Dynamics of an Inflatable Structure in Vacuum and Ambient Conditions

Slade, Kara N.; Tinker, Michael L.; Lassiter, John; Engberg, Robert

doi:10.2514/2.1393

Cited by 16 publications

(4 citation statements)

References 7 publications

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“…In addition, excitation methods have to be carefully chosen because the extremely exible nature causes point excitation to result in only local deformation. Grif th and Main 4 used a modied impact hammer to excite the global modes of the structure while avoidinglocal excitation.Slade et al 5 tested a torus attached to three struts with a lens in a thermal vacuum chamber. They found significant differences in the response between the structure in ambient and vacuum conditions.…”

Section: Introductionmentioning

confidence: 99%

Vibration Testing and Finite Element Analysis of an Inflatable Structure

et al. 2003

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Vibration testing and nite element analysis of an in ated thin-lm torus are presented. In atable structures show signi cant promises for future space applications. However, their extremely lightweight, exible, and high damping properties pose dif cult problems in vibration testing and analysis. Smart materials are used as sensors and actuators for performing vibration tests of an in ated torus. In addition, a predictive model has been developed, which can be compared with experimental results. A commercial nite element package, ANSYS, is used to model a prestressed in atable structure. Both experimental and nite element results are in reasonable agreement with each other. The predictive model can be used for analyzing the dynamics of in ated structures and for designing control systems to attenuate vibration in an in ated torus.

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Section: Introductionmentioning

confidence: 99%

Vibration Testing and Finite Element Analysis of an Inflatable Structure

et al. 2003

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“…First the system does not induce mass loading which can significantly alter the dynamics of the structure. This issue was found in [14,15] during testing of ultra lightweight inflatable structures for use in future satellites. Second, the system provides a force distributed over larger area than a shaker.…”

Section: Resultsmentioning

confidence: 95%

“…Following the identification of the magnetic flux generated by the permanent magnet, the eddy current density can be calculated. When calculating the eddy current density the image method [15] is used to satisfy the boundary condition of zero eddy current density at the conducting plate's boundaries. By accounting for the edge effects of the conductor, the accuracy of the predicted eddy current density will be greatly increased.…”

Section: Modeling Of the Eddy Current Forcementioning

confidence: 99%

Non-Contact Eddy Current Excitation Method for Vibration Testing

Sodano

2006

Exp Mech

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When a conductive material is subjected to a time changing magnetic field, eddy currents are induced in that structure. The eddy currents circulate inside the conductor resulting in a magnetic field that interacts with the applied field. The eddy current field is such that it opposes the change in flux resulting in a force between the source and conductor. The time changing magnetic field necessary to induce an electrometric force in the materials can be generated through a variety of different ways. In the present study, a permanent magnet will be mounted to the tip of an electromagnetic shaker such that the motion of the magnet relative to the structure will cause a time changing field and the formation of eddy currents. The actuator will be demonstrated to be beneficial due to its ability to apply actuation forces without contacting the structure. This study will show that the non-contact nature of the system eliminates mass loading and added stiffness which are downfalls of traditional excitation techniques. Additionally, it will be shown that the use of a non-contact device preserves the mode shapes of the structure, whereas a stinger results in distortions due to the added constraint. Using this concept, a model of the actuation system will be developed, allowing the beams response to be simulated. The actuation system will then be used to excite a cantilever beam to obtain the modal parameters without contacting the structure. The novel noncontact actuation system developed in this paper provides a new method performing vibration testing of on lightweight or flexible structures while preserving their dynamics.

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“…Salama et al (1994) investigated on-orbit shape control to adjust the parabolic reflector dish of an inflatable antenna using piezoelectric film. Slade et al (2001) performed a dynamic analysis of the inflated Shooting Star experiment under both ambient and vacuum conditions, and compared their experimental results to a finite element model. Similar trends in frequencies in both ambient and vacuum conditions were identified between the experimental and finite element data.…”

Section: Introductionmentioning

confidence: 99%

A Comparison between SISO and MIMO Modal Analysis Techniques on a Membrane Mirror Satellite

Ruggiero

Inman

2005

Journal of Intelligent Material Systems and Structures

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The future of space satellite technology lies in the development of ultra-large, ultra-lightweight space structures, orders of magnitude greater in size than the current satellites. Such large crafts will increase communication and imaging capabilities from orbits. Many such proposed ultra-flexible satellites are inflated structures. To get these ultra-large structures in space, they will have to be stored within the Space Shuttle cargo bay and then inflated on-orbit. However, the highly flexible and pressurized nature of these ultra-large spacecraft poses several daunting vibration and control problems. Disturbances (i.e., on-orbit maneuvering, guidance and attitude control, and the harsh environment of space) wreck havoc with the on-orbit stability, pointing accuracy, and surface resolution capability of the inflated satellite. Fortunately, recent advances in integrated smart material systems promise to provide solutions to these problems. Recent research into the use of Macro-Fiber Composite (MFC®) devices integrated into the dynamic measurement and vibration control of inflated structures has had promising results (Wilkie et al., 2000). These piezoelectric-based devices possess a superior electro-mechanical coupling coefficient making them superb actuators and decent sensors in dynamic analysis applications. Initially, research was performed on an inflated torus using single-input, single-output (SISO) testing techniques. Since then, steps have been taken to outline a new, multiple-input, multiple-output (MIMO) testing technique for these ultra-large structures. This study applies these results to an inflated torus with bonded membrane mirror to extract modal parameters, such as the damped natural frequencies, associated damping, and mode shapes within the frequency bandwidth of interest for these structures (5–200 Hz). Further, the nonlinear dynamic behavior of the inflated torus and membrane mirror is accentuated through a comparison of SISO and MIMO modal analysis techniques, and a discussion of the nonlinear results follows. The purpose of this work is to apply the results from prior works to an inflated torus with bonded membrane mirror to accomplish the following three goals: (1) to establish a baseline dynamic characterization of the test structure using SISO modal analysis techniques;(2) to perform a MIMO modal analysis of the test structure to identify natural frequencies, mode shapes, and damping ratios, and compare these MIMO results to the SISO analysis; and(3) to use the discrepancies between the two testing technique results as a platform for discussing the nonlinear nature of the test structure. In the future, the results of this work may form the premise for an autonomous, self-contained system that can both identify the vibratory characteristics of an ultra-large, inflated space craft and apply an appropriate control algorithm to suppress any unwanted vibration – all while on-orbit.

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Dynamics of an Inflatable Structure in Vacuum and Ambient Conditions

Cited by 16 publications

References 7 publications

Vibration Testing and Finite Element Analysis of an Inflatable Structure

Vibration Testing and Finite Element Analysis of an Inflatable Structure

Non-Contact Eddy Current Excitation Method for Vibration Testing

A Comparison between SISO and MIMO Modal Analysis Techniques on a Membrane Mirror Satellite

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