelength of detected radiation (about 0.5 micron for visible light, 0.1 micron for ultraviolet light). This requirement is common to a broad class of optical sysetms. The challenge for CSI arises when such systems become large, with spatially distributed optical elements mounted on lightweight, flexible structure. This paper will present an overview of the approach that is being taken by JPL's CSI program to address this challenge. In particular, the paper will discuss the application of CSI technology to a specific example of a future large optical space mission. Experimental demonstration of the technology on ground-based testbeds will also be presented.
structures↗
Study Of Active Vibration Isolators
Report presents study of single-link ibration-isolating active suspensions, used to suppress vibrations in structures or to protect delicate scientific instruments from vibrations generated by nearby machinery. In study, suspensions analyzed in terms of mechanical impedance.
Lurie, Boris J.↗
Active Suppression Of Vibrations In A Truss
Report discusses recent and expected future developments in continuing research on active suppression of vibrations in truss structure. Focuses on development of digital controller as part of vibration-suppressing feedback control system including noncollocated vibration sensors and actuators.
Chu, Cheng-Chih↗
Studies Of Positive-Position-Feedback Control
Report discusses theoretical and experimental studies of positive-position-feedback control for suppressing vibrations in large flexible structures. Positive-position-feedback control involves placement of actuators and sensors on structure; control voltages applied to actuators in response to outputs of sensors processed via compensator algorithm. Experiments demonstrate feasibility of suppressing vibrations by positive position feedback, and spillover of vibrational energy into uncontrolled modes has stabilizing effect if control gain sufficiently small.
Fanson, James L.↗
Vibration Testing Of Trusses By Use Of Active Members
Report describes experiments conducted to determine whether, in vibration tests of truss structure, active structural members can be used to excite test vibrations yielding accurate data on vibrational modes of structure. Results indicate accuracies equal or exceed those obtained from external-excitation tests.
Chen, Jay Chung↗
Adaptive structures for precision controlled large space systems
The development of adaptive structural systems is reviewed and the potential of these systems in meeting some of the requirements for NASA future space missions is demonstrated. Particular attention is given to the characteristics of a viscous damper in the micron displacement regime; the optimal placement of active and passive members into a truss structure; a system identification test using the active members as excitation sources; a concept for deforming a lightweight composite honeycomb optical panel to correct for on-orbit distortions by using piezoelectric actuators attached to the back facesheet; and the results of an active member vibration control experiment in a reduced gravity environment.
Garba, John A.↗
Using adaptive structures to enable future missions by relaxing ground test requirements
Future NASA missions will require large space structures that must maintain accurate surface tolerances for up to 20 years; most flight programs require a ground test verification of the hardware. Because of the influence of gravity, the current state-of-the-art ground test technology cannot accurately determine whether the hardware complies with the requirements. The incorporation of adaptive structures into the spacecraft will enable a relaxation of the ground test requirements necessary to validate the hardware for flight. This paper describes the challenges in testing large precision structures, adaptive structures, the data establishing the current state of the art in ground testing, and the utilization of adaptive structures to alleviate the ground test requirements.
Wada, Ben K.↗
Adaptive structures for precision controlled large space systems
The stringent accuracy and ground test validation requirements of some of the future space missions will require new approaches in structural design. Adaptive structures, structural systems that can vary their geometric congiguration as well as their physical properties, are primary candidates for meeting the functional requirements for such missions. Research performed in the development of such adaptive structural systems is described.
Garba, John A.↗
Ground test validation for precision structures
Future proposed NASA missions will require large precision truss type structures that are deployed or assembled in space. To date, space structures that are important to missions success have been ground tested to validate their performance. Evaluation of the performance requirements of future systems has shown that using current and projected design and test approaches, the structure cannot be adequately validated by ground test. A problem exists since it is believed that unless important structure systems can be validated by ground tests, they will never be adopted for future missions. New design or ground test approaches are necessary to enable future missions. The inability of current approaches to validate future structural systems is discussed.
Wada, Ben K.↗
Damping and structural control of the JPL phase 0 testbed structure
This paper describes recent advances in structural quieting technology as applied to active truss structures intended for high precision space based optics applications. The active structure incorporates piezoelectric active members which exert control forces internal to the structure and thereby improve the structure's dimensional stability. The control architecture involves two layers of feedback control. The first utilizes collocated measurements of force and velocity at the active member to achieve active damping, the second utilizes noncollocated measurements of acceleration at the location of a simulated optical component to achieve structural stabilization. The local control loops are based on the concept of impedance matching, the global control loops are designed using robust control methods. These two levels of control are intended to operate simultaneously; however, in this paper each approach is applied individually. The combined implementation is left for future work.
Fanson, James L.↗
System identification test using active members
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Chen, Jay-Chung↗
Joint U.S./Japan Conference on Adaptive Structures, 1st, Maui, HI, Nov. 13-15, 1990, Proceedings
The present volume of adaptive structures discusses the development of control laws for an orbiting tethered antenna/reflector system test scale model, the sizing of active piezoelectric struts for vibration suppression on a space-based interferometer, the control design of a space station mobile transporter with multiple constraints, and optimum configuration control of an intelligent truss structure. Attention is given to the formulation of full state feedback for infinite order structural systems, robustness issues in the design of smart structures, passive piezoelectric vibration damping, shape control experiments with a functional model for large optical reflectors, and a mathematical basis for the design optimization of adaptive trusses in precision control. Topics addressed include approaches to the optimal adaptive geometries of intelligent truss structures, the design of an automated manufacturing system for tubular smart structures, the Sandia structural control experiments, and the zero-gravity dynamics of space structures in parabolic aircraft flight.
Wada, Ben K.↗
An experimental evaluation of uncertainty models for a flexible structure control problem
The authors describe results in applying robust control techniques of an active precision truss structure at the Jet Propulsion Laboratory. The active structure incorporates piezoelectric members which serve as both structural and actuator/sensor elements. Several characterizations of uncertainty are studied and the controllers are compared experimentally.
Smith, Roy S.↗
Active structures for use in precision control of large optical systems
This paper discusses the application of active structures technology to the control of precision structures for future space-based astrophysics observatories. The state of the art in active structures is reviewed and technology developments applicable to large optical systems are discussed.
Fanson, James L.↗
Development of an active truss element for control of precision structures
An active structural element for use in precision control of large space structures is described. The active member is intended to replace a passive strut in a truss-like structure. It incorporates an eddy current displacement sensor and an actuator that is either piezoelectric (PZT) or electrostrictive (PMN). The design of the device is summarized. Performance of separate PZT and PMN actuators is compared for several properties relevant to submicrometer control of precision structures.
Anderson, Eric H.↗
Experiments On Active Members In Large Space Structures
Report discusses continuing research on structures including active members, which incorporate sensors, actuators, and electronic circuits to monitor and control vibrations. Describes experiments on two structures with active members, progress in design, testing, and simulation of behavior of active members. Objective is to develop systems to enhance performances of large, flexible structures in space. Also applicable to some terrestrial structures and testing equipment involving close tolerances in feedback control of forces and/or positions.
Fanson, James L.↗